Advances in Transportation Geotechnics IV

The rapid development of the high-speed railways and air transportation networks is leading to an increasing demand of the combination of these two modes of transport. Some modern integrated transport hubs have been operated, and at least 32 airports in China are planning to combine air transportation with high-speed railway transportation. To realize the “seamless transfer” between the airport and the high-speed railway station, some high-speed railways were constructed beneath airport runways. It is necessary to study the dynamic interaction between these two kinds of infrastructures. Based on a project with a high-speed railway tunnel beneath an airport pavement in south China, an aircraft–runway interaction model and a vehicle-tunnel-foundation coupling model are proposed to investigate the dynamic response of the complete system. In this paper, the cumulative plastic deformation of the airport runway caused by the dynamic load of high-speed trains is comprehensively predicated. The influence of the aircraft dynamic load on the deformation of the tunnel and the operation safety of high-speed trains is investigated. The results show that the settlement of airport runway rises to 9.80 mm after ten years of operation of the high-speed railway. The amplitudes of the vertical and horizontal displacement of the tunnel affected by the aircraft dynamic load are 0.192 mm and 0.099 mm, respectively. The rate of wheel load reduction of the high-speed train is not evidently excited by the aircraft dynamic load.

Slurry preparation and pressure maintenance of slurry balance shield should be carefully treated during tunneling in complex sand stratum. On basis of the slurry shield tunnel project in Fuzhou, slurry pressure was determined by two different theoretical methods. Then, an indoor test was conducted to explore the influence of constituents on slurry property. The influence of slurry properties on filter cake forming process under different slurry pressure was also analyzed through slurry penetration test. The test results indicate that the bentonite and silt soil had dominated influence on relative density, while the bentonite and CMC had dominated influence on viscosity. It is found that the water discharge, which is the index to evaluate the effect of filter cake, decreases firstly and then increases as slurry relative density increases. The water discharge also decreases as slurry viscosity increases. Meanwhile, the influence of viscosity on the water discharge was found less than that of relative density. Finally, a segmented slurry control scheme suitable for sand stratum in Fuzhou was presented.

With continued development of urban rail transit networks, the quantity of overlapping metro tunnels is increasing. Long-term service performance of the tunnel structure can be threatened a lot by complicated dynamic response of tunnel–ground system under train load, especially in the overlapping cases. Based on a case of four overlapping tunnels in soft clay region, dynamic response of the tunnel–ground system and long-term settlement of the tunnels are investigated with finite element method (FEM) and empirical method. It is shown that, maximum acceleration and dynamic principal stress of the lining in overlapping zone are 48.2% and 19.8%, respectively, larger than that in non-overlapping zone. The ten-year accumulation settlement of the tunnel in overlapping zone is 173.7% larger than that in non-overlapping zone. Uneven settlement occurs in the overlapping zone, and the radius of curvature of the tunnel (12,461 m) exceeds the requirements of the specification (15,000 m). Grouted reinforcement can control the uneven settlement well. Radius of curvature of the tunnel can be refined to 33,967 m, which meets the requirements of the specification.

The problem in dynamic stability of soft soil between closely and obliquely overlapped metro tunnels during operation will aggravate cumulative settlements which affects the safety of metro systems. Based on Shenzhen Metro Line 5 and Line 11 overlapped tunnels, a three-dimensional vehicle-track-tunnel-soil model has been established. Meanwhile, the dynamic shear strain and its transfer characteristics of the soft soil layers between overlapped tunnels under moving train loads has been studied. In longitudinal direction, the most unfavorable position for the soft soil is located in the place where the maximum overlapped degree exists between two tunnels. In transverse direction, the dynamic shear strain in soft soil between tunnels diffuses obliquely at a certain angle from the arch waist of tunnel and gradually decreases with the increase of distance. It also increases nonlinearly with the number of operating lines. Besides, the dynamic stability of soft soil was evaluated by the cyclic threshold shear strain parameters of Vucetic and the value exceeds the linear cyclic threshold shear strain. The plastic deformation of soft soil under moving train loads will accumulate obviously and the dynamic stability problem cannot be ignored. Therefore, high-pressure jet grouting pile is adopted to reinforce the soft soil between two tunnels. And the result shows that the dynamic shear strain of soft soil after reinforcement is much smaller than that before.

A practical cost estimation about the design model of the utility tunnel is essential for the management of the utility tunnel in the design stage. However, the process for quantity calculation based on the design model from the utility tunnel is inefficient because of the inaccurate recognition. Issues in quantity calculation will be resolved with the method related to Revit secondary development (RSD) proposed in the paper. On the basis of Application Programming Interface (API), programming language C#, and programming platform Visual Studio, we established a tight correspondence between the design model of utility tunnel and the external database for quantity calculation. Consequently, results of the quantity calculation based on utility tunnel depended on the clarified model of utility tunnel were available. A case of utility tunnel in the new southern district of Nanjing was studied. It has shown that the results of RSD are better than that of the existing third-party calculation software, in terms of recognition accuracy and data integrity. The results of the study verified the reliability of method proposed in the paper.

This paper investigates the influence of the variation in the groundwater table on ground vibrations from underground tunnels by an analytical model. The saturated porous medium is used to model the soil layer under the groundwater table, and the dry single-phase medium is applied to simulate the soil above the groundwater table. The transfer matrix method and wave transformation are applied to derive the solution for a tunnel in a dry/saturated layered half-space. Ground vibrations from a tunnel in a three-layered half-space are computed by using the proposed model. The numerical results demonstrate that the vibration levels increase as the groundwater table drops. The displacement field is similar to that of a saturated half-space when the groundwater table is above the tunnel, while it is similar to that of a dry single-phase half-space as the groundwater table is under the tunnel.

This paper presents three types of vibration isolators to enhance the comfort for residents inside buildings near subways. Stacked sandbags formed the first type of isolator. An elastic and closed capsule filled with sand and rubber particles is the second type of isolator. The third type of isolator is laminated thick rubber bearing with a sliding bottom. The materials and components of the three isolators are described first. Then, the vertical stiffness values, the damping ratios, and the ultimate bearing capacities of the above isolators are tested in a laboratory, and the suppression effectiveness for subway-induced vertical vibrations are investigated by two full-scale buildings near subway transportation. The results indicated that the bearing capacity of the first isolator is the lowest, but the damping ratio is the highest. For the second isolator, the vertical stiffness and damping ratio can be adjusted by changing the mixture ratio of sand particles, and the bearing capacity is improved significantly. For the third isolator, the damping ratio is the smallest, but the sliding bottom is capable of isolating earthquake ground motions. After installation of the three isolators, the human comfort inside the buildings satisfied the limit values, proving that they are effective as base isolation methods for buildings near subways.

The steel spring floating slab track is widely adopted for its remarkable performance on vibration isolation. With the increase of the operation time of floating slab track, the damage or failure of the steel spring is inevitable, which will have a bad effect on the track dynamics and vibration-mitigating effects. The steel spring’s forces were calculated by the vertical coupled dynamics model for the metro and the floating slab track. The dynamic response of tunnel and soil subjected to the steel spring’s forces was analyzed. The influence of steel spring failure position of floating slab track on the dynamic response of infrastructure was investigated. The results showed that the failure position had a significant effect on the dynamic characteristics. Although the infrastructure displacement varies little with the failure position, the reaction forces of the steel springs and acceleration of the track, the tunnel, and the soil notably increased when the steel spring failed at the end of the track. The tunnel acceleration with one pair of damaged springs at the end of track is 40% greater than that with the same failure springs in the middle of track.

In this paper, the effect of boundary permeability on the dynamic response of a layered poroelastic half-space under moving loads in a tunnel is studied analytically. The tunnel is modeled by an Euler–Bernoulli beam located between two horizontal layers. The Biot’s dynamic equations for the poroelastic soil medium are solved by utilizing the Helmholtz decomposition and Fourier transformation. Combining the boundary conditions and the continuity conditions between each layer, the explicit analytical solutions for the dynamic response of each layer in the transformed domain are obtained by the transmission and reflection matrices (TRM) method. The solutions in time–space domain are expressed in terms of infinite Fourier-type integrals, which are evaluated by an adaptive version of extended integral trapezoidal formula. The validity and accuracy of the proposed methodology and numerical integration scheme are confirmed by comparison with some existing results. Two different boundary permeabilities are considered, and the numerical results show that the influence of the boundary permeability on the dynamic response is related to the permeability of the soil and the moving load speed.

Deformation measurements from 17 real cases of excavation spanning subway tunnels in soft soil were collected for examining the deformation reaction of the tunnels due to the above unloading. The investigation showed that (1) tunnel may be uplifted owing to the above excavation; (2) the deformation of the tunnel section due to above unloading exhibits vertical elongation and horizontal shortening, and the transversal shape of the tunnel changes from approximate circle to vertical ellipse; (3) the main influential factors include the excavation unloading ratio (N), the excavation area (A), and the excavation shape coefficient (α). It indicates that, with the increase of excavation depth and the increase of unloading ratio (N) of foundation pit, the rebound of tunnels may increase, and the higher the width of the excavation, the larger the range of vertical uplift that will be induced around the tunnel. For 12 out of the 17 examined cases, the vertical uplift measurements of the tunnels are smaller than the alarmed value of 10 mm, indicating that the maximum displacement of the tunnel can be controlled by purposed engineering measures, such as pre-reinforcement of the soil around the tunnel, installation of the anti-pulling piles around tunnel, and stacking around the bottom of the excavation. 2-D FEM modelling was also carried out to study the effect of excavation characters and the effectiveness of the control procedures. The combination procedure of soil improvement by cement mixing and anti-pulling pile installation is verified to be effective to reduce the adverse impact from above excavation on tunnels.

A newly developed intelligent compaction method, automatic frequency control (AFC), has been tested in full-scale field tests. The technique utilizes measurements on the drum to determine the resonant frequency of the dynamic roller-soil system and provides continuous feedback to the roller for automatic adjustment of the frequency. This facilitates compaction at the resonant frequency, even for spatially varying soil properties. Previous tests have been conducted with simplified conditions in indoor full-scale tests and in field tests on low embankments. Those tests showed an increased compaction effect with higher surface stiffness that could likely reduce the number of required passes. This paper describes an additional field test, where a rock-fill embankment has been compacted under realistic conditions. The results confirm that compaction is conducted more efficiently when utilizing AFC, compared to conventional compaction. In addition, AFC increases compaction homogeneity, which provides an embankment less sensitive to rearrangement in the serviceability limit state. Implementing this novel technique can thus reduce costs and environmental impact.

Field fill materials often contain gravel particles larger than the allowable limit for standard laboratory compaction tests. In such cases, the maximum dry density (ρd)max of a material containing large gravels is obtained by correcting laboratory test results for specimens without large gravels. Usually, the Walker–Holtz (WH) method is used for this correction, but there are many materials whose gravel ratio (P) is 0.3 − 0.4, which is usually considered to be the application limit. Moreover, accurate stress-strain properties under field compaction conditions are necessary for relevant stability analysis of soil structures including embankments. However, with unbound granular materials, it is difficult to obtain undisturbed samples for laboratory tests or to carry out field shear tests. Also, large-scale triaxial compression tests on specimens containing large gravels are difficult to perform in ordinary engineering practices. In this study, a series of laboratory compaction tests were performed changing the maximum particle size (Dmax), compaction energy level (CEL) and P to examine the validity of the WH method and a series of drained triaxial compression tests were performed varying the Dmax and the degree of compaction. Based on the test results, a method to modify the WH method is proposed to properly estimate the (ρd)max value after adding or removing gravel particles when compacted at a certain CEL. Also, a method is proposed to correct the strength for a given gravel ratio to estimate the in-situ strength from the strength obtained from laboratory tests.

The conventional method of estimating the contact area of compaction rollers is based on simplifying assumptions such as the homogeneous and linear elastic behavior of the underlying compacted geomaterials. This study evaluates a stress-dependent approach for estimating the contact area of roller compaction considering the nonlinear behavior of compacted geomaterials. For this purpose, a finite element model was developed to simulate the roller compaction of unbound materials considering both the nonlinear behavior of geomaterials and the soil–drum interaction by means of using advanced contact algorithms. The contact area of the drum was estimated based on the stress distribution at the soil–drum interface for more representative pavement responses than those obtained from Hertzian models. The contact areas from this approach showed good agreement with those measured in the field.

In earthworks, testing using density ratio is applied widely in quality control. Density ratio tests take significant time for results to be reported. Yet because of its widespread usage, this now acts as an impediment to the development of alternative methods of testing. Modern geotechnical and pavement designs are based on modulus and strength values. It is, therefore, reasonable to investigate the use of alternative test methods which measures these parameters directly. Several in-situ devices have been available to industry for the past 2 decades and research has shown these have significant benefits. However, studies then try to corelate those measured parameters with the density ratio. Correlating to density is flawed. Given the poor correlations associated with relating density to other measured parameters an alternative approach was developed. This is based on matching probability density functions (PDFs) for quality assurance (QA). This methodology first recognizes density is normally distributed, but other more accurate tests are non-normally distributed. The derived best fit distribution is compared with the normally distributed density measurements. Data using a range of alternative testing equipment was used for this QA method of matching PDFs. The methodology has been successfully used on a major earthworks project in Australia.

Due to the impact of modern information technology, the construction of transportation infrastructure has entered the “Intelligent Era.” The conventional construction technology is also undergoing a paradigm shift. In this paper, the term “intelligent construction” is defined, and the status quo of global transportation infrastructure construction with emerging intelligent construction technologies is summarized. The framework of intelligent construction is presented on all aspects of the integration of modern information technology and the conventional highway technologies. The essential elements of intelligent construction include sensing, analysis, decision-making, and execution. Big data, machine learning, and expert system are applied to provide practical technical solutions for intelligent construction. This paper also elaborates on the process of intelligent decision-making and auto-feedback machine controls. Finally, the future development of intelligent construction is laid out. The globally coordinated efforts by the International Society for Intelligent Construction (ISIC) will help the leading development and implementation of intelligent construction into the future.

One of the main objectives of utilizing intelligent compaction (IC) technology is to increase the uniformity and consistency of compaction operation. In this study, intelligent compaction measurement values (CMVs) in a reclaimed base project in Route 117, Vermont were used to perform a geo-statistical analysis. Semivariogram models were constructed to investigate the spatial structure and uniformity of compaction during the first and second reclaimed phases. The uniformity of the compaction operation was evaluated using the semivariogram model parameters (range, sill, and nugget). Furthermore, the semivariogram models of in-situ spot measurements were generated to verify the suitability of different types of measurements in capturing the geo-spatial trends in pavement layers. Then, the spatial statistics of each measurement were compared to the univariate statistics. It was found that the data variance might be closely related to each other, but there is no relation between these values and the spatial uniformity of the compacted area. The results indicated that the spatial structures of both compacted layers (i.e., first and second reclaimed layers) were successfully captured through all three types of measurements, where the second reclaimed phase revealed a higher degree of uniformity. In addition, geo-statistical analysis of both reclaimed layers revealed a higher degree of uniformity in dynamic cone penetration index (DCPI) data compared to other compaction measurements. On the other hand, a relatively high degree of inconsistency observed among the CMV measurements. It should be acknowledged that the conclusions of this study are based on data from only one project, specific to the characteristics/conditions of that project.

Intelligent Compaction (IC) and Continuous Compaction Control (CCC) systems have seen major developments in recent years. The Institute of Geotechnics of TU Wien investigated established CCC systems for vibratory rollers and developed a novel system for work-integrated compaction control with oscillatory rollers. The various CCC systems in the market yield to numerous measurement levels and units with each manufacturer pursuing their own system. This has become a great challenge for contractors and authorities and resulted in a demand for a single measure to be able to combine and compare results from different rollers. The theoretical basis and differences of common CCC systems for vibratory and oscillatory rollers are explained in the paper. Moreover, experimental field tests have been performed with a tandem roller with vibratory and oscillatory excitation. Five different CCC values—CMV, Omega, Evib, kB and CCC for oscillatory rollers—were evaluated based on acceleration measurements. The results of the theoretical and experimental investigations are presented and compared to create a better understanding of why results of different CCC systems or rollers cannot simply be converted into each other.

Intelligent compaction (IC) is an emerging technology for efficient and optimized ground compaction. IC combines the roller-integrated measurements with the Global Positioning System (GPS), which performs the real-time quality control and assurance during the compaction work. Indeed, IC technology is proven to be capable of providing a detailed control system for compaction process with real-time feedback and adjustment on full-area of compaction. Although roller manufacturers offer typical recommended settings for rollers in various soils, there are still some areas needing further improvement, particularly on the selection of vibration frequency and amplitude of the roller in soils experiencing significant nonlinearity and plasticity during compaction. In this paper, the interaction between the road subgrade and the vibrating roller is simulated, using the three-dimensional finite element method capturing the dynamic responses of the soil and the roller. The developed numerical model is able to simulate the nonlinear behavior of soil subjected to dynamic loading, particularly variations of soil stiffness and damping with the cyclic shear strain induced by the applied load. In this study, the dynamic load of the roller is explicitly applied to the simulated cylindrical roller drum. Besides, the impact of the frequency and amplitude on the level of subgrade compaction is discussed based on the detailed numerical analysis. The adopted constitutive model allows to assess the progressive settlement of ground subjected to cyclic loading. The results based on the numerical modeling reveal that the roller vibration characteristics can impact the influence depth as well as the level of soil compaction and its variations with depth. The results of this study can be used as a potential guidance by practicing engineers and construction teams on selecting the best choice of roller vibration frequency and amplitude to achieve high-quality compaction.

Use of intelligent compaction (IC) is a growing technique for compaction in the field of construction. It provides an efficient way of evaluating the soil compaction level with a higher degree of certainty than traditional quality control methods. IC involves the interpretation of measured values received through the accelerometer and other sensors attached to the roller. The key objective of this paper is to analyse the dynamic roller–soil interaction via a three-dimensional nonlinear finite element model, capturing soil nonlinear response and damping in both small and large strain ranges as a result of dynamic load applied via the vibratory roller. In particular, the impact of soil plasticity index (PI) on the response of a typical vibratory roller is assessed. Indeed, the soil plasticity impacts stiffness degradation with shear strain influencing the soil stiffness during compaction and the roller response. The numerical predictions exhibit that the soil plasticity can significantly influence the response of the roller and the ground settlement level; hence, practising engineers can consider the soil plasticity index as an influencing factor to interpret the intelligent compaction results and optimize the compaction process.

In recent years, a geothermal heat pump de-icing system (GHDS) has been introduced as an alternative for conventional snow and ice removal systems (CSRS). Application of the CSRS for bridges highly prone to ice formation is not a satisfactory solution as it has a negative impact on the environment, bridge deck condition, motorist safety, and travel time. Although GHDS has proved to be a sufficient and feasible solution, it is only applicable to new bridges. However, a new method of GHDS has been developed which utilizes an external hydronic pipe attached to the bottom surface of the bridge deck and is applicable even for existing bridges. In this study, the performance of the external hydronic heating system, installed and tested on the full-scale mock-up bridge deck, was investigated in Texas. The system has experienced several cold events and de-icing tests, in which it was successful in maintaining the surface temperature above freezing. However, the results show the system is capable of de-icing the bridge deck and provide an ice-free surface. In order to enhance the de-icing operation, the system requires about 8 h of preheating; however, less time is required during mild events. Furthermore, the system is energy-efficient with a coefficient of performance (COP) of more than 4.

It is critical to accurately predict the seismic compression of backfill soils supporting bridge decks, pavements, or railways as small backfill settlements may have substantial impacts on the performance of these overlying transportation systems. Although several studies have evaluated the seismic compression of loose unsaturated soils, there has not been significant focus on the seismic compression of denser soils. This study presents the results from series of strain-controlled cyclic simple shear tests performed on unsaturated sand specimens having different initial relative densities and initial matric suctions representative of near-surface backfills. Although the seismic loading process may involve rapid, undrained shearing, the cyclic simple shear tests were performed in drained conditions with a slow shearing rate to isolate the effect of matric suction. The results showed that soils with higher initial suctions (or lower initial degrees of saturation) experienced smaller volumetric strains, but the effect of suction (or degree of saturation) decreases as the relative density increases.

The Japanese road authority specifies that, in designing pavement subgrade, non-frost heaving materials shall be used for 70% of the frost penetration depth of the subgrade. However, some concrete pavements in snowy/cold regions have been found to have cracks that are categorized as structural damage caused by frost heaving. To examine the necessity for revising the subgrade design, an onsite survey to clarify the frost damage of concrete pavements and an evaluation of the impact of frost heaving on the lifespan of pavements by using FEM analysis and fatigue calculation were conducted. It was estimated from the onsite survey that the void between the concrete pavement and the subgrade, which was generated by frost heaving, would reduce the lifespan of the concrete pavement. To clarify this point, an FEM model was created to reproduce the frost heaving and an analysis was done using this model. In the analysis using the model that reproduced frost heaving, the tensile bending stress due to wheel loads at the bottom of the concrete slab increased. The pavement life was obtained in a fatigue calculation that incorporated the increase in tensile stress. The result was that a concrete pavement had structural cracks in a short period of a few dozen days after it experienced frost heaving. Based on these findings, we propose that, in designing concrete pavement subgrade in snowy/cold regions, it may be appropriate to use non-frost-heave-susceptible materials for the entire frost penetration depth.

Soil anisotropic strength and strain behavior under principal stress rotation, caused by traffic loading, have been widely studied, while anisotropic permeability is of little concern. Large settlement will be induced by consolidation or secondary consolidation of soft clay, particularly for reclaimed clay. Permeability behavior is thus very important. Since current experimental setups do not take into account the influence of dynamic loading on the permeability of soil, hollow cylinder apparatus (HCA) was modified so that it can be utilized to determine the hydraulic conductivity of clay. HCA is usually used to simulate complex stress paths and to determine anisotropic strength and stiffness of soil under different directions of major principal stress. As no permeation experiment has been conducted by HCA before, firstly this paper proposes the test procedure for measuring the hydraulic conductivity of samples. Then, a series of permeation experiments under different K0 consolidations were conducted. Horizontal and vertical permeabilities were measured before and after traffic loading. Experimental results show that under K0 consolidation condition, the anisotropic permeability of remolded kaolin increases with the applied axial stress in spite of the same K0 value. Hydraulic conductivity decreases in both vertical and horizontal directions after traffic loading. Dynamic load has a greater impact on permeability behavior in its main consolidation direction, which leads to an increase in the anisotropy ratio of permeability. Findings in this paper will help understand the settlement and uneven settlement of embankments in soft ground, where permeability is normally regarded as a constant.

The main geotechnical aspects of the southwestern Brazilian Amazon are the absence of rocks to provide gravel for pavements and the widespread occurrence of expansive soils along the natural subgrade, associated with high rainfall indices. Although most of the local soils are rich in 2:1 clay minerals and amorphous material originated from Andes volcanic ashes—which is quite different from other Amazonian soils—geotechnical studies about the behavior of these materials are still very limited. The high volumetric variation of these expansive soils has been causing financial losses and making transportation by land difficult in the region. This paper presents the case study of a pavement built over expansive subgrade in Rio Branco city, state capital of Acre. Disturbed and undisturbed samples were collected in order to evaluate the swelling parameters of the soil. A suction-based model from Texas A&M University was used to predict pavement roughness caused by both expansive soils and traffic. The results showed the high swelling potential of the samples and the importance of developing a methodology for the control of expansive soils when building over these materials at the studied site.

This paper presents results from permanent deformation tests carried out on fine tropical soils in order to study the effect of moisture variation. Shakedown limit was defined through repeated load triaxial tests under different stress states for 5000 load cycles. A mathematical model to classify permanent deformation behavior proposed by Werkmeister (Doctoral thesis, Technical University of Dresden [Werkmeister S (2003) Permanent deformation behavior of unbound granular materials in pavement constructions. Doctoral thesis. Technical University of Dresden, 189 pp]) was used to rank the shakedown limit of the materials. In this research, a lateritic clayey soil, according to the classification MCT (Miniature, Compaction, Tropical) from Nogami and Villibor (Brazilian Simposium of Tropical Soils in Engineering. Rio de Janeiro, RJ, pp 30–41, [Nogami JS, Villibor DF (1981) Uma nova classificação de solos para finalidades rodoviá-rias. In: Brazilian simposium of tropical soils in engineering, Rio de Janeiro, RJ, pp 30–41]), was tested in the optimum content and at the high moisture induced by capillary post-compaction. The resilient behavior was studied to characterize the mechanical behavior of the material. The results of permanent deformation tests showed that fine tropical soils may have a nonsignificant reduction of their shakedown limit, with the increase moisture of 1%. The proposed model showed a good agreement for this tropical soil at an optimum moisture. The understanding of the shakedown phenomenon from tropical soils may help to bridge the gap between the materials accepted by traditional classification and those not accepted, although they present good mechanical resistance.

Volumetric water content (VWC) and matric suction vary temporally in the foundation layers of pavements and railways due to various influencing environmental factors. The resilient and permanent deformation behaviors of railway foundation materials are strongly linked to the suction within the soil, reinforcing the need for the measurement thereof. This paper reports on the installation of VWC sensors, tensiometers and fixed-matrix soil-water suction sensors in different configurations within the foundation layers of a new 26 tonne/axle railway line near Ermelo in South Africa. Local weather data was recorded using a weather station at the site. The VWC sensors and the fixed-matrix soil-water suction sensors also monitored soil layer temperature. The measurement techniques used are critically compared with regard to their ability to respond to weather events. Practical aspects pertaining to the installation procedures and maintenance required for the different techniques are also reported. It was found that tensiometers require careful consideration to ensure pore-water continuity when installed in the field. Nonetheless, tensiometers were the most reliable and accurate form of measurement in this study. The use of VWC sensors to infer suction in silica flour is a novel idea. However, this method showed limited success in this study. Fixed-matrix soil–water suction sensors provided the best long-term stability and ease of installation. However, the accuracy of these sensors requires further investigation.

Water content is one of the causes of railway tracks’ poor performance. Implementing its effects into design and management numerical tools is not always straightforward because the relevant descriptive partial differential equations (PDEs) involved are highly nonlinear. The paper describes the creation of a surrogate model to predict water flow in rail-track layers or other multilayered systems, increasing performance of conventional 2D and 3D models so as to enhance their utility and validity for rail-track maintenance management. The model takes advantage of the mainly 1D vertical direction of infiltration through unsaturated layers and the mainly 1D horizontal direction for saturated flow in the lower layers to create an assemblage of one-dimensional domains using a co-simulation technique. Mathematical formulation is included for both of the 1D simulations and for the assemblage. 1D models are verified, and some results of the assembled model are compared with existing experimental results. Available results suggest a suitable predictive model for multilayer flow.

Climatic events such as precipitation result in unbound structural layers of pavements being in a partially saturated condition during their service life. With unsaturated testing being relatively complex and costly, the presence of relatively low matric suction in granular geomaterials, practitioners have been reluctant to explore the utilization of unsaturated geomechanics in the analysis and design of the mechanical behavior of pavement structural layers. In this research, unsaturated mechanical characteristics of three types of recycled geomaterials were firstly investigated using repeated load triaxial testing and the incorporation of their soil–water characteristics in the analysis of their resilient moduli response. This was to demonstrate the importance of understanding the unsaturated mechanical behavior of compacted granular material. Next, a virgin compaction surface (VCS) was developed within a moisture content-based framework to interpret the loading, unloading and wetting-induced volume change of the compacted materials. Outcomes of this research, for the first time, extend the application of the well-established Monash Peradeniya Kodikara (MPK) framework, originally developed for fine cohesive soils, to granular materials. A distinctive attribute of the proposed approach is the relative simplicity in the testing methodology by utilizing the conventional geotechnical testing equipment. The findings of this research can be used for estimation of the settlement of a granular structural layer that is compacted, loaded and then wetted through precipitation or flooding.

There is a need for rational methods to estimate behavior of unsaturated soils for analysis and design of pavement structures. The attributes of a desirable method would comprise low cost, reasonable accuracy and technical soundness. The equilibrium suction has a direct influence on the subgrade resilient modulus and vertical movement due to swelling and shrinking of expansive clays. The current AASHTOWare Pavement ME software package utilizes the enhanced integrated climatic model (EICM) for applying the effects of climate on the pavement materials. The EICM utilizes the depth to groundwater table to compute moisture content and the corresponding suction in the subgrade. However, research studies have revealed that other critical factors also influence the equilibrium suction. In this study, a mechanistic model is presented to predict equilibrium suction considering the effects of the unsaturated soil moisture diffusion coefficient. Based on a statistical analysis, an equilibrium suction prediction model is generated from readily available parameters, i.e., Thornthwaite moisture index (TMI), clay content (%) and relative humidity. The results of this study showed that the regression model provides reasonable prediction accuracy with a small test MSE of 0.03.

About 6 million tons of steel slag are generated in Germany every year during the production of steel. About 14% of them is landfilled due to some technically or environmentally relevant properties. Nevertheless, increasing costs for the deposition on landfills make their use in earthworks for transportation infrastructure more and more attractive. The utilization of steel slags in earthworks seems to be promising due to their advantageous mechanical properties but requires the protection of soil and groundwater against possible exposure to leached substances. Several construction methods in earthworks are described in a recommendation (M TS E) of the German Road and Transportation Research Association, where soils/materials with environmentally relevant substances can be used with additional capping systems, and without additional liners if they are of low permeability, respectively. Thus, experimental investigations were carried out to study how the permeability of steel slags could be reduced by the addition of clay powders. In order to analyze the seepage flow through earthworks built of such materials, their saturated and unsaturated hydraulic properties have to be determined. These include the coefficient of permeability kf, the unsaturated hydraulic conductivity function and the soil–water retention curve, which have been determined carrying out various tests, among others one-dimensional evaporation tests. Based on the experimental results, numerical simulations with the finite element software Seep/W were performed to study the percolation of an embankment section built in a lysimeter. The results showed that the percolation of mixtures of steel slag and clay is low.

High-speed railways will be exposed to high water level caused by extreme water conditions, such as floods and heavy rainfall, which may influence the soil structure of roadbed, leading to excess accumulative deformation under dynamic train loads. The development of uneven deformation of railway track will then exacerbate the wheel–track interaction, which in turn accelerates the degradation of high-speed railway roadbed and jeopardizes the safety of train running. To verify the long-term performance of high-speed railway road under various water level conditions, a full-scale physical model of a ballastless railway and a sequential loading system were developed which can simulate train moving load at speeds up to 360 km/h. Water level in the physical model can be raised and lowered with a water level control system. Train moving loading tests were carried out at three typical water levels: at the subsoil bottom, at the subsoil surface and at the subgrade surface. In each water level condition, three different train velocities: 108, 216 and 360 km/h were simulated for a certain number of cyclic loads. Some results of dynamic pore water pressure are presented in this paper.

A series of undrained torsional shear tests were conducted to investigate the variation of excess pore water pressure of saturated sand during undrained cyclic loadings. The test results indicate that there is a threshold of cyclic stress ratio for specimen to reach liquefaction. Above the threshold, the excess pore water pressure gradually increases during undrained cyclic loading and is eventually equal to the initial effective confining stress. The double amplitude of shear strain also increases gradually, showing a weakening development of the shear strength of the specimen. Beneath the threshold, the excess pore water pressure stops increasing eventually regardless of how many cycles are applied. Moreover, the excess pore water pressure rises sharply just after the reverse of the loading direction, which suggests that an evident tendency of negative dilatancy is accordingly induced. The excess pore water pressure cannot always increase with the shear stress, and it decreases when approaching the phase transformation line. Based on introducing a variable that is defined as the increment of the excess pore water pressure during a unit variation of the shear strain, the tendency of volume change of the specimen can be well represented.

The soil–water characteristic curve (SWCC) defines the relationship between water content and matric suction in soil, which contains fundamental information needed for the hydromechanical behavior of expansive soil that generally lies within the unsaturated soil mechanics framework. Moreland clay is highly expansive soil abundant in northern Louisiana, part of Arkansas, and Oklahoma. Unsaturated soil properties for shear strength, permeability, and volume change are needed to identify expansive soil-induced stresses on pavement or railroad track due to seasonal variation of moisture content in the subgrade layers. Determination of the two critical variables obtained from the SWCC, i.e., the air-entry value (AEV) and the residual state suction, is essential for the prediction of unsaturated soil deformations. In this research, an experimental testing program was conducted on the expansive Moreland clay to investigate the soil–water retention properties by adopting the axis translation technique to control suction in the range of 0–1500 kPa. A computer program was developed to fit experimental data, and it was compared with predicted SWCC using empirical relationships. The AEV and the residual state suction, two critical variables, were obtained from the SWCC formulation of Fredlund and Xing equation. Finally, the shrinkage curve was determined to interrelate between elastic deformation and SWCC of Moreland clay.

The stability of transportation infrastructure can be affected by seasonal rainfall infiltrated adjacent excavations and natural slopes. The paper investigates the rainfall-induced deformation of an anchored excavation constructed in unsaturated soils. An advanced constitutive model based on the theory of bounding surface plasticity is employed to predict the behaviour of partially saturated soils. The collapse characteristics of unsaturated soils due to wetting are captured in the model by introducing a suction-dependent hardening law. The proposed model has been implemented in a finite difference code with a two-phase flow and deformation formulation. In the numerical algorithms, the validity of the effective stress principle in unsaturated soils is emphasized and the coupling between various phases of porous media has been considered. The problem of an anchored excavation subjected to rainfall is then simulated with the implemented model. The lateral deformation of the supported excavation during the infiltration of water into unsaturated collapsible soils is obtained and compared with the case where the plastic collapse is prevented. Finally, the effect of anchors on minimizing and changing the mode of the deformation is explored.

Seasonal frozen ground is mainly distributed in the north of 30°N, with an area of 5.137 million km2, covering approximately 53.5% of the national territory in China. In recent years, with the rapid development of Chinese railway, many lines have been built passing through seasonal frozen areas. At the same time, with the increase of traffic volume, transport capacity would become larger year by year, so the requirements of low frost heave for the subgrades would also be made more stringent. Based on the stress release holes (SRHs), several special experiments are designed and implemented in a one-dimensional freezing condition from a sample’s top to bottom, which are targeted to verify the effectiveness and feasibility of SRHs on decreasing frost heaves. Also, a measure to decrease frost heave of subgrade filler in seasonal frozen area is proposed. There are seven laboratory tests carried out in the open system. And the frost heave effect of saturated soil samples within 72 h was explored with a certain HRA set as 4% and SRHs filling materials.

Environmental actions and geotechnical characteristics are vital in the global behavior of railroad track. Climate, can be crucial to railroad geomaterials behavior, especially in tropical regions. In addition, railroad track behavior depends on water content, retention, and suction pressure over time, being dependent on geotechnical characteristics. These aspects directly influence the amount of water available to infiltrate into the soil, which can percolate or be retained, modifying its water content. Thus, unsaturated soil mechanics should be applied to assess climate–track interaction. This paper evaluated the unsaturated hydraulic response of a railroad track profile in Brazil considering fouled ballast under tropical climate conditions through laboratory tests and numerical simulations. Physical–hydraulic tests were performed with railroad track materials. A numerical FEM model was developed to evaluate the infiltration/suction profile and to quantify drainage, considering laboratory results, distinct fouling levels, and seasons. The results reveal that the hydraulic analysis of the track must consider the unsaturated condition of the materials, which will help to understand the ballast fouling influence on track in terms of hydraulic concerns. Significant suction variation was observed in the subballast when fines are strongly present. Thus, the presence of a fouled layer reduces water transfer to the subgrade due to its water barrier effect. Additionally, in the wet season, suction decreased over the fouled ballast in contrast to the one verified in the dry season. Water balance on the fouled layer surface showed an important amount of runoff, in contrast to the dry period, when a water deficit and high suction values were predominant.

Frost heave is a long-recognized issue contributing to the railway track upheaval in cold regions. Generally, frost heave is believed to happen in the subgrade layer of transportation infrastructure, referred to as the volume expansion of frozen soils, which are susceptible to frost action with the presence of moisture. The aggregate layer, such as highway base course or railroad ballast, is believed not to be prone to the frost heave due to its large void ratio and low capability to hold moisture content. However, recent reports around the world, such as Norway, USA, China, and Japan, etc., indicate the frost heave does happen in the ballast layer even when the moisture content is low. Existing literatures, which often believe track upheaval should not happen on aggregate like ballast, cannot well explain the recently observed phenomenon. In this study, the researchers conduct a series of laboratory experiments aiming to identify the possible reason that cause ballast frost heave in a well-controlled environment. Clean ballast is prepared with different moisture conditions, including half submerged condition and fully submerged condition. The growth of ice and movement of particles are tracked and qualified through image analysis. The findings from this study provide evidence to prove the effect of ice formation on ballast and would help to explain the root cause of ballast frost heave.

It is a common practice to use traditional criteria in the selection of materials in railway paving projects as well as the use of optimum moisture in pavement design through the California Bearing Ratio (CBR) method. However, variations in the weather can change the conditions of the infrastructure components over time, especially of the railway tracks since they have no coating and thus are exposed to the elements. These criteria, based only on the mechanical behavior of materials, are not adequate to evaluate the tropical soils and their hydraulic behavior so that soils with good performance can be discarded if more efficient criteria of analysis are not adopted. Therefore, the main objective of this research is to evaluate the variation of humidity over time in the railway platform when subjected to the action of rainwater for five different soil types when used in the sub-ballast layer, from the numerical–experimental analysis, considering as reference case the infrastructure of the Carajás Railway. For this purpose, tests were carried out on the HYPROP and WP4-C equipment in order to obtain the retention and hydraulic conductivity curves of the studied soils. The hydraulic functions in question were performed with the help of the IVFlow program and the input parameters such as section type, precipitation of the region, as well as the van Genuchten hydraulic model as a constitutive model. The results revealed that sample 1 (LS) has the best performance in the presence of water and is suitable for employment in the sub-ballast layer. The other samples presented unsatisfactory results.

A numerical analysis on the stability of soil–cement column-reinforced riverbank along a river delta region in Viet Nam is presented in this paper. The numerical analyses based on the limit equilibrium method (LEM) were performed to assess the safety factor of the column-reinforced riverbank system under various river water level (RWL) conditions. Several factors influencing the riverbank slope stability including the position, length, quantity of soil–cement columns, and RWL changes were investigated. The simulated results showed that the riverbank stability is improved with an increase in the column quantity and the column length when subjected to a constant RWL. Moreover, the predicted results by LEM indicated that the column location and the RWL change significantly influence the stability of riverbank with column reinforcement. The column location between the middle and the slope toe had a significant improvement of the riverbank slope stability, where an initial drawdown of RWL resulted in a notable reduction of the riverbank slope safety factor. These factors should be taken into consideration in the design of a riverbank slope, reinforced with columns, under variable RWL. It is worth mentioning that the use of soil–cement column-reinforced riverbank could be a practical and possible engineering countermeasure to prevent a steep riverbank slope under RWL variations from sliding failure.

A cloudburst and flash flood in June 2013 in the state of Uttarakhand, India caused landslide at Govindghat located along a major highway. Large boulders in soil matrix were encountered in the area. Water seeping through the open pores between the boulders and erosion of the soil was the major causes of the slope-failure. Erosion of the accumulated debris on the valley side during periods of high discharge in the area also added to the instability. The stabilization measures adopted include a secured drapery of rock anchors and steel mesh on the hill side, nailed gabions at road level, reinforced soil wall to ensure the desired road width, and river-side gabion wall for erosion protection.

The geotechnical stability design for cantilever retaining walls is often determined by a factor of safety expressed as a ratio between resistance and disturbing load. Many variations of this ratio exist, but most consider the disturbing load extending to the toe level of the wall. Questions are asked: Is the earth pressure a load or a resistance, particularly for the part of wall that penetrates beyond the critical depth at which the wall is at critical rotational equilibrium, and if it is not a load then what is it? The quest to the answers has led the author to formulate the ‘What You Design Is What You Get’, the WYDIWYG model, for stability design of propped cantilever walls. The new design method is shown to be consistent, numerically stable for all soil conditions. The formulation is suitable for Load Resistance Factor Design (LRFD) method, and it allows the Factor of Safety (FoS) to be expressed in terms of the wall critical restoring capacity. For example, the wall designed with a FoS of 2 using this method will have two times the restoring capacity at critical equilibrium, and what you designed is what you get. The calculated FoS can be meaningful and easily comprehensible. The new method could provide a platform for designers to compare between cases and assess adequacy of the level of stability with improved certainty. A worked example is included to demonstrate simplicity of the calculation process.

This paper presents a computational framework to assist in maintenance planning for geotechnical structures. The most suitable maintenance strategies are determined by optimization regarding the deterioration of structure and the cost of maintenance when satisfying constraints that translate demands for adequate levels of service. Uncertainties are accounted by considering model parameters as random variables. The framework is applied to the case study consisting in optimal maintenance planning for a highway slope belonging to the Portuguese network. The obtained results show the validity and usefulness of this framework. The framework can be also applied to different types of infrastructure assets.

With slope movements man does not encounter every day, but it should be noted that this happens, and it happens more often. These movements are influenced only by two factors, namely nature and humans themselves. Slope deformations are one of the most widespread and to some extent one of the most dangerous country geohazards and represent significant geobarriers to urbanization planning. With gradually expanding populations comes extensive and demanding technical works built in increasingly complex and less favorable geological conditions. In complex geological conditions, it is mainly about understanding the overall geological environment with the development and effectively designing geotechnical structures to ensure long-term stability. The term effective design encompasses a set of geotechnical construction, which complement each other, so that their final effect has the desired influence. In this paper, we have attempted to describe ways of determining global stability, which is directly conditional on the building progress of stabilizing construction. This procedure creates and directs geotechnical engineers. Any change in construction has an impact on the global calculation, which should be adapted and subsequently verified. This calculation also influences new geological and geomechanical conditions that are specified by the construction process. Contractors may skip these essential steps, due to time and cost skips and thus embarks on the risky work, often with fatal consequences.

Expansive clayey soils undergo significant volumetric changes, and desiccation cracks develop due to wetting and drying cycles. The presence of desiccation cracks changes the soil's hydro-mechanical properties and allows rapid infiltration of rainwater to the underlying deeper layers. The abrupt increase in moisture content and swelling reduces the soil's peak strength to fully softened strength. Consequently, these slopes experience shallow failures that are approximately parallel to the slope surface. The purpose of this study is to assess the impact of weathering cycles by studying the failed highway embankment slope located in Denison, Texas. The experimental laboratory studies, including direct shear test, fully softened strength test, soil water characteristic curve, and soil hydraulic conductivity tests, were conducted on samples that were collected from scarp of the failed slope. A comprehensive inverse analysis was conducted using a finite element method-based software package. The analyzed results suggest that the surficial slope failure was attributed to (i) the formation of desiccation cracks, (ii) increase in soil permeability, (iii) reduction in shear strength, and (iv) the formation of the perched water table in the weathered surficial soil during intense rainfall events.

The use of grass to protect the slopes from erosion of road embankments is a common practice. However, quantifying the changes in shear strength of such bio-structured (with grass roots) soil is a complex procedure. One of the important factors affecting the shearing resistance of such soils is the direction of grass roots with respect to the slope angle. An experimental investigation was taken up to quantify the changes in shear strength of soil due to the direction of grass roots. Direct shear tests were conducted on field samples from a slope with grass roots and compared with remolded samples without roots. The field samples were obtained by pushing the samplers in a sloping ground in vertical, horizontal, and in 45 ° inclination. Direct shear tests were conducted on these samples by keeping the direction of the roots in perpendicular, parallel, and inclined to the failure plane during the direct shear test. Thirty-five samples were tested with in-situ moisture content, and fifteen samples were tested in saturated conditions. For the samples tested with in-situ moisture conditions, the test results indicate that the soil with the vertical and inclined root direction experienced a similar overall increase in cohesion and a near negligible change in friction angle. However, the samples with roots parallel to the failure plane experienced the least increase in cohesion in comparison with the other two root directions. A similar trend was observed for the samples tested in saturated conditions. Additionally, slope stability analysis was performed using software SLIDE (version 7) to determine the effects of the root direction on the factor of safety.

This communication analyzes the latest experiences in slope and foundation drainage and runoff water management to improve resilience in roadway infrastructures. The actions resulted from temporary rain and adverse weather conditions during the months of January and February 2012 and 2013, which caused singular damage to several road slopes in Northern Spain. The objective of the repair was to restore road safety and road stability. Regarding runoff water, heavy rains cause loose and scattered stone movements along the slopes of the La Hermida Gorge and in the limestone rocky massifs that make up the Gorge. There are also many karst caves exiting that load their levels to the fullest and produce impressive waterfalls on the road. The energy of these waterfalls was dissipated, and the water curtain was channeled into the Deva River through an innovative solution. With regard to the drainage of slopes and foundations, the action carried out on the slope of the A-8 motorway includes its stabilization by biological engineering. All the actions presented in this article have proven to be valid throughout the last year of road operation. Furthermore, the monitoring system used in full-scale tests for dynamic barriers according to ETAG-27 is reliable to better understand the force transmission mechanism and also for future design purposes.

This paper presents the study of a slope stability failure due to a roadway widening using an FEA program. It consists of a case study of static load induced liquefaction in a simple roadway widening project constructed in the north eastern part of Ohio in 2008. The widening required an embankment fill, which moved nearly 4 feet vertically and 1 foot laterally after days of installation. The main objective of the work is to compare different approaches dealing with this static liquefaction situation; in this case, limit equilibrium method (LEM) and finite element analysis (FEA) method are being studied. The use of two approaches is important to show how the results can be compared and to determine the reliability of the factor of safety (FS). The mechanism that caused the rotational slope failure was the liquefaction of sand layers beneath the road embankment. The study explains how this loose sand layer could be simulated with the use of FEA which provides an advanced tool to perform a more complete and accurate analysis. The study concluded that each method has its advantages and limitations; however with the use of FEA, it was possible to build a more realistic model since advanced material model and properties could be defined which are more adequate for such cases as liquefaction in sands.

This paper summarises work to evaluate the effectiveness of innovative geotechnical repair techniques for Highways England’s slopes. The techniques assessed were live willow poles, fibre reinforced soil (FRS) and electrokinetic geosynthetics (EKG) used in place of conventional approaches in order to reduce the overall impact of various challenges including environmental constraints (habitat and visual), access and utility constraints, and the need to reduce the scale and/or cost of traffic management and traffic delays. Trials of these techniques have been undertaken over the last 20 years or so, but monitoring was generally limited to just a few years post-construction; longer-term evaluation has not generally been undertaken. This paper presents a summary of the assessment of the effectiveness of live willow poles, FRS and EKG as aids to increased stability. The success, or otherwise, of the techniques led directly to recommendations for future use ranging from the development of design guidance and specification information for willow poles, guidance on the execution of further trials of EKG, to the cessation of use of FRS. The results of a life cycle assessment (LCA) are reported, and more generic lessons learnt from the trials and the practical application reported were used to produce guidance for future trials of innovative geotechnical repair techniques.

A section of the recently completed Hunter Expressway in the Hunter Valley, Australia, traverses steep side sloping topography covered by colluvium overlying weathered coal measures rocks. The rock mass contained seams of very low-strength and highly moisture-sensitive tuffaceous claystone interbedded in sandstone, siltstone and coal. The blocky and transmissive sandstone beds overlay the weaker, aquiclude siltstones and claystones creating a geological terrain vulnerable to rockfalls, surficial colluvium instability and deeper translational failures on the slope next to the alignment. The design of the motorway vertical alignment required a 10 m high reinforced soil wall (RSW) to retain the fill on the downslope side. Foundation works for the RSW were an early construction activity in the area. The construction of the RSW involved a large foundation excavation into the colluvial capped slope which had the potential to destabilize global stability of a marginally stable slope whilst boulder fall hazards presented both a construction and operational risk to be managed. Therefore, the construction of the RSW foundation was assessed as a high-risk activity. The team had to deal with challenges of additional hazards associated with inclement weather during excavation of the foundation. This paper discusses how the risks and challenges were successfully managed during construction through a broad range of mitigation measures including implementation of a responsive design development strategy, stakeholder engagement, on-site close geotechnical engineering oversight and staging of works which led to good design outcomes and allowed the works to be completed without any occurrence of slope instability or safety incident.

Having the aim of promoting the application of BIM—Building Information Modeling—in the railway sector, this paper’s main objective is to analyze the BIM implementation in the particular case of rail track rehabilitation and inspection. BIM enables the computational development of projects during their lifecycle including all the phases. Three-dimensional (3D) modeling using Civil 3D® software was applied to the rehabilitation of a rail track in service. The following tasks were carried out: (1) the modeling of the geometry of the railway infrastructure; and (2) the capacity analysis to extract diverse information from the model, in particular the geometric parameters of the rail track: gauge and transversal leveling. Revit® software was also used to model the project. Families were created relating to the sleepers and fastenings and to the rails. Other rail track components, such as the ballast, sub-ballast, geosynthetics, and foundation, were generated as slab layers in the infrastructure component. In order to create a four-dimensional (4D) model that includes the time factor, Navisworks® software was used. The 4D model allows for simulation of the rehabilitation sequence of the rail track, including the application of geotextile and geogrid under the ballast layer. It was concluded that the use of the 3D model can present limitations to the implementation of the BIM methodology, particularly with respect to interoperability in the transference of models between softwares. Regarding the inspection and maintenance of the rail track, some limitations were observed in the storage and processing of relevant information.

To prioritise and optimise mitigation with sustainable and value engineered solutions, a targeted asset management (TAM) regime has been established. The early stages have been successfully implemented at an embankment site at Wrabness in Essex which has experienced long-term instability issues. The site is located on sidelong ground leading to the Stour estuary with evidence of natural mass movement and drainage issues. Temporary mitigation, including local toe weighting and drainage improvements, has helped to control slope movements. Detailed geomorphological mapping, interrogation of ground investigation data, slope instrumentation data, and review of track monitoring data have allowed development of good ground models and understanding of geotechnical issues. Early ecology surveys, upfront preliminary designs and site risk zonation have enabled network rail to plan budgets and decide on the works in each five yearly funding cycle.

The paper presents the results of the development of integrated technology engineering and geological surveys and design foundations. It is shown that the currently existing information systems for data transmission and processing, information measuring systems allow not only to manage the process of testing soils and process test data, but also to simultaneously perform calculations of the deformation and strength of the foundation. Modern methods of field research of soils, such as static, dynamic and boring sounding, allow to obtain continuous information about the physical and mechanical properties of soils in depth and rather cheaply with an increase in the number of test sites within the studied survey area. The recording of sensing parameters data can be performed at any depth interval. Using known or local correlation equations and sounding data, soil depth characteristics are found. Further, the calculated values ​​of the characteristics of the soils are determined, and then, the deformations and strengths are calculated directly in the field conditions during the soil sounding process. The proposed complex technology combines engineering and geological surveys and the design of building foundations into a single production process. The result is a reduction of the survey time due to the application of soil sounding methods with automated control of the test process and interpretation of test data. In this case, the results of engineering and geological research provide not only information about the properties of soils, but also an assessment of their influence on the behavior of the designed building or structure.

One of the major challenges for modern society is to continue providing sustainable, affordable, and available transportation networks for people and goods. The challenge is twofold: (1) new structures should be built in a more resilient and a more durable and affordable manner, and (2) existing structures need to be maintained, retrofitted, or reset for a new purpose. Over recent times, different visions for improving transport engineering in these areas have been defined in Europe. Like many transport and geotechnical engineering platforms, European Large Geotechnical Engineering Platform (ELGIP) declares the readiness of the field of geotechnical engineering to contribute to the realization of these visions. The focus is on both engineering approaches and those which are helping to add a new dimension to Earth Structures in transport engineering—sustainability, availability, and affordability. This paper describes some opportunities that are currently on offer in this field. In Europe, the engineering approach is recorded in EC 7—Eurocode 7 in which the principle of limit state design was accepted, and the geotechnical categories classification is used. The second generation of EC 7 is now undergoing the final phase of preparation. The question on how to consider sustainability in Earth Structures in Transport Engineering is covered by describing geotechnical solutions for reducing energy and resource consumption. Moreover, proactive measures to guarantee transport infrastructure availability and affordability under extreme circumstances (e.g., natural and man-made hazards) are discerned. In conclusion, this paper explains why geotechnical engineering should devote appropriate attention to the use of the building information model (BIM) for Earth Structures in Transport Infrastructure generally.

The French rail network comprises more than 30 thousand kilometers of lines with over 15,000 trains running each day. Most of the lines are more than 100 years old. As a result, the rail network is aging due to natural wear and tear of the materials and environmental conditions despite regular maintenance. Various and non-necessary optimized maintenance practices, either extended or localized, to improve the condition of the railway lines are carried out every day. Besides, accurate knowledge of the substructure condition is necessary to assess the quality of the track line. In order to (a) improve the network performance, (b) increase the traffic on this network, (c) maintain a high level of safety, and (d) improve the comfort and accessibility of infrastructures, the French railway company SNCF planned to use a holistic assessment approach for the rehabilitation and modernization of hundreds of kilometers of rail lines. The results obtained in the studies showed that it is possible to carry out an optimal classification of railway sections which require a structural reinforcement of the platform, propose drainage rehabilitation, or complementary investigations for better decision making. The crossing engineering domain described here has included procedures for assessing the optimum engineering solutions to acceptable long-term performances for railway line. This multidomain approach gives an adapted rehabilitation technique.

This paper presents the results of pre- and post-improvement cone penetration test (CPT) results executed at the site where Rammed Aggregate Pier® elements were used for the liquefaction mitigation. The effectiveness of these elements is attributed to the lateral pre-stressing that occurs in the matrix soil during construction and to the high strength and stiffness of the piers. The improvements provided by Rammed Aggregate Pier® elements mitigate liquefaction potential include (i) soil densification (ii) transferring a major portion of the seismically induced shear stresses from the soil to columns (iii) increasing the horizontal stress of the surrounding soil (iv) dissipation of excess pore water pressure. In the case history presented in this paper, the soil profile consisted of a thick hydraulic fill layer (characterized by silty, clayey sand) overlying sea bottom sediments of soft to medium stiff silty clay (CL) and medium stiff silty clay with sand (SM) down to almost 40 m depth which are underlain by a stiff to very stiff silty clay layer. Installation of 50 cm diameter Rammed Aggregate Pier® elements which are constructed by Impact® System construction procedures (bottom-feed dry displacement method) is aimed to mitigate liquefaction risk in the hydraulic fill layer and to limit settlements, by forming an improved soil crust of desired thickness at the surface. Rammed Aggregate Piers of 16 m length were installed in square and triangular patterns with 1.5 m and 1.7 m on-center spacing, respectively. CPT testing was performed before and after the installation of the piers. The results show that the additional densification and improvement in non-cohesive soils due to vibration and ramming during the pier construction has increased the safety factor against liquefaction by 2.5–3.0 times.

Observational method is a powerful approach to dealing with uncertainty in subsoil conditions. In the presented case study, Kujala Interchange, constructing test embankments and applying the observational method enabled to replace many initially planned pile slab foundations with ground-supported road embankments. The residual settlements of these embankments were controlled by means of preloading accompanied with monitoring. This paper demonstrates how a decision tree analysis can be employed to assess the feasibility of constructing the test embankments. The prior probability of acceptable settlements of the ground-supported embankments is estimated for a typical soil profile in Kujala area via Monte Carlo simulation. This prior probability is then updated via monitoring results and Bayes’ theorem. Lastly, the expected costs of each design alternative are derived based on their respective probabilities and the actual cost savings acquired at Kujala Interchange. The results of the decision tree analysis confirm that constructing the test embankments and minimizing the pile foundations were the optimal decision in this case study. In sum, this paper shows how the observational method can be employed to reduce the expected costs and environmental impact of foundation design characterized by significant uncertainty in subsoil conditions. However, it is concluded that besides monetary costs, one should also include non-monetary consequences such as carbon dioxide emissions.

Peat soils exhibit very high organic and moisture contents with corresponding very high compressibility and creep characteristics and very low strength. These poor engineering properties make peat soils particularly unsuitable as a foundation material for road pavements with attendant high risks of instability during both initial construction and in service with unpredictable and often excessive long-term deformations. Almost 20% of Ireland is peatland and roads have been historically constructed directly on peat, albeit with mixed results and often high, long-term maintenance costs. Ground improvement by means of excavation and replacement of peat is frequently adopted and more recently piled embankments are increasingly used in areas of deep peat deposits in Ireland for major roads. However, these mitigation measures can have high construction costs and attendant risks as well as large resultant waste volumes and environmental sustainability impacts. The paper briefly reviews the historical approaches to road construction in peat soils both in Ireland and internationally. Analytical methods to assess flexible pavement foundation stability and deformation under static embankment and dynamic traffic loading are reviewed. A number of case histories of low capacity (less than 2000 AADT) road foundation design and performance on Irish peat soils are described. The benefits of surcharge upon the creep performance of peats are discussed and back calculated, and field performance data from one site is presented. Some conclusions are drawn as to the potential for increased application of geosynthetic base reinforcement and ground improvement approaches in peat soils which are less commonly adopted at present in Ireland.

The major highway network in the UK was developed from the 1960s, and the earthworks are generally well engineered. However, as many of the earthworks get older, slope failures are becoming more common, with some posing a threat to the safety of transport operations. Field measurements of soil water content and pore water pressure changes within the surface zone of a highway cut slope in London Clay at Newbury, Berkshire, UK, have been carried out continuously since 2003. This paper describes and gives examples of the long-term field measurements from the site at Newbury and details a number of significant findings from the observations from the site. The paper explains how these have been used to calibrate appropriate models of seasonal cycles of pore water pressure and slope deterioration.

The experience with the first generation of high-speed railway lines (HSR) has shown that the cyclic-dynamic impact should be considered in order to limit maintenance efforts, disturbance of operations and increase passenger comfort. Due to the country-specific conditions, different methodologies and requirements are applied by different railway authorities. Serviceability and stability requirements need to include the cyclic-dynamic impact. If the operational train speed exceeds the surface Rayleigh wave velocity in soil, deformations will be amplified, which may cause damages to railway tracks or set a demand for extensive maintenance influencing operation of a line. Therefore, it should be ensured that embankment and subsoil conditions meet the required capacity; and that maximum operation speed could be achieved without damages or limitations. It is commonly accepted that the Rayleigh wave velocity associated with generated vibration is identified as being the criterion to be achieved to mitigate the risk of amplifications of ground movements and deterioration of the track system. This is currently considered the state-of-the-art approach by most railway authorities. However, from existing projects in different countries, it seems that the ultimate criterion is dynamic displacements which should be considered along with Rayleigh wave velocity in order to limit maintenance efforts and to increase passenger comfort. This paper aims to discuss the criteria required for a proper design of HSR including a methodology, with showcasing examples of projects both in Germany and the Netherlands.

Geosynthetic reinforced soil (GRS) structures with excellent engineering performance are extensively utilized throughout the world in embankment engineering. GRS structures are commonly not utilized for applications where large settlements are anticipated. In this study, a GRS bridge approach reinforced with uniaxial geogrid and backfilled with graded crushed stones was instrumented during and post-construction for almost one year. Owing to the high construction height and the compressibility of the foundation soil, the GRS bridge approach has settled more than 0.3 m and continues to settle. That unexpected settlement induced a series of complicated response mechanisms related to the behavior of the reinforcement and vertical earth pressure at the base of the wall. Overall, even for such large settlements, the GRS bridge approach still performed adequately.

Effective assessment of bearing capacity of the existing pavement structure as well as proper characterization of materials used in the construction of pavement layers provides critical inputs for rehabilitation design of urban roads. This study presents the findings from a comprehensive pavement geotechnical investigation that was performed on approximately 2300 ft of composite pavement (AC on top of PCC) located on Curtis road in Savoy, Illinois. Non-destructive testing program included falling weight deflectometer (FWD) as well as ground penetrating radar (GPR) at both center and transverse joint locations. Additionally, destructive testing program including pavement borings, pavement coring at crack locations, deep and shallow soil borings, dynamic cone penetration (DCP) testing on aggregate base, and subgrade as well as soil sampling and laboratory testing was performed. GPR scans obtained at three different antenna’s frequencies including 2 GHz, 900 MHz, and 400 MHz were analyzed and calibrated by pavement cores to generate pavement layer thickness profiles. Statistical analysis methods were used to identify trends and develop correlations between the laboratory and field test results. This includes finding linkage between the pavement thicknesses obtained through coring and what was estimated using GPR. The findings from this study showed that strength, bonding status, and thickness variability of pavement layers as well as groundwater table and in-situ moisture condition of the subgrade soil significantly affect the surface pavement deflections.

Boubyan Island, which is the largest island within the geographic boundaries of the State of Kuwait, is characterized with its challenging ground conditions. Results of the extensive geotechnical investigation program indicated that the soil profile in the island is comprised of thick, soft, silty clay layer, with thickness ranging between 19 and 26 m, underlain by a dense to very dense fine sand layer. The silty clay layer is characterized as very soft to soft, calcareous, low to intermediate plastic, light brown to brown clay with cone resistance value less than 1 MPa, which is locally referred as “Boubyan Clay.” Due to the existence of the thick, soft Boubyan Clay deposits in the island, ground improvement works in the form of surcharging with prefabricated vertical drains was adopted for limiting settlement of the road embankments after formation and for enhancing stability of the embankments. This paper describes in detail the challenges that Boubyan Clay imposes in developing sustainable infrastructures and in particular the analysis of the embankment slope stability under temporary and permanent load conditions using Morgenstern and Price method of slices by adapting the numerical modeling program of SLOPE/W. Analysis indicated that embankments were stable under temporary as well as permanent loading conditions. Results also proved that margin of safety in the drained long-term loading condition is much larger than those under the undrained loading conditions.

March 2014 Oso landslide, which demolished Steelhead Haven Community near Oso, Washington, is the deadliest in US history. Several factors have been suggested for the initiation of this landslide by various researchers including, the heavy rainfall before the landslide, timber harvesting on the upper plateau, river erosion at the slope toe, groundwater rise due to rainfall infiltration, and irregular 3D topography of the slope. This study utilizes 3D limit equilibrium and 3D finite element seepage analyses to investigate the effect of rainfall infiltration in the 7.5 acres timber harvest area at the top of the slope as well as potential changes of groundwater elevation on the initiation of 2014 Oso landslide. To achieve these objectives, the infiltration rate was varied in the harvested area to investigate its effect on the first phase initiation. Also, two potential groundwater levels were examined to assess the sensitivity of the first phase slide mass to changes in groundwater conditions. The 3D factor of safety for the critical slip surfaces was obtained for the two groundwater levels using two conventional limit equilibrium methods. The safety factor for the critical slip surface is slightly different for the first and second groundwater levels. The difference is such small that it can be concluded that a reasonable rise in groundwater level would not have been the triggering factor for the 2014 Oso landslide. The impacts of other potential factors such as shear strength reductions of upper layers due to the rainfall infiltration, timber harvesting, and/or 3D slope geometry effects appear to have been more influential in the initiation of the landslide.

One of the most challenging issues transportation managers face is maintaining the condition of low-volume roadways during and immediately following wet weather events, such as heavy rainfall and the spring time thaw period. Specifically, high moisture contents in the road base and subgrade weakens the overall structure, causing excessive rutting and structural damage, leading to costly repairs, load restrictions, and/or closures. The main objective of this study is to evaluate the impact on structural performance of low-volume roadways constructed with geosynthetic wicking fabrics, which are designed to act as both a drain to move water out of the pavement structure as well as a moisture barrier to prevent a capillary rise in the unbound layers of the roadway. A low-volume roadway in Northern New England was constructed where a Mirafi® H2Ri wicking fabric was installed in the subgrade layer of the pavement. The pavement section was instrumented with moisture and temperature sensors at different depths to monitor the effect the fabric had on the moisture content of the subgrade. The data, collected and monitored over a period of one year, was then used to predict the stiffness of subgrade layer. The layered elastic analysis was used to predict the rutting performance of the pavement section. These performance predictions were then compared to the previously unmodified section with no fabric installed. Ultimately, the results showed significant improvements in the rutting resistance of the pavement structure with the fabric compared to the unmodified section, particularly during the spring time thaw period due to the improved drainage capability the fabric provides. The findings from this study suggest that geosynthetic wicking fabrics offer significant advantages when installing in roadways to prevent damage during the spring time thaw period in cold regions and could be a useful tool for transportation managers with low-volume roadway networks as well as adapted in pavement design practice.

As train speeds increase on existing rail networks, and new high-speed routes are constructed, the likelihood of a line experiencing the large track displacements commonly termed critical velocity effects increases. The phenomenon occurs as the train speed approaches the speed of surface (Rayleigh) waves in the underlying ground. At a certain proportion of this speed the track deflections begin to increase above those for static loading, slowly at first and then more rapidly, reaching a maximum at a “critical” velocity. Larger trackbed deflections may cause increased rates of track deterioration, maintenance needs and in the worst cases risks to safety. Therefore, it is important to be able to predict which sites are susceptible to critical velocity effects and to determine threshold speeds below which they are not influential. Where these thresholds are exceeded mitigation measures can be considered. Reliable prediction of critical velocity effects using numerical modelling and other analytical tools require selection of a representative ground model and parameters. This paper describes a programme of site measurements, sampling and advanced laboratory testing to create a ground model for a site on the UK railway network known to experience critical velocity effects.

Kannur International Airport Ltd. (KIAL) is a new Greenfield airport project with airside development on an undulating terrain with an average height of 90 m above mean sea level (MSL) and a maximum height of 142 m. To accommodate the desired Runway length and runway end safety area (RESA) at both the ends along the proposed alignment, it resulted in 45.5 million cubic meters in cutting and filling. The insufficient availability of land for the construction of free slope embankment at RESA 07 end resulted in the design and construction of reinforced soil slope (RSS) system with a maximum slope of 65°. An embankment fill of average 70 m height with steep slopes located in high rainfall area is a unique feature of this project. The fill was reinforced with high-strength uniaxial geogrids laid perpendicular to the slope. Weld mesh wrapped with coir mat acted as facia units to protect it against surface failure. Considering high rainfall received on this table top airport site, extensive drainage system was designed for the high embankment fill. Gabion wall up to 9 m height were also designed and constructed along the boundary to accommodate the toe of the RSS fill beside the jeepable track at the base level. The design of RSS fill was done using ReSSA software and verified in PLAXIS 2D modeling. The site won excavated laterite soil was used as the fill material for the construction. Extensive field and laboratory tests were conducted during the construction of RSS system for quality assurance.

According to Hay (Railroad engineering, Wiley, New York, 1982), the support of railway track is a critical requirement to achieve the potential of railway track to serve as one of the most cost-effective types of infrastructure in terms of long-term maintenance cost. Uniform resilient support provided to the track structure (rails and ties) is needed to maintain stresses in the track structure that result from the applied train loading within an acceptable range. Excessive track deflection due to poor track support contributes excessive stress to track components. The shallower the support deterioration, the more severe the effect on the track structure and the deeper the support deterioration the more difficult it can be to locate and repair. Saturated-undrained soil conditions would not be expected to compromise track support in railway track built using commonly specified materials. However, changes in track drainage patterns and contamination of open-graded aggregate ballast has been known to result in roadbed saturation and associated softening that is listed in the FRA Railway Accident/Incident Reporting System as derailment cause code T001 Roadbed Settled/Soft. The technical cause of deterioration is often a moisture content increase associated reduction in strength. Repeated load behavior of saturated undrained soils is known to cause specific types of problematic failures that might be mitigated with operational limitations or maintenance. The potential for saturated-undrained repeated load soil failure modes in track can only be assessed if situations susceptible to these conditions can be identified. In this paper, the classic conditions related to these soil failures are discussed as a basis for review of two case studies illustrating the field conditions associated with two distinct failure scenarios.

In order to solve existing engineering problems, such as variable and dynamic slope stability issues of railway embankments, limited soil bearing capacity, and post-construction settlement of foundations in fluid-plastic soft soil, etc., the Cement-Fly Ash-Gravel (CFG) rigid pile composite foundation has been used as the main foundation design method. However, due to the lower shear strength and the thixotropy of fluid-plastic soft soil, and the lack of research on pile-soil interaction mechanisms especially for the pile-soil modulus ratio, these will influence the effectiveness of CFG rigid pile foundation design. Therefore, it is crucial and essential to study the anti-shear contribution and the failure mode of CFG rigid piles in the foundation treatment of fluid-plastic soft soil. This paper starts with the finite element analysis of the structural mechanism of single rigid piles in the fluid-plastic soft soil under different working conditions. The results show that the stiffness of the pile body itself, the pile-soil modulus ratio, the shear strength of soil, and the angle between pile and the sliding arc tangent of soil are the main influencing factors of the apparent shear strength (defined as the maximum anti-shear force the pile can provide). Furthermore, with an increase of the angle between the pile and the shear plane, the failure modes of piles will gradually transition from the tensile bending failure to compression bending failure. When the pile-soil modulus ratio is greater than 4000:2, the CFG pile and other rigid piles are not suitable for fluid-plastic soft soil foundation. Considering both safety and economy factors, drainage consolidation treatment should be used to improve the shear strength of fluid-plastic soft soil foundation, then follow with the CFG rigid pile composite foundation treatment. Based on research achievements and some investigations from new-built railway construction projects, these combined treatment methods can significantly improve the effectiveness of foundation treatment and increase the slope stability of railway embankments.

Research on the mesoscopic geometrical characteristics of joint surfaces has been a topic of considerable interest. Based on discrete cosine transform theory, this paper presents a novel morphology characterization and reconstruction method to quantitatively analyze the 3D geometrical characteristics of rock joints. The joint surfaces are segmented and transformed into standard grid data sets, which are termed, the discrete time-domain signals. Based on discrete cosine transform algorithm, it is possible to convert discrete time-domain signals into a discrete spectrum. Then, the normalized amplitudes of the spectrum are defined as descriptors, which are found to be applicable to characterize and reconstruct the joint surface. Further, the proposed method is used to analyze 205 measured 3D joint samples, and is validated by comparing the surface of the real rock joint with that of reconstructed surface. The research provides an insight into the rapid random reconstruction of joint surfaces, which is beneficial for field identification of discontinuities and providing virtual test samples for numerical modeling.

High-speed railways (HSR) set strict limits on subgrade settlement. Excessive settlement, especially the differential settlement at the transition part between viaduct lines and embankment lines, could lead to discomfort on HSR trains and even accidents like derailments. Thus, proper ground treatment measures are inevitably needed. Screw-shaft pile reinforced subgrade was adopted in the transition section of Yancheng–Nantong HSR. However, limited research has been done to investigate the performance of screw-shaft pile reinforced subgrade. In this paper, numerical models were established to analyze the performance, especially the long-term settlement, of the reinforced subgrade. It was found that shaft-screw pile reinforced subgrade could control the long-term settlement better than the traditional shaft pile subgrade. The advantage becomes greater when the train speed increases. Moreover, the application of shaft-screw pile reinforced subgrade could reduce the material usage by about 10%. Briefly, shaft-screw reinforced subgrade could satisfy the settlement control requirements and achieve greater cost efficiency in sandy subgrades.

With the rapid development of road network, it is inevitable that new tunnels will be constructed under existing highway or railway bridges. Open excavation method is a typical way for building a new tunnel under bridge, leading to significant influences of the existing pile friction. Accounting for these issues, pile side grouting reinforcement method has been widely employed to improve the load bearing capacity of existing piles. However, the mechanism of this method is still not clear. In this paper, the compressive load capacity of pile with side grouting reinforcement is investigated. The research results reflect the effect and mechanism of pile side reinforcement on the enhancement of pile friction. For the existing pile in this paper, the reinforcement width has a reasonable range. The compressive load bearing capacity of the pile cannot be improved indefinitely with the increasing of the reinforcement width. Pile with a reinforcement width within 1000 mm shows similar characteristics of enlarged diameter pile. Although ultimate compressive load bearing capacity of these piles is greatly improved, they need a larger displacement to exert load bearing capacity. Shear strength and friction characteristics of the contact surface between the reinforced zone and the pile and supporting capacity of the soil under reinforced zone are the keys to enhance the pile compressive load bearing capacity.

The growing scale of the high-speed railway network and that of the metro leads to an increasing number of intersections between these two traffic modes. To ensure the structural safety during the construction process of metro tunnels constructed beneath existing high-speed elevated lines, rows of isolation piles between these two different kinds of traffic infrastructures have been widely utilized. However, the vibration isolation effect of these piles during the metro vehicle operation process is still not well studied. In this paper, a model that accounts for the interaction between structures (i.e., high-speed bridge, isolation piles and metro tunnels) and soil foundations is established by employing a three-dimensional finite element method to investigate the vibration isolation effect of the isolation piles. The influence of different design parameters of isolation piles on the vibration characteristics of the complete system is investigated. Besides, this paper summarizes the law of wave peaks formation in the vibration magnification area. The results show that: (i) For surface, vibration isolation effect is influenced greatly by the spacing and diameter of isolation piles. The vibration isolation effect of the isolation pile is weakened considerably with increasing pile net spacing and is enhanced with increasing pile diameter. (ii) For high-speed bridge pier top, geometric parameters of isolation piles have little effect on the isolation efficiency. (iii) The increase of pile diameter and spacing makes wave peaks appear easily in the vibration magnifications region.

Phononic crystal is a new type of functional material, which can shield elastic waves at different frequencies by properly setting the parameters and distribution of constituent material. Based on the phononic crystal theory, this paper uses the finite element software COMSOL multi-physics to calculate the band gap characteristics of three-dimensional periodic row piles structure and discusses the influence of soil density, elastic modulus, radius of row piles, configuration mode and section shape. The results show that the radius of row piles and the elastic modulus of soil are the main factors affecting the band gap; the appropriate section shape can be selected according to the frequency range that one needs to shield and the amount of material that is needed to use. Compared with the periodic pile barrier in a square configuration, the pile in a triangle configuration can obtain a higher initial bound frequency, terminal bound frequency and a bigger band gap width. The research results are expected to provide some reference for the vibration isolation design of high-speed railway.

Metamaterials have come to the fore in the fields of electromagnetics and acoustics due to their superior performance in targeted frequency ranges. However, the related application such as in vibration mitigation in civil engineering is rare. In this paper, the dispersion relation of a new kind of metabarriers is obtained according to the theory of periodic structure in solid mechanics. The dispersion of the metabarriers is generated by local resonance. A simplified model is established to explain the mechanism of bandgaps. The effective mass density, effective shear modulus and effective bulk modulus of the metabarriers are calculated by finite element method. It is found that the resonance of the oscillator produces a negative effective mass density, which prevents the wave propagating in soil, thus creating bandgaps. At this point, the effective shear modulus and effective bulk modulus of the metabarriers are both positive. The findings of this paper are beneficial for the design of periodic pile barriers to isolate elastic waves propagating in soil.

Rock is not homogeneous and isotropic due to the presence of discontinuities and weak planes within its body. This brings in terms of ‘rock material’ and ‘rock mass’ for practical applications. A rock mass is an assemblage of intact rock pieces separated by discontinuities presented in different scales such as micro-fractures, rock joints, stratification, faults. For design in civil and mining engineering geo-structures, it is often necessary to investigate the behaviour and role of discontinuities on rock mass performance. In many cases, failure is governed by the shear behaviour of discontinuities in excavations. In this context, evaluation of the effects of small repetitive earthquakes on the shear strength parameters of rock joints especially in tunnels and dam foundations is also important. The main scope of work is to study and investigate shearing behaviour of jointed rocks infilled with gouge materials under monotonic and cyclic loading vis-a-vis the theoretical background to shearing behaviour under loading conditions to compare the shear strength values for a variety of jointed rocks. In case of cyclic loading, under the initial loading cycles, the rate of increase of displacement is slow corresponding to the rate of increase of shear stress. In later load cycles, the rate of displacement is rapid with a corresponding increase in shear stress until the peak shear stress value is reached. Under cyclic loading condition, post peak behaviour sometimes exhibits a tendency to drop suddenly and assumes a constant value called residual shear stress.

Geogrid has been widely used in composite foundations or embankments supported by rigid or rigid-flexible piles in the past two decades. However, the research on the deformation behavior of geogrid supported by rigid or rigid-flexible piles under cyclic loading are very limited. Some model tests on the deformation behavior of geogrid supported by rigid-flexible piles were designed and completed under cyclic loading with changing the load amplitude, waveform, and cyclic frequency. The geogrid strain at different locations in the different cyclic process was analyzed based on the model test results. The test results showed that the deformation behavior of geogrid varies with the location. The strain variation trends of geogrid under cyclic loading are consistent with that of applied cyclic load shapes/amplitude. When the waveform of cyclic load is changed singly, the strain of the geogrid will change accordingly. The geogrid strain amplitude at the edge of flexible pile under cyclic load frequency is the largest, and it is also most affected by the cyclic load amplitude.

Coastal areas along the Pacific Ocean suffered extensive damage owing to the 2011 tsunami due to the Tohoku earthquake. Hence, reinforcement methods against tsunamis need to be developed for existing caisson type breakwaters. This study proposes installing a row of piles behind the caisson using backfilling, with rubble in the space between, as reinforcement against tsunamis. To determine the cross-section and embedment length of the pile used in this structure, understanding the load condition acting on the pile is necessary. Model experiments were conducted based on bending moment distribution to estimate the external force acting as distributed load on the pile’s offshore side. The subgrade reaction acting on the pile from the onshore side was assumed by correcting the coefficient of the subgrade reaction and its depth direction in the Winkler–Spring type subgrade reaction model. There are insufficient points in the external force distribution estimated in this method owing to insufficient evaluation of the subgrade reaction. The impact of the subgrade reaction on a pile’s horizontal resistance characteristics depends on its deformation mode. Hence, it is necessary to evaluate the subgrade reaction in the pile deformation mode under distributed load along the perpendicular pile axis direction. This study conducted loading experiments on the piles using different ground conditions and loading methods to examine the difference in horizontal resistance of the piles. The deformation mode of the piles was found to cause changes in the coefficient value of the subgrade reaction and its changing behavior along the depth direction.

Piled embankments over the soft soil can effectively reduce the post-construction settlement by soil arch effects. To investigate the soil arch effect under train moving loads, the authors established a full three-dimensional finite element model including train set, track structure and piled embankment. Based on the model, dynamic stress under moving train loads is calculated and the influence of soil arch effect is discussed. The numerical analysis reveals that: (1) soil arch effect leads to the redistribution of dynamic stress in piled embankment; (2) geogrids contribute to reducing the dynamic stress on the interpile soils; (3) track structures decide the dynamic stress distribution in the superficial layer in piled embankment, while the dynamic stress distribution at deep layer is mainly related to the pile foundation.

This study reports a group of field tests on cyclically loaded piles installed in soft clay in Huzhou, China. Two 29.5 m long pipe piles were instrumented with transducers to measure the accumulated settlement at the pile-head, the pore water pressure and total pressure at the pile-soil interface, and axial load at the pile end, respectively. The major objective of the field testing is to gain a better understanding of the evolution of the pile-head settlement and the effective stress at the pile-soil interface. The results of cyclic loading tests under different combinations of static load and cyclic load are discussed with reference to changes in the pile capacity, the permanent settlement, and the radial stresses. It is found that the permanent settlement of piles can be characterized as quickly stabilized (QS), progressively developing (PD), and dramatically failed (DF) patterns. Under low-level loading (QS pattern), the pile-shaft earth pressure is nearly undisturbed, final gains in effective stress are observed due to slight dissipation of pore pressure. For intermediate-level loading (PD pattern), significant reductions in pore pressure, earth pressure, and effective stress are observed after cyclic loading. Regarding high-level loading (DF pattern), the quick accumulation of pore water pressure leads to a slight increase in earth pressure, resulting in a continuous decrease in effective stress.