IACGE 2018: Geotechnical and Seismic Research and Practices for Sustainability

A numerical model is presented of lateral spreading induced by liquefaction during 1989 Loma Prieta earthquake. An advanced plasticity constitutive model PM4sand is used to simulate the dynamic behavior of liquefied soil and the non-liquefiable soils are simulated by Mohr-Coulomb model within the soil profile. The soil strength and PM4sand parameters are estimated by SPT blow count. The motions recorded near the site are deconvoluted as input motions using equivalent linear method in FLAC 2D. Hysterics damping model and Rayleigh damping are used in the numerical model. The predicted lateral displacement is compared to the observed lateral spreading of the case. It is concluded that simulation of the lateral spreading could capture the generation and dissipation of pore water pressure of liquefied soil and the nonlinear behaviors of soil during the earthquake.

A simplified fractional-order elasto-plasticity model is proposed by using the concept of fractional-order plastic flow. Fractional differentiation on the modified Cam-clay surface is performed to determine the plastic flow direction. Unlike the classical model, the obtained flow direction changes with the fractional order, which makes the model capable of simulating various kinds of material deformation without changing the details of the yielding function. The proposed model is further validated by simulating multiple series of experimental results of different granular soils subjected to drained and undrained loading conditions.

The results of triaxial tests are always susceptible to instruments and operations, and it will also take considerable time and money to conduct the tests. However, the numerical simulation can reduce the unfavorable effects mentioned above and verify each other with the triaxial tests. In this paper, consolidated-undrained triaxial tests of silty clay under normal temperature were simulated by FLAC3D. Different models were built by combining some basic grids, such as cubes, pyramids, and so on. A kind of hexahedron grid model suitable for the simulation of triaxial tests conducted on silty clay with high precision was established. Then an effective method based on FLAC3D was proposed for the simulation of triaxial tests of silty clay. Comparison of experimental and numerical results indicate that the stress-strain curve has a good consistency in the ascent stage, and the relative error of ultimate strength is less than 5%. The numerical results are in good agreement with those of tests, and there is a good coherence in the stress path. It can be concluded that the numerical simulation can be employed to replace some tests and regarded as a supplement to the laboratory tests, which can reduce the workload and lower discreteness of the results. The paper is also a micro-level validation for the rock-soil mass analysis. The new understanding obtained here will provide some reference to numerical simulation based on FLAC3D.

In the near future several offshore wind farm are planned to be built in China with relatively high water depths. For these jacket and tripod constructions with mainly axially loaded piles are suitable as support structures. The current design of axial bearing resistance of these piles leads to deviant results regarding the pile resistance when different Chinese code methods are adopted. Hence, also a strong deviation regarding the required pile length must be faced. The reliability of a design method can be evaluated on the basis of a model error which describes the quality of a considered design method by comparing measured and predicted pile bearing resistance. However, only few pile load tests exist with regard to the thick overburden layer in coastal region of China. This paper presents 2 field axial pile load tests which were incorporated within a model error approach for the current used design methods for the axial bearing resistance, namely API, USACE, NGI, Chinese Building Code, and Chinese Harbor Code method. In addition also the reliability of the introduced design methods was evaluated. It is shown that the Chinese code methods are not reliable and lead to a significant deviation, and the NGI method seems to be more suitable for the determination of the tensile capacity for offshore piles compared to the other investigated design methods.

Originally constructed 1927, Hemet Elementary School was closed in 2009 and demolished in 2015 as a result of continued long-term settlement and structural damage. The cause of the settlement was evaluated to be hydro-collapse of loose alluvial foundation soils that extend deeper than 50 feet below existing grades. The new Hemet Elementary School will be located on the same site. The primary geotechnical design issue for the new Hemet Elementary School is the potential for more than 20 inches of seismically-induced settlement due to the presence of the San Jacinto fault less than one mile from the site. To mitigate the seismic settlement potential, multiple foundation options were evaluated, including piles, vibro-stone columns (VSCs), and ground improvement using the deep mixing method (DMM). DMM was selected as the preferred alternative since it could reduce potential seismic settlement to acceptable levels and accelerate the overall reconstruction schedule. The DMM-stabilized ground allowed the proposed structures to be supported on conventional shallow foundations. This paper highlights the ground improvement design and implementation methods.

Studies on the correspondences among shield tunneling parameters and their relationships with geological/hydrogeological parameters have significances to maintain good shield tunneling posture, to meet the requirements of construction schedule, safety, and quality, and to control ground subsidence effectively. In this paper, taking diameter 8.8 m shield tunnel of Zhuhai City to Zhuhai Airport intercity rail transit project as the background and according to real-time tunneling parameter recordings and engineering geology/hydrogeology prospecting reports, the correlations among shield tunneling parameters, and between shield tunneling parameter and geology/hydrogeology parameter were analyzed by normalizing each parameter in the process of shield tunneling, and by weighting processing on the contributions of geology/hydrogeology parameters of different strata, such as ground bearing capacity and permeability coefficient, to shield tunneling. The change trends of the tunneling parameters after “normalization” and weighted processing were illustrated and the corresponding rules between every two parameters were summarized. At the same time, the correlations between tunneling parameters and geological/hydrogeological parameters were analyzed. The results show that there is a good positive correlation between the total thrust force and the torque of the cutter head; there is a good negative correlation between the cutter depth and the cutter torque and the total thrust; and it is feasible to identify stratum based on the parameters of soil, including basic bearing capacity and soil permeability coefficient, and parameters of shield tunneling.

Owing to the requirements of shield machine posture adjusting and direction changing in curved tunnel, the hydraulic cylinders of the thrust system are diverged from the axes of the segments, which will make the segments in an unfavorable loading state. In this paper, combined with the construction characteristics of large diameter shield tunnel with small radius curve in the intercity rail transit engineering from Zhuhai urban to Zhuhai Airport and based on the practical engineering condition and tunneling parameter recordings, a 3-D space finite element model was set up for the shield tunnel during construction stage. Further, numerical simulations were carried out according to different working conditions, and the force and deformation of the segments were analyzed and given. Also, through parametric analysis, the influences of several factors, such as curve radius and magnitude, direction, and deviation of the jacks, on the force and deformation of the segments during shield construction stage, were studied. The results show that the lateral deformation of the segment in curved tunnel is significantly greater than that in straight line section; when the magnitude of the jack thrust is changed from small to large, the position of maximum lateral deformation (MLD) of the segment in curved tunnel is gradually transitioned from the inside to the outside of the curve; and as the magnitude of the jacks increases, MLD of the segment decreases but the minimum principal stress increases with the increase of jack pressure difference and obliquity.

Numerical simulation has been used to research the problem how to select the lateral artificial boundary distance for the uniform site and layered uniform site. The main factors and its influence on the seismic analysis results have also been studied. The main results can be summarized as following: the ratio between one side lateral artificial boundary distances and the soil depth (L/h) is the key parameter to affect the numerical results. But the error of the finite element method does not always decrease with the increasing of the L/h, in some range of L/h, the accuracy decreases as the L/h goes up. The ratio L/h corresponding to steady value are not affected by those parameters such as the site shear velocity and damping ratio and the excitation frequency, but the spectrum characteristics of the seismic wave have obvious effect on the calculating results, especially for the free-field boundary condition. For the one-dimensional site, tied degrees of freedom boundary condition achieved the best results, followed by free-field boundary condition and the viscous boundary condition is less suitable for seismic responses analysis of site. Whatever boundary conditions, we can get the steady results under the ratio of L/h larger than some value. The ratio of L/h usually can be moderately reduced for the layered uniform site than the uniform site.

Grouting method has been adopted to prevent the leakage and seepage in tunnel excavation. In order to investigate the diffusion behavior of grouting slurry in water-rich sand layer under hydrodynamic condition, series of model test were conducted using model chamber. Resistivity method was used in the model test to detect the slurry diffusion and compared with test results to verify the feasibility of this method. Grouting bulk was also inspected after grouting. Test results indicated that grouting slurry in water-rich sand spreads in an ellipsoid shape under hydrodynamic condition. The center of the grouting bulk is under the grouting outlet due to the effect of gravity action. Grouting method can effectively improve the physical and mechanical properties of water-rich sand and reduce the leakage risk. The range of slurry diffusion detected using resistivity method agreed well with the boundary of grouting bulk in the model test. This indicated that the resistivity method was effective in detecting the slurry diffusion under hydrodynamic condition.

Seismic-induced liquefaction is complicated and involves many aspects within the process, including shaking-induced volumetric strains, increased pore water pressure, ground water migration, reduced effective soil strength, water, and soil ejection potentially resulting in significant vertical and horizontal ground deformations. All these effects can impact lifeline infrastructure systems. Lifeline systems include water, wastewater, storm water, electric power, communications, transportation, solid waste management, gas, and liquid fuel systems. Increasing the complications, there are many cases where multiple liquefaction-related mechanisms impact the same lifeline components. This paper diagrams the earthquake-induced liquefaction problem in detail and tabulates known impacts to lifeline systems. Engineers and geologists can use the results to better understand the range of effects liquefaction may have on different lifeline systems, improving diagnosis of mechanisms and their impacts, and increasing lifeline resilience to earthquakes.

According to the study of the bearing capacity of GFRP (glass fiber reinforced polymer) composite pile, the model test of the reinforced concrete (RC) pile and GFRP composite pile are carried out. The horizontal load characteristics of these two kinds of piles are studied by stepwise loading method. The elastic modulus, the horizontal displacement of pile top, and the bending moment of the two piles are gotten from the loading test. The test shows that under the surrounding of a layer GFRP fabric around the RC pile, the elastic modulus is increased by 17.26%, the horizontal displacement of the top pile under 2000N is reduced by 22.13% and the maximum bending moment of the pile is reduced by 14.8%. The testing results show that GFRP fabric can improve the mechanical properties of the RC pile effectively.

The pile in slope under complex load is a very complex pile-soil system. In order to study the bearing capacity of pile in slope under the vertical and moment loads, and the effects of different moment loads on horizontal bearing capacity, a model test were studied. The test results showed that under the effect of applying vertical load in advance. With the increase of the bending moment load, the horizontal bearing capacity of the pile top is reduced. The bending moment increased from 0 N·m to 45 N·m, and the horizontal ultimate bearing capacity decreased from 396 N to 297 N. The moment load has a significant effect on the horizontal ultimate bearing capacity.

In order to study the development of the displacement and the axial force of the anchor during the excavation and support of the high and steep slope reinforced by the prestressed anchor, the high and steep slope project of Shimen Mountain in Dalian was taken as the background. The displacement response and the change of anchor axial force were studied by field measurement and numerical simulation during the slope excavation, and the influence of the anchor parameters on slope stability was analyzed. The results show that it is possible to infer the unstable position of slope according to the displacement response of slope and the stress of anchor determined by the continuous monitoring data, which can provide reference for the design and construction of slope engineering. The displacement response and the change of the internal force got by numerical simulation are consistent with the measured results, which shows the numerical simulation method can predict the deformation of slope and the axial force of anchor well. As important parameters of prestressed anchor, prestress, and anchor spacing have great influence on the stability of slope. Both increasing prestress value and reducing anchor spacing can limit the displacement and increase the stability of slope effectively, but the influence will be less obvious if exceed the limit value. Different excavation and support methods have significant effect on the safety and stability of the slope. The layered excavation method behaved better than the excavation method of one slope to the end in limiting the displacement of the slope, which is more conducive to ensuring the safety and stability of slope.

The dynamic time-history method is one of the methods with high accuracy to analyze the seismic response of the shield tunnel structure. However, it is hard to apply in engineering practice for complex boundary conditions and nonlinear constitutive. This paper has derived the analytical solution of internal force of the structure with the soil-circular tunnel in no slip. The internal force and displacement of Suai shield tunnel structure has been calculated by PROSHAKE and ABAQUS under the action of artificial wave and Iwate wave. It can be shown that the distribution of internal force in different position of analytic solution is similar to the numerical solution after comparation. Though the internal force peak value of numerical solution is larger than analytic solution, the relative error in different case is less than 10%. It can meet the requirement of accuracy in engineering and prove a simple algorithm for the analysis of lateral seismic response.

A plasticity model for simulating three-dimensional (3-D) hysteretic behavior of frictional materials is presented. The target application of the model is 3-D nonlinear seismic analyses involving simultaneous cyclic loading in multiple directions. The model, implemented in the program FLAC3D, is a generalization of the one-dimensional (1-D) parallel Iwan model, in which a number of components are connected in parallel, each component consisting of a linear elastic spring in series with a perfectly plastic slider. This simple arrangement produces non-linear stress-strain curves and hysteretic, Masing behavior for 1-D cyclic loading. Remarkably, this approach can also be used for simulation of 3-D cyclic loading. For generalization to 3-D, the constitutive model consists of a number of 3-D linear-elastic, perfectly-plastic components with Mohr-Coulomb yield conditions. All components are subjected to the same strain, with the global stress defined as the average of the component stresses. This simple framework is straightforward to implement numerically, leading to a robust tool for analysis of general 3-D stress paths. The model’s performance for a complex non-proportional loading path is demonstrated through simulations of drained true triaxial tests involving stress rotation in the deviatoric plane.

This paper present a simplified multiple yield surface (MYS) plasticity model. For each yield surface, the Drucker-Prager type of yield function is used to represent the stress states for which plastic flow occurs. To simplify the formulation, the plastic potential function is selected such that pure shear results in pure shear deformation and a hyperbolic relation is used to represent the stress-strain backbone curve. In the development of numerical algorithm for the model, the concept of “virtual surfaces” is applied to locating which yield surface is activated after plastic flow occurs. The numerical algorithm is implemented into the finite difference computer program FLAC through a FISH (a special language) subroutine. To evaluate the model performance, numerical simulation of triaxial tests, and numerical prediction of the bearing capacity for a shallow footing are performed and the numerical results are compared with the test results and the closed-form solution or other method, respectively. The comparison indicates that the simplified MYS plasticity model can represent the soil material behavior reasonably well.

The shear behavior between soil and solid surface is of importance for foundation structures such as pile, suction caisson, retaining wall, and anchors. In this study, the interface behavior between concrete plate and silty clay were investigated. The interface friction angle of interface was calculated through analyzing test results. In addition, the set-up effect of shear stress between concrete plate and silty clay was also discussed. All tests were performed in a modified direct shear device under different vertical normal stresses. Test results indicated that the friction resistance between concrete plate and silty clay is closely related to normal stresses and consolidation time.

Elderberry Forebay Dam is a zoned earthfill embankment dam. This paper presents a seismicity study that was performed to develop the design ground motion in terms of response spectrum for the dam. In the study, the current state-of-practice methodology was applied in accordance with standards and guidelines available for the California Division of Safety of Dams (DSOD) jurisdictional facilities. Deterministic seismic hazard analyses (DSHA) were used considering all appropriate seismic sources within the vicinity of the dam site. Response spectral values were calculated using the 2014 NGA GMPEs and input parameters for these equations were based on systematic site and source characterization efforts. Based on the results of the DSHA, it is recommended that the controlling maximum considered earthquake (MCE) event for the dam is a magnitude 7.2 event on the San Gabriel Fault. The design response spectrum for the dam is provided.

Elderberry Forebay Dam is a zoned earthfill embankment dam. This paper presents results of seismic stability analyses on the dam using the recently developed design response spectrum. In the analyses, the Bray-Travasarou method was used to estimate earthquake-induced embankment slope displacements. For comparison purpose, earthquake-induced embankment slope displacements were also calculated with the Makdisi-Seed method. To represent the dynamic resistance of the dam, the yield accelerations determined from the pseudo-static analyses were used. The results of the analyses indicate that the dam is expected to deform under the maximum credible earthquake. The estimated earthquake-induced displacement for the most critical full reservoir condition is approximately 13.34 to 49.57 cm (0.44 to 1.63 ft). The sliding displacement may result in minor settlement and cracking of the crest and in surface raveling of the embankment slopes, but are not expected to compromise the integrity of the dam. The displacements are not expected to adversely affect the outlet conduit. The dam is likely to survive the potential earthquakes with only minor damage, and thus does not pose a significant safety hazard.

A study was conducted to evaluate ongoing erosion of the upstream riverbank slope at the Pleasant Valley Dam. There is continued erosion concerns along the western shoreline abutment and potential future damage to dam structures due to slope failure caused by erosion. The dam is composed of compacted earth fill containing a mixture of gravel, sand, and silt; and the abutments are composed of Bishop Tuff. A geotechnical and geochemical investigation was performed consisting of core rock sampling, bulk sampling, and reservoir water sample testing. Geotechnical, geochemical, and wave runup and wind setup analyses were performed to provide mitigation recommendations. Geochemical analyses indicated that chemical dissolution of the earth materials is insignificant, and that clay swelling is also not a factor. The wave runup and wind setup analyses simulated wave action and erosive forces; indicating wave heights of 1.5 to 1.8 feet and strength testing along this zone did not indicate weakened rock. The freeze thaw mechanical weathering is considered one of primary causes for the erosion. The overall results indicate that mitigation should focus on controlling sequential wetting and drying near the air-water interface, and/or limit the penetration of water in the erosion area to avoid mechanical weathering.

In this paper, based on basic thought of discrete element method, a 2D generation algorithm of irregular particle generation and particle contact interface generation was adopted. Particle contact constitutive model is induced. Started from microscopic structure of jointed rock mass, microscopic particles parameters, and macroscopic mechanical of rock mass parameters are unified. The damage numerical model of jointed rock mass is established by the microscopic realization of rock material damage from the bonding strength degradation of particles. After its feasibility is proved, by sandstone uniaxial compression experiment, the damage numerical model is applied in Eastern Qinling tunnel collapse. It is found that the model can reproduce the features of rock mass behavior. Moreover, it is useful for the prevention of future tunnel collapse accident.

The research of islands is a new area for many countries to improve their comprehensive national power and compete for long-term strategic advantages. China enjoys abundant resources of islands, but Chinese islands are earthquake-prone, for the reason that they are distributed in the intersection zone of the Pacific plate and Eurasian continent plate, which is seismically active. The characteristics analysis of island earthquake disaster mainly references to the study of earthquake disasters of inland or ocean, and is not analyzed as a specialized theme. This paper systematically analyzes the historical earthquake disaster data of China's islands, and forms the influencing factors of earthquake disaster of island, considering its sea and land comprehensive characteristics and unique disaster-bearing body feature. Finally, the characteristics system of island earthquake disaster is constructed in seismological background, geological background, disaster-causing factors, disaster-bearing body, climatic characteristics of the island, and evacuation after earthquake.

To obtain the dynamic response of vertically loaded pile close to rigid boundary, a computational model of a pile embedded in viscoelastic soil is established. Based on plane strain assumption of the soil, axisymmetric governing equation in cylindrical coordinates system is established. To obtain zero displacement for the rigid boundary condition, mirror method is adopted to solve the governing equations of the soil. The dynamic response of pile is then obtained based on the perfect contact condition on pile-soil interface. The present solution is validated through comparisons with Novak’s solution. The effects of pile length and distance from the rigid boundary are analyzed. The results are potentially useful to understand the vibration characteristics of piles constructed in irregular topography and geology conditions.

The 2008 Wenchuan M_s 8.0 earthquake caused extensive naturally deposited gravelly soils liquefied. The merit of the observation overwhelms the engineering point of view of gravel as non-liquefiable soil, and greatly enriches archiving field cases of gravel liquefaction worldwide. Though years of systematical studies, we mapped the 92 identified gravelly soils liquefied zones (sites) as sporadically lay in an area of more than 3000 km² in Chengdu Plain. The gravel contents (G_c-values) of liquefied gravelly soils range from 5% to 85% or even larger. The liquefied gravelly soils are loose, but their measured shear-wave velocities (V_s) start from 133 m/s to 267 m/s, and are corrected to 154 m/s to 314 m/s. The PGA-values are predicted from 0.15 g to 0.49 g at liquefied gravelly sites. The shallow soil structure under Chengdu Plain basically consists of an impermeable capped layer and underlain gravelly soils ranging from meters to hundred meters, which provides a fundamental interpretation for gravelly soils liquefaction. A minimum ground shaking of PGA 0.15 g is essential to trigger natural gravelly soils liquefaction, yet massive gravelly soils liquefaction requires 0.20 g to 0.40 g of ground shaking intensity.

Culvert is commonly constructed in the highway embankment at regular intervals. When subjected to certain serious damages, such as top cracking, culvert sinking, etc., its normal operation will be affected to some extent. Therefore, it’s essential to study the mechanical and deformation characteristics of highway culvert. From the perspective of the interaction between the fill, the culvert, and the ground, this paper investigates the influences of the ground stiffness, range of ground treatment on the mechanical and deformation characteristics of the culvert, and the surrounding soils. Comparisons with the previous studies indicate that the results are reliable and capable of providing preliminary guidance for design and construction of highway culvert.

Seismic analysis of monopile supported offshore wind turbine is studied, with the Lely offshore wind farm as an example. Based on the unified plasticity model for large post-liquefaction shear deformation of sand, a three-dimensional dynamic finite element analysis is established. Then following results are got. Under the load coupling of wind and earthquake, the pile occurs large displacement and inclination which exceeds the operation safety line 0.17°. The increase of bending moment is small, which indicates that the pile has weak anti-overturning capability and relies mainly on the soil reaction force around. Therefore, the pile rotates in center of the pile bottom under load, showing the increase in displacement. And the seabed sand liquefaction increases the pile inclination. Both the inertial interaction of the structure and foundation and the pile-soil interaction are large, which increases the deformation and results in residual bending moment of the pile. Therefore, seismic analysis and safety assessment of pile foundation must be studied for offshore wind farms in earthquake areas.

Solidification/stabilization technology has been used extensively to reduce the mobility of heavy metal contaminants and improve the mechanical properties of the soils. Its effectiveness depends on the complex interaction among curing agent, heavy metals, and soil, which could be significantly affected by the external environment. However, the effects of long-term extreme weather conditions including freeze and thaw on the strength of the stabilized lead contaminated soils have not been investigated. This study presents a systematic investigation on the impacts of freeze-thaw (F-T) cycle on the strength properties of stabilized lead contaminated soil. The lead contaminated soil was prepared in the laboratory using a systematic strategy. Several series of tests are conducted including unconfined compression tests (UCTs) and direct shear tests on the soils subjected on the freeze-thaw cycles as well as standard cured conditions (temperature of 20°C and a relative humidity of 95%). The results show that the freeze-thaw cycles have much significant impact on the strength of stabilized lead contaminated soils. After the freeze-thaw cycle tests, the unconfined compression strength, as well as the friction angle and cohesion force, were significant decrease. However, the strength loss ratio of unconfined compression depend on the binder, freeze-thaw cycles times, and extreme temperature of the freeze-thaw cycles. This study provide scientific basis for remediation of heavy metal contaminated site and prevention and treatment of heavy metal pollutant in seasonal freezing area.

With the rapid development of road and railway constructions, it requires more stringent standard for the safety and stability of road and railway foundation. The pile foundation will be affected by the static and dynamic loading. A new quasi-distributed fiber Bragg grating (FBG) optic fiber monitoring technology is used to study the deformation characteristics of pile, the static and dynamic loading test system based on FBG is developed for the pile dynamic monitoring. The test system can measure the dynamic response of pile under working condition. It provides reference for the study of pile under dynamic loading and promotes its application in the related road and railway projects.

Soil liquefaction has a strong influence on ground motion so that an effective analytical method of seismic response of liquefiable sites has to be established. The key of a liquefaction model is to simulate pore-water pressure process during liquefaction. The existing pore-water pressure models are mainly total quantitative models which can seldom simulate the process of liquefaction under irregular loadings. The pore-water pressure modes predicted by the incremental quantitative model which was obtained by regressing dynamic triaxial tests data are noticeably different from those of shaking table tests and centrifuge tests. A revised incremental pore-water pressure ratio model is proposed by modifying the pore-water pressure increasing modes proposed by Sun et al. The proposed model was testified by shaking table testing results under sinusoidal and irregular loadings. The results indicate that the revised model can better simulate the pore-water pressure buildup process under sinusoidal and seismic loading than the original model.

Affected by underground mining, the ground surface undergoes significant subsidence and horizontal movement. Therefore, the pile foundations above the mining area not only bear the vertical load, but also the additional load caused by the horizontal movement of the surface. Based on the surface horizontal movement of the mining area, the horizontal movement pattern of the surface is divided into four modes: rectangle, triangle, inverted triangle, and parabola. The effect of the horizontal ground surface movement on the pile is mainly caused by the pile-soil relative displacement. The lateral movement modes of the different mining soils have different effects on the horizontal bearing characteristics of the pile foundation. Two types of flexural deformation occur in the pile under the four soil lateral movement modes. The elastic strain, additional earth pressure, and compressive deformation of the pile present two kinds as well. Under the same displacement, the rotation point of the pile is the lowest and its inclination is the maximum, and it is subjected to the positive triangular lateral displacement mode. The inclination of the pile is the smallest and its bending moment is the largest when induced by the inverted triangular soil lateral displacement. Under the parabolic soil lateral movement, the pile deflection is the smallest.

Previous studies have shown that site-city interaction (SCI) is important for sustainable seismic design in a congested urban environment. However, due to its complexity, the phenomenon is not yet fully understood. A fully integrated 3D model was developed herein to analyze the problem using a transportation hub in Hong Kong as a testbed. The site assumes a typical downtown layout with a central plaza, a large underground chamber surrounded by 16 high-rise buildings with deep foundations. This investigation aims to explore SCI emphasizing soil-underground structure-soil interaction (SUSSI) and contamination of the site response caused by the dense building cluster. To simulate visco-elastic wave propagation, a discontinuous Galerkin spectral element code (SPEED) is employed. Key SCI effects manifest in a wavefield propagating from the buildings and surface waves trapped in-between them. The propagated wavefield travels up to 450 m with 20% increase in peak ground accelerations (PGA) compared with the free field. In the center plaza, 70% increase in PGA is observed. Furthermore, a coherency analysis was conducted to quantify the spatial variation of ground motions. The building layout and subsurface structures govern the SCI phenomena, which highlights the importance of realistic fully integrated modeling for sustainable urban design.

Deformations induced by the unstability of residual cavities have seriously harmed the safety of the building in mining area. In order to analyze the influence of the residual cavities on the buildings, an effective method called high density resistivity tomography geophysical technology has been used. Then the residual cavity zones and their horizontal locations and vertical depth have been obtained. Based on the detection results and related theory, the mechanism of deformation and reasons of building damage in mining overburden residual cavities under construction load have been analyzed. According to the locations of the residual cavity zones and the distribution of the additional stress of buildings, the safety of buildings affected by residual cavities has been investigated. The calculated-depth of foundation deformation is suggested to be above the depth where the ratio of additional stress p_z to the soil gravity stress σ_z is 0.1(p_z=0.1σ_z). If the depth of the residual cavities located beneath this calculated-depth, the foundation deformation range should be chosen above the depth of residual cavity zone. The method and analysis process proposed in this research will provide an important reference for safety evaluation of the buildings located in the areas affected by mining residual cavities.

A series of compaction tests were carried out on calcareous sand which were mainly source of hydraulic fill foundation in a reef of the South China Sea. With the increase of water content, compacted dry density of calcareous sand decreased firstly, and then increased and finally decreased. It means that calcareous sand has both optimum water content and worst water content. By comparing compaction curves of calcareous sand with different gradings, the influences of gradings and evolution law of special compaction characteristics of calcareous sand were revealed. The results show that the quality of gradings affects variation range of compacted dry density. Fine particle content affects the value of worst water content and peak water content as well as the overall value of compacted dry density. Based on the saturation-water content curves, a fitting function for compaction curves of calcareous sand was established. The above conclusions provide theoretical references for the design and treatment of hydraulic fill foundation of reefs.

Considering the low bending strength of the ordinary tabular EKG and low efficiency of drainage in the late period of electro-osmosis in combination with vacuum preloading method, six laboratory tests were researched using improved tabular EKG and new-style tubular EKG in a self-developed device. The electrode conversion and applying stepped voltage were used in the laboratory tests. By monitoring drainage rate, current, moisture content, settlement, and strength, the treatment effect of these methods were compared with each other. It showed that: (1) The drainage amount of soil treatment using the improved EKG is 2,054 ml. It is much larger than the drainage amount using the ordinary EKG. The drainage effect of the improved EKG is better. (2) The effective potential and current intensity using the improved tabular EKG process better than tubular EKG, but drainage rate and the drainage amount using the tubular EKG are larger than the improved tabular EKG in the early 10 hours. Therefore, the effect of the test in the further studies can be improved, if the above two EKG electrodes can be used together for marine clay treatment. (3) In comparison to applying 20 V constantly, the technique of stepped voltage decreased the decay rate of current, which also caused the increasing of drainage amount and electroosmotic efficiency in the late period of experiment. Furthermore, reasonable stepped voltage applying plan is needed to meet the requirements of energy-saving, and therefore pose contributions to the improvement of electro-osmosis combined vacuum preloading method.

The cone penetration test (CPT) has been widely used as one of the most popular performance test for ground improvement. Most of the acceptance criteria based on CPT result is only correlated with single factor—relative density. It is rarely common to see the acceptance criteria is built based on multi-factors incorporating relative density, liquefaction susceptibility, bearing capacity, and allowable long-term settlement. Therefore one comprehensive acceptance criteria ground improvement is proposed for Al-Zour LNGI project in Kuwait. In accordance with the analysis, the compaction criteria can be built by applying Baldi method based on the site specified correlation between relative compaction and relative density. While for the liquefaction susceptibility criteria, it can be built by the Youd and Idriss method using soil behavior index $I_c$ based on the reclamation quality controlling class. Moreover, the bearing capacity and allowable long term settlement criteria can be built based on CPT test. In order to verify the comprehensive criteria, one zone load test (ZLT) with four CPTs being performed at four corners was analyzed. Based on the CPT result, the performance result might fail if only considering one compaction criteria, however, the ZLT result shown that the bearing capacity along with the predicted long term settlement can meet the design requirement. Hence, the criteria taking into account the liquefaction susceptibility, bearing capacity, and allowable long-term settlement together with compaction degree seem more reasonable and reliable.

Inevitably, a lot of dredging silt is produced in the process of port construction and waterway dredging projects. Since the traditional process of abandoning and burying causes environmental problems, how to deal with it is a hot issue which draw both domestic and foreign attention. Mix other materials into dredged silt bricks and then test the basic mechanical properties of the silt bricks. Considering different cement content, curing age, and slag addition proportion, the results of the test indicate that there is a linear relationship between the compressive strength and cement content of the bricks, and failure strain gradually decreases with the increasing cement content. By keeping the total amount of cement and slag under certain circumstances, the compressive strength of bricks first increases and then decreases with the increase in the amount of slag, indicating that there is an optimal alternative amount of slag for cement. After dredging silt treatment, the compressive strength of silt bricks can be up to MPa magnitude. These silt bricks can be used as channel slope and parkway, which provides a viable, economical, and beneficial solution for dredged silt treatment.

Active fault is one of the major problems in engineering geology research. The ground ruptures generated by the activity of the faults are great hazards to the projects. The location and activity of active fractures have a major impact on the site selection of railways, highways, water conservancy, and hydropower projects. During the construction of a certain railway, the author studied the activities of the faults distributed across the entire line, and conducted a deep research on the Zhongtiaoshan north piedmont fault (ZNPF), which has significant influence on the project. Based on the data collectiong and efield investigation, together with the remote sensing, geophysical prospecting, drilling, trenching, and other methods, the location and activity of ZNPF is determined. The potential zone influenced by active fault is evaluated, based on which the suitable engineering measures are adopted crossing the whole active faults.

This paper presents an experimental investigation on the shear strength behaviour of expansive soil reinforced with bagasse fibre. Bagasse fibre, an agricultural waste by-product left after crushing of sugar-cane for juice extraction, was employed in this study as a reinforcing component for expansive soil reinforcement. The expansive soil used in this investigation was collected from Queensland, Australia. To experimentally investigate the influence of bagasse fibre reinforcement on the shear strength of expansive soil, a series of non-reinforced and fibre reinforced soil samples was prepared by changing randomly distributed bagasse fibre content from 0% to 2%. An array of intensive experimental tests using triaxial compression apparatus was carried out and its results are presented and discussed in further detail. The experimental results reveal that bagasse fibre reinforcement exhibited significant effects on shear strength characteristics of reinforced soils in terms of relationships between deviatoric stress and axial shear strain, ultimate deviatoric strength, and shear strength parameters.

In the case of earthquake, soil is prone to damage and its dynamic characteristics will change so that it has great influence on seismic response characteristics of the slope. Therefore, it is of importance to accurately identify the seismic damage for improving seismic performance of retaining structures of reinforced slope. In view of this, based on Hilbert-Huang transform (HHT) method and marginal spectrum identification theory, the slope reinforced by sheet pile wall was selected as the research object to analyze the seismic damage of soil. According to the analysis, it is found that marginal spectrum amplitude (MSA) of measuring points in a same sequence basically satisfies linear growth trend and the amplitude doesn’t change greatly when there are no obvious ruptures in soil, whereas the curve of MSA mutates somewhere due to the damage of soil if peak ground motion acceleration (PGA) is large enough. Therefore, seismic damage in soil can be judged by the mutation of MSA. Additionally, the results are consistent with those observed from shaking table test and it also confirms that the feasibility of HHT method can identify seismic damage of slope soil.

Buried gas pipeline is the lifeline of national economy, and inevitably crosses fault when pass through rivers and mountains. In view of this, it is of great necessity to make clear the response characteristics of buried gas pipeline under different fault movements. In this paper, the software ABAQUS was used to carry out related studies. On the basis of nonlinear theory of materials and structures, contact model was used to simulate slide, separation, and closure between pipeline and soil. The application of the constitutive three-fold line model and Mohr-Coulomb model in the simulation were realized. The boundary condition was determined by considering the application of fault displacement. The influence of different fault types was studied by stress/strain-pipe axial length curves. In addition, the deformation, distribution of stress and strain, location of potential damage, and interaction between pipeline and soil under different fault movements were analyzed. The damage level of pipeline was evaluated by plastic dissipation energy. The analysis results show that the response characteristics of buried pipeline are closely related to the fault type, and relatively sensitive to reverse fault. The peak stress-strain of pipeline appears near both sides of fault, which is the location of potential damage of the pipeline. The analysis results can provide reference for seismic measures of cross-fault buried gas pipeline.

Bender-extender element tests have been commonly used in a laboratory to obtain shear wave velocity and compression wave velocity of soils. There are obvious advantages of bender-extender element test method, e.g. its apparent simplicity and ease of use. However, there is still no unified standard for the test because the reliability of result is affected by a number of factors. In this study, the effects of boundary conditions on measurement of shear wave velocity and compression wave velocity of soils in bender-extender element test are investigated. In order to compare compression wave velocity of distilled water and shear wave velocity of dry sand, a series of calibration tests are performed by varying boundary materials, heights, and wall thickness of the sample constraints. It reveals that the compression wave velocity of distilled water does not be affected by the boundary conditions of sample, but the experimental results of shear wave velocity of dry sand are indeed affected by boundary conditions and the excitation frequency of bender-extender element.

The earthquake dynamic responses of a landslide with low dip angle under different governance conditions were simulated through computational modeling. Five conditions with different governance schemes are studied. The results turn out that the main cause of the landslide is the groundwater produces a floating force acting on the bottom of the landslide body, and the hydrostatic pressure acting on the trailing edge, coupled with the groundwater and rainfall which weakened the soil strength and a sliding plane formed. The maximum horizontal displacement by different governance schemes is decreased by 45.4%, 70.9%, 72.6%, and 83.6% under gravity, respectively, and the maximum horizontal displacement is reduced by 21.56%~26.67%, 61.44%~69.62%, 60.26%~68.33%, and 74.41%~82.26% after earthquake with different amplitudes, respectively. The anchor on the trailing edge is effective and vital in the governance of landslide with low dip angle. The bending moment of the slide-resistant pile in each case increases with the burial depth and peaks at 2~3 m beneath the sliding plane, then the bending moment decreases with depth gradually.

In the process of excavation and sinking of the open caisson, there is a risk that the excavation quantity is too large to cause the influx of the lateral soil of the open caisson to the inside of the borehole wall. Which caused the gushing sand or sudden sinking of excessive sudden situation. The bearing capacity of the soil surrounding the open caisson cutting edge is the key factor of the excavation settlement and the limit of mud height. This article is based on the finite element numerical simulation, by controlling the variable method, with cohesive force and angle of internal friction of the soil surrounding the open caisson cutting edge as variables, analyzed the impact on the excavation of the open caisson sinking. Analysis the influence factors of the internal friction angle as the main. At the same time, through curve fitting of angle of internal friction, the excavation settlement and mud height to the change of the relations, and determined the limit mud height of this calculation model. The results show that the soil cohesion at the cutting edge has an effect on the total sedimentation under the caisson load, and the effect of the total amount of the excavation is small. During the process of sinking, the friction angle of the soil at the cutting edge has a great influence on the total sedimentation under the caisson load and the total amount of excavation. The larger the internal friction angle is, the smaller the total sedimentation under the caisson load, the larger the total settlement of the caisson excavation, the smaller the height of the caisson mud surface, and the smaller the decrease of the mud surface. The internal friction angle and the initial mud surface height satisfy the first order linear relationship, and the total settlement of the excavation also satisfies the first order linear relationship. The total amount of excavation and excavation meet the second-order linear relationship. The total amount of excavation and excavation in different soil layers can be calculated by using the formula given in this paper, and the maximum excavation and mud surface limits are calculated.

Large hydropower plants in southwestern China usually involve the excavation of underground powerhouses. The underground cavern complex of Baihetan hydropower plant is the largest underground cavern complex currently under construction. As a study case, its seismic stability was comprehensively studied in the current paper. Firstly, the magnitude of ground motion level of design ground motion and ground motion earthquake are discussed according to the results of earthquake safety assessment, as the basis of earthquake power problems. With which the seismic wave forms used in the analysis were synthesized. Then, a medium-rate cyclic loading test was adopted to provide reasonable dynamic strength parameters of rock mass in the seismic dynamic analysis. Finally, two kinds of layout schemes of underground caverns are discussed from the point of view of seismic stability with three-dimensional numerical dynamic simulation. Meanwhile, the seismic capacity of supporting measures was checked. The results show that the improved design with a cylindrical tail surge shaft is safer than the origin design under the impact of earthquake. And the stability of the cavern complex can be well maintained under both the design basis earthquake and the safety evaluation earthquake.

The two models commonly used of response displacement method for seismic analysis of underground structures were introduced, the theoretical calculation of these two models for response displacement method were compared and analyzed, put forward a simplified response displacement method (SRDM) for shallow buried underground structure using new load-structure (NL-S) model. Based on the classical response displacement method (CRDM), SRDM simplified the earthquake action of input underground structures, and neglected some computations which are cumbersome and small. Finally, SRDM was verified by an example. In the calculation, the general analysis of SRDM was carried out by changing the following 3 aspects: soil properties, seismic wave type, PGA. The 3 methods of time history method (THM), CRDM, and SRDM were used for calculation. The results of SRDM were compared with the results of the other two methods. The calculation results showed that the SRDM is the most convenient and suitable for practical engineering application, and its calculation precision is high.

Landslides always cause catastrophic disasters, and rainfall is one of the most important factors to stimulate landslides, especially for the slope with weak interlayer. Most of existed studies are aimed at the homogeneous structure of slope or the dual structure of slope. The paper was based on the unsaturated soil seepage theory, and a slope model with weak interlayer was established, and the strength reduction FEM was used to analyze the slope with weak interlayer under rainfall infiltration. During the rainfall, the variation regularity of the saturation, pore pressure, displacement, and plastic strain in the slope were revealed, and the mechanism of the buckling failure of such kind of slope was discussed. The results would have a great practical value for the prevention and treatment of landslides.

In order to compare the different probabilistic approaches based on cone penetration test (CPT) and standard penetration test (SPT), seven pairs of CPT-SPT field test were collected from Al-Zour LNGI project in Kuwait and was analyzed. Based on the collected data, the correlation of CPT-SPT was investigated. The results show that the tradition correlation using soil type index Ic is not applicable, however the direct correlation analysis for qc/N equaled to 0.58 presents a good result with coefficient up to 0.8528. Besides, the two adopted probabilistic methods are compared with deterministic method, the comparison results depict that the boundary curve of SPT and CPT deterministic method are equal to 30% and 50% respectively for mapping function probabilistic (MFP) model. While for logistic regression probabilistic (LRP) model, the boundary of SPT and CPT deterministic method are characterized by probabilities ranging from 10~50% and 30~50% respectively. Moreover, the CPT-based probability curves obtained from LRP method are quite matched with MFP model. While in the case of SPT probabilistic, the differences between LRP model and MFP model are increasing with probabilities increasing. Further, two different probabilistic method based on 65 pairs of CPT-SPT data and equivalent SPT data, i.e. N₆₀ value and FC value were both calculated from empirical correlation, are applied to calculate the probability and the liquefy percentage, the result depicts a sequence relation for probability and liquefy percentage: SPT group>CPT group>equivalent SPT group for LRP model or MFP model. While for the same probabilistic method, the MFP obtained a higher probabilistic than LRP model.

A series of shaking table model tests on a sawdust mixed clay site model were conducted at the shaking table testing system with 9 sub-tables in Beijing University of Technology. The tests were performed using a rigid prefabricated continuous model box with dimensions of 7.7 meters long, 3.2 meters wide, and 1.2 meters high. The test system was subjected to strong ground motions from El Centro record and Tianjin record. Through shaking table tests, the dynamic characteristics of the model site were obtained, including the peak ground accelerations and their amplification factors, acceleration time histories, and their Fourier spectra for the site responses. The test results show that: (1) With the increase of intensity of input ground motion, the peak ground acceleration of the site response at the same test point increases, but its acceleration amplification factor decreases. (2) The main frequency components move from high to low frequency. It means that the soil became soften and soil modulus decreased gradually with the increase of intensity of input ground motion.

The dynamic compaction method is commonly used to improve the compaction effects of granular soil foundation since it can’t be easily compacted via conventional methods. Based on the field test performed in Chongqing Jiangbei International Airport, this study firstly analyzed the reinforcement mechanism of the dynamic compaction. The calculation method for the effective treatment depth as well as the influences of key design factors on the reinforcement effect were subsequently investigated. The proposed comprehensive detection method, is capable of assessing the compaction effect from multiple aspects, qualitatively and quantitatively. In addition, the detection results are both economic and reliable. The effective treatment depth calculated by the theoretical solutions agrees well with the measured results, indicating the effectiveness of the compaction method and the applicability of the proposed comprehensive detection method.

Comparisons between an Euler modelled large diameter pipe pile and a Timoshenko modelled large diameter pipe pile are developed to obtain the steady-state response of horizontally loaded pipe pile embedded in a homogeneous soil and resting on a rigid base. In the analysis, the soil is simulated as an axisymmetric linear viscoelastic continuum and the pile is modelled as an elastic Euler rod and Timoshenko beam, respectively. In the process of comparative studies, second-order effects of vertical loads applied on the pile head are considered and the soil surrounded in the pipe pile is also taken into account. Based on the existing analytical solution, comparisons between the Euler model and Timoshenko model are performed to investigate effects of shear deformation and inertia, second-order effect, and inner soil on horizontal dynamic response of the large-diameter pipe pile. Furtherly, the plots developed from the parametric study can provide reference for engineering application.

Small strain stiffness properties of soil play an important role in predicting the deformation of deep foundation pit and tunnel excavation. Based on a case of safety analysis for surrounding pipelines adjacent to a deep excavation of subway station in Changzhou City, a two-dimensional finite element model to analyze this typical problem is proposed. Small-strain of soil is considered to investigate the effect on surrounding pipelines of deep pit excavation. Based a series of laboratory tests, the small strain properties of typical undisturbed soils in Changzhou are investigated and the related parameters involved in the hardening soil model combined with the small strain model (HSS) are determined. By comparing simulation results with the actual measurement, it shows that the deflection of retaining wall is obviously reduced when the small strain stiffness of soil is considered in numerical analysis. And the calculated result is much close to the observed. Meanwhile, a simplified analytical method for safety analysis of underground pipelines adjacent to the deep excavation is proposed and the applicability of HSS model is verified.

This paper presents results of a geotechnical investigation for relocating two towers to accommodate widening the existing highway of Caltrans SR-138 in Cajon Pass, San Bernardino County, California, USA. These two towers, numbered as 203-I-3 and 203-II-4, are part of the Victorville-Century Transmission Lines 1 and 2 owned by Los Angeles Department of Water and Power (LADWP). Tower 203-I-3 was located on the south side of SR-138 and proposed to be relocated 30.63 m (100.5 feet) away from the existing location along the transmission line to the southeast. Tower 203-II-4 was located on the north side of SR-138 and proposed to be relocated 23.53 m (77.2 feet) away from the existing location along the transmission line to the northwest. The geotechnical investigation consisted of a field exploration and laboratory testing program, engineering analyses, development of recommendations, and preparation of a report. The field exploration included drilling two hollow-stem auger borings and conducting two seismic refraction surveys. Based on the information obtained from the field exploration and laboratory testing program, the proposed tower relocation sites are generally underlain by a layer of dense to very dense sands and silty sands with gravel. In accordance with the subsurface conditions and anticipated tower loads, cast-in-drilled-hole (CIDH) reinforced concrete piers are recommended to support the new towers. Axial capacity and lateral response analyses were performed on 1.22-m (4-foot) diameter CIDH piers. The analyses considered the situation that one of the piers is located near a slope with a height of 2.44 m (8 feet) and a gradient of 1.667:1 (horizontal:vertical). The results of the analyses are summarized in the paper.

Landfill seismic instability often leads to disastrous consequences of accidents, which makes it particularly important to the stability analysis of landfills in the landfill engineering. The seismic stability analysis of this paper focused on the composite failure mode of landfills. In order to study the seismic stability of the landfill against composite failure mode, the log-spiral slip surfaces were introduced into the internal failure of the landfill body. In the combination of log-spiral method and wedge method, this paper developed a new method to analyze the seismic stability of the landfill against composite failure mode based on the limit equilibrium principle. Through analysis for the safety factors from the landfill against translational failure mode and against composite failure mode, the critical failure mode would be found in specific working conditions.

This paper focuses on new countermeasures against liquefaction. Firstly, an overview of liquefaction triggered by the 2016 Kumamoto earthquake in Japan is presented. The tilt angle of 68 houses and buildings in liquefied areas in Kumamoto City was measured as liquefaction-induced damage to residential houses. Next, shaking table tests in a 1-g gravity field concerning on new countermeasures against liquefaction are introduced here. One of them is a log pilling into a liquefiable sand layer against the settlement of structures during earthquake. Shaking table tests were conducted using the model ground to clarify the effects of installing logs into liquefiable sand layer and relationship between duration time of shaking and settlement of structure. Another method is geosynthetics along with gravel installed at liquefiable ground. The effects of the gravel and geosynthetics were evaluated.

Loose accumulation slope is widely distributed in southwest China. Compared with conventional soil and rock slope, the stability of such slope is poorer and the deformation and failure mechanism is more complex. In addition, the stability problem under the earthquake condition is especially prominent. In this paper, an accumulation slope in Chongqing is taken as an example. By utilizing the particle flow code (PFC), the wave propagation equivalent relationship in the continuous medium and the discrete medium is established under the condition of the ground motion peak acceleration as 0.1g, 0.2g, 0.4g, and 0.6g, respectively. The dynamic boundary conditions under earthquake condition are analyzed as well. The movement and deformation of the particles in the accumulation slope are analyzed during a short period of 30 s. Based on the analysis of the displacement field, the velocity field, the stress field, and the change of slope microstructure, such as porosity and coordination number, structural damage accumulation characteristics, and failure mechanism of loose accumulation slope are explored. The results show that the landslide hazard analysis method based on discrete element method can reflect the process of degradation and instability of loose accumulation slope accurately. The weak links in the accumulation body damage gradually and the particle displacement develops from the bottom to the top of the slope. Under the difference in dynamic response between the overlying accumulation body and the lower bedrock, the slope damage is exacerbated and the cracks are rapidly expanded until it perforates, and the surface of the slope exists local collapse in a certain degree. Under different ground motion peak acceleration, the failure mechanism of accumulation slope is similar, but the scale of damage is different.

Tunnel gushing not only affects the tunnel construction, but also will affect the safety and stability of the tunnel after operation. In this paper, Nanshan Tunnel is taken as an example to introduce the drainage of operating tunnels in karst trough area and to forecast and evaluate the drainage of operating tunnels. The main conclusions are as follows: (1) It is very meaningful to study the gushing water in the karst trough area by collecting a large amount of data of the gushing water in the Nanshan Tunnel, and it is concluded that the tunnel in the karst area is easy to gush and the water is very large. (2) The water volume of the Nanshan Tunnel is calculated and the results of the water inflow are analyzed. It is concluded that the right hole of the Nanshan Tunnel is more susceptible to surface water. (3) It is found that the predicted value is consistent with the initial period of the Nanshan Tunnel through the three-dimensional numerical simulation, which indicates that the parameter selection is reasonable and the numerical simulation method is feasible.

Using the geological survey data of Nanshan, combined with numerical simulation, this paper studied the regional seepage characteristics of tunnels under the condition of tunnel construction (considering and not considering the waterproofing measures) in the karst trough area, and forecasted the water inflow of proposed tunnel and compared with the calculated value of the existing water inflow. The reason of the gap is discussed. The results show that the calculated results of groundwater runoff modulus [unit water inflow 10.10 m³/(d·m)] are similar to those of atmospheric precipitation [11.11 m³/(d·m)], and is close to the numerical simulation results [11.50 m³/(d·m)]. Under the influence of tunnel excavation, the water discharge of Tongluoshan Tunnel decreased by 2.4%; the left hole of Nanshan Tunnel dropped by 6.9%; the right hole dropped by 4.7%. The left hole of Nanshan Tunnel is the most affected by proposed tunnel, right hole is the second, and Tongluoshan Tunnel is the smallest. When the proposed tunnel is constructed in time for waterproofing and second lining, the waterfall of the left hole of proposed tunnel is reduced by 66.3% and the right hole is reduced by 66.2%. Under the condition of multiple tunnels in the karst trough area, the excavation of proposed tunnel has little effect on water inflow and seepage characteristics of the existing tunnels in a certain range, and has less influence on the deep tunnel.

In order to investigate the relationship between strains of slope body and its factor of safety, numerical model was built via finite difference software-FLAC. By applying a gradually increasing load on top of slopes with different heights, the strains were numerically recorded until the failure state. The results indicated that the linear strain mutation along the potential sliding surface can be used as a criterion for slope failure. In addition, this paper presented the progressive failure progress of slopes of different heights, during which the factors of safety and the corresponding strains were analyzed. Based on the results, an empirical equation relating the factor of safety to the characteristic horizontal strains was derived. It can be used as a theoretical guidance for preliminary slope stability assessment based on the instrumented strain or deformations.

Combined with the surrounding environment and supporting design scheme of deep foundation pit project, three-dimensional finite element numerical simulation and analysis of the influence of excavation, and support on adjacent subway tunnel are carried out by using MIDAS software. Some deformation is calculated produced by the construction of pit foundation, including the deformation of the retaining structure and supporting structure of pit foundation, the lining structure of adjacent subway tunnel. The results are shown as follows: ground disturbance will be produced by the excavation and supporting construction of pit foundation. Therefore, the settlement and deformation of adjacent subway tunnel structure will be also produced. According to actual construction conditions, under normal operation conditions for the supporting structure, the maximum horizontal displacement of 4.8 mm and the maximum vertical deformation of 0.12 mm for the adjacent subway tunnel structure are produced by the construction of pit foundation. The above deformation meets the requirements of rail transit deformation of adjacent subway tunnel operation track, and which has some influence on the safe operation of adjacent subway tunnel. The above research results have important practical significance to the accurate prediction on the influence of foundation pit construction on the existing subway structure, also have important practical significance to guarantee for the safe operation of subway structure.

Taking an accumulation slope in Chongqing as an example, the relationship between the progressive failure process and the water content of the accumulation slope was studied using the discrete element method, and the critical water content of the slope was proposed to provide a basis for the research on the prediction criteria of such landslides. It was found that accumulation slope was stable without rainfall, but with increasing rainfall time, the settlement at top of slope and the horizontal displacement at surface of slope were both enlarged. Particularly, obvious deformation was observed on the surface of slope. Under continuous intensive rainfall, the slope failure mode was different from the traditional circular slide, since the slope failed layer by layer until a “debris flow” was generated.

Earthquakes often cause secondary disasters. These include landslides that result from soil changes. Due to the lack of shear strength parameters data and lack of understanding of the shear strength variation under different peaks, the shear strength parameters of sliding zone soil are usually obtained from drilling field sampling and indoor test methods, this is inadequate for earthquake prevention engineering. So we studied the performance of a vertical loaded multilayer soil shear model box which is based on existing multilayer shear box designs. Shear strength parameters and changes of the shear strength of the slip zone are evaluated under the influence of different peak acceleration levels of seismic waves using the shaking table test and the vertical loaded multilayer shear model box. The test results show that the top vertical loading device can simulate the stress states of soils at different depths. The dynamic responses of soils at defined depths, under seismic wave action, can be accurately recorded. When the normal stress is small, with the increase of the peak acceleration, the shear stress generally shows a decreasing trend; when the normal stress is large, this trend is not obvious.

Soil-structure interaction (SSI) influences the many aspects of structure i.e. cost, safety, and serviceability. Therefore, it plays an important role in substantial development of any country where the devastating earthquakes have occurred repeatedly. SSI techniques have been come out as powerful methods to incorporate multiple degrees of freedom. But, the concerns of practitioners are paved in hectic efforts to incorporate SSI. Practicing engineers are facing many challenges to implement SSI practice due to difficult literature and time consumption. Therefore, the overall aim of this research program is to incorporate SSI practice in analysis and design of building structures. The goal of this study is to investigate, through literature research, the performance based assessment of SSI effects and identify an efficient method for practicing designers to incorporate SSI in analysis and design of structures. Thus, the documentation of development regarding SSI, preferably, in last five years was carried out. It is concluded that N2-SSI is an efficient and easy to adopt SSI method in which the soil effect is introduced on the non-linear response of structure. This work will increase the awareness of SSI effects and convince practicing designers to incorporate SSI in their analysis and design of structures.

In traditional model test, the soil deformation around the pile is difficult to obtain under soil lateral movement. Therefore, a series of model tests based on the combination of transparent soil model testing technique and particle image velocimetry (PIV) were carried out to measure the soil deformation in a non-intrusive way. The results indicate that shielding effect, i.e. soil displacement difference between the back and side of the pile, is becoming more obvious with embedment depth. The displacement difference of the soil in front of the pile is less than the soil behind the pile at different buried pile depths.

In order to solve the problem that it is difficult to be obtained the surrounding rock wave velocity in the long and deep tunnel, we present a method to inverse the parameters of wave velocity under the constraint of borehole core. Firstly, the correspondence between the wave velocity parameters and the electrical parameters of the surrounding rock is established by drilling core specimen, then the velocity generalized inversion is carried out with the optimal inversed algorithm, after that, the tunnel surrounding rock is grade according to the inversed wave velocity. Based on this method, we develop a software to classify the surrounding rock, and robustness of the software has been validated by the excavated tunnel rock data. The results of classification system display good correspondence with the data from excavation.

The pile responses to lateral soil movements induced by the adjacent deep excavations have attracted increasing attention from geotechnical engineers. The lateral displacements of soils caused by deep excavations could pose significant impacts on the adjacent piles according to field instrumented data. In this paper, the FE analyses considering soil of HSS constitutive model were carried out to establish the excavation induced pile behaviors by varying the depth of excavation, pile length, pile distance from excavation, system stiffness, soil stress state, pile head fixity, unsupported length of pile, axial loadings exerted on the pile. This study provides design guidelines for lateral deformation estimations of foundation piles and the buildings above and preliminary stability evaluations.

Liquefaction vulnerability indices (LVIs) are computed for an interbedded soil site at St. Teresa's School, Christchurch, New Zealand, to evaluate how various factors may have contributed to the standard LVI computations overestimating the potential for liquefaction damages during the 2010–2011 Canterbury earthquake sequence. The observed performance of the St. Teresa School site and its subsurface conditions are reviewed. An inverse filtering procedure is used to correct the cone penetration test (CPT) data for thin-layer and transition zone effects. LVI indices are computed using the CPT data from the site for a range of assumptions, including common default practices, site-specific fines content calibrations, inverse filtering of the CPT data, uncertainty in the triggering correlation, uncertainties in the correlations for shear and volumetric strains, and partial saturation. Other sources of potential conservatism in the LVI evaluations are discussed, including the potential contributions of the surface crust layer, dynamic response, and excess pore water pressure diffusion.

Aiming at the cyclic weakening mechanism of pile-soil interface of different interface roughness, particle clusters of different shapes are randomly created by using the cluster as an alternative to the traditional single disc to simulate the shearing interface of different roughness and establish the PFC2D constant stiffness cyclic shear model. The results show that the shear stress shows a logarithmic weakening with the increase of the number of cycles, diminished by about 30%~46%, and the weakening coefficient of shear stress ratio is between 0.10~0.16, which gradually increases with the heightened interface roughness; the thickness of shear band formed by the broken particles through cluster breakup reaction is approximately 3 to 6 times the median particle size, and the shear band thickness increases with the increase of the relative roughness of the interface.

By use of the MTS815 Flex Test GT rock mechanics test system and the PCI-II acoustic emission (AE) test system, the failure mechanics tests of the salt rock under the condition of indirect tensile and direct tensile loading and unloading were carried out. The test results show that the tensile strength of pure salt rock under indirect tensile cyclic load is about 1.823 MPa, and the tensile strength under direct tension is about 0.585 MPa, the tensile strength of salt rock under cyclic loading is far lower than that of compressive strength; the direct tensile tensile strength of salt rock is affected by impurities. The post peak deformation of pure salt rock under indirect tension and direct tension shows a slow decline, but the deformation after direct tensile peak of impure salt rock is brittle, and the turning point of the stress-decline slope is more obvious than that of pure salt rock. The spatial distribution and evolution of AE during indirect tensile and direct tensile failure show that the damage mechanisms of the two tensile modes are different. Under the influence of the compressive stress of indirect tension, the AE event occurs earlier on the predefined failure surface; under direct tensile load, the damage occurs later, and the degree of AE accumulation on the failure surface is far less than that of indirect tension. It is further revealed that the characteristic parameters of AE under direct tension are in a quieter period before 20% F, and the AE is active in the post-peak deformation stage; under the indirect tensile load, the AE characteristic parameters are changed in the "low tide period—active period—second active period". Indirect tensile and direct tensile AE activity in the process of unloading variation characteristics are different, the former is affected by compressive load stress, AE is relatively active in the unloading process, while the latter has no significant AE activity.

In order to reveal the permeability law of pure and intercalated salt rocks during the complete triaxial stress-strain process, the permeability test in triaxial path was performed using the THMC rock mechanics test system in Sichuan University. And the CT scanning experiments was also performed to investigate the meso-structure characteristics of salt rock with interlayers before and after the permeability experiments. The permeability experiment revealed the relationships between the permeability and the stress-strain. During the complete stress-strain process, the permeability range of pure and intercalated salt rock were 1.06×10^-18~3.73×10^-15 m² and 5.56×10^-19~3.55×10^-15 m² respectively. The permeability difference between the two kinds of salt rocks was mainly in the stage before the force peak, especially the stage after the volume strain inflection point. The porosity characteristics indicated that the interlayers were denser than salt rock layers and the stress concentration effect is significant at the interfaces. And cracks were constrained by the confining pressure and the constraint effect would be more significant with the higher confining pressure. The crack distribution characteristics indicated that the salt rock layer and brittle hard interlayers cements well at the interfaces and the interface was affected by the stress concentration effect when starting loading. The meso-structure study found the ring-shaped crack distribution form in salt rock layer and the strip distribution form in interlayers. The sparse crack distribution near the end faces revealed the end friction effect from the meso perspective. The interlayer did not have as many connected cracks as the interfaces, although the interlayer had a great number of cracks. Owing to the meso-structure characteristic analysis, the permeability properties of intercalated salt rock were well revealed.