Proceedings of China-Europe Conference on Geotechnical Engineering

World population increases day by day. In order to meet this increasing population’s basic needs such as sheltering, transportation and social activities, necessity for underground structures gradually increase. As a result, deep excavations become more important each passing day while excavations deepen. In order to design the optimum system which ensures the safety of environment, roads, structures and the excavation, the excavation properties should be modelled so that it reflects the actual geometry and boundary conditions. The ground parameters, which have crucial effect on the solution, should also be determined precisely. In this study, a deep excavation with a depth of 33.0 m performed on over-consolidated Ankara Clay is investigated. The excavation system was designed to be consisted of double-row of piles supported by multilevel anchors. Inclinometer and load cell installations on the shoring elements have been made for the inspection of the pile wall displacements and anchor forces. Back analysis is made in order to obtain the ideal ground parameters which give the measured displacements and anchor forces. This analysis is conducted by a series of Plaxis analysis in which ground parameters are changed iteratively in order to find their values that give the measured displacements and forces. For these Plaxis analyses, three different models namely; Hardening Soil, HS small and Mohr Coulomb are used and ground parameters are determined. Finally, ground parameters obtained by back analysis for different soil models and the parameters determined from field tests are compared and a correlation is proposed to simulate the behavior of over consolidated Ankara clay.

In this paper are presented the main design criteria for the excavation and earth retaining wall solutions developed for the construction of the underground floors of a building located ta Rua do Benformoso, near to Intendente Square, in Lisbon down town, Portugal. Two different earth retaining wall solutions were developed considering local constraints, mainly geological features, topography, urban envelope and building architecture. The first solution is a Berlin-type wall braced by temporary ground anchors and steel struts. The second solution is a conventional retaining wall with reinforced concrete buttresses. This solution was performed at the garden back area due to the impossibility of using permanent ground anchors.

The pile base plays an important role in increasing its bearing capacity. Several studies have been carried out to produce types of piles which are enlarged at their bases. Therefore, it was thought in this study to design a mechanism on enlarged base for the pile at a selected depth so that it does not intersect with pile driving process. The manufactured pile is square open-ended from both sides and provided with two or four gates. The gates are linked on the pile shaft at the base by steel hinges which allow the gate to rotate at an angle of (90°). The pile is driven alone while the spreader (inner Shaft) is kept inside the pile using a hammer. The driving in this stage is stopped when the penetration of the pile and spreader is equal. At the end of this stage, the spreader is extruded from the pile shaft and the pile becomes ready for loading test. This type of piles (steel piles with gates) does not demand reaching the strong soil layer or knowing its depth, because this type of piles is suitable for soft to medium soils and it provides very good results, so that the required pile length will be shorter than in ordinary piles. This means lower cost and time but with additional efforts.

Gravity grouting technique is commonly used in soil nailing and ground anchorage systems to increase pull out capacity of soil inclusions. Bond strength in between soil-grout interface estimates the pull out capacity of a grouted soil nail/anchor. The bond strength improvement due to gravity grouting and pressure grouting is very limited and grout likely shrinks after setting, resulting in reduction of skin friction between cement grout and surrounding soil of drill hole. One of the major concerns of soil nailing techniques is excessive lateral movement or creep behaviour over the service life and a case study of instrumented ground anchor wall reported that gravity grouted soil reinforcement technique experience excessive creep behaviours. The application of fracture grouting technique in soil nailing is very new and presumably it not only provides drill hole expansion but also provides mechanical interlocking between the penetrating grout and surrounding soil, which could resist the creep behaviour of soil-nails as well as enhance the bond resistance. The application of fracture grouting in soil nailing system could also be a cost-effective method since it likely to increase the pullout resistance of soil-nails, resulting in reduction of the number of soil-nails.

Safety alarm method is the key to the deformation of deep excavation engineering control security technology. A new safety alarm system was put forward by the deformation behaviors of soil-rock mass because that the alarm value of control in the code was too preliminary, which could not effectively reflect the deformation state of deep excavation engineering. The new safety alarm method involved three kinds control indicators: the accumulative value, monitoring rate and monitoring acceleration; and four levels of alarm: blue alarm, yellow alarm, orange alarm and red alarm. Alarm levels and the safety control key indicators were corresponded to the tasks and responsibilities. The one excavation example was verified for the practical application of the alarm system.

Given the sudden rise of the construction market in Portugal, allied with the growth of tourism, a need to build more hotels has emerged. This project takes place in Lisbon, close to the Oriente Station (Metro and Railway) at Parque das Nações. The Moxy Hotel, with fifteen raised floors, will be built over a hill, thus rising from the ground. In order to respect the neighbor conditions, a bored piles earth retaining wall (BPW) was designed, reaching a maximum depth of approximately 22 m. The geological and geotechnical conditions of the site are pointed out, as well as the geometrical and topographic conditions. This BPW will be braced differently, depending on whether it is the temporary or the final stage. Therefore, one solution was designed, taking into account those two stages, aiming to find an economic-safe balance. At last, a numerical analysis is presented, where the deformations and efforts are predicted.

Possessing a few geological boreholes distributed along the tunnel alignment is likely to lead to an inability of understanding the complex geological structure of worksite and optimising the tunnelling parameters. This lack of geological borehole will result in a high potential of geo-hazards for tunnelling works. This study proposes an alternative method to dynamically determine the major and other components of ground by taking the pipejacking parameters and spoil characteristics into account. The validity of the proposed method is verified via a case study.

The dynamic behavior of 2 × 2 pile group has been investigated under rotating machine induced vertical vibration using both field testing and numerical analysis. Forced vibration tests have been performed in the field on a pile group (pile length = 3 m, pile diameter = 0.114 m) embedded in silty soil. The frequency-amplitude responses of the pile group are measured for four different eccentric moments. It is found that the measured response curves are nonlinear in nature. The numerical analysis has been performed using continuum approach and superposition method to determine the nonlinear frequency-amplitude responses of the pile group. From the analysis, the boundary parameters and soil-pile separation lengths are predicted for different eccentric moments. The analytical frequency-amplitude responses of the pile foundations are compared with the dynamic field test results and it is found from the comparison curves that the nonlinear frequency-amplitude responses obtained from the analysis have a very close match with the field nonlinear response curves.

This paper reviews the modern technologies of precast concrete piles applied in Europe. Supported by the long-time experience of the company in manufacturing and driving precast concrete piles on a large scale in numerous European countries, the up-to-date standards and directions of technology development have been discussed. Presented in the paper the examples of executed pile foundations for various types of structures – from single piles under the support structures of railway overhead lines, through buildings of various sizes and intended use, wind farms, harbour embankments, to large industrial plants and bridges, which verify the broad opportunities to apply precast concrete pile technology in construction engineering.

The Building Information Modeling (BIM) methodology is spreading across the Architecture, Engineering, and Construction (AEC) industry. The need of leaner processes from the concept to the execution of projects are opening space for this approach. One of the advantages of BIM methodology is an early coordination and communication among the different project’s stakeholders, a key issue for the geotechnical project where uncertainty is high. This case study approaches the use of BIM for a geotechnical project of an excavation for a residential tower in the center of Lisbon, with a deployment area of 4600 m and a maximum excavation depth of 17.60 m. The solution proposed was a Bored Pile Wall (BPW) system with anchors and bracing slab stripes. The solution was modeled coordinated with the 3D BIM model from the architecture and was then exported to a soil analysis numerical software and a structural analysis software to improve the solution proposed.

This study presents the details of a newly developed bucket foundation breakwater. The bucket is sunk and penetrated into the foundation soil when it is installed. Centrifuge model tests are performed to study the penetration behaviour of the bucket foundation during the sinking process. The details of the test model and procedure are presented. It is found that the total penetration resistance increasing linearly in the muddy clay layer. An inflection point is found when the bucket reaches the silty clay layer. The penetration resistance corresponding to this inflection point can be thought to be the suction required to install the bucket foundation.

The unloading effect of excavations can cause a change in the stress field and displacement field of surrounding strata, which may seriously influence the existing bridge pile foundations adjacent to excavations. Based on a foundation pit excavation in Kunshan, Jiangsu Province, the finite element method considering the small strain of soil is adopted to study behavior of the excavation and its influence on deformation of the nearby pile foundations. The major calculation parameters of HS-Small model are determined to well describe the deformation characteristics of the soil. Through numerical calculation and simplified analysis, the influence zones for deformation of bridge pile foundations adjacent to the excavation are divided into three types, considering various deformation controlling criteria for existing pile foundations as well as the relative spatial relationship of the pile foundation and the excavation. Dividing lines between these types of zones are the allowable displacement line and the warning displacement line. Accordingly, the adjacent piles are divided into three types. During the construction of foundation pit, it is useful to take corresponding measures depending on which influence zone that the bridge pile foundations in.

As a newly developed gravity installed anchor, the OMNI-Max anchor is an efficient anchoring foundation due to its dynamic installation and diving property during keying. However, due to the complex geometry of the anchor, it is with difficulty to predict the anchor final penetration depth embedded in the seabed. This study carried out 1g model tests in normally consolidated (NC) and lightly overconsolidated (LOC) clay to investigate the effects of the impact velocity, and the soil strength on the anchor final penetration depth. The anchor dynamic penetration process in the soil was recorded by a micro-electromechanical systems (MEMS) accelerometer. By integrating the anchor acceleration recorded by the MEMS accelerometer, the anchor velocity-displacement curve was obtained. Finally, an empirical formula is put forward to predict the final penetration depth of the OMNI-Max anchor. This study may be beneficial for the engineering design and application.

The influence of vertical load on the lateral stiffness and capacity of the pile is merely considered in the current design practice and therefore deserve a further investigation. This study presents detailed centrifuge tests results on the lateral behavior of a single pile in normal (NC) and over consolidated clay (OC), with and without application of vertical loading at the pile head. In the meantime, three-dimensional finite element analyses (FEA) were carried out to offer further insights into the effect mechanism of vertical loads on lateral pile behavior. Both physical and numerical investigation reveal that after applying the vertical load and allowing the dissipation of excess pore pressure in NC, the stress ratio (q/p’) of the soil around the pile decreases while the mobilisable undrained shear strength (s_u) increases, resulting in 10% and 50% increase of the lateral initial stiffness and bearing capacity of the pile, respectively. In contrast, due to application of vertical load to a single pile in the over consolidated clay, the q/p’ prior to lateral loading increases while the mobilisable s_u decreases, consequently leading to 13% and 33% reduction of the lateral initial stiffness and bearing capacity of the pile, respectively.

Mono-piles are widely used in offshore wind industry, and it will be necessary to consider the influences of scour for mono-piles under combined waves and currents. There are about two main effects on the mono-piles when scour occurs: the first is to reduce the ultimate resistances and the other is to reduce the impedances (stiffness and damping ratio). While impedances play a dominant role on the natural frequencies and dynamic responses of offshore wind turbines, the risk of resonance and fatigue will increase dramatically due to the presence of scour holes. In this paper, the evolution of dynamic characteristics of model mono-piles under different scour depths and excitation frequencies are studied by model tests. The scour depths are calculated by laboratory tests or field observations in the literature. By means of Fourier transform and modal analysis, the dynamic responses of mono-piles in time domain and frequency domain are obtained and analyzed. The important parameters for mono-piles are obtained, including the resonant frequencies and resonant amplitudes. The experimental results are compared with a dynamic numerical analysis. The results of this paper will be helpful to understand the dynamic characteristics of offshore mono-piles in complex ocean environment.

In order to study the effect of spatial variability of soil parameters on foundation settlement. In this paper, the method of combining the theory of random field and numerical analysis is used to systematically analyze the settlement probability of the soft soil foundation in the south of China. The influence of spatial variability of soil parameters on probability settlement of foundation is studied. The results indicate that the settlement value of foundation increases with the increase of parameter variation coefficient, which is the most sensitive to deformation modulus. When the spatial variability of soil space is relatively large, the auto-correlation function selection has a great influence on the settlement of the foundation. The settlement value based on the exponential square is larger, and the single exponential is smaller.

Self-developed visual horizontal drawing strip anchor plate model test and numerical simulation experiment showed that there existed a triangular soil core before anchor plate under ultimate pulling condition, whose two bottom corner’s variation could reflect the symmetry of failure slip-line field indirectly. Along with the increasing of buried ratio, the upper bottom corner enlarged from φ to π/4 + φ/2, and the lower bottom corner reduced from π/2 to π/4 + φ/2 with the sum of two corners basically remained unchanged. In this course, the failure slip-line field before anchor plate evolved from asymmetric to symmetric gradually. Base on this knowledge, corresponding assumptions were put forward to construct the ultimate bearing mechanical model of vertical strip anchor plate under horizontal drawing, and ultimate mechanical equilibrium analysis method was used to derive the unified theoretical formula of ultimate bearing capacity at last. Calculation of four tests and comparison to other two theories indicated that unified theoretical solution had good applicability to vertical strip anchor plate in sand.

Large driven piles are used widely in both onshore and offshore construction. Predicting their limiting capacities and load-displacement behaviour under a range of static and cyclic, axial, lateral and moment loading conditions is critical to many engineering applications. This paper reviews relevant recent joint research by groups at Imperial College London (ICL) and Zhejiang University China (ZJU). Two tracks of enquiry are outlined: (i) assembling and analysing a major and open database of high quality load tests conducted on industrial scale piles at well characterised sites; and (ii) modelling the effective stress regime developed around piles driven in sands. Both avenues of research are vital to enabling scientifically well-founded and yet industrially credible improvements to practical pile design methods. The scope of future joint research is also outlined.

Existing rafts under the design loads sometimes experience excessive settlements or confront such a possibility in the future if the modified functionality of building is induced to increase the foundation loading. Differential settlement and deflection may also be observed in case of eccentric loading especially when these structures are built on soft soils. One of such precedents was observed in a silo structure used as a cement plant located in Douala, Cameroon. The structure that is founded on deep, soft clay with high ground water table rests on a raft supporting the storage tanks located at one side of the building conveying non-uniform loading to the existing raft. In one and a half year after completion of the construction, the silo structure had significantly settled and deflected. The underpinning pile remediation system allowing the continuity of cement production is applied from the outside of building using the rigidly connected protruding reinforced concrete section as a capping beam. In this study, the entire foundation system is numerically analyzed using the presented 3D finite element (FE) models. The back-analyses are used for the calibration concurring with the actual measurements of settlement and deflection at the site. The foundation systems with and without the underpinning piles are compared with each other to reveal how the remedial improvement is achieved by the presented underpinning pile system.

The smart structures provide more efficient designs. In smart structures electronic components, sensors and actuators are well distributed and integrated, capable of controlling vibration for self-actuation and self-diagnostics. The purpose of structural control is to absorb, refract and reflect the energy induced by seismic wave propagation due to dynamic disturbances. This paper investigates semi-active control strategy for walls retaining granular material. It has two components, the seismic protection of retaining structure and the mitigation of wave induced vibration in retaining structure. An ideal semi-active motion equation of a retaining structure that consist of cantilever retaining wall with granular backfill bounded with a PZT patch was analyzed. The stress-strain analysis was performed by varying material properties and geometric configuration of the wall and granular fill. The stress- strain behavior of granular fill with PZT patch is presented in graphical form. A mathematical analysis is performed to examine the vibration induced effect of provision of PZT on in retaining structure due to the dynamic loading.

Rammed from the deep layer gradually to the ground surface along the ramming tube can be achieved by the in-tube deep dynamic compaction method, which is a new dynamic compaction construction technique. Based on the field test in Fujian, the reinforcement effect was explored during reinforcement. The test results show that the accumulation of excess pore water pressure during the tamping process can be effectively avoided by the in-tube deep dynamic compaction method, and the excess pore water pressure will dissipate completely after 24 h of dynamic consolidation; The effective depth of foundation treatment can reach more than 13 m depth, the defects of long period of dissipation of excess pore pressure and shallow depth of effective reinforcement in conventional dynamic consolidation method were overcame.

X-section cast-in-place concrete pile (referred to as XCC pile) is a new type of abnormal section pile developed in geotechnical research institute of Hohai University and patented in China. It has been widely applied in practice for its larger bearing capacity and use of less concrete than the common circular section pile. In this paper the construction techniques are introduced firstly, then comparative field study on load transfer mechanism of X-section and circular section pile rafts are presented. To reveal the bearing characteristics of the XCC pile raft foundations, the load-settlement relationship, side friction and so on are detailed analyzed. The results show that XCC pile raft has superior bearing capability compared with the circular pile raft, especially at the stage of high load pressure. The side friction percentage of XCC pile is larger than that of the circular pile while the tip resistance percentage is smaller.

In the concrete diaphragm wall (CDW) construction, the L-shaped diaphragm wall is used to form an enclosed retaining structure. Due to the complicated stress change in trenching, the L-shaped trench has the lower stability than the regular rectangular trench. This paper investigates the trench instability during the L-shape slurry trench excavation based on the upper bound analysis. A 3D kinematically admissible mechanism defining the failure for the L-shaped trench is constructed. The safety factor on the trench and corresponding failure pattern are obtained through the upper bound analysis. The influence of trench geometries and the soil properties on the trench stability are discussed by the parameter analysis.

Many structures namely tall buildings, offshore platforms, bridge bents and electric transmission towers are subjected to lateral loads of considerable magnitude due to wind and wave actions, ship impacts, or high-speed vehicles. Significant torsional forces can be transferred to the foundation of transmission towers due to the laterally loaded high tension wires. Inadequate consideration of torque in design of the piles against these loads result into disastrous consequences. The design and analysis of pile foundations present a complex problem to the engineers because of several factors that affect the foundation behaviors. Such factors include mode of loading, soil properties, pile geometry, placement and method of construction. The mode and magnitude of loads transferred from the superstructure influences the selection of pile foundation to resist the imposed loads. The present work considers a mechanism of applying torque to a model single pile and model (m × n) pile groups; secondly, to find out experimentally the torque-twist curves of a model single pile and model (m × n) pile groups; and to analyse basis of pile-soil-pile interactions in model (m × n) pile groups subjected to torque. The experiments on a model single pile (1 × 1) and model (m × n) pile groups consisting of (1 × 2), (1 × 3) and (2 × 2) piles were performed to analyse the effect of torque on a model single pile and model (m × n) pile groups. The experiments were performed in loose and dense sand. The results of application of torque on a model single pile were compared with that of model (m × n) pile groups.

This paper investigates the application of permeable piles (reinforced concrete pipe piles with drainage holes) to accelerate soil consolidation during pile driving. To achieve that, finite element models are generated in ABAQUS with infinite element boundary condition. The results of numerical analyses show that the performance of permeable piles can be improved by drilling drainage holes. However, the influence of these openings on the structural performance of permeable piles has not been evaluated before. The structural behavior of permeable piles is investigated in this study using uniaxial compression tests and four point flexure tests. Although drainage holes could reduce the ultimate compressive strength of pile specimens, the measured values were much larger than design specifications. For bending tests, cracks with smaller width were initiated and propagated over an increasingly wider area in permeable piles, and an improved flexural capacity was obtained. These results of the current study show that permeable pile is an attractive alternative to accelerate soil consolidation.

In order to better understand the origin of ageing on driven micropiles in sand, a series of field pull-out tests on small diameter driven piles were carried out in Dunkirk. The micropiles were about 51 mm in diameter, 8 mm wall thickness and 2 m embedment. The micropiles were made of different steel types (mild steel or stainless steel) with different shaft roughness. Sand characteristics, field penetrometer tests and pile tests are summarized. Tension tests were performed at different intervals of time after micropiles installation in attempt to investigate the influence of: (i) physiochemical effects, by testing both stainless and mild steel piles; (ii) the early stages of ageing. A significant increase of capacity was observed in the case of mild steel micropiles, regardless of the shaft roughness, while no ageing effects were observed on stainless steel micropiles. Some micropiles have been pre-loaded in compression at different energy levels. These results suggest the great influence of physiochemical effects (corrosion) for small diameter piles driven in sand. In the case of a prior compressive plastification, the loss of the benefit of ageing is obvious.

The construction of diaphragm walls requires a high level of technical experience to cope with one of the most challenging tasks in geotechnical engineering, the interlock of discreet panels to a continuous wall. The joint inspector is a new tool that supports the quality check of diaphragm walls during construction by providing real-time data to initiate corrective actions during construction, if necessary.

Temporary cofferdams for foundations of bridge pillars are ranked among the demanding constructions, and they often require high resources for their construction. The newly planned bridge over the Danube River in the Komarno city between Slovakia and Hungary has been designed as an asymmetric cable-stayed bridge with single pillar. The cofferdam made of double – row sheet pile wall of ground plan dimensions of 20 × 44 m is designed for foundation of the pillar. A narrow space between sheet piles will be filled by an atypical concrete.The paper focuses on stability analysis of the cofferdam, which construction differs to typically proposed constructions of excavation pits for founding of the bridge pillars. It was necessary to verify stability of the cofferdam in several design situations, such as construction process of the cofferdam, injection of the subsoil from the cofferdam, which is backfilled by the soil and the process of excavating the pit in several phases with gradual installation of struts. The task was solved using an analytical method and numerical method – FEM. Modeling the behavior of the construction of the cofferdam using different methods allowed wide analysis of results and more reliable verification of the stability of the construction as well as the design of individual elements.

The dynamic response of footing depends on several influencing parameters such as the shape and size of the foundation, effect of embedment, static load and dynamic excitation intensity. Here, efforts have been made to experimentally investigate the dynamic response of embedded block foundation under vertical vibration. Field experiments and analytical investigations using elastic half-space theory are carried out to study the dynamic response of embedded block foundation of aspect ratio L/B = 1.5 under vertical vibration for three different embedment depths (D = 0, 0.25 and 0.5 m) under static load of 6.6 kN. The block vibration tests are carried out using a Lazan-type mechanical oscillator under four different eccentric moments (W.e = 0.2, 0.8, 1.4 and 2.0 Nm). The frequency amplitude response of the block foundation obtained from elastic half-space theory are compared with the response obtained from the experimental investigations and it is observed that the maximum resonant amplitude decreases and resonant frequency increases as the embedment depth increases.

Free vibration characteristics for an Euler-Bernoulli beam supported using a simple Winkler linear elastic foundation are calculated. The method of solution is by He’s variational iteration method developed for various boundary (end) conditions. The beam’s natural frequencies and mode shapes are obtained, with rapid convergence noted during the calculations. The calculation method is tested using a clamped-clamped beam. In this paper a robust and efficient algorithm is also given, based on He’s method, which can be easily modified for more complicated elastic foundations.

Recently, barrette piles have been used to replace conventional bored piles in order to increase allowable vertical pile capacity in the limited space projects such as high-rise building projects and elevated train projects. The basic of construction equipment, the slurry used during construction and construction time between barrette pile and bored pile construction are totally different. Therefore, their design parameters for pile capacity estimation should be different. In this research, pile load test was carried out on the fully-instrumented barrette piles. The test result can be separated into friction of each soil layer and end bearing. By considering stress-strain relationships, adhesion factor of clay layer, friction factor of sand layer and end bearing factor of sand layer can be calculated. These factors were found to be able to estimate ultimate pile capacity. Based on these factors, the estimated pile capacity was compared with another barrette pile tests. This estimation agreed well with the test results.

Public transport systems excite ground vibrations that are transferred to nearby buildings and may exceed the comfort level or legal limit values for residential use. The paper aims to present application examples in China, where the assessment was based on Chinese and German standards.

In view of principles of the theory of plasticity, the stress field is not independent of the displacement and/or deformation fields. Therefore, a more reliable analysis will be achieved if the bearing capacity and load-displacement behavior of piles are analyzed simultaneously. In this study, a new analytical-numerical method has been proposed to estimate the bearing capacity and axial load-displacement behavior of driven piles in granular soils using CPT records. For this purpose, the method of stress characteristics is used to analyze the stress field below and around the pile and in effect, the failure mechanism. This failure mechanism is then used by implementation of the kinematical approach of the limit analysis to compute the displacement field. This procedure is employed in a step-wise manner to gradually calculate the stress and displacement field as the pile is assumed to penetrate into the ground. One should note that the mobilization of the friction angle is linked to the gradual increase in shear strains in the field. This is done by making use of the CPT results which are both continuous and reliable in comparison to standard laboratory tests often conducted on disturbed samples at discrete intervals. Hence, the step-wise procedure is expected to give rise to a complete load-displacement behavior of driven piles shown in a practical case.

On basis of the slurry preparation of diaphragm wall construction in Jinshan Metro Station in Fuzhou, firstly, laboratory tests are conducted to obtain 3D characteristic figures which exhibit the effects of silt soil and bentonite content on slurry properties including density, viscosity and water loss. Furthermore, influence of slurry density, viscosity on filter cake forming process under different slurry pressure is analyzed through laboratory tests. The test results indicate that: the 3D characteristic figures can give a variety of slurry proportion combinations of specific density, viscosity and water loss. The final unit water filtration first drops then starts to increase as slurry density increases. As for viscosity and slurry pressure, the final unit water filtration decreases as viscosity increases and it increases as slurry pressure increases. In addition, the influence of viscosity on final unit water filtration is less than that of density. Finally, optimization of trench construction is proposed based on filter cake formation time obtaining from the test results and construction conditions.

Construction of tunnels often causes uneven settlement of the above buildings, resulting in engineering accident such as the skew or even collapse of buildings. Assuming that the vertical displacement distribution mode of buildings is built, then the variational control equation is established. A calculation method of building settlement caused by construction of double line parallel tunnels based on variation method is put forward. Through two engineering examples, it is concluded that the building settlement curve calculated by this method is in agreement with the measured value, which verifies this method.

Although compaction grouting beneath the pile tips has been proven to improve the vertically loaded capacity of piles, its design is still largely based on empirical experience and lack of rational design guide. An analytical model that relates the tip resistance to the pressure to expand a spherical cavity for prediction of pile tip bearing capacity is presented. The proposed approach prediction matches quite well with tests results. However, more tests should be done to confirm the correctness of this method. In this paper, a new laboratory setup for investigating the effect of compaction grouting on pile capacity was designed and assembled. This apparatus allows a model pile to be driven into or buried in the sand sample and then a low mobility grout is delivered through a grouting tube inside the model pile into a membrane that is used to prevent grout fracture the sand sample. Then soil stress and pore pressure change are monitored by soil pressure and pore pressure transducer buried in the sample. Pile load test is conducted after the grout have been cured and the pile penetration resistance is measured by the load cell.

The response surface method (RSM) is introduced to identify the model parameters of a synthetic cross-section of high-fill foundations. Four different initial exploration regions are employed to show the robustness of the RSM. The results show that, the method can effectively search the satisfactory parameters. Thus, it can be applied for parameter identification in realistic engineering problem once enough field monitor data is obtained.

Pre-excavation dewatering (PED) can cause a significant wall deflection. How to predict this deformation is an urgent problem to be solved. The elastic foundation beam method is widely adopted to predict the wall deflection. A key issue that need to be addressed in the use of this method is to obtain the distribution of the horizontal foundation modulus. However, the distribution pattern of horizontal foundation modulus under PED is not clear. In this study, a numerical model is established and verified, and a series of numerical simulations are carried out to investigate the distribution of horizontal foundation modulus along depth under conditions of different excavation width and depth. The numerical results are compared with those computed by the ‘m method’, which is a traditional excavation design method recommended in the Chinese Code. The results indicate that under the common conditions of PED, the horizontal foundation modulus decreases greatly compared with the values determined by m method, and the larger the excavation width and dewatering depth, the greater the decrease extent. When using the elastic foundation beam method to predict the PED-induced wall deflection, the deflection will be underestimated if the m method is used to determine the horizontal foundation modulus.

A new method for determining the bearing capacity of the foundation based on the plate loading test is proposed in this paper. Assuming that the p (pressure)-s (settlement) curve of the foundation is a hyperbolic equation, the method back calculates the strength and deformation parameters of the soil from the plate loading test and then derives the p-s relationship of specific foundation by using a ‘Tangent Modulus Layer-wise Summation Method’. Eventually, based on the predicted p-s curve of the specific foundation, the bearing capacity of the foundation can be determined by the strength safety and foundation settlement, which we call it the ‘double control principle’.

Deep mixing is a technique to stabilize soft soils in situ by mixing with cementitious binders to form columns. An innovative soil-cement column is proposed, with an enlarged column cap at shallow depth, and as such the column shape is analogous to a letter “T”. This paper presents a numerical investigation on the performance of T-shaped soil-cement column supported embankment over soft ground. The sensitivity of differential settlement between soil and column, as well as soil and column stresses in the middle of the embankment to the diameter and the height of the enlarged column cap is systemically studied.

Model test of coastal excavations is based on the excavation of Gongbei tunnel located in the Ling-ding Ocean, which is a part of the famous Hongkong-Zhuhai-Macau Bridge project. A series of model tests are carried out in the ZJU multifunctional wave-current flume to study on the effects of wave factors on the pore pressure response around clayey silt excavation. It is shown that the attenuation of the amplitude of the oscillatory and accumulated excess pore pressure are related to the wave height, the wave period and the water depth. Oscillatory excess pore and accumulated excess pore pressure along with maximum seepage path are affected by various wave factors.

Centrifuge model tests are carried out to study the composite foundation under embankment which is reinforced by rigid piles with caps on the layered ground that the upper layer was soft clay and the lower layer was stiff sand. Variable acceleration loading method, constant acceleration loading method and gasbag loading method are applied to simulate the construction process, operation process and failure process of embankment. Working behavior, which including displacement of embankment and ground, internal force and deformation of piles in different position, soil stress and pore water pressure between piles, and failure modes of composite foundation are analyzed. Results show that the ground deformation is presented as settlement, horizontal displacement and toe heave. The pile-soil stress ratio in the middle of embankment (25.0) is greater than that in slope shoulder (17.4). Failure modes of piles in different position under embankment are different. To the piles under the middle of embankment, the most likely failure mode is compression failure. The piles under slope shoulder may be subjected to press-bending failure or overturning failure, and the piles under slope toe may occur tension-bending failure or overturning failure.

Accurate calculation of lateral displacements and internal forces of retaining structures and analysis of stability against sliding has great significance. This paper presents an analytic method to calculate displacements of anchored retaining piles and analyzes excavation stability with the modified mechanical model specified in the Chinese code of excavation. This research work is financially supported by the National Natural Science Foundation of China with Grant No. 51379122.

Pre-excavation dewatering (PED) is an important stage in deep excavation in soft ground with high groundwater level. The PED-induced deformations of retaining wall and surrounding environment can reach centimeter level. However, the method to control this deformation has not been yet proposed by the traditional pit design theory and relevant research. In this paper, a countermeasure, which is called as staggered layout of dewatering well, is proposed. In this method, it is recommended that deeper wells and smaller spacings of neighboring wells are employed near the retaining wall. The numerical results show that this method can effectively limit the PED-induced wall deflection.

This study analyzes the temperature effect on the anchoring behavior of the resin anchoring agent and bolt. Fully resin anchoring specimens consisting of surrounding rock-resin anchoring agent-bolt were designed. Through push-out experiment of specimens at 25 °C, 30 °C, 40 °C, 45 °C and 55 °C gradient temperature of, variation laws of anchor force and anchoring interfacial shear stress response rules along the anchor length direction were obtained. Results showed that, with temperature increase, maximum anchoring force and the average anchoring interface shear stress became smaller, Moreover, the failure mode of the anchoring interface gradually changed from brittle failure to plastic failure similar to rock. Under same temperature, the shear stress shows obvious non-uniform distribution, and the shear stress gradually transferred away from the load side. With the distance from load side increased, the shear stress became smaller. The interfacial shear stress tends to power function distribution with the increase of temperature.

In order to improve the active node structure in steel tube bracing system, an innovative Bolt Fasten Wedge (BFW) active node is proposed in this study. Firstly, the BFW active node was researched on its working principle, function and structure by theoretical derivation and numerical simulation. Then, the elastic and ultimate bearing capacity of the BFW active node were obtained by laboratory loading tests. Finally, the bearing capacity and stiffness of the BFW active node were compared with those of many different types of commonly used steel tube bracings and the applicability of the BFW active node was evaluated. The results show that the BFW active node has good bearing capacity and strong stiffness. In conclusion, the BFW active node is of simple structure, reasonable stress, large bearing capacity and strong stiffness which meet the requirements of deformation and stability for braced excavations.

Based on leaky theory, the analytical solution of exit gradient in the excavation base near the retaining structure was derived due to groundwater fluctuation, and a simplified method was proposed to calculate seepage stability of the excavation base considering unsteady seepage. The validity of analytical solution was verified and the influential factors of exit gradient in the excavation base were analyzed based on idealized case studies. The results showed that the influence factor of exit gradient was described by the dimensionless factor, which was positively correlated with the coefficient of permeability and the constrained modulus of the soil, but was negatively correlated with the angular frequency of groundwater level variation and the squared of total thickness of the fine-grained soil in the analytical model. The results also imply that the exit gradient variation was asynchronous with the groundwater level variation when the permeability is low, such situation should be avoided that the exit gradient did not reduce timely and efficiently through dewatering process to prevent seepage damage of the excavation project.

Native soils are often deposited in layers. The evaluation of ultimate bearing capacity of shallow foundations on sand overlying clay has been relevant topic. This problem is complex as it is highly dependent on geometric and geotechnical properties of a given soil. Moreover, the conventional methods provide oversimplified approaches, yielding unreliable results. In this study, the bearing capacity and failure mechanism of footings placed on sand overlying clay are evaluated using discontinuity layout optimization (DLO). By introducing a reduction coefficient, a set of design charts that can be directly applied to the classical bearing capacity formulation is presented. A regression-based approach, relevant to a wide range of geometric and strength parameters, is then developed to accurately capture the bearing capacity. The model uncertainty for the proposed method is investigated with the artificial data and results from literatures. The model bias is characterized as a lognormal random variable with a mean of 1.126 and a coefficient of variation (COV) of 0.186.

This paper presents a practical renewal project in soft soil area, and the site foundation should be improved owing to the increasing load from superstructure. The installation of “new” pile foundation was a great challenge due to the existing square piles in the foundation. A group of field tests were conducted to investigate the compressive bearing capacity of the PGP pile and bored pile, and the applicability of these two piles in soft soil area with existing pile foundation was also studied. The results show that the ultimate unit skin friction of the PGP pile is about 1.22 times the ultimate unit skin friction of the bored pile. The PGP pile was chosen as the foundation of this renewal project, and the existing square piles around were scarcely disturbed during the PGP pile installation process.

Current research gradually recognizes that resisting moment M_s, induced by vertical shaft resistance developed on the passive side of pile shaft, has non-ignorable influence on the lateral bearing characterize of large-diameter pile embedded in stiff soil layers. This work firstly presents numerical solution for resisting moment which is suitable for any type of side friction models. Accordingly, a series of analytical expressions for resisting moment versus slope are established with hardening and softening τ-s curve models (i.e., shaft resistance). Furthermore, the comparison of case study indicates that the influence of shaft resisting moment cannot be ignored for large-diameter pile embedded in stiff soil material. Finally, parametric study is performed and results reveal that for hardening τ-s curve, resisting moment M_s will increase with increase of pile diameter, equivalent limit friction τ_u,eq and as decreasing critical displacement s_eu; for softening τ-s model, M_s will increase with increasing pile diameter, ratio of residual-critical displacement to peak displacement and ratio of residual shaft friction to maximum shaft friction.

The paper stresses the difficulty of estimating the potential damage induced by tunneling on sensitive buildings. This situation justifies the adoption of protective measures. Among a wide range of solutions two comforting techniques are described: Compensation grouting and protection walls. In the first case attention is given to the response of pile foundations to the tunnel volume loss. A semi-analytic solution, which includes a few fundamental solutions, is outlined. It is an alternative to expensive numerical analysis which may prove to be accurate enough in practice. The tunnel-protection wall interaction was also analyzed by a similar simplified solution. Main dimensionless parameters controlling the wall performance are identified and their relevance is discussed.

In-situ stress is an important factor that controls the behavior of rock mass. Since 1990s, a few methods have been suggested worldwide to rate the in-situ stress level so as to facilitate underground rock engineering design. Among them, the method by Hoek et al. (1995) and Martin et al. (1999) is widely used. The method is based on the ratio of the maximum principal in-situ stress to the uniaxial compression strength of rocks. After clarifying some concepts, 25 case histories of large-scale underground excavations constructed in hard rocks in China are studied to validate the method. The results show that the rating method is effective in general to delineate high stress conditions and the rating can be improved if the dry uniaxial compression strength (UCS) of rocks is used.

Seismic liquefaction can cause severe damage to underground structures in saturated sandy soil, and vertical ground motion is considered as an important factor for such damage. This paper investigates the bidirectional seismic response of underground structures in layered liquefiable grounds using a high fidelity finite element calculation method. A unified plasticity model for large post-liquefaction shear deformation of sand is used for the liquefiable soil to fully capture the behavior of saturated sand. A technique of combining beam elements with quadrilateral elements is developed to simulate reinforced concrete structures. Shallow buried underground structures in level and sloping layered liquefiable ground are analyzed under horizontal (H-input) and bidirectional (HV-input) motions, respectively. Comparison of the results show that the effect of vertical seismic excitation is significant for vertical axial force, but has little effect for the shear force, bending moment, and shear de-formation of the structure.

This article presents a case study of underground utility mapping survey carried out for a proposed Bridge site in Ahmedabad, Gujarat. The main focus was on mapping possible underground metallic as well as non- metallic utilities, viz, water line, sewer line, gas pipeline, cables etc. using Ground Penetrating Radar (GPR). With the growing needs and ever pinching demand for progressive infrastructure, the pre-existing infrastructure needs to be preserved. GPR is one such tool that can be used for non-destructive survey for utility mapping, concrete inspection, road inspection, archaeology, environmental assessment and many more. An area of around 15000 m2 is scanned over the bitumen road surface of stretch 700 m length and 22 m width. A GSSI GPR system SIR-3000 was used equipped with 400 MHz ground coupled antenna to cover the depth of penetration up to 3 m. The data was collected at spacing of 6 m across the road where as 2.5 m along the road to map possible utilities in both the directions. In comparison to traditional methods of excavation and trenching which involve a huge loss in terms of time, money and man power GPR can prove to be cost efficient, less invasive and more reliable. GPR survey is expected to be a more efficient technique for underground survey especially in infrastructure projects which involve huge quantum of money in excavation and filling and where cost cutting is a must.

In conventional tunnelling, under difficult ground conditions, the fronts are commonly stabilized by employing expensive and time-consuming soil reinforcement techniques. The design of these soil reinforcement techniques is commonly based on the analysis of unreinforced front mechanical response.In a previous paper, the authors numerically analysed the mechanical response of deep tunnel fronts under undrained conditions and suggested the employment of a non-dimensional front characteristic curve. In this paper, the same approach is employed to study the influence of the excavation rate on the front response. The soil behaviour is modelled by employing the Modified Cam Clay model.

Regulation of thermal regime of mines, mine workings and underground constructions of the North is conducted both with the purpose of securing stability of the mine workings constructed in permafrost rocks as well as creating comfortable working conditions for the mine workers. The regulation process itself is quite costly and requires significant economic expenditure. In order to decrease these costs, it is suggested to use different classes of air conditioning systems based on special heat-retaining workings (HRW). In this work, we have considered the task of choosing the optimal parameters of borehole system used in the mine air conditioning system. The aim of the work has been to determine the optimal number of boreholes and their length depending on the differing air expenditure in the system. Various economic indicators influencing the efficiency of the system, such as the cost of the electric and thermal energy, and the cost of constructing the boreholes, have been considered as well. It is established that usage of boreholes significantly increases the energy and economic efficiency of mine air conditioning systems. With conditions characteristic of the mines of the North, the usage of boreholes allows to increase energy efficiency of the mine systems three times.

During excavation and operation of geotechnical projects such as tunnels, their deformation affects other infrastructure facilities. Therefore, continuous monitoring is required to minimize potential hazards. This task can be realized with the methods of DSTS - technology. Fiber optic sensor technology has progressed at a rapid pace over the last decade. Strain measurement with a distributed Brillouin scattering based sensor system provides excellent opportunity for geotechnical monitoring. Using this technology, it will be possible to create the wide metrological basis for an evidence-based risk assessment in geotechnology. This makes it possible, among other things, to optimize the construction process in such a way that a balance is created between improving safety and reducing costs.

Large section non-circular shield tunnel has been used for a new metro line where the underground space was not enough for the traditional parallel twin circular shield tunnel in the central area of Ningbo city in China. Ground of the construction site contains layers of very soft sensitive clay having a typical mechanical behavior of stress softening and others due to the destruction of the soil structure. In consequence, long-term consolidation settlement and inclination of the adjacent buildings could occur. In this paper, 2D soil-water coupling elastoplastic FE-analyses have been carried out to predict the impact of tunneling on the pile foundation of adjacent buildings, using FEMtij-2D program. As the constitutive model of soils, the Subloading t_ij model has been used which properly consider typical consolidation and shear behaviors of various kind of soils under general three-dimensional stress conditions.

Large shield tunnels with double decks inside have been developed rapidly for highway tunnels in China, and prefabricated structural members are applied frequently for their internal structures. Based on the engineering practice of Zhuguanglu tunnel in Shanghai, the mechanical performance of two different column-base connections is studied through three-dimensional numerical analyses. Results showed that: the specimen with grouted splice sleeve connection had the same load-bearing capacity as the specimen with cast-in-site connection. Plastic hinge appeared at the bottom of the columns in both cases, while the upper region of the grouted splice sleeve connection shows significant stress and severe plastic damage indicating a second plastic hinge.

A series of model experimental tests were conducted to compare the performance of reinforced embankments with geocells. Several design factors of reinforced embankments were studied in tests, these design factors include embedment depth of geocell, number of geocell layers. Experimental results suggested that, compared with unreinforced embankments, reinforced embankments effectively improved bearing capacity, reduced vertical and lateral displacements, and more uniformly distributed additional stresses. These characteristics indicate that the reinforced embankments can effectively enhance the stability of embankments. This study also revealed an optimal embedment depth for the geocell layers. The bearing capacity of geocell-reinforced embankments increased with the number of reinforcement layers, meanwhile the vertical and lateral displacements decreased.

Large-diameter shield tunnel is wildly adopted to accommodate the increasing traffic demands in China. As the diameter of the tunnel segmental lining increases, the external loading condition also becomes more complicated, resulting in highly non-uniform and nonlinear internal forces. Depend on the loading condition, the segments joints exhibit different mechanical behaviors. To obtain an accurate evaluation of the internal forces in the segmental lining, it is of great importance to precisely characterize the joint stiffness in prior. In this paper, the internal forces of the tunnel segments, as functions of the joint stiffness, are derived based on force method. Various types of external loading, including the grout buoyancy force, are considered in the derivation. Based on the evaluated loading condition, the mechanical behaviors of the joints are categorized into different cases, in which the effective bending stiffness of the joints is derived accordingly. The coupled nonlinear equations of the joint stiffness and internal forces are solved via fixed-point iteration method. The approach proposed in this work is applied on a large-diameter road tunnel project in China. The calculation results show a good agreement with field measured data and numerical results. It is found that the joint bending stiffness differs from each other greatly at different locations, which is influenced significantly by outer loads. The joint bending stiffness of tunnel can be quickly obtained with this method mentioned in this work.

A finite element model simulation was conducted to evaluate the influence of coal mining on the performance of two parallel 7.3 m diameter inclined shield tunnels located approximately 15 m above a coal seam in China. The tunnels will be excavated by a tunnel boring machine and supported by a segmented concrete liner; this is the first application of this method in a coal mine in China. The 2D finite element model was constructed to study the influence of the coal mining on the stresses and displacements in the tunnel liner. The modelling was also performed to determine the allowable distance that mining could encroach on the tunnel location and thus the optimal size of the coal pillar to leave below the tunnels.

The geometry and mechanical properties of the discontinuity as well as opening dimensions are the govern parameter in the instability of the shallow underground tunnels. Presented research is relate to the analyses such structure using small scale experimental and numerical models. In the tested models beddings dip varies from 0 to 90°. Layer thickness is considered 16 mm. The tunnel width and height are considered 10, 12, and 14 times as big as the bedding thickness. Also, the joint spacing is one to two times as big as the bedding thickness. Based on the 72 model results the extension of the collapsed zone measured and its variation analyzed. Among other considered parameters, the bedding dip has notable effect on collapsed zone for shallow underground spaces.

Semmering Base Tunnel, a major infrastructure project in Europe, consists of two 27.3 km single-track tubes, numerous cross passages and a complex underground emergency and ventilation station with two 420 m deep ventilation shafts. Intermediate access points include a 1.2 km long access tunnel with two 220 m deep sub-surface shafts for connection to the main tunnels, temporary 100 m deep shafts from the surface and large caverns at the shaft bases. The dimensions of the larger caverns are in the range of 20 m by 18 m. The maximum overburden is approximately 950 m in difficult geological conditions with large fault zones and extensive water inflow, which requires complex heading concepts, extensive support measures and partially special ground improvement works such as grouting. Sophisticated numerical 2D- and 3D-calculations were carried out to verify the adequacy of the designed solutions.Construction using the NATM and TBM method is ongoing from 2014 until 2026.

Shield tunneling beneath an existing railroad leads to the track differential settlement, which will directly affect the operation safety of the railroad and the ride comfort of the passengers, especially in culvert-embankment transition zones. In this paper a case study is taken to investigate the track differential settlement distribution discipline due to an adjacent shield tunnel construction based on a tunnel construction project in Jinan, China. A double - line shield tunnel is planned to be constructed beneath an existing railroad between Beijing and Shanghai. A three-dimension finite element method combined with field monitoring data is employed to investigate the influence of the shield tunneling on the track differential settlement in a culvert-embankment transition zone. The results show that the construction of shield tunnel under-passing railway will cause uneven settlement of the railway subgrade and bridge transition culvert section, and by monitoring the feedback in real time, controlling the construction parameters and taking protective measures, the deformation of railway bridge can meet the control requirements.

This paper presents a large-scale experiment for studying the effects of fault zones on the failure process and failure pattern of tunnel. Firstly, appropriate synthetic materials representing fault zones and rock mass were developed. The mix of fine sand and grease was adopted to model the fault zones. Secondly, an experimental model was then performed to investigate the effects of fault zones on the progressive failure of tunnels. It was found that the presence of fault zones caused the asymmetry of convergent deformations and failure patterns. The fault zone itself failed initially and became a slip surface, which then led to the failure of surrounding rock masses and eventually caused the collapse of the tunnel. Failure mechanisms of tunnels with a fault zone obtained by model tests are helpful for the implementation of optimum support designing.

This paper presents bi-directional O-cell loading tests on two super-long and large-diameter drilled shafts with diameter of 2 m and lengths of more than 110 m. The field test results show that the ultimate bearing capacity of the shaft after post-grouting at the shaft tip and side is 1.95 times that of the shaft without post-grouting, and the total side resistance and the base resistance of the shaft after grouting at the shaft tip and side are 183% and 280–314% larger than that of the shaft without post-grouting, respectively. Consequently, the combined tip-and-side grouting has a significantly effect to improve the bearing characteristics of super-long and large-diameter drilled shaft. As the load reaches the maximum test load, the proportion of the load carried by the shaft base is not more than 20% before and after combined grouting. Furthermore, the relationship between side resistance and shaft-soil relative displacement for super-long and large-diameter drilled shaft is described by the hyperbolic model, and this model is also used to capture the base resistance-base displacement relationship. In addition, the base displacement required to fully mobilize the base resistance for the shaft after combined grouting is about 1.0% of shaft diameter.

The formation of ground fissures is caused by tectonization activities such as earthquake or by human engineering activities such as excessive pumping of underground water. The latter has become a major cause of ground fissures formation in Xi’an, China. These ground fissures are still active and has become an obstacle for metro construction. In this paper, Xi’an metro line 3 was taken as a practical example to analyze the dislocating effects on shallow buried tunnels. The method proposed in Chinese tunnel design code was employed to evaluate the safety of tunnel liner and was implemented by using the programming language embedded within FLAC3D. The results show that tunnel passing crossing ground fissures cannot serve well without multiple deformation joints and that the failure scopes of the tunnel liner are approximately 23 m in the case. In addition, an engineering countermeasure was proposed to mitigate the dislocating effects on tunnel.

The interlayer drift ratio of underground structures is an important seismic design index in China’s Seismic Design Code. However, existing elastic and elasto-plastic limit of drift ratio are adopted from ground structures, and those of underground structures have yet to be comprehensively studied. Based on the design practice of underground structures in China, a set of finite element pushover analysis is conducted on underground structures in this paper to investigate the seismic deformation of six common subway stations. A technique of combining beam elements with quadrilateral elements is utilized to capture the realistic elasto-plastic behavior of structural components. Computation results show that 1/550 and 1/1000 are appropriate elastic drift ratio limiting values for underground structures two stories or lower and underground structures three stories or higher, respectively. The elasto-plastic drift ratio limit of 1/250 that is adopted from China’s Code for Seismic Design of Building (CCSDB) is a conservative limiting value. The influence of buried depth and soil stiffness is also analyzed.

This paper presents a three-dimensional numerical model simulating a small-spacing overlapped shield tunnel driving course. Using this model, the influences of shield tunnel construction parameters on ground settlement, and existing shield tunnel axis floating are studied. The driving process of the shield will bring inevitable impacts upon the surrounding stratum and the existing tunnel. Therefore, the determination of construction parameters of shield tunnel, including support pressure in the face, decrease of soil modulus caused by shield machine, grouting pressure and properties of lining grouting slurry is a big problem. The Hardening soil (HS) model as it is implemented in the finite element code PLAXIS 3D, is used to simulate construction parameters and tunneling construction process. It is shown based on the analysis of construction parameters that when construction parameters were controlled reasonably, the ground settlement and deformation of existing tunnel lining induced by shield tunnel construction can be decreased effectively. The first tunnel construction produced disturbance on surrounding soil making the following tunnel longitudinal and transverse settlement value increasing than the first hole. Influence of the following tunnel construction to the first of the hole was a process (arrival, passes through this process), which is illustrated in the transverse settlement curve, the first cave settlement increased first and then decreased.

Subaqueous shield tunnels in offshore or coast conditions are constructed in a complex environment. The tunnel face stability is highly affected by tides and waves. The pore water pressure response near the tunnel excavation face is very important during the construction of the tunnel. Based on the Qingchun Road Tunnel in Hangzhou, a three-dimensional numerical model was established and the pore water response on tunnel surface to tide impact is studied. It is shown that the water level fluctuation is easier to propagate in silty soil with the increase of the soil permeability or the decrease of the soil compressibility. The seepage force on the tunnel face varies with time and the maximum value is smaller than that calculated in static water condition with the highest tidal level. The characteristics of the total head, pressure head and hydraulic gradient at different locations near the tunnel face are investigated. The phenomenon of phase lag is more obvious as the depths increase. It is also found that the phase difference on the same horizontal plane is almost equal.

This paper involves the effects of longitudinal gradient into the stability analyses of tunnel face in undrained clay. A kinematical approach of limit analysis based on continuous velocity field is employed to estimate the upper-bound solution of supporting pressure on tunnel face. The obtained results demonstrate significant influences of the longitudinal gradient on the stability of tunnel face below an inclined ground surface. When tunnels are excavated below a horizontal ground surface, the influences are minor and then can be ignored in practice.

In order to have a better understanding of the seismic behavior of the tunnel-shaft junction in shield tunnel, a shaking table test precisely targeted on this part of the tunnel is conducted. A flexible wall barrel is used as the model container. The structure model is made of concrete. The model soil is a combination of saw dust and dry sand. Both the longitudinal and the radial joints are simulated in the test. This paper presents the design of the test and the maximum openings of the circumferential joints.

Tunnel excavation may have impact on adjacent pipelines. Ignoring soil nonlinearity, the analysis of responses of pipelines under tunnel excavation will exhibit conservative results. A Winkler subgrade reaction model is developed, in which soil nonlinearity is considered based on the soil stiffness degradation model and the soil shear strain along the pipeline. The soil shear strain for the tunnel-soil-pipeline interaction is evaluated from two aspects. One is the tunnel excavation induced soil strain from the free soil movements. The other is the pipeline-soil interaction induced soil strain, based on a multi-layer-disc elastic model for a laterally loaded pile. The rationality of the Winkler based method in considering soil nonlinearity for the problem of tunnel effects on adjacent pipeline is proved against the published elastic continuum solution.

In this research, a 3D numerical simulations of tunneling in saturated soil are conducted. The tunnel shield and lining segments with different diameters are explicitly modeled during the progressive excavation. Special attention is paid to accurate simulation of the grout hydration in the tail void where a constitutive model that accounts for the time dependent stiffness is developed to describe the hardening behavior of grout mortar in the coupled hydro-mechanical analysis. Additionally, the effect of grouting pressure distribution along the lining segments is investigated as well. The results reveal that neglecting the evolution of stiffness may lead to underestimation of surface settlements. The results also indicated the insignificant impact of the shape of the annular gap on the soil deformations and lining forces.

Tunnelling in rock–soil interface mixed ground has often been faced with cutterhead torque fluctuation, a reasonable penetration rates to reduce the torque fluctuation and improve tunnelling efficiency is of great significance. In this paper, the cutting torques model was established. Torque changes with the rotation angle of cutterhead has been studied when the cutterhead in rock–soil interface with different hard rock area ratios (Fc). The results show that the average torque of cutterhead increases with the increase of Fc. The torque fluctuation cannot be eliminated, and torque fluctuation reaches its maximum when the Fc is about 10%–20%, which most likely to cause blockage and damage for the cutterhead. Such compound stratum sections should be avoided as far as possible when designing of tunnel lines. In the case of the same average torque, the penetration does not decrease linearly with the increase of Fc because of torque fluctuation. The penetration decreases slightly when the Fc reaches 10%–20%, and decreases obviously when the Fc exceeded 30%. The reason is that the penetration needs to be reduced to decrease the torque as well as torque fluctuation; when Fc reaches 60%, the penetration reaches the lowest; when Fc exceeds 60%, the penetration increases slightly to improve the tunnelling efficiency because torque fluctuation is reduced.

Based on the governing equation of steady-state seepage, the semi-analytical solutions of seepage field of twin tunnels considering the effect of lining is derived rigorously using the technique of conformal mapping. These solutions can provide the values of total hydraulic head at an arbitrary point in the seepage field and the tunnel water ingress. Discussion is given about the effects of the tunnel distance on the distribution of the total hydraulic head outside the twin tunnels and the tunnel water ingress. It is found that simplifying the twin tunnels as a single tunnel in analysis could overestimate the hydraulic head around tunnels and the tunnel water ingress.

Based on the patterns of the hydraulic head outside the lining layer obtained from numerical simulation, a new boundary condition for the tunnel is proposed that the hydraulic head appears sinusoidal distribution on the lining’s external circumference. The analytical solutions about the hydraulic head and water ingress are derived rigorously, which could consider the effect of the lining property such as the lining thickness and permeability. The new solution is compared with another three classic analytical solutions in the existent literature. It is found that the traditional assumption that the lining layer is an equipotential surface could overestimate the water ingress especially when the tunnel is buried shallowly.

The estimation of soil surface condition from climatic parameters is of great importance in soil-atmosphere analysis. This paper deals with the estimation of the surface suction of soils using meteorological data. The rate of evapotranspiration (AE/PE) is related to the soil surface suction by the Wilson equation and it is generally used when the potential evapotranspiration (PE) and the soil surface suction are known while hydrological models allow the calculation of the evapotranspiration rate (AE/PE) by introducing complementary relationships. In this paper, a complementary hydrological model was combined with the Wilson equation in order to estimate the soil surface suction in time. To test the validity of the results, the approach was applied to the Toulouse region in the south of France in 3 different years (1999, 2003, 2004). The 2003 year was distinguished as a high intensity drought period in France that has caused many damages by triggering shrinkage and swelling in clays. By comparing the estimated total surface suction for these three years, the 2003 year showed higher values compared to the two other years as expected.

The mixed pollution of LNAPL and DNAPL is a common problem in environmental geotechnical engineering. Leakage, migration and extraction of pollutants will affect the distribution of pollutants in the unsaturation and the saturation zone. Furthermore, they will also affect the disposal efficiency of pollutants. The paper mainly focused on the migration of LNAPL under the influence of DNAPL. With the software of T2VOC, the distribution of pollutants under the whole process of “leakage-migration-extraction” was studied, especially about LNAPL. The studies showed that LNAPL will penetrate into the saturation zone through the unsaturation zone with the action of DNAPL, while it is only distributed in the unsaturation zone under the pure LNAPL condition. Meanwhile, with the increase of DNAPL quality ratio, the distribution area of LNAPL in the saturated zone increased accordingly. The study also indicated that extraction process will lead to the increase of LNAPL and DNAPL in some area. The results of the study have practical significance in revealing the migration of pollutants under the mixture conditions of LNAPL and DNAPL in engineering area.

Pyroclastic soil covers in Campania region (South Italy), usually of 2-3 m depth, are systematically affected by rainfall induced shallow landslides in wet season, causing catastrophic consequences. This paper introduces an experimental study aimed to investigate the use of vegetation as a sustainable practice for stabilizing these soils. The first step of the study is focused on both (i) the growth of perennial graminae grass species with long roots in a 1D column and (ii) its effect along depth on induced soil suction during evapotranspiration in wet season. Results show that the effect of roots on increasing soil suction is observable in shallowest layers and it decreases with depth. Moreover, the presence of roots can change the initial soil suction conditions in soil during wet season, when rainfall induced flow-like landslides systematically occur.

The shear strength of soils is an important index to evaluate the stability of slopes reinforced with roots. This paper based on the common direct shear test results gives a quantitative analysis of the effect of roots on the stability of the slope. A simple model for the shear strength of root-soil composite was proposed based on the strength data for both the root and soil material. The influence of the root system was investigated with a new soil strength enhancement factor of β to represent the strengthening of shear strength. The influence of root diameter and root density on the shear strength of root-soil composite was discussed. Results show that within a certain range of root reinforced soils, the shear strength of the root-soil composite gradually increased at higher root densities. After reaching the peak value, the root density in the root soil had no significant effect on the shear strength. The small and densely distributed roots exhibit larger effect on the shear strength of root-soil system than that of the large and sparse roots. The results may provide guidance for stability estimating and engineering design of slopes.

A field test was conducted to evaluate the use of GM and KMP to stabilize zinc (Zn) and chloride (Cl) contaminated soil at an abandoned industrial electroplating plant site in this study. The stabilized field soil was cured for 1, 3, 7, and 28 days and tested for dry density, dynamic cone penetration, soil pH and leachability. The results showed that the soil pH and leachable concentrations of Zn and Cl were well below their corresponding remediation goals. Furthermore, the KMP stabilized soil possesses superior performance in terms of higher dry density and strength in the early curing stage (7 days) and also lower dynamic cone penetrometer index and leachable Zn. While GM exhibited superior immobilization of Cl in the contaminated soil.

The simulator TOUGH2 was adopted to study the air phase flow during in situ air sparging in sands. It was found that the vertical profile of upward air flow is in the shape of water drop before reaching the groundwater table. As the air phase flows upwards, it also moves horizontally, especially when the air reaches the vadose zone. Finally, the zone of influence in air sparging connects the saturated zone with vadose zone and forms a U-shaped area. The air phase saturation degree is symmetrically distributed around sparging well. The air phase saturation degree decreases with the increase of the distance to the sparging well in the horizontal direction. From the sparging point up to the ground, the air phase saturation degree increases first and then decreases.

An innovative three-layer (silt/gravelly sand/clay) capillary barrier cover system has recently been proposed for minimizing rainfall infiltration in humid climates. Its performance has been preliminarily verified by both physical and numerical modelling subjected to a short extreme rainfall. However, the long-term performance of this three layer cover system is not yet clear in humid climates, such as Hong Kong and Singapore, where an annual rainfall of over 2000 mm is expected. In this study, the long-term feasibility and effectiveness of this three-layer cover system are investigated. A series of numerical simulations were carried out based on a calibrated numerical model. It was found that the long-term feasibility and effectiveness of this three-layer cover system are investigated. A series of numerical simulations were carried out based on a calibrated numerical model even k_s in the clay layer increases to 5 × 10−9 m/s due to the occurrence of cracks, the long-term effectiveness of the three-layer cover system on preventing water into the waste is still satisfactory.

The re-utilization of steel slag, a kind of by-products, is relatively rough in China for lack of activity. The adjustment concept of the cement clinker was introduced by adding metakaolin and lime to imitate the suitable cement components. Hereafter the formed composites were activated by NaCl to enhance the strength. The results showed that the strength of the composite slag-based materials arrived at 4.5 MPa after adjustment, furthermore, the maximum strength after NaCl activation is 8.2 MPa, showing great improvement. XRD and SEM results revealed that after adjustment and activation, calcium silicoaluminate hydrate (C₃ASH), calcium silicate hydrate (C-S-H) and calcium ferrite hydrate were generated for the composite. Among them, the new hydrate of Friedel’s salt (Fs) was found after NaCl activation, which is the main reason for the obvious increment of the cementation and strength.

The negative impact of climate change calls for more sustainable and environmentally friendly techniques to be developed to improve the engineering performance of our civil infrastructures such as slopes in urban built environments. Soil bioengineering using plants and microorganisms is considered a low-cost and aesthetically pleasant solution for shallow slope stabilisation. Although extensive research has been conducted on the mechanical effects of root reinforcement in past decades, the hydrological effects of plants on shear strength and water permeability of vegetated soil slopes are not clear. This extended abstract presents an all-round, cross-disciplinary research programme consisting of indoor and field experiments, centrifuge testing and theoretical analysis to examine the plant hydrological effects on slope stability. It was revealed that some plant species native to southern China and Europe could preserve a credible amount of suction after heavy rainfall, which is positively correlated with the leaf area index (LAI), the root area index (RAI) and the ratio of root to shoot biomass. The total amount of water infiltration were found to be considerable higher in bare than those in soil covered by grass and tree. Plant-fungus interaction caused a significant increase in root tensile strength, hence potentially the mechanical reinforcement to soil. By developing novel artificial root systems in the centrifuge and deriving new theoretical closed-form stability equations, it was discovered that heart-shaped roots produced stronger stabilisation effects than either tap- or plate-shaped roots. This root architecture preserved higher suction (hence higher soil shear strength) and provided greater mechanical reinforcement effects due to multiple branching. These findings advance the fundamental understanding of plant-soil interaction and its influence on slope bioengineering applications.

In municipal solid waste landfills, a triple-layer composite liner consisting of a geomembrane liner (GML), a geosynthetic clay liner (GCL) and a compacted clay liner (CCL) is commonly used at the landfill bottom to isolate the leachates from surrounding environment. This paper presents a numerical investigation of the effect of liner consolidation on the transport of a volatile organic compound (VOC), benzene, through the GML/GCL/CCL composite liner system. The numerical simulations were performed using the model CST3. The performed numerical simulations considered the impact of consolidation on contaminant transport for a GML/GCL/CCL liner system. The simulation results indicate that, depending on conditions, consolidation of the GCL and CCL can have significant impact on the transport results of benzene, both during the consolidation process and long after the completion of consolidation. The traditional approach for the assessment of liner performance neglects consolidation of the liners and fails to consider the consolidation-induced transient advection and concurrent changes in material properties and, therefore, can lead to significantly different results.

A new method of using composite slurry is proposed to increase the compression modulus and decrease creep deformation of rockfill materials for the construction of high rockfill dams. The composite slurry is a mixture of fly ash, cement and sand with the properties of easy flow and post-hardening. During the process of rolling compaction, the slurry admixture sprinkled on the rockfill surface will gradually infiltrate into the inter-granular voids of rockfill. Compression tests were carried out to investigate the compression characteristics of rockfill with composite slurry. Experimental results show the filling of composite slurry can effectively reduce the porosity of rockfill materials, especially for soft and gap-graded rockfill materials.

Previous studies demonstrated that soil nutrients help plant growth and enhance the stability of bio-engineered slopes through plant-induced soil suction. Therefore, soil nutrient effects on the variations of suction and volumetric water content (VWC) in heavily compacted soil during evapotranspiration need to be studied. In this study, three replicates of Schefflera heptaphylla (Ivy tree) were grown for 6 months in nutrient poor and nutrient supplied compacted soil. Soil suction and VWC changes during drying of vegetated soils were measured after 3 and 6 months of plants growth. After the 3rd and 6th month of drying, suction increased by 5–10 kPa and 15–40 kPa, respectively in nutrient supplied vegetated soil compared to the nutrient poor soil due to increase in leaf area index (LAI) and root area index (RAI). In contrast, soil VWC was higher in all the vegetated soils after drying on the 6th month compared to the VWC after drying on the 3rd month. This might be due to soil-pore structure changes via bio-chemical root activities and organic matters.

Wrinkles commonly form in geomembrane-based liners system due to exposure to the fluctuations of solar radiation. Generally, air-gaps are present underneath the wrinkles in the geomembrane if devoid of defects. These air-gaps have low thermal conductivity, which may lead to a reduction of the temperature gradient across the liner including the subgrade soil. This paper presents a two-dimension numerical analysis of heat transfer for a geomembrane-geosynthetic clay liner composite liner system. The 2-D numerical analysis of heat transfer shows that the positive effect of the air-gap was minimised due to the lateral heat transfer. Two-dimensional finite element predictions have confirmed that the air-gaps may not significantly reduce the heat transfer towards the subgrade soil.

This study describes the effects of grass reinforced slopes. Centrifuge tests were performed on sandy slopes of 55$$^\circ $$∘ with a void ratio (e) of 0.9 (loose conditions) and a initial water content of 11.5%. Three different types of grasses were used as a root reinforcement, namely Loliumperenne, Hordeumvulgare and Festucaarundinacea. Centrifuge tests show that for slopes that are reinforced the period until failure is extended. The Hordeumvulgare reinforced slope performed best as no failure took place, likely this was due to the root system of Hordeumvulgare that developed more extensively compared to the other grasses.

The treatment of organic-rich sludge is significant in geotechnical engineering, which contributes to the resource utilization of sludge and environmental protection. In this paper, several solidifying materials, namely cement, quick lime, potassium ferrate, and super absorbent polymers are selected to treat sludge. Experimental results show that the unconfined compressive strength of treated soil samples is significantly enhanced, and the heavy metal ions concentration measured from the exudation fluid of soil samples is reduced by treatments. Furthermore, the treatment mechanism is investigated by using X-ray diffraction and Scanning Electron Microscopy at the micro scale. The mixing of solidifying materials into sludge leads to the formation of cementitious compounds and the flocculation of clay particles.

Soil-water characteristic curve (SWCC) is an important characteristic of unsaturated soil. This paper investigates the total suction of the MX-80 bentonite, under different saturation and different concentrations of sodium chloride solutions. To create the soil-water characteristic curves for different amounts of NaCl, but same dry densities, the study used chilled-mirror dew-point WP4 potentiometer. The experimental results show that the concentration of salt in pore water has significant influence on the bentonite. With the increase of the NaCl concentration, the samples total suction increased gradually and the matric suction decreased. When the soil saturation was greater than 50%, the pore solution’s addition led to the rapid increase of the soil’s total suction. The low concentration of salt has relatively little effect on the matric suction of the MX-80 bentonite; while when the ion concentration is high, the solutions’ matric suction has a very significant impact on the soil matric suction.

In order to investigate the mechanical properties of frozen saline sandy soil, a series of triaxial compression tests were conducted on frozen saline sandy samples with Na₂SO₄ contents of 0%, 0.5%, 1.5%, 2.5% and 3.5% by weight at the temperature of −6 °C. The strain softening/hardening, shear contraction and dilation properties as well as pressure melting of ice and particle crushing under high pressure are studied. The experimental results indicate that strain softening/hardening phenomena occur when the confining pressures are below and above 6 MPa, respectively, together with high dilation characteristics. The strength increases to a peak value and then decreases with the increasing confining pressure. The grain size distribution varies greatly after triaxial compression test compared with the original one, indicating that particle crushing occurs during the test. Thus, a double-yield-surface elastoplastic constitutive model is developed by employing the non-associated flow rule. The proposed model is verified by comparing the simulation results with the experimental data. It is found that the stress-strain relation and volumetric deformation can be predicted well under both low and high confining pressures.

To study the strength property of frozen soil under complex stress states, a series of directional shear tests on remoulded frozen clay were conducted under four mean principal stresses (p = 1, 3, 4.5 and 10 MPa) and four coefficients of intermediate principal stress (b = 0, 0.25, 0.5, and 0.75) at three temperatures (−6, −10, and −15 °C) using the hollow cylinder apparatus (HCA). The experimental results indicated that stress-strain curves of frozen clay all performs as strain hardening under directional shearing. In the p-q plane, the strength of frozen clay increases with increasing mean principal stress at first, and then decreases with a further increase of p. An elliptic strength criterion is proposed to describe this variation law. The test results also showed that the strength of frozen clay increases with decrease of temperature significantly. Then, temperature parameters are introduced into the elliptic function to consider the temperature effect.

In this contribution, an elastic-viscoplastic constitutive model of the Maxwell-Type to describe the time-dependent behavior of frozen soils is proposed based on results of unconfined and triaxial creep tests and strain rate-controlled compression tests from Orth (1985). The model is able to capture essential features of the behavior of frozen soils, as temperature-, rate- and mean-pressure-dependence for quasi-monotonic loading realistically, including the creep-failure-type observed in frozen soils under constant deviator stresses. The model has been validated by means of experimental data of a frozen sand and used to predict creep and rate-dependent behavior of frozen soils for monotonic loading.

To investigate mechanisms and principle for the salt expansion, theoretical analysis, micro-fabric observation and salt expansion tests are conducted to a silty clay containing sodium sulfate. Equations are provided to calculate the crystalized sodium sulfate through theoretical analysis. Long strip crystal bridges and bulky crystal are found in the micro scanning images of saline soil. When these crystals grow upon cooling, soil is supposed to expand. In salt expansion tests, the effects of compaction effort, water content, and salt content of soil are considered. Three compaction levels, i.e. 0.85, 0.90, and 0.95 are used. Three water contents, i.e. 13.2, 15.2 and 17.2% are used. Both pure Sodium sulfate soil and soil containing Sodium sulfate and Sodium chloride are used. The salt expansion data demonstrate that the volumetric content of crystal seems to have a unique relation with the volume strain of saline soil. A unified formula is established and can be used to predict the salt expansion strain for silty clay containing Sodium sulfate and Sodium chloride with any water content, salt content and dry density. Because the salt expansion tests used in this study use small sample and are without water supply, the salt and moisture migration in these tests is insignificant and the tests can be regarded as element tests. The unified formula can help to build constitute models for salt expansion.

Mechanical properties of warm frozen soils are similar to those of unfrozen soils. In recent years, the mechanical properties of warm frozen soils have attracted great attentions. However, there is no definition of warm frozen soil according to the mechanical behaviors of frozen soils so far. This paper attempts to define the temperature threshold for a warm saturated frozen sand in terms of mechanical properties. The Chinese ISO standard sand was taken as study object. Triaxial and confined compression tests were carried out on the saturated frozen samples. Mechanical properties such as cohesion, modulus and compression index were obtained and their changing tendency along with temperature were analyzed. It is found that the range of −1.0 °C to −0.5 °C seems to be the temperature when the mechanical properties change abruptly. Therefore, −1.0 °C can be defined as the temperature threshold for warm frozen soils with regard to the material tested in this program.

The processes of thawing and freezing and their associated complex hydrothermal coupling can significantly affect variations in mean annual temperatures and the formation of ground ice in permafrost regions. In this article, using soil temperature and moisture data in the permafrost region of the Nanweng’he River in the Da xing’anling Mountains, the freeze-thaw characteristics of the permafrost were studied. Variations in the soil temperature and the moisture were analyzed during each stage of the freeze-thaw process, and the effects of the soil moisture and ground vegetation on the freezing-thaw were discussed in this paper. The study results show that the thawing in the active layer is unidirectional, while the ground freezing is bidirectional (upward from the bottom of the active layer and downward from the ground surface). During the annual freeze-thaw cycle, the migration of soil moisture had different characteristics at different stages. In general, during of a freezing-thawing cycle, the soil water molecules will migrate downwards, i.e., soil moisture will transport from the entire active layer to the upper limit of permafrost. In the meantime, freeze-thaw in the active layer can be significantly affected by the soil moisture content and vegetation.

Thermokarst lakes can change the thermal regimes of foundation under the embankment and cause failures of embankment in permafrost regions. This paper analyzes the thermal impact of thermokarst lake on the permafrost based on the monitoring data. The results indicate that: (1) The thermokarst lake extend the time of warm season and shorten the time of cold season for permafrost; (2) The average ground temperature of permafrost is increased by the effect of thermokarst lake. The increment of temperature became larger with the decrease of distance from the thermokarst lake; (3) The thermokarst lake can inhibition the heat dissipation of permafrost in the cold season to make a thermal impact on the permafrost. Therefore, the embankment always absorbs heat from thermokarst lake, asymmetry thermal regimes of permafrost under the embankment is enhanced, which induces differential settlements and harms the safety and stability of embankment.

In seasonally frozen ground regions, the pile foundation embedded in frost-susceptible soils can be subjected to tangential frost-heave force, which is defined as an uplift force that acts along the pile-frozen soil interface. The belled pile in seasonally frozen ground regions was designed to produce a self-anchoring force so as to enhance bearing capacity against to frost-heave force. In order to reveal the function of anti-frost jacking of belled pile and the effect of different base angles belled pile embedded in seasonally frozen ground area, one-dimensional freezing test was conducted for three different base angel belled piles and a uniform-section pile. Freezing process, displacements of piles and soil surface, and soil pressure were monitored respectively. The results showed that the ultimate displacement of three belled piles were approximately 1/5 of uniform-section pile. The frost heave of ground surface beside the pile presented a funnel-shaped state, which illustrated that the pile restricted the free frost heave of the soil. The soil pressure beside the enlarged base presented different patterns with the change of frost depth and base angle. On this basis, the function of anti-frost jacking of belled pile embedded in frost-susceptible soils could be put forward ultimately.

There are many large gas (or oil) pipelines whole or part to be built in permafrost areas all over the world, in these areas, the problem of pipeline engineering in low temperature environment is quite serious. For this reason, we carry out a mechanism experiment of the interaction between the pipe and the frozen soil in order to explore the deformation and stress coordination of the pipe-soil during the frost heave process. In this experiment, we can monitor the temperature, moisture content, soil pressure and pipeline strain of the whole model box. Finally, through analysis of experiment data, it turns out that with decreasing the temperature, unfrozen water content decrease, the frost heave increase, the soil pressure and pipeline strain increase gradually, at the same time also pipeline warp, but the amount of frost heaving is far less than free soil due to pipeline constraints, the pressure at the bottom of the pipe shows a tendency to be larger than the middle. With the increase of the number of freeze-thaw, the residual deformation of the pipe becomes more and more, and the pipeline strain and the pressure of pipe bottom gradually attenuate.

The frozen soil hollow cylinder apparatus is the main experiment instrument to study the mechanical behaviour of frozen soil under complex stress paths including stress rotation. However, it is difficult to prepare hollow cylinder specimen due to the thin wall. In this paper a novel preparation device for remolded hollow cylinder specimen of frozen soil is designed. The universal test machine is used to provide an axial compressive stress, for it can ensure accurate control in axial force and deformation along preparing process. Hence, it can improve the efficiency in specimen preparation. Two pedestals with 8 blades can directly shape grooves on the upper and bottom surfaces of specimen, which can reduce the disturbance while cutting the specimen. The applicability and reliability of specimen prepared by the novel preparation device in frozen soil hollow cylinder tests is verified.

The performance of thermosyphon cooled sandbags supporting the warm pipeline in permafrost was simulated in a centrifuge model test. Two pipes of an unsupported and a supported section were evaluated over a period simulating 20 years of operation with seasonal oil and air temperature cycles along the China-Russia Crude Oil Pipeline (CRCOP). The results showed that pipe settlement of the supported pipe was 45% of the settlement of the unsupported pipe. The final thaw bulbs extended about 3.6 and 1.6 times the pipe diameter below the unsupported and supported initial pipe elevations, respectively. The sandbag supports remained frozen throughout the test period due to cooling effect of thermosyphons. The maximum bending stress induced over the span length from bearing of the full cover is equivalent to 40% specified minimum yield strength. Potential buckling of the pipe should be considered as the ground thaws. Suggestions for design considerations for the field conditions along the CRCOP are made based on the model test observations.

The shear properties and creep properties of thawed saturated clay were studied at different stress levels based on a series of undrained triaxial shear tests and creep tests. A hyperbolic creep model was employed to fit the obtained strain-time curves based on analyzing the evolution of the creep strain, the fitting parameters were also determined. The results show that the hyperbolic creep model can be used for predicting the evolution of creep strain for thawed saturated subgrade clay.

Now in China, more and more clay-gravel mixtures in clod regions have to be used in a variety of geotechnical applications. Compaction state of compacted soil mixtures is closely linked to the properties of permeability, stiffness and strength. However, compaction behaviors under different temperature conditions are seldom studied. In this study, a series of dynamic compaction tests on clay-gravel mixtures under normal (room temperature) and cold temperature (−10 °C) were conducted to investigate the effect of gravel content and temperature on the compaction behaviors. The experimental results show that the compaction behavior under cold temperature is significantly different from that under normal temperature. The finding has potential implications for the construction of earthworks in cold or seasonally frozen regions.

A set of directional shearing tests using hollow cylinder apparatus (HCA) was carried out on remolded frozen clay at −6 °C to study the strength properties of frozen soils in π plane. During the shearing, the stress Lode angles was fixed at five different values (θσ = −30, −16.1, 0, 16.1 and 30°) under four mean principal stresses (p = 1, 3, 4.5 and 10 MPa). Through the tests, the strength locus of frozen soil in π plane with θσ ranging from −30 to 30° were gained experimentally for the first time. The test results show that the strength envelope of frozen clay changes from a curve-sided triangle to a circle with increasing p. And a combination of the Spatially Mobilized Plane (SMP) criterion and Mises criterion, the Generalized Non-linear strength theory, can better describe this strength envelope evolution law in π plane.

Experiments using GDS triaxial test apparatus were carried out on size-reduced coarse-grained soils with different moisture content (ω) (9%, 11.5%, 14%) and different dry density (ρ_d) (1.9 g/cm3, 2.0 g/cm3, 2.15 g/cm3) to study the mechanical properties under different freeze-thaw cycles (C) (0, 1, 3, 5, 7, 9, 12, 15, 20 times). The results show that the uniaxial strength of coarse-grained soils decreases with the increase of cycle times, and tends to be steady around 9 times, the deformation modulus of coarse-grained soils was gradually decreasing. With the increase of water content, the strength of coarse-grained soil was constantly decreasing, the deformation modulus was reducing. The stress-strain curves of coarse-grained soils were gradually changed from strain softening to strain hardening with the increase of moisture content, but the high dry density was an exception. With the increase of dry density, the strength and deformation modulus of the coarse-grained soils were increasing, and the slope of post-peak curve was increasing, the residual strength was also aggrandizing, and the strain softening was more obvious. Meanwhile, the strain hardening characteristic of high moisture content also changed to softening with the increase of dry density.

Pile foundation has been widely applied in cold regions. In a special geological condition that subpermafrost water is developed, the shortage of bearing capacity is often encountered in these complex geological areas. In this paper, bearing capacity of pile foundation is studied by finite element method. Combined with geological and geothermal data of some bridge pile in permafrost region, temperature field is simulated by the finite element software ANSYS. Subpermafrost water at the depth of 20 m plays fixed boundary in the calculation model. Environmental temperature plays thermal boundary on the natural surface, including normal environmental temperature with rising amplitude 2.6 °C/50 a. According to the nodal temperature of pile-soil interface, the bearing capacity of pile foundation is calculated by interpolation method. The simulation results indicate that the subpermafrost water is especially significant to the geothermal field. Under impact of subpermafrost water and environment, pile-soil interface is warming, and permafrost base is rising. The bearing capacity of pile foundation decreases obviously with pile-soil interface warming.

The compressibility of frozen soil must be taken into consideration when the deformation of highway and high-speed railway is strictly controlled in permafrost regions. In this study, the frozen saturated Chinese ISO standard sand was taken as the study object, and step load tests under different temperatures were carried out using a self-developed confined compression apparatus for frozen soils. Tests were conducted at the loads of 1, 2, 3, 5, 10 MPa and under temperatures of −0.5, −1.0, −2.0, −3.0, −5.0 °C. The coefficient of compressibility was obtained according to the e-σ_z curves for both unfrozen and frozen samples under different temperatures. The experimental results of temperatures ranging from room temperature to negative temperature were then obtained. The test results indicate that the compression curve of the frozen material are similar to that of the samples under room temperature; for warm frozen samples, the compressibility is considerable; the compressibility of frozen soil is closely related to temperature, i.e., the coefficient of compressibility increases with the increase of temperature in a form of exponential function.

Brine leakage due to pipe fracture is threatening the safety of frozen wall in artificial freezing facilitated engineering and the performance of the produced frozen soils will be deteriorated with salt inclusion. This paper takes the frequently soft clay in Wujiang District as the study object and five levels of calcium chloride solutions were supplemented to produce saline specimens. The soil freezing point for specimens at various water-salt combinations was measured by the thermocouple. Results indicate that the freezing point exhibits nonlinear increase at higher water contents and a critical value may exist close to the liquid limit, beyond which the gradient of freezing point to the water content lowers. An approximately linear decrease with the saline content was observed. By fitting experimental data, an empirical equation was proposed for the freezing point affected by both water and saline contents. The results may provide guidance in engineering design and numerical modeling in frozen ground engineering.

The lime soil pile was employed to melt the frozen soil and improve the bear capacity of thawed permafrost foundation. Firstly, the preliminary mixing proportion of lime soil was determined by indoor tests, and optimized by the insite temperature field monitoring. Secondly, a series of lime soil piles were constructed and the changes of temperature, displacement and bear capacity are monitored. Finally, the effects of lime soil pile on water content, uplift displacement and bear capacity pile and composite foundation were analyzed and discussed, respectively. The field experimental results could provide the experiences on the designation and construction of lime soil pile in warm permafrost regions.

The integrity of the rock continues to decrease with the number of freeze-thaw cycles increases. This paper takes the coarse and fine sandstone collected from the Muli coal mine slope in Qinghai, northwest China, as the research object. Physical and mechanical properties of the rocks before and after freeze-thaw cycling are measured. Based on the decay equation suggested by the previous studies, the decay laws of rock integrity are analyzed by taking the uniaxial compressive strength (UCS) as the integrity index. It is found that the decay index λ is not a constant as generally recognized previously, but it keeps changing with the number of freeze-thaw cycles increases. At the same time, there are some differences in the changing laws of λ in different rocks. Finally, a relationship is established for the decay index and the velocity of longitudinal wave in the fine sandstones.

Ground temperatures under a buried warm China-Russia oil pipeline were monitored to evaluate permafrost thawing and cooling performance of thermosyphons installed near the pipe in sporadic permafrost regions. Field observations demonstrated that warm oil thawed the underlying permafrost and increased the active layer thickness. Thermosyphons can cool the soils surrounding the pipe and effectively mitigate the permafrost thawing depending on their number and working duration. But now the heat dissipated from the warm pipeline and construction disturbance were not completely removed by two pairs of thermosyphons after two winters of operation. There was still a thawed layer beneath the thermosyphons even in winter. Further long-term monitoring of the cooling performance of thermosyphons is needed. This study provided basic data and analytic references for other similar cold region pipelines.

Spread-footing foundations embedded in frozen soil are subject to both the wind-induced uplift and frost heave forces. The stress and deformation of foundations in the Qinghai-Tibet Power Transmission Line (QTPTL) engineering were monitored to investigate the stress state of the tower foundations. The results showed that the stresses at the bases of tower foundations had a close relationship with air and ground temperatures. Seasonal variations in the contact stress depended on the seasonal freezing and thawing of foundation soil. The contact stress increased with the cooling of the underlying soils and decreased with the warming of the underlying soils. The numerical simulation results showed that the frost heave force induced by soil freezing potentially threatens the safety and normal operation of the QTPTL. Thaw settlement may lead to harmful deformation of tower foundations if global warming is considered in the numerical model. The remedial measure with thermosyphons only can reduce the settlement of the foundation and will increase the frost jacking risk of the foundation.

A linear interpolation function fitting the nonlinear relationship between void ratio and compression modulus was proposed and corresponding strategy guaranteeing calculation accuracy and efficiency was developed for the nonlinear numerical analysis of 3-D large strain thaw consolidation of ice rich frozen soil. It was verified by a series of ice rich thaw consolidation tests that, with the proposed numerical implementation strategy, the calculated results match well with the tested results of pore water pressure and thaw displacement. Further analysis on the different stress-strain relationships shown that the prediction values and accuracies on pore water pressure and thaw displacement of nonlinear relationship is higher than that of linear relationship. This also leads to higher prediction accuracy on thaw consolidation degree and pore water pressure at thawing front of nonlinear relationship.

In permafrost regions, high-grade highways with a wide and dark-colored asphalt pavement can cause the degradation of underlying permafrost. However, the embankments with single commonly cooling technique, e.g. two-phase closed thermosyphon (TPCT) embankment and crushed-rock embankment cannot effectively solve the problem. Therefore, a composite embankment for high-grade highways, combined with L-shaped TPCTs, crushed-rock revetments and insulation was designed. The L-shaped TPCTs were used to cool the core of the embankment, the crushed-rock revetments with different thicknesses was intended to cool the side slopes and to diminish the sunny-shady slope effect, and the insulation was designed to strengthen the cooling effect by increasing the thermal resistance of the embankment. Here, we experimentally and numerically evaluated the cooling performance of the composite embankment. The results indicate that the composite embankment can effectively raise the permafrost Table (0 °C isotherm) and cool the underlying permafrost under a separated high-grade highway with a wide and dark-colored asphalt pavement (double lanes each direction). Therefore, the composite embankment structure should be considered to be applied to the construction of high-grade highways in permafrost regions.

This research aims to investigate shear wave velocity and small-strain shear modulus of saturated thawed clay. Various numbers of no-water supplied freeze-thaw cycling were experienced on the saturated clay firstly, then the wave velocity measurement setup was employed to carried out a series of non-destroyed wave velocity tests on each sample. During which, one pairs of BE were install on the top surface as transmitter and another on bottom surface as receiver, respectively, and another two pairs of BE were installed on horizontal direction. The effects of compaction degree and numbers of freeze-thaw cycles on elastic properties for vertical and horizontal direction were analyzed and discussed. The results indicate that initial density and freeze-thaw cycling exhibits a notable effect on elastic properties. The shear wave velocity and small strain shear modulus in vertical direction are greater than in horizontal direction, and both of them increase with increasing of initial density. However, they decrease after various numbers of freeze-thaw cycles and sharply drop at 1st F-T.

The saturated frozen soil is composed of solid grains, ice and unfrozen water. The mechanical behavior of this engineering material is strongly associated with the amount of ice. Meanwhile, the amount of ice depends on the temperate and pressure and its existence is the main reason that induced the huge difference between the frozen and unfrozen soil. Furthermore, considering that ice is the highly rate-dependent material, the rate-dependency behavior of the frozen soil can be expected. A rate-dependent constitutive model based on the critical state theory is proposed for describing the rate-dependency of frozen soil. Being a variable parameter, the ice content is directly related to the temperature with can be correlated by the unfrozen water content curve. The tension strength and the pseudo-preconsolidation pressure can be expressed by the ice content. Meanwhile, the compression and recompression coefficient are related to the ice content and the values at the unfrozen condition. The rate-dependent behavior is considering by the over stress method. When the temperature is higher than 0°, the ice content will be null. Then, the model will reduce to the conventional elastic-viscoplastic model. The predictive ability of the model is validated by simulating the 3D undrained triaxial compression test.

Buried water mains, sewers and storm water pipes are critical infrastructures in the urban environment. In Hong Kong, a great number of pipes are buried in slopes, and catastrophic consequences due to landslides may happen upon pipe leakage. This study aims to investigate the infiltration process of leakage water with respect to the current Hong Kong mainlaying practice and explores its impacts on slope stability using geotechnical centrifuge modelling. Test results indicate that deep-seated slope failure, and surface erosion induced by concentrated flow of leaked water may occur when the pipes are subject to leakage.

In Georgia, landslide and debris flow/mudflow processes and water erosion are at the top of problems due to related eco-geological disaster risks and negative impact. By the scale of development of these events and their negative impact on the population and economy of the country, Georgia occupies leading position among high land countries of the world. Besides, the almost whole territory of the country is under the risk of earthquakes, the magnitude of which is 7–9. Impact of such earthquakes is directly stimulating and provoking gravitational landslide and debris flow processes. In Georgia major part of the population, agricultural lands, roads, oil and gas pipelines, hydro-technical – melioration facilities, power transmission lines and mountain tourism zones periodically are subjected to disastrous processes and the areas under the risk are expanding substantially. Around 70% of the territory of the country, about 3000 settlements (62%) are under the risk of geological disasters; 14,2% of agricultural lands were seriously damaged by geological processes and require conducting of cardinal protective measures; and 13,1% of agricultural lands are located within the high risk area. Consequently, more than 80% of the economic damage was caused to mountainous regions and the majority of eco-migrants are from highland areas. This causes vacation of villages.

In this work the physical-mathematical model of stress-strain state evolution of loaded geomedium is developed with the purpose of numerical simulation of main shock and aftershock line of Chuya earthquake, occurred on the $$27^{th}$$27th of September 2003 in Gorny Altay, Russia. Structural model which includes main blocks and faults is constructed on the base of seismotectonic and paleoseismogeological investigations. It is shown that results of numerical simulation are in satisfactory agreement with field observations and simulated seismic process satisfies the laws of Guttenberg-Richter and Omori for aftershocks line.

More than 90% of the territory of Ukraine has complex ground conditions. As a result, Ukraine is becoming a region of integrated influence of regional flooding and seismic activity on formation of landslides. 4 case studies will be considered in the presentation: results of visual and instrumental inspections of the landslide protection structures (1); direct dynamic method for calculating and analysis of the stress-deformed state of landslide slopes under dynamic influences (2); technical and software means of the automated real time monitoring system for landslide of the Central Livadia Landslide System of the Autonomic Republic of Crimea of Ukraine (ARCU) (3); landslide stabilization in building practice: methodology and experimental investigation from ARCU (4). Only case study (4) is described in more detail because of the limited scope of the extended abstract. One of the most efficient solutions for landslide protection is the short underground piles (SUP). They are shortened bored piles, immersed below the slide surface on the calculated value and output above it at a distance providing overlapping of slipping soils. In the process of experimental work there appeared the need to choose the optimal testing mode. Selected results of experimental studies of the SUP are presented.

In geotechnical engineering, back analyses are generally used to investigate uncertain parameters. Back analyses can be done by considering known conditions, such as failure surfaces, displacement, and structure performance. In fact, a complex nonlinear optimization function is typically required for most geotechnical problems in order to gain better understandings of these uncertainties. Therefore, Particle Swarm Optimization is utilized in this study to assist in back analyses based on finite element upper bound limit analysis method. This technique is an evolutionary computational approach, which is suitable for solving nonlinear global optimization problems. By using Particle Swarm Optimization with numerical upper bound method, a simple case study showed that the obtained results are reasonable and reliable. The usability of the proposed method is demonstrated. It could be seen as a new potential approach for geotechnical back calculations.

There is general evidence that the good performance of geosynthetic-reinforced earth retaining walls (GRWs) observed after strong seismic events can be attributed to their capacity to redistribute seismic-induced deformations within the reinforced zone, provided that the reinforcements are characterised by adequate extensional ductility. Therefore, it is desirable to promote the activation of internal (or local) plastic mechanisms, involving the reinforcement strength, since the design phase. In this study, the seismic performance of two earth retaining walls is compared. Specifically, a pseudo-static approach is adopted to conceive a GRW with a seismic resistance, expressed by the critical seismic coefficient k_c, that involves activation of an internal plastic mechanisms, and a conventional retaining wall, in which the same critical seismic coefficient k_c is attained for an external (or global) plastic mechanism. Finite difference dynamic analyses are carried out to evaluate the seismic performance of the two walls. In the analyses, a real acceleration time history is applied at the base of the models. The results of the dynamic analyses show that, compared to the wall in which external plastic mechanisms develop, the wall designed to activate internal plastic mechanisms exhibits a better seismic performance, with lower permanent displacements computed at the end of the seismic event.

Under heavy rainfall, the surface soil is saturated quickly. Rainwater percolates down as a wetting front, displacing air in soil. Rainwater infiltration into the unsaturated zone is potentially affected by air compression ahead of the wetting front. For a large and shallow slope area, air compression ahead of the wetting front will lead to a fluctuant air pressure in excess of atmospheric pressure. In this study, the process of air compression and counterflow ahead of wetting front was simply analyzed. An extended Green Ampt model is introduced considering air compression and counterflow. Based on the model, the infiltration of a shallow slope subjected to an intense rainfall was studied. The limit equilibrium method and the Mohr-Coulomb failure criterion were readily applied to calculate the safety factor of slope. Considering the effects of the air pressure fluctuation produced by air compression and counterflow ahead of the wetting front, a stability analysis model was presented, which can be readily used for estimating the likelihood of a shallow landslide triggered by intense rainfall. It is found that the gauge air pressure ahead of the wetting front, on the one hand, leads to the formation of static water pressure that serves to reduce the normal stress of the interface at wetting front in saturated zone, hence has an adverse effect on the stability of slope, on the other hand, delayed the downward movement of the wetting front, accordingly, decrease the likelihood of landslide.

The shear strength of the municipal solid waste (MSW) varies during the service years of the landfill and it is also affected by the particle compressibility. First, a pore-water pressure reduction coefficient, which attributes to the compressibility of a particle and the solid matrix, is introduced to the effective stress formulation to modify the Terzaghi’s principle. This coefficient is also dependent of the landfill age. Then, based on the upper bound limit analysis theorem, the rotational-translational mechanism previously introduced by Huang [1] is generalized to analyze the multilayer municipal solid waste landfill slope. Finally, the stability of a landfill slope case is analyzed considering the influence of the particle compressibility. The computed safety factors of the landfill slopes decrease when the particle compressibility is considered.

The area of Ukraine is characterized by active development of landslide processes within different tectonic and landscape-climatic zones. For assessing and predicting landslide processes two main approaches have been applied. The first approach is based on a comprehensive analysis of the factors of formation of landslide processes using statistical methods, GIS analysis and cartographic modeling. The second approach assumes field work, monitoring and numerical modeling of landslide processes with the aim of local prediction of landslide hazard. Determination of stress-strain state of rocks within a particular landslide-prone slope has been made taking into account a number of geological and geomorphological factors. The basic summary factors taken into account in the construction of physical and mathematical models and calculations are water saturation; effect of the gravitational field of the Earth; type of rocks with its inherent thermomechanical properties, linear expansion ratio, density; boundary conditions on the boundary of the proposed mass (by displacement or stress); geometric characteristics of the selected mass (size, slope angle). The studies determined the composition and structure of the most dangerous landslides. There are predominantly structural landslides, landslides formed in inhomogeneous, anisotropic environment.

In this study, the ultimate lateral soil pressure $$p_u$$pu on stabilizing piles is discussed and the empirical equations and analytical models to predict $$p_u$$pu are reviewed. The plastic deformation theory is modified by introducing a new parameter $$K_f$$Kf, which is back calculated by a numerical calculation. The parameter is then compared with the corresponding soil stress in the numerical model. The modified theory is able to evaluate the $$p_u$$pu in a larger range of pile spacing.

Prediction of the runout of a debris flow is of great significance for hazard mitigation. Laboratory tests were carried out to simulate debris flows under different bulk densities and slopes. A linear negative relationship between bulk density and runout-ratio-with and volume was found. Results show that the morphology of the deposited sediment is strongly influenced by the inclination of the channel. Moreover, a new empirical formula has been developed to estimation of inundated volume and runout-ratio-width.

A significant research gap in quantitative risk assessment for landslides is the quantification of physical vulnerability of buildings subject to landslide impacts. In this paper, an explicit time integration program LS-DYNA is utilized to analyze the response of RC framed buildings. The analysis gives an insight of the failure process of buildings impacted by a landslide and provides a viable approach to assessing the vulnerability of buildings to landslides.

As the application of micropiles being extended from foundation engineering to landslide engineering, some transforms of the mechanism and behaviors of micropiles have happened. A scaled slope was modeled in the lab to simulate three slope failure modes respectively, including sole slope, slope reinforced with single piles and composited piles. Besides, theoretical analysis about influencing factors was researched which was aimed to compare the slope failure and resistance and anti-sliding characteristics of micropiles. Taking the displacement, lateral loading and moments along micropiles shaft as main targets, the results illustrate that micropiles have provided higher resistance to slope compared to sole sliding slope. The reinforcement effect of composited piles performs better than single piles. It also turns about to present several deformation stages covering compaction, elastic deformation and plastic deformation and ultimate failure stages. In addition, a close insight into the influence of soil load, pile diameter and length, coefficient of subgrade on micropiles’ performance has been given respectively. The application condition and circumstance of micropiles can be concluded consequently. It is expected that micropiles are considerably suitable for shallow landslide reinforcement while slope height less than 10 m, or sliding force under 300 kN/m, or coefficient of subgrade greater than 10000.

Wetting-drying cycle is a strong weathering process which considerably changes the engineering properties of metastable loess. It has been considered in slope stability evaluation and slope surface protection. In this study, rainfall intensity, volumetric water contents and ground temperatures in loess road cut slopes were monitored at two study sites, Dingxi and Pingliang, northwest China, to determine infiltration depth of rainfall and frost depth. The monitored data indicated that water contents from the ground surface to −20 cm deep changed significantly, less changed below the depth of −40 cm. The surficial loess of road cut slope had experienced strong wetting-drying cycles in the rainy season. Based on the monitored data, the wetting-drying and direct shear tests were carried out in laboratory to estimate the influence of wetting-drying cycle on dry density and shear strength of undisturbed loess samples. The mean dry density and shear strength of Dingxi loess samples decreased from 1.60 g/cm3 and 30.3 kPa to 1.30 g/cm3 and 17.8 kPa after 30 cycles, respectively. Concerning the Pingliang soil samples, they decreased from 1.66 g/cm3 and 31.7 kPa to 1.40 g/cm3 and 15.7 kPa, respectively. Wetting–drying cycle significantly reduced the dry density and strength of loess samples and became a key factor leading to the failure of loess road cut slope.

Generally, cantilevered structure-foundation systems supporting highway signs, signals, and luminaires in the areas exposed to severe wind loadings (e.g., hurricane) have been designed under coupled torsion and lateral load scenario. Especially, mast arm cantilevered structures constructed near or on an embankment slope may have more concerns on the torsional and lateral resistance of the foundation. However, most research works have merely considered drilled shaft foundations under torsion-lateral load case with an embankment in proximity. In this study, a numerical study is performed with different soil layers to: (1) understand the combined torque-lateral load behavior of drilled shafts near an embankment slope; (2) examine the effect of both the torsion and lateral resistances in the proximity of an embankment slope. It was found that torsional stiffness decreases with increase in slope angles. Finally, design criteria (e.g., minimum allowable distance from the embankment, maximum allowable point load near the embankment) of the mast arm assembly and loads are provided.

Reactivated landslides are generally associated with residual shear strength. Residual shear strength mobilized in such landslides are important parameters in slope stability and landslide simulation analysis. The present study involves estimation of residual shear strength of landslide reactivated soil at Marappalam area of Nilgiris district, Tamil Nadu state, India where landslides being reactivated frequently due to rainfall infiltration. A series of torsional ring shear tests performed under different normal loads to study the shear behaviour and estimate the residual shear strength parameters of soil. Since the residual soil at Marappalam area formed due to weathering, an effort made to study the weathering effects along with clay fractions and clay minerals on residual shear strength of soil. The test conducted on soil samples collected from various depths which is having different clay fractions with varying plasticity characteristics and fines content. The mineralogical and micro fabric analysis shows the presence of kaolinite clay mineral formed due to weathering. As the depth increases, the gradation of soil increases that decreases the clay content and degree of weathering. Hence, it is observed that the residual shear strength of the soil decreases with increase in clay content in presence of kaolinite clay mineral.

This study investigated the impact of rockfall impact against a granular cushion layer via 3-D discrete element method (DEM). In the numerical model, the rock boulder was modeled as a single sphere with an incident velocity, and the granular layer was modeled as an assembly of poly-dispersed spherical particles. The numerical model was calibrated and validated by comparing the numerical results with experimental data reported in the literature. It was further used to investigate the effect of rock boulder mass on the maximum impact force, impact duration and penetration depth. The obtained numerical results are in good agreement with available experimental observations.

Measurement of pore water pressure is helpful to locate the position of the zone of weakness, and its changes may indicate the formation of slip surface at hazard of mass movements. It is shown in the paper, based on some studies, that the pore water pressure measurements have helped to determine the area where the increase of deviator stress and this way the effective stress reduction and the development of the slip surface. In the process of destroying the geological structure of the center the apparent increase of pore pressure follows, and then it declines shortly after the end of the process. The changes are particularly evident after periods of heavy rainfall and are related to the permeability of ground. The paper discusses the results of pore pressure tests in dry and wet conditions.

The main aim of this study was determination of tree root architecture and its influence on soil reinforcement on the case of shallow landslide activated in May of 2010 in Polish Flysch Carpathians. The research was divided into few stages: recognition of geotechnical conditions of analyzed site, determination of root area ratio (RAR) of tress using trench wall method, laboratory tensile tests of root samples, shear strength tests of non-reinforced and root reinforced samples, characterization of soil microstructure by high resolution X-ray computed microtomography (mXCT). The site investigations revealed surficial soil layer, which is composed of silt and silt-loam soil. RAR measurements showed the significant decrease of root number with the depth. Maximum value of RAR was equal to 0.25%. The direct shear apparatuses were used for shear strength tests of rooted samples. The roots cause slight increase of internal friction angle and cohesion values. The mXCT method provide evaluation of the density and orientation of the roots in the sample. This data enabled for more accurate assessment of the root effect on the development of shear stress within soil.

Rainfall-induced shallow landslide is a significant issue in the south and southwest of China. It generally exhibits the behavior of progressive failure. However, the overall stability of coefficients can’t reflect the development of the local failure. In this article, a simple method, which is utilizing the progressive failure combined with the improved Green-Ampt model, is proposed to solve this problem during the rainfall. Taking the Guzhang shallow landslide as an example, it shows that the initial failure area of the shallow landslide is revealed in the front and middle of the landslide during the rainfall.

A set of analytical solutions achieved by the upper bound theorem of limit analysis and the pseudo-static approach is presented for the assessment of the stability of homogeneous c, ϕ slopes manifesting vertical cracks and subject to seismic action. Rotational failure mechanisms are considered for slopes with cracks of known or unknown depth and location. Charts providing the stability factor for fissured slopes subject to both horizontal and vertical accelerations for any combination of c, ϕ and slope inclination are provided. Yield seismic coefficients are also provided. Finally, Newmark’s method [1] was employed to assess the effect of cracks on earthquake induced displacements.

The initial impoundment and periodic water level variation may change the balance of geological environment of the reservoir area and bring different kinds of geohazards. Reservoir induced landslides typify such hazards that present challenges to the long-time operation of the Three Gorges Water Conservancy and Hydropower Project of China. The Huangtupo landslide, with multiple sliding stages and masses, is one of the largest and most destructive landslides still deforming in the Three Gorges Reservoir area. From 2008, we take the Huangtupo landslide as a typical case, and build a large field test site to provide an unprecedented opportunity for the research on the evaluation and prevention of reservoir induced landslides. The test site is composed with a tunnel group with a total length of 1.1 km and a series of monitoring system on both earth surface and underground. Through the tunnel group and multiple monitoring systems, visitors can directly enter the Huangtupo No.1 riverside sliding mass to closely observe the bedrock, sliding zone, and sliding mass, and also operate related scientific experiments and deep monitoring, such as large scale in-situ mechanical tests, underground hydrological tests, deep stress, deformation and environment monitoring. Now, the test site becomes an important site for international research, education, and academic communication about geohazards.

Since the impoundment of the Three Gorges Reservoir in mid-2003, slope displacements have occurred and existing landslides have been reactivated. The movement are a threat to the community and the environment. High precipitation in the area increases landslide susceptibility. The relationships among landslide displacement, rainfall and reservoir drawdown were analyzed for the Baijiabao landslide with the Grey relational analysis approach and using eight years of monitored displacement. The results suggest that rainfall triggered the landslide deformation in the earlier years. Then reservoir drawdown and the combined effect of rainfall and drawdown became preponderant. The identification of the triggers is important for selecting mitigation measures and evaluating the risk due to slope movement.

The Castaño Viejo mine, located in the Andes Mountains of San Juan Province, Argentina, was in operation between 1956 and 1964. A series of tailings dams were built during operation. One of these dams collapsed and the tailings flowed downstream for 3 km causing 3 causalities. This paper describes the Material Point Method modelling of this case history. An ASTER GDEM digital elevation terrain model and in-situ GPS measurements were used to generate the boundary condition for the MPM three-dimensional model. The tailings material was modelled as an equivalent fluid using Bingham constitutive equation. Results of the model runout are compared with GPS measurements of flow relicts and estimation of tailings deposits depth.

Movement of sliding mass, also known as the mechanism of sliding, is very complex. It is possible to observe the products of movement, i.e. displacements and deformations in the landslide body. In addition, displacements and deformations have an impact on artificial structures. The soil-structure interaction in landslide body has to be understood, whether we decide to save the existing structure or to design a new one.In this paper, the observation of displacements, deformations and soil-structure interaction at the landslide Bogatići is presented. The structure of hydro-power dam was exposed to the passive pressure of sliding mass, while the retaining structures have been overturned as a result. A geological fault was the barrier to the sliding. The Bogatići landslide is about 1400 m long and from 80 to 100 m wide. It spreads up to 300 m in the foot. Sliding surface is about 10 to 15 m deep in the upper part and up to 30 m in the foot. Activation of the landslide occurred in May 2010 after a period of heavy rainfall. Reactivation of the landslide occurred in June 2011 due to heavy rainfall again.Transport of sliding mass has been characterized by “push-pull” system. Reduction of strength in the foot and the secondary overload produce secondary sliding. The paper analyses different types of soil-structure interactions. Research results are to improve methodology of structure remediation.

Construction on soft clay deposits is assumed to be significant concern in geotechnical engineering field. Soft clays are characterized by low bearing capacity, high ductility and low permeability, which lead to certain constraints in embankment design. Therefore, to ensure safety of structures on soft grounds, it is necessary to define the capacity that foundation can bear before construction process. In addition, the behavior of structure has to be predicted to avoid failures or other unfavorable circumstances that could take place in the future. A number of prediction methods have been proposed, but the predictions could suffer from a lack of accuracy, resulting in a lack of confidence in practice. In this study, numerical simulation of embankments on soft soils using finite element method (FEM) is performed to evaluate existing methods for predicting performance of embankments on soft clays and to propose the most accurate stability analysis approach among reviewed methods.

A great proportion of slopes are located on the bedrock, and the excavation at the slope toe often induces the slope failure. In this paper, centrifuge model tests were performed to investigate the excavation-induced failure of soil slopes overlying the bedrocks. The slope failure mode could be categorized to two types: sliding along the bedrock or failing inside the soil. The slopes underwent significant progressive failure process, and the failure mechanism could be described with a significant coupling of deformation localization and failure. The bedrock shape influenced the deformation localization and induced different failure morphology.

The discrete element method (DEM) has been employed to analyze the Tangjiashan landslide induced by the 2008 Ms 8.0 Wenchuan earthquake. In the DEM model, the layered structure of the slope mass can be obtained by generating each sub-layer separately, with assigned different strength and stiffness properties. The bottom intact rock layer was initially bonded together with the basal failure plane to represent initially intact slope, and the site-recorded seismic shaking wave components are used as base excitations. The numerical results show that the slope mass can maintain a stable state under relatively low seismic shaking motions. As the seismic shaking intensity increases, the fractures/cracks occur and propagate gradually along the basal failure plane. The numerical simulations illustrate clearly the progressive failure and subsequent valley damming of the Tangjiashan landslide, from which some mechanisms of slope motion and deformation, as controlled by the complex layering geometries are presented.

The reservoir landslide is of sudden, uncertain and destructive characteristics, and the deformation stage of the classic landslide is divided into three stages: initial deformation, constant velocity deformation and acceleration deformation (see Fig. 1). In the case of a landslide with accelerated deformation indication, it is of great significance to accurately judge which stage of acceleration deformation it is in for forecasting impending slide and risk and disaster assessment. Taking the 5 million m3 slide mass high-speed reservoir entry event of Muzhuping landslide as an example, in this paper, the failure mechanism and instability characteristics of high-speed deformation landslide are analyzed. Combined with the successful forcasting experience of two high-speed reservoir entry landslide cases and a wide range of geological survey and related theoretical analysis, this study provides some useful experience and enlightenment for landslide hazard and forecasting impending slide.

To evaluate the influence of slope angle on lateral force acting on anti-slide row piles in c-φ soil landslide, this work firstly proposes the numerical solution to determine nonlinear sliding surface of sliding wedge of soil. Accordingly, recursive solution for lateral pressure acting on active side of stabilizing piles is derived by flat element method. Furthermore, analytical solution for distribution of soil-pile pressure acting on anti-slide piles is obtained by utilizing the improved plastic deformation theory which takes account of soil-arching effect. The subsequent comparison shows that the results from predictions match well with which from tests and implies that the proposed approach can be employed to evaluate lateral force on stabilizing piles effectively. Finally, parametric study is performed and results illustrate that landslide thrust (i.e., passive load) on stabilizing pile will increase with increasing soil inner friction angle (φ), inclined slope surface angle (α) and with decreasing cohesion (c) and the ratio of pile spacing to pile diameter (D₁/d).

The operating modes of energy piles depend on the thermal energy requirements of the built structures. The various operating modes of the energy piles lead to variations in the energy utilisation and ground temperature distribution. This paper presents the results obtained from a field-scale energy pile subjected to different modes of operations. In particular, it is found that cyclic temperatures provide better energy utilisation compared to monotonic temperatures. Also, the ground temperatures reduce with increasing radial distance from the pile for all operating modes.

Energy pile is a ground source heat pump technology that couples foundation pile with ground heat exchangers for geothermal energy exploitation. However, the thermally induced contraction and expansion of the concrete affect the heat transfer performance and sustainable operation of the energy piles. In order to minimize these effects, a set of concrete samples was tested by deploying heating-recovery-cooling-recovery cycle. Three different concrete samples including plain concrete, polypropylene reinforced and steel fiber reinforced concretes are prepared. Temperature and stain development of the concrete samples were continuously recorded during the testing process. The results show that heating expansion and cooling contraction are both reduced for steel fiber reinforced concrete. For polypropylene fiber reinforced concretes, only the heating expansion is reduced but the contraction is larger than the plain concrete. Finally, the content of steel fiber of 1.3% is optimized to minimize the thermally induced mechanical effects on steel fiber reinforced concrete for energy piles.

Enhanced Geothermal Systems (EGS) is a potential carbon-neutral form of renewable energy whereby fractured granite at depths of around 2–4 km. Such geothermal reservoirs are high-temperature rock formations located at deep underground and therefore with ultra-low permeable characteristics. Therefore, natural and artificially created rock fractures provide major flow pathways for the reservoir fluid circulation process. Evolution of permeability through such rock fractures under potentially existing extreme geothermal conditions is quite important for an effective application of EGS systems. This study therefore discusses the experimental results of a series of flow experiments conducted on artificially fractured Australian Strathbogie granite under wide range of pressure (30 MPa confining pressure, 5 MPa to 25 MPa injection pressure) and temperature (from room temperature to 250 °C) conditions using a newly developed high temperature-high pressure rock triaxial test apparatus with capability of simulating environment of EGS reservoirs. The steady state flow rates through fractures found to linearly increase with increasing injection pressure under the considered injection pressures and temperatures. Permeability along rock fractures was therefore calculated by employing cubic law and relevant temperature and pressure dependent fluid properties. According to the experimental results, both stress level and the temperature have significant influences on fracture flow characteristics of the tested granite. Increasing of temperature caused a significant non-linear increment in flow rate and permeability through fractures due to the thermally induced micro crack generation.

Bentonites are usually selected as the engineered barrier material of repositories for radioactive waste. The saline solution from surrounding rock fissures can affect the mechanical behaviour of bentonite for the reason that the osmotic suction in pore water can act as an additional total stress component on bentonite. The osmotic coefficient, as the key to calculate the osmotic suction, is usually obtained by measuring the vapor pressure of a solution and that of the pure solvent with a differential manometer in experimental method. Considering that the vapor pressure is affected by many factors such as solute type, concentration, and temperature, it is very complicated to obtain the osmotic coefficient by experimental method. In this paper, the osmotic coefficient is calculated according to the modified Debye-Hückel equations and the calculated results are validated by comparing with the experimental data in other literature. In this way, the osmotic suction for different solutions under different temperatures can be obtained by calculation.

Soil mechanics is a powerful theoretical analysis tool in geotechnical engineering. The principle of effective stress is a basis of classic soil mechanics. However, it in fact is an approximated method. This is attributed to three factors. Firstly, the effective stress is an equilibrium equation rather than an independent state variable. Secondly, the effective stress is a variable controlled the deformation behavior and the shear strength of soil, but not the only one. Thirdly, the principle of effective stress is an equivalent method, but not an accurate one. The above viewpoints are justified in this paper as follows. Firstly, it is demonstrated that the soil is a variable and sensitive material. Thus, it is difficult to quantitatively describe soil behaviors by only one variable. Secondly, the definition and the comprehension of the effective stress are discussed. Finally, to deal with complex problems most frequently encountered in geotechnical engineering, two approaches are advised, i.e., choosing additional variables except for the effective stress and using the multi-factor theory.

The aim of the paper is to adopt the equivalent microstructure approach, originally formulated for saturated soil with respect to thermal conductivity [1], to the case of unsaturated one (3-phase medium). For that purpose, we propose two methodologically different approaches within the framework of Mori-Tanaka homogenization scheme. The first one is based on the replacement of the 3-phase medium with a 2-phase one. In this case, thermal conductivity of the mixture of water and air is estimated using the Hashin-Shtrikman lower and upper bounds. The latter approach treats the soil as the 3-phase medium. This requires a deep reformulation of the equivalent microstructure approach introduced in [1]. The second approach is recognized as the proper one, providing the remarkable agreement between the measurements and predictions of thermal conductivities at whole range of saturation degrees.

The osmotic, hydraulic and self-healing efficiency of bentonite based barriers (e.g. geosynthetic clay liners) for containment of polluting solutes are governed both by the physico-chemical intrinsic parameters of the bentonite, i.e. the solid density (ρ_sk), the total specific surface (S), and the total fixed negative electric surface charge (σ), and by the state and fabric parameters able to quantify the soil density and microstructure, i.e. the total (e) and nano (e_n) void ratio, the average number of platelets per tactoid (N_l,AV), the effective electric fixed-charge concentration ($$ \bar{c}_{sk,0} $$c¯sk,0), and the Stern fraction (f_Stern). In turn, the fabric parameters seem to be controlled by the effective stress history, ionic valence and related exposure sequence of salt concentrations in the pore solution. A theoretical framework able to describe chemical, hydraulic and mechanical behaviours of bentonites has been set up. In particular, the relationships, linking the aforementioned intrinsic, state and fabric parameters of a given bentonite with its hydraulic conductivity (k), effective diffusion coefficient ($$ D_{s}^{*} $$Ds∗), osmotic coefficient (ω) and swelling pressure (u_sw) under different stress-histories and solute concentration sequences, are presented. The proposed theoretical framework has been validated by comparison of its predictions with some of the available experimental results on bentonites.

The proper estimation of soil solids conductivity, λ_s, is of primary importance for evaluation of soil conductivity at various degrees of saturation. This property, i.e. λ_s, cannot be measured directly. Its value is usually estimated by various semi-empirical relations which have been reported in the literature to be improper in many of engineering applications. One of the possible reason is the fact that these models do not take into account the influence of organic matter. The aim of this paper is to create the ‘Feret-like triangles’ where λ_s values are plotted as a function of soil texture. For that purpose, a series of numerical simulations is carried out. The micromechanics approach, formulated in [1], is used. The nomograms provide information on the solids conductivities as a function of the soil texture, namely the percentage of individual separates. Different cases, with respect to the organic matter content, are also analyzed.

Microstructure of compacted bentonite is an important aspect which controls its hydro-mechanical behavior, also is vital in constitutive modelling. In order to understand this mechanism, the wetting and drying behavior of compacted bentonite with initial dry densities of 1.9 g/cm3 was investigated by environmental scanning electron microscopy (ESEM). The attempt of quantitative interpretation was done by digital image analysis at aggregates level (in micro meters). The macro pores between aggregates were clearly sensitive to change of suction, while there were only small volume changes of the aggregates. Volumetric strain of the measured aggregates varied. After one wetting-drying cycle, some new macro pores were formed and the hysteretic behavior of inter-aggregate pores was observed.

This study presents the results of plate load tests conducted on an unsaturated silty sand. The soil samples were subjected to wetting and drying, by raising and lowering of the water table, to mimic conditions which exist in the field. The suction values at different depths were measured by the vibrating wire piezometers. The effects of hydraulic loading histories, soil densities and suctions on the ultimate bearing capacity were studied. An equation was developed to interpret the experimental results based on the relative density dependent peak friction angles and suction profiles. The estimated bearing capacities agree well with the values measured in the plate load tests and the differences can be partly attributed to the superposition of the bearing capacity factors.

The paper presents a study of thermo-mechanical behaviour of heat energy storage materials of a packed bed made of ceramic pebbles undergoing thermal charging and discharging cycles. Both experimental and numerical results show that the pressure on the storage wall increased over the charging and discharging cycles, but tended asymptotically to a stable threshold value, which can be derived as design values for the packed bed pressure.

The measurement of the hydraulic properties of an unsaturated soil is time consuming and complex, and the water evaporation loss may cause error to the measurement of hydraulic conductivity in multi-step outflow experiment. In this paper, an improved pressure plate instrument is introduced, which can overcome the deficiency of the impact of the water evaporation loss on the measurement of the hydraulic properties. Then, the hydraulic properties of silicon micro-powder (SMP) and Guangxi Guiping clay (GGC) were conducted under five cycles of drying and wetting by this instrument, respectively. We found that the hysteresis effect was apparent less with the number of drying and wetting cycles increases, and tended to exhibit a zero hysteresis under fifth cycle. Additionally, the transient water content curves (TWCCs) of these two soils can be obtained, and the hydraulic conductivity for these two soils can be calculated by Shao et al. (2017) method based on TWCC and SWRC, which can get more data points to present the variation of hydraulic conductivity during each step of the outflow process.

To investigate the influence of the surface moving load on the underground tunnel, an analytical solution for calculating vibrations from a circular tunnel buried in a half-space due to a surface moving load was firstly given in this paper. The surface load was represented by a moving harmonic point load, and the half-space with a circular tunnel was visco-elastic with a cylindrical hole. The analytical solution of the half-space foundation and tunnel were obtained in the frequency domain based on the fundamental solutions of governing equation of elastic ground in Cartesian and cylindrical coordinate systems. Also, the transformations between the plane wave functions and the cylindrical wave functions and the surface boundary conditions should be used. Then response in the time domain was obtained by inverse Fourier transform. The influence of surface moving loads on the vibration of underground tunnel can be investigated by using the analytical model. The displacement and acceleration of the tunnel surface under different load velocities and tunnel buried depth are analyzed in this paper. The results show that both the dynamic stress and the acceleration responses above the vault of the tunnel increases significantly as the moving speed of the load increases. The dynamic stresses decay rapidly as the buried depth of the tunnel increases, while the acceleration responses decay relatively slowly.

The road base and subbase materials are normally in unsaturated condition, and fouled by fines due to subgrade pumping. These unsaturated fouled materials usually present different properties due to combined effects of matric suction and fine content. To study the long-term behaviors of these materials, a series of large-scale cyclic triaxial tests were conducted. Crushed tuff aggregates, incorporated with corresponding kaolin contents, were selected to be the testing materials. Cyclic loadings with two amplitudes were applied on the mixture specimens under four initial matric suctions and two fine contents. The matric suction was controlled by axis-translation method. The accumulated axial strain and resilient modulus were focally analyzed. The testing results show that for materials with higher fine content, the hysteresis phenomenon during the drying and wetting path of the soil-water characteristic curve will be more obvious. Under cyclic loadings, the resilient modulus increases with the increase of matric suction, and the increase rate decreases with the increase of matric suction. The accumulated axial strain decreases with the increase of the matric suction, and the decrease rate decreases with the increase of matric suction. Larger cyclic loading amplitude and higher fine content will amplify the influence of matric suction.

Shanghai is located in the coastal region of the Yangtze River Delta which has a phreatic aquifer and five confined aquifers labeled from Confined Aquifer I (CA I) to Confined Aquifer V (CA V). During nearly 100 years of groundwater exploitation, the main exploited aquifers have been switched from CA II and CA III to CA IV and CA V. The deep soil layers went through great compaction because of groundwater withdrawal and became relatively stable after adoption of groundwater recharging measures. However, the shallow soil layers are still deforming as a result of construction activities i.e. underground space exploitation, which causes different responses of transportation infrastructures buried in different depths. Of the three investigated transportation infrastructures, the elevated roads suffer the least from land subsidence and the subsidence of the ground roads is the largest while the subsidence of metro tunnels is between the other two infrastructures.

Phosphogypsum is an industrial waste generated during the production of phosphoric acid. Its amounts in the world are significant and still increase. This waste is mainly stored and its storage is a problem for the natural environment. Road construction industry allows for the use of large amounts of industrial waste, such as fly ash, coal mining waste and metallurgy industry by-products. However, due to its properties, phosphogypsum is a waste with high limitations for use. The research of technical and chemical properties of Phosphogypsum is still being carried out. According to previous studies, the use of unprocessed phosphogypsum in building materials causes deterioration of their properties, therefore processing is required. The paper presents the results of testing phosphogypsum-fly ash mixture and this mixture processed into a granular form with sulphur and various additions of a modifier. The solidification of phosphogypsum into granules was aimed at improving geotechnical properties and reducing the leaching of heavy metals. The paper discusses the geotechnical properties of the mixture before and after granulating it in terms of the possibility of use its in road engineering as the geotechnical structures. The presented research was carried out as part of the RID-6 (Road Innovation Development) research project “Use of recycled materials”.

A composite trapezoidal MSE-embankment system was designed and constructed to support the embankment widening project at a Highway Bridge in New Zealand. The widening necessitated the construction of retaining walls on the existing abutment slopes and under the existing bridge. To suit the constructability and achieve a customized cost effective solution, the use of traditional rectangular MSE reinforcement lengths, which would require vertical excavation into the existing abutment slope, was replaced by the use of Trapezoidal-shaped reinforcement lengths. This paper assesses the consideration of a designed and constructed Trapezoidal Wall for a highway Bridge abutment, and variations on the conventional assessment of failure mechanisms to ensure the wall achieved the design intent. A few options are discussed and compared. Numerical analysis is carried out to establish the achievement of wall stability and serviceability requirements. The successful application of this wall is demonstrated by observed stability and the monitoring during and post-construction.

To investigate the effect of creep characteristics of soft soils on time-dependent deformation of root-caisson foundation, long-term lateral loading tests were performed about 120 days in Wangdong Yangzi River Highway Bridge. The displacement of caisson head, the deformation of the caisson along depth and displacement field of soil ahead the foundation were measured under the constant load. Comparing the short-term deformation and long-term displacement of root-caisson, soil creep effect and time-dependent displacement of foundation are revealed. The results show that deformation of this root-caisson presents characteristic of the flexible foundation. From the entire process the lateral displacement of caisson vs time curve, the horizontal displacement at the top of caisson increases gradually with the continuous time of the constant load, the displacement rising rate declines gradually, and the horizontal displacement finally tends to a stable value. The deformation of the caisson in the holding load stage is larger than the one in the loading stage, the final horizontal displacement of the caisson top is 2–3 times the instantaneous displacement. The rebound displacements of the caisson are small with experiencing a long-term horizontal load after unloading, the creep deformation of the soil occurs under long-term horizontal load.

Design and construction of linear structures for transport like road or railway lines in areas with active or historical deep mining operations is always challenging due to various additional influential geotechnical data which needs to be considered. Surface subsidence and its negative impact on road geometry over time needs to be compensated by protection systems designed and implemented prior to time when real influence occurs. Linear or non-linear deformations are one of the most critical parameters to be overlooked at design stage. Also use of mining materials for construction of embankments as alternative to natural soils brings additional challenges and need for good identification of all geotechnical parameters of such material. As Silesia is region with one of the most concentrated deep coal mining activity in Europe problem of constructing safe and environmental friendly infrastructure is always critical. This paper discusses selected aspects of geotechnical practice implemented in the region for protection of transport infrastructure in such challenging geotechnical environment.

Defective piles within piled embankments have the ability to cause significant project delays and require costly remedial works. At present, the ability of the load transfer platform and embankment fill to redistribute loads away from defective piles and reduce differential settlements that develop between defective and non-defective piles is not well understood. Synchrotron X-ray computed tomography was performed on a small scale model piled embankment comprising a defective pile with digital volume correlation analysis implemented on pairs of reconstructed volumes to study the kinematics of soil arching above a defective pile. Results indicate that a plane of equal settlement can still develop above a defective pile.

Verification of nonlinear dynamic numerical analysis was performed using dynamic centrifuge test results for pile supported track under seismic loadings. The numerical analysis models were constructed in the same dimensions with the centrifuge tests in prototype scale. Verification was conducted by comparing the measurement data obtained from the centrifuge test and numerical analysis output directly. Total 4 different numerical models corresponding centrifuge test are verified with changing thickness of soft soil layer, embankment, input motion intensity and history. Numerical analyses were conducted in time domain by an explicit time integration method. Dynamic hysteretic damping model was adopted for nonlinearity behavior of soil under seismic excitation. The piles were modeled with shell element that can show interface behavior with surrounding soils. The other structural members are modeled in a hexahedron solid element that has an interface. Seismic responses of the pile supported track were quite similar for both numerical analysis and centrifuge test.

Open caisson foundation has been widely used as anchor foundation for cable-stayed bridge in recent years. Large scale open caisson displays different mechanical characters compared with small and medium-sized open caisson in both construction process control and spatial mechanical performance. Generally, the drainage sinking of a large open caisson is more dangerous than the non-drainage sinking. At the beginning of caisson subsidence, the blade foots tend to deviate outwards because there is no buoyancy force or lateral constraint at the blade edge, which may lead to larger tensional force at the bottom of the caisson structure. Therefore, proper design of the first sinking scheme is particularly important for large-scale open caisson. A three dimensional soil- structure interaction finite element modeling, which is based on a large-scale open caisson for anchor foundation of a highway bridge project, is carried out to analyze the influence of the caisson structure diameter on the internal force in condition of first sinking. Numerical results indicate for large-scale open caisson the initial sinking method has a great influence on the tensional force generated in the caisson structure. It is also revealed the model of structure on Winkler foundation may lead to significant error in calculating the deformation pattern and internal force of the caisson structure. The numerical results and conclusion will provide reference for properly design of initial sinking method of similar large-scale open caisson projects.

Artificial islands are adopted in Hong Kong-Zhuhai-Macao Bridge (HZMB) project to form the transition between the bridges and tunnels. A transition foundation solution along the longitudinal direction is introduced, including cast in place piles and PHC piles. Large area of backfill at both sides of the tunnel structure can result in unacceptable settlement as well as differential settlements along the transverse direction. Several measures have been suggested in the real project to deal with this problem, including increasing the length of piles underneath the tunnel structure, and adding two rows of isolating piles at both sides. These treatments are systematically introduced in this paper and a 3-D soil-structure interaction finite element analysis is also carried out which thoroughly models the construction steps. Mechanism of isolating piles in reducing tunnel settlement and uneven settlement is investigated. The study outcome provides reference for similar immersed tunnel projects.

We propose a new type of mechanical tests, named the lateral decompression tests, to evaluate the mechanical properties of the surrounding rocks in the shifts based on elastic stress solutions of circular openings. We carried out lateral decompression test with a developed autonomous device to evaluate the mechanical properties of the Callovo-Oxfordian (COx) claystone, the hosted rock and geological barriers of the repositories for radioactive waste disposal in France. In the tests, the samples were firstly subjected to a hydrostatic stress that corresponds to the representative in situ mean stress (p = 12 MPa). Then, the samples were loaded to a possible failure at the given constant mean stress (∆p = 0). The results show that the COx claystone failed in the lateral decompression tests at the in situ mean stress of 12 MPa. A shear band controls the failure pattern in lateral decompression tests, which is similar to that in conventional triaxial tests. However, the failure prior to rupture is more brittle than the failure in conventional triaxial tests. The failure of the COx claystone under the tested mean stress suggests that the excavated galleries need external supports to keep its stability after tunneling in the COx formation.

Shakedown theory provides a rational tool for prediction of the long-term plastic behavior of pavement subjected to variable or repeated loads. A dynamic lower-bound shakedown solution has been proposed to estimate the critical shakedown limit load, over which plastic collapse or excessive permanent deformation of the pavement takes place. However, dynamic effects on the shakedown limit remains unexplored, particularly when rolling and sliding contact between vehicle and pavement are involved. In this paper, a finite-infinite (FE-IF) dynamic numerical method is presented to calculate the dynamic elastic stresses resulting from rolling and sliding contact at different moving speed for computing the shakedown limit. It is found that the shakedown limit decreases with the increasing moving speed initially and then turns to increase when the moving speed exceeds the Rayleigh wave speed of the pavement system. This dynamic effect is more profound as the horizontal force component reduces. The influence of frictional coefficient on shakedown limit is also discussed.

The natural frequency of dam-foundation system is a function of its stiffness and the participating mass. In the present study, an attempt is made to understand the effect of rock joint orientation on the natural frequency of the dam-foundation system. Discrete element simulations are carried out using UDEC (1993) software for the intact rock foundation and rock foundations having joint inclinations of 0°, 30°, 60°, 90°, 120° and 150° with 20 m, 10 m, 5 m, 2.5 m and 1 m joint spacing in the rock mass. Results, confirm that the joint orientation affects the natural frequency of the system significantly. The natural frequency of the dam-foundation system is found higher for the intact rock foundation as compared to other jointed rock foundations. Results also reveal that the magnitude of the natural frequency of the system increases as the joint spacing increases in the rock mass.

Although the concept of sheet pile bridge abutments is not new, they do not enjoy as much widespread usage as reinforced concrete bridge abutments. This paper provides a design case-history involving replacement of two existing road bridges with proposed new bridges supported by a combination of steel sheet piles and concrete bearing piles as abutments. The steel sheet piles have been designed to provide lateral earth support while concrete piles, vertical deck loads. Sheet piles of different types: anchored, tied-back and cantilever, have also been proposed for wingwalls. The arrangement for abutments was selected to minimize traffic interruption over existing road bridge, to enable faster construction in a restricted space environment and reduce ‘possession’ of railway track, and to provide an economic and durable solution. The two road bridges are a part of preparatory works for electrification program of Denmark state railway network between Aarhus and Lindholm.

A safe and economical design of high-speed railway subgrade-bridge transition zone nowadays relies heavily on the accuracy of the geotechnical parameter measurements, while inherent variability, testing error and transformation error often stand in the way. This paper presents a fuzzy set-based robust geotechnical design (RGD) methodology for the transition zone, freeing the design from the requirement of precise geotechnical parameters. Based on the theory of vehicle-track coupling dynamics, a plane stress finite-infinite element model of the transition zone is proposed to investigate the influence of 3 simultaneously varied subgrade material parameters on the system dynamic response. Using the vertex method, the subgrade system’s robustness is evaluated by the signal-to-noise ratio. The results indicate that the influence of the dynamic elastic modulus of the graded broken stone on the robustness of the vehicle system is considerably larger than that of the dynamic elastic modulus of the subgrade bed surface layer. The system is more robust when the dynamic elastic modulus of the graded broken stone is between 625 Mpa and 750 Mpa.

The structure size effect with regard to the deformation behavior of high filled geotechnical structures is investigated. Theoretical analyses and numerical Monte Carlo simulations reveal that the relatively large variability of the mechanical properties, especially those related with plastic deformations, can be the main cause of this kind of size effect. Although variability of material properties implies both degradation and upgradation of the material parameters by certain probability, computations show that the parameter degradation dominates the final results and gives rise to the structure size effect.

The highway, R2, between cities Trencin and Prievidza in Slovakia was constructed under adverse geological conditions. Some sections of the motorway were designed on embankments and require the use of soil improvement because of the unsuitable subsoil. Original subsoil was improved using vertical drains, stone columns, dynamic compaction, preloading and stone drainage ribs. This paper deals with the numerical analysis of selected profiles where the subsoil for road embankment can be improved using stone columns. The subsoil consisted of compressible soft soils with low permeability. Stone columns reduced the settlement of a road embankment and reduce the time required for consolidation. Stone columns with a diameter of 600 mm and length of 5 m were designed in a square mesh with an axial distance of 2 m. Numerical modelling was executed with Plaxis software using FEM. Stone columns are a displacement technique which significantly changes properties of the original subsoil. The geotechnical monitoring included results of road embankment settlement using horizontal inclinometers, as well as geodetical measurements. The analysis included the comparison of road embankment settlement determined using measurements with results of numerical models, which assumed different ways of stone column modelling. The results showed that numerical modelling leads to the acceptable determination of road embankment settlement. Advantages and disadvantages of different ways of stone columns modelling are discussed.

This paper focuses on the experiences and benefits of using the Finite Element Method (FEM) in order to describe soil-structure interaction behavior taking the example of two successfully completed lock repair projects. It turned out that the influences and interactions of the repair works on the existing lock, in particularly the deformation of the lock, earth pressures acting on the lock and structural forces in different lock sections, could only be determined in a realistic way by calculations with the FEM. Based on the calculation results, limit values for the monitoring system, which is necessary to check the system behavior and to verify the calculation assumptions during the repair works, were defined. An additional focus is on the relevance of small-strain stiffness in the analyses. For this purpose, an extension of the Hardening Soil model (HS-model) that accounts for a higher stiffness at small strains was used.

Large-scale direct shear tests were carried out to explore the shear behavior of the ballast-subballast interface with and without the inclusion of geogrids. Fresh granite ballast and subballast with an average particle sizes (D₅₀) of 42 mm and 3.5 mm respectively, and triaxial geogrids with different aperture sizes were used in this study. Tests were performed at different normal stresses (σ_n) ranging from 20 to 100 kPa at a constant shearing rate (S_r) of 2.5 mm/min. The experimental results reveal that the shear strength of the ballast-subballast interface improved significantly with the inclusion of geogrids. The interface efficiency factor (α), defined as the ratio of the shear strength of ballast-geogrid-subballast interface to the shear strength of ballast-subballast varies from 1.15 to 1.17 and the ballast-geogrid-subballast friction angle (φ) lies in the range of 51.1° to 67°. These test results emphasize the role of triaxial geogrids in stabilizing the ballasted rail tracks and thus reducing the maintenance cost.

Shakedown limits can be used to predict different long-term responses of geo-structures under repeated moving loads. Based on lower-bound shakedown theorems, static and dynamic shakedown limits were obtained respectively for slab substructures under train loads of various speeds. The determination of the dynamic shakedown limit is relatively complicated due to the calculation of stable dynamic elastic stresses in the substructures. It was found the change of the dynamic shakedown limit from the corresponding static one is highly dependent on soil friction angle and a velocity factor (train speed over critical speed of the substructure). A simple relation between the dynamic shakedown limits at various speeds and the static one is then proposed which can serve as an efficient approach to estimate the influence of the train speed on the long-term performance of substructure.

Many exiting embankments along river have been enhanced by enlarged construction. This paper proposed a practical method of determining enlarged embankment loads induced vertical superimposed stress in subsoil by considering the effect of existing embankment and variations in foundation properties underneath existing and enlarged embankment. The Stochastic stress diffusion theory is used to establish an equation of calculating contact stress for overcoming the assumptions of traditional trapezoidal stress distribution. The elastic solution is used to calculate the vertical superimposed stress. An empirical coefficient is employed for incorporating the effect of variations in properties of subsoil. The method was applied to analyze one case in Korean. Comparisons of the calculated values with field data indicate that the proposed method is useful for designing the enlarged embankment on soft subsoil.

This paper discusses designing of geosynthetic tension strain in Geosynthetic-Reinforced Pile-Supported (GRPS) embankments. Traditionally, filling period of the embankment is not considered among design codes, and the arching model is applied to the final state. The paper attempts to adapt existing designing methods to increasing filling height and static compaction load. Adapted designing approaches include codes distinguishing partial-arching and full arching. The variations of stress concentration ratio and tension in the geosynthetic layer are studied with increasing filling height and different overcharge load. Results show that, for certain cases, the maximum geosynthetic strain is acquired while filling, during partial arching with compaction load. This phenomenon is analyzed and validated with two reported cases of field-test data and full-scale experiment, and relative design suggestions are proposed.

Soil levees are widely constructed in thousands of rivers in China. While due to the limitation of on-site materials, some projects have to use sandy soil as the filling material. The South-North Water Transport Project, flood control projects of the Yangtze River and Yellow River, water diversion irrigation projects in the northwest of China, and some coastal seawall projects all contain sandy soil levees. Considering the slope stability, many sandy soil levees are designed with slope ratio 1:4 or 1:5, which need a lot of land cover and soil filler. So the section design and construction technology of sandy soil levees are improved. To increase the stability and narrow the section, methods such as the geotextile reinforcement, sand geotube construction, “sandwich” filling and soil modifying methods are common ways. Among them, the geotextile reinforcement and sand geotube construction are quite effective and widely applied. And engineering applications are listed. So, the sandy soil levee can be widely promoted.

The issue of large steel structure derrick in mine of freeze sinking on deep alluvium suffering from deflection and security enhancement is studied using the auxiliary shaft derrick of Dingji Coal Mine as a model system. First, the study analyses the mechanisms of uneven settling of the foundations in frost-thawed soil, the experimental results show that the bearing capacity and compression modulus of the soil mass decrease after freeze thawing. Since the soil texture and artificial freeze temperature field are uneven, resulting in uneven settlement of the foundation soil of the derrick footing and causing the deflection of the derrick. Secondly, the analysis of finite-element numerical values indicates that in the event of uneven settling, the greatest tensile stress in the derrick structure of Dingji auxiliary shaft increased by 39.83% and the largest pressure stress increased by 33.33%. These stresses have seriously affected the security enhancement of the derrick and ground stabilisation and deviation rectification of the derrick is urgently required.

Electro-osmosis combined with vacuum preloading is numerically studied. The influence of vacuum degree attenuation, simultaneously vacuuming at both electrodes and permeability of sand interlayer on pore water distribution were analyzed. The results of comparison show that excess pore water pressure is consistent with the analytical solution. In the center area and vicinity of anode, the absolute value of excess pore pressure is smaller than that of no-attenuation firstly, and then it becomes larger. Vacuuming at both electrodes can greatly shorten the reinforce period by 70%. The impact of permeability coefficient was investigated through a sand interlayer with different permeability. Permeability ratio between the sand interlayer and the clay will affect pore pressure dissipation time, and the higher the ratio, the shorter the consolidation time. The analyses of pore water pressure in electro-osmosis combined with vacuum preloading can help to predict settlement and optimize design.