Tunneling in Soft Ground, Ground Conditioning and Modification Techniques

In roadway pavement design, one must consider the performance of the pavement structure and mixture design. The tendency for pavement to be more flexible in nature gives increased importance to the properties and condition of the underlying soil subgrade. Traditional foundation design normally considers the static strength response of the soil from stationary loads. Roadway pavement design, however, must consider the dynamic strength response created by moving traffic loads. This dynamic strength of soil, or “stiffness,” is known as its resilient modulus (M_R). The resilient modulus is determined by costly and time-consuming laboratory tests. For these reasons, it would be greatly beneficial to find an effective, yet simpler method to determine the values of M_R. The goal of this study was to utilize multiple regression analyses to determine the relationships between common soil index properties, M_R, and use these relationships to create an equation to model. The methodology used in the creation of these equations will be described as well as a statistical evaluation of their performance. Subgrade soil property data for 253 different soils found in northeast Texas was mined from Arizona State University’s “National Catalog of Natural Subgrade Properties Needed for the ME-PDG Input.” The common soil index properties studied include five sieve analysis gradations, liquid limit, and plasticity index. These properties were analyzed against M_R.

Expansive soils, also known as swell-shrink soils have been a problem for civil infrastructures including roads and foundations from ancient times. The use of chemical additives such as cement and lime to stabilize expansive soils is a common practice among geotechnical engineers, especially for lightly loaded structures. However, several occurrences of subgrade failures have been observed after stabilizing with chemical additives. Hence, engineers are in search of sustainable stabilization alternatives. Microbial Induced Calcite Precipitation (MICP) is gaining attention as an environmentally friendly soil improvement technique. Several researchers have successfully tested its feasibility in mitigating liquefaction-induced problems in sandy soils. In this research, the authors are evaluating its effectiveness in stabilizing expansive soils. For this purpose two natural expansive soils with high and low plasticity properties were subjected to MICP treatments. The soil samples were first augmented with bacterium Sporosarcina Pasteurii and then treated with Calcium Chloride and Urea. Variables such as microbial concentrations and curing times were studied in this research. Geotechnical testing including Atterberg limits and unconfined compression strength were performed to evaluate the efficacy of MICP treatments. Preliminary results indicate that there is a reduction in plasticity and swelling characteristics of the soils and increase in the unconfined compression strength.

The different size of transverse cracks was appeared on the upper surface of rock-anchored beam in the process of excavation of underground powerhouse of hydropower station. Detailed cause analysis of these cracks was made based on the in situ geological condition, construction process, monitoring data, geophysical survey and numerical simulation. The results showed that the layered rock and faults are the premise of differential deformation of surrounding rock. Monitoring data and geophysical test results indicated that sidewall surficial surrounding rock was cracked by the blasting excavation which promoted the differential deformation of surrounding rock, easy to the generation of transverse crack on rock-anchor beam. Numerical analysis results revealed that differential vertical deformation of surrounding rock is the most important reason for the rock-anchored beam transverse cracks while the lithological differences as well as the existence of the faults are the main reason for the differences on the vertical deformation. The procedure of excavation and the nearby cavern excavation which resulted stress redistribution and differences on the deformation also leaded to another cause of rock-anchored beam transverse crack.

Since the ability of many available jacking force models to characterise the tunnel bore conditions is limited. A simple approach to characterise the tunnel bore conditions is proposed and applied to a case study where four sewer pipelines of the Shulin district sewer network in Taipei County, Taiwan were constructed to verify its validity. Four jacking force models are benchmarked in this study. Based upon the given soil properties and pipe dimensions as well as the pipe buried depth, the calculated normal contact pressure (σ′) from each model and the measured frictional stress (τ) in each baseline section are utilised for the back-analysis of the frictional coefficient (μ_avg). The μ_avg values outside the range of 0.1–0.3 recommended for lubricated drives can be ascribed to the increasing pipe friction resulting from the excessive pipe deviation or ground closure or the gravel formation not being long enough to establish lower face resistance. JMTA has indicated a further potential use in assessment of the interface performance during pipe-jacking works.

Expansive soil is a kind of geological body with special hazards to the construction engineering. It has the engineering properties of shrinkage, fracture and overconsolidation. Its engineering hazard is rich in water content in soil. The expansive geomaterials can produce wetting and shrinkage deformation, which adversely affect the subgrade, slope and tunnel support structure. In order to solve this problem, the dry and wet cycle model test device was established by simulating the “rain” and “sunshine” cycle, and the typical dry wet circulation, shrinkage and other factors, focusing on the expansion and contraction of soil tunnel rock failure instability development model, the scope and its conditions and the impact of factors such as simulated rainfall under the conditions of the tunnel excavation and support, the stress, strain and deformation of the surrounding rock of the tunnel are analyzed, and the possible damage modes are analyzed, and the mechanism of the surrounding rock disaster in the shrinkage fracture zone is revealed.

This paper investigates the integrity test ability of the sonic echo (SE) test by using a field constructed group pile foundation. Due to the energy reflected stress wave is generally faded with wave travel path for the testing of a pile with pile cap, a signal process techniques were generally used to enhance the signal interested. The purpose of this paper is to study an improved signal processing approach to detect the pile length of a pile with pile cap. This paper utilized the amplitude and phase message of complex continuous wavelet transform to determine pile length of pile foundations by analyzing the time-frequency-phase angle diagram in the different frequency band. Two- pile group and four-pile group pile were tested. Six piles with different types of defects were installed and tested to verify the proposed approach in this study. The results show that complex continuous wavelet transform is able not only to provide high-resolution results in different frequency bands but also to simplify the identification of the reflection of defects using 3D phase spectrogram. The location of reflected stress wave of pile toe can then be determined using phase diagram.

Stratum in shallow buried excavation section of Zi-Zhi Tunnel is generally upper-soft and lower-hard. To reduce the rock disturbance and ensure the construction progress, excavation method conversion from Cross Diaphragm with Step method to bench method should be conducted ahead of schedule. To determine the excavation methods conversion opportunity, considering different positions between tunnel face and the interface of stratum, based on displacement direction angle theory, the change laws for the displacement direction angle and three-dimensional deformation of surrounding rock under different conditions were analyzed by FLAC^3D. Then, an excavation methods conversion opportunity is derived. Meanwhile, the rationality of the opportunity is validated by the field monitoring data. The results indicate that: when the distance of working face cutting through the interface is 1.5B (B = tunnel width), displacement direction angle of surrounding rock reaches a stable state and the longitudinal stress concentration is weakened. It is conducive to utilize the self-bearing capacity of the rock mass. Hence, it is suggested to convert the excavation methods when the distance is greater than 1.5B; the stable value and the convergence rate of vault subsidence in site were both below warning value, which can meet the safety and economic benefits of engineering.

Local cavities around the tunnel lining due to imperfect construction or ground water erosion will lead to local contact loss and discontinuity in the ground-lining interaction. This paper evaluated the effect of local cavities on the mechanical and cracking performance of an existing tunnel lining. The geometry and position of the local cavity were defined according to the results of field investigation. Numerical analyses were performed to investigate how the local cavities affect the stress state of the concrete lining and to check the stability of the tunnel. Extended Finite Element Method (XFEM) was used to illustrate the development of cracking directions and patterns on the existing tunnel lining in the vicinity of the cavity. The above results was then verified by comparing with field observations. The presented study suggested an effective way for modelling tunnel lining cracking, and shown a systematic method to preliminary evaluate the cracking performance of an existing tunneling lining with local cavities behind.

The current practice of safety management in bridge construction depends on the voluntary effort of the contractors and relevant government agencies. Due to varying degree of experience and knowledge of the inspectors, results of bridge inspection could not be analyzed in a systematic and consistent way. This study focuses on the use of Fault tree and Bayesian-network to analyze and generate a risk analysis model for falling risk in Precasting Prestressing Segmental Bridges Construction Method. After comparing the risk analysis model with the traditional inspection method, it is found that the risk analysis model is consistent with the traditional inspection method in their ability to predict falling hazards.

Blasting pretreatment is commonly used to break boulders before shielding to ensure shield machine tunneling safely. Considering that rock fragments after blasting should be met the special dimensional requirement of shield machine’s mucking system, so the explosive consumption is usually larger than explosive charge of conventional blasting and should be determined accurately. However, explosive charge is usually determined based on empirical formula and regulation of rock fragment distribution is unknown, resulting in that the blasting effect is unsatisfactory. In order to solve these problems, model test of blasting is carried out and the following contents are studied. The contents conclude: the explosive consumption corresponding to the average size of rock fragment; the relation between explosive charge and the overburden depth; the relation between explosive charge and regulation of rock fragment distribution. There results show that: the explosive consumption of blasting at land is 5.4–6.5 times that of conventional blasting when the size of rock fragmentation after blast is less than 30 cm. The explosive consumption increase linearly with depth of overlying stratum in double logarithmic coordinates and the relation between average size of rock fragment and depth of overburden is quadratic polynomial. The influences of explosive charge and depth of overburden on average size of rock fragment after blast is different. Explosive charge is the main influence factors for average block degree when the boulder is buried in a shallower depth, but thickness of overlying stratum’s influence on average block degree will exceed that of explosive consumption when the boulder’ buried depth exceed a certain value.

The development of a web-based ground settlement prediction system for subway construction is presented. The system is developed based on STEAD, and it is named STEAD-Web. STEAD is a ground settlement prediction system developed in China earlier. It is short for Subway Tunneling-induced ground-Environment-damage Assessment and control Design system. STEAD works well in predicting ground settlement. Unfortunately, it works off-line and it is not so convenient to deal with massive measured data every day. STEAD-Web is an upgraded version of STEAD, which runs in Browser/Server mode. The server automatically analyzes the monitoring data and makes a prediction by a back-analysis method using the real-time measured data. Users can access the results through web browsers from anywhere after authorization. Finally, the paper presents two case applications of the new system in Beijing subway construction.

A remarkable development of high strength concrete and reinforcement has been achieved nowadays. The purpose of New RC project is aimed to reduce member section size by using high strength concrete (\( {\text{f}}_{\text{c}}^{\prime} > 70\;{\text{MPa}} \)) and high strength rebars (\( {\text{f}}_{\text{y}} > 685\;{\text{MPa}} \)). Material consumption can be further reduced owing to the upgrade of strength. However, the nature of brittleness of high strength concrete may also cause early cover spalling and other ductility issues. Addition of steel fibers is an alternative as transverse reinforcement in New RC infrastructure systems. Highly flowable strain hardening fiber reinforced concrete (HF-SHFRC) has excellent workability in the fresh state and exhibits the strain-hardening and multiple cracking characteristics of high performance fiber reinforced cementitious composites (HPFRCC) in their hardened state. This study aims to investigate the cyclic behavior of New RC bridge columns made of HF-SHFRC. Five large scale bridge columns are subjected cyclic lateral loading to verify their responses and deformation capacity. The test results show that by adding 1.5% of high strength hooked steel fibers, great deformation capacity is developed either stirrups spacing is even increased to two times of that of control specimen or elimination of all tires in New RC bridge columns. Implementation of HF-SHFRC to New RC infrastructure offers opportunities to significantly simplify the design and construction of members for sustainable urbanization, while ensuring adequate ductility and damage tolerance.

In winter, ice and snow on pavement slabs and bridge decks cause serious driving conditions to motorist both in safety and ability to accelerate and clime grade. Geothermal energy has gradually emerged as a new heating source for heating bridge decks and pavements to keep bridges and roads free of snow and ice in winter. However, current geothermal bridge deicing design and studies mostly focus on new bridges that hydronic loops are embedded in concrete deck during construction phase, which is considered as internal heating. This paper presents a conceptual design and numerical analyses of external geothermal bridge deck heating that the hydronic loops are attached to the bottom of bridge deck and encapsulated in a layer of geofoam. A series of parametric analyses is performed to investigate the principles of external heating process. The controlling factors, such as ambient temperature, inlet temperature, wind speed, flow velocity, and foam thickness are considered. The results show that the temperature of the proposed external heated bridge deck can rise above freezing in mild winters through heating for at least 3 h. Limitations of the design are also discussed that the proposed heating system would be unfeasible in the area where the ambient temperature and inlet temperature are lower than −2 and 12 °C, respectively, and wind speed is higher than 6 m/s. It is also found that foam thickness slightly affects the heating process.

The construction of shallow tunnels using a pre-support system based on pipe canopies may require important decisions during the planning stage. Once the decision of using pipe canopies has been made, the engineer has to choose between steel cylinders or steel tubes for the canopy. If the later ones are chosen, it is necessary to decide whether to keep the soil inside, remove the soil or remove the soil and fill the tube with concrete. In order to clarify the benefits and harms that guide this interactive solution, a study about the influence of the filling material in the bending behavior of the canopy was conducted. The results were obtained for steel behaving as an elastic-perfectly plastic material and concrete being represented by the parabola-rectangle diagram, however the methodology may be applied for different stress-strain curves. A case study, based on the site conditions proposed in Domingues et al. (Society for Mining, Metallurgy and Exploration, The World Tunnel Congress 2016, San Francisco, California, United States, 2016) exemplify the usefulness of the methodology proposed. As a result, it was shown that it may be favorable to keep the soil inside the beam instead of replacing it by concrete or use a massive structural element. In other words, as any other structural system, there is an optimal solution that leads to an economic and safe construction. Hence, this paper provides important tools for decision-making as it expands the possibilities of using the pre-supported pipe canopy technology in tunnel construction.

There are a number of offshore wind farms where the monopile is socketed into rock layers. Since it is socketed into rock, it may behave different from monopile embedded in soil. A numerical modelling of rock socketed monopile is done using finite element (FE) software Abaqus. A stiffness degradation method (SDM) is applied to FE model in order to predict the behaviour under cyclic loading conditions. Parametric studies are carried out by varying rock socketed depth (d), length of monopile below seabed (L), intensity of horizontal loading (H) and subsoil conditions to evaluate the long-term permanent deformation of offshore rock socketed monopile foundations. Suitable permanent deformation factors are proposed for offshore rock socketed monopiles for the first time in the literature. It is observed from the results that the deformation behaviour of the monopile changes from stiff to flexible with increase in rock socketing and in turn the pile head deflection going down. From the bending moment diagram, flexible and stiff behaviour of monopile can be identified and is an indicator of curvature of the deflection line of pile.

There are multitudinous major river bridges in India which were built prior to the development of seismic codes and it is very difficult to predict the performance of those bridges during earthquake. Since bridges are the lifeline structures, it is essential to requalify these structures in light of the new and better understanding of seismic resistant design philosophies. This paper aims to carry out a requalification study of an important river bridge supported on caisson foundations (or Well Foundations). Field investigation and laboratory tests on soil samples from the bridge site are carried out and the data achieved are used as input values for the soil model. Two different types of earthquakes, each having different dynamic properties are considered for the study. The effective stress site response analysis is carried out and the liquefaction potential of the bridge site is evaluated. Analysis revealed that a large number of the soil layers are liquefied under the applied earthquake motions. Considering the liquefied soil, seismic analysis of the bridge is carried out. The seismic analysis gives the damage levels in terms of bending moments and displacements of the well foundation. The moment of resistance of the well section is calculated and the maximum bending moments under the considered earthquakes are checked with the moment capacity of the well. It is found that the well is safe under both the earthquakes. Hence, no strengthening or retrofitting strategies of the bridge structure are required for this study.

In this study, an efficient numerical method coupled PFC3D and FLAC3D was presented to simulate the tunneling behaviors of EPB shield. Groups of tunneling cases with different muck-discharging ratios were conducted in PFC3D and FLAC3D with data exchanging each other in every step. The results show the muck pressures in the back of spokes are invariably less than those behind the opening of cutterhead. Moreover, pressure differences exist permanently not just between left side and right side in chamber, but in different longitudinal positions within the domain affected by tunneling, and the values of these pressure differences are subjected to muck-discharging ratio in chamber. These findings extend knowledge regarding the tunneling mechanisms of EPB shield. Besides, the proposed coupling method can be popularized with all studies about the interaction between engineering devices and soil as well.

The Norwegian Public Roads Administration is currently running the “Ferry-free coastal route E39” project, which reduces the travel time along the Norwegian coast from Trondheim to Kristiansand. The plan includes the creation of several long tunnels, which will generate a surplus of blasted rocks; these could be used in the road unbound layers close to the place of production. The research presented here has three goals. The first aim is to map the geology encountered along the E39 road alignment. The second aim is to check whether the rocks fulfil the existing code requirements for road unbound layers, defined in terms of Los Angeles and micro-Deval limit values. The third aim is to investigate the crushing and the variation in grain size of the unbound materials during both construction phase and service life phase. The construction stage is achieved by a full scale testing to assess rock soundness after rolling, the service life stage is simulated by the repetition of a specific load in the triaxial cell apparatus. The current tunnelling operations located south of Bergen are producing blasted rocks, they adequately represent the geology spread along the entire E39 alignment. Three types of crushed rocks are selected and tested. The major part of the rocks excavated are suitable for direct use in pavement unbound layers. The most significant modification in grain size distribution curve takes place during the compaction phase for all the materials.

The coupled Eulerian-Lagrangian (CEL) method is a latest technology for simulating the large deformation and discrete geotechnical problem. In this paper, we use this new method to simulate the long-runout landslide which occurred at the Hong’ao landfill on December 20th, 2015, in Shenzhen, China. This landslide killed 77 people and destroyed 33 houses, regarded as one of the largest landfill landslide in the world. The field survey and previous research results after the accident are applied to validate the numerical model of the landslide. The long-runout behavior of the landslide is studied in terms of runout area, velocity, kinematic energy. The runout area of the simulation landslide is close to that of the actual. The maximum simulated velocity of the landslide is up to 35.41 m/s at 68 s which is close to the result simulated by the LS-RAPID. The maximum kinetic energy of the landslide is 2230.4 GJ at 68 s, and the frontier buildings might be impacted at 78.3 s, when the total energy of the landslide can be 2097.4 GJ, roughly equivalent to the explosive energy of 5 t TNT.

Signal synchronization is an important countermeasure to improve efficiency and relieve congestion for urban arterials. Scientifically evaluating the effects is the foundation for signal synchronization optimization. A signal synchronization evaluation and optimization model is proposed based on delay and queue length assessment at arterial intersections. With traffic wave theory, taking intersections’ phase and sequence, split, movement, link length and offset into considerations, the model can simulate the evolution of queue endpoint phase by phase, and get a polygon which can be used to calculate the control delay. The case study indicated that the model can accurately designate the influence of variable signal coordination parameters, and can be used to arterial signal synchronization appraisal and optimization.