In order to study the influence of the temperature change on the consolidation for saturated soils, this paper presents a semi-analytical solution to the one-dimensional thermal consolidation equations considering the heat conduction of the semi-permeable drainage boundary on basis of the seepage and heat transfer equations. The semi-analytical solutions of excess pore pressure, temperature difference and soil settlement are firstly derived by using the Laplace transform upon the one-dimensional thermal consolidation equations considering the coupled and uncoupled thermo-mechanical models, respectively. Then the analytical solutions for a given time domain are obtained by the Crump’s method. Verification is conducted by reducing the proposed solutions into those under the conditions of the single drainage boundary and the assumptions of Terzaghi’s consolidation, which shows that the proposed solutions are reliable and in good agreement with the existing solutions from literature. Finally, several examples are analyzed to investigate the effects of semi-permeable boundary parameters, thermal diffusion coefficient, consolidation coefficient and temperature increase on the consolidation process of saturated soils under varying loading. All results demonstrate that the consolidation behavior is significantly affected by the investigated parameters.

In order to accurately describe the evolution of plastic strain for soft soil, an improved plastic potential theory is proposed, in which a plastic potential surface with an inclination angle is employed. In addition, the plastic potential function shares the same form as the yield function. During deformation, the plastic flow direction varies following the rotation of the plastic potential surface until the limit state is reached. By analyzing the results of conventional triaxial tests, it can be found that during the shearing process, the initial and final values of the rotation angle of the plastic potential surface and , are basically stable and independent on the confining pressure. Considering such observations, a normalized rotation angle and a state parameter describing the stress state of the soil are introduced, in the case that the egg-shaped function is used as plastic potential function. A piecewise linear relationship can be obtained. Then an improved plastic flow rule is established, only two additional parameters are required. Finally, the proposed plastic flow model is verified, and the results show that the trend of plastic strain can be reflected well in this model.

Mural plaster deterioration poses great threat to the long-term preservation and daily maintenance. The migration of soluble salts by moisture movement is one of the most important factors that causes mural plaster deterioration. The plaster plays an important role in supporting the murals. The soil-water characteristic of the mural plaster is related to the formation and development of mural deterioration. In order to study the soil-water characteristic curve (SWCC) of mural plaster in full suction range, laboratory reconstituted plasters were prepared by the same materials as the mural plaster in Mogao Grottoes, and the pressure plate test method and vapor equilibrium technique were employed. The SWCC test data was fitted by van Genuchten (VG) model and Fredlund Xing (FX) model. The SWCC of the reconstituted plaster samples with different compositions showed different characteristics, while the morphological differences between the coarse plaster and the fine plaster on the SWCC were not obvious. Under the same suction condition, the moisture content of the coarse plaster is higher than that of the fine plaster, and the coarse plaster has the characteristics of rapid release of moisture in the high suction range. By analyzing the trend of the SWCC in the high suction range, it is recommended that the humidity in the Mogao Grottoes should not exceed 58% in daily maintenance, and the humidity should be stable with no major fluctuations. Based on the experimental data in the full suction range, highly accurate SWCC can be obtained.

In this paper, a plane-strain element analysis model is proposed on the basis of the inelasticity-separated finite element method (IS FEM). The 2×2 Gaussian points as the inelastic strain interpolation points are considered for the linear quadrilateral isoparametric plane-strain element. The inelastic strain field and the corresponding governing equation are established only in the in-plane three directions since there are no strain components out of the plane. In addition, the solving process of the governing equation only contains many times back-substitutions of the initial stiffness matrix and the sparse matrix and vector multiplication by using the Woodbury formula and the combined approximation approach. The computational efficiency of the proposed method based on the time complexity theory indicates that it significantly improves the total efficiency as compared with the conventional FEM with the updated stiffness matrix. The critical ratio of the inelastic degrees of freedom (IDOFs) is also improved by comparing with the exact Woodbury formula. The stress transfer method of the Drucker-Prager criterion is applied for the nonlinear analysis of the classical plane-strain model. Numerical examples verify the accuracy of the proposed model and the efficiency of the proposed algorithm for the nonlinear analysis of the plane-strain model.

A two-stage method for dewatering high-water-content dredged slurry by flocculation and vacuum-assisted prefabricated horizontal drain (PHD) was proposed to increase the dewatering efficiency by addressing the issues of serious bending and clogging that are typically encountered when using the prefabricated vertical drain (PVD). Firstly, comparison of model tests using PVD and PHD, respectively, under vacuum preloading indicates that the PHD has advantages of uniform settlement of soil, negligible bending of the drain board, uniform dewatering rate and better dewatering efficacy. For the cases considered in this study, the mass of water drained out by PVD was only 77.4% of that by PHD. Effect of flocculation on the dewatering efficacy was investigated and the results indicated that impact of the flocculant (APAM) dosage on the dewatering rate was significant. With moderate addition of APAM (e.g., 0.45% of dry soil mass), the time required for dewatering was shortened by 35%. Lastly, the influence of sedimentation time (i.e., waiting time before applying vacuum pressure) on dewatering rate was studied. The results showed that if the sedimentation time is insufficient, the effect of flocculation cannot be mobilized fully , and as a result, will lead to significant non-uniform consolidation and reduced dewatering efficacy. The best time to start the vacuum pressure is 24 hours after the beginning of sedimentation.

To reveal the physical process and nonlinear mechanical behaviour of rock failure under stress disturbance and unloading confining pressure, the fatigue and triaxial unloading confining pressure tests were carried out on marble by using GCTS RTR-2000 servo loading testing machine. Moreover, the X-ray computed tomography (CT) was applied for the visualisation analysis of crack morphology of damaged specimens after compression. The results show that periodic loading and unloading play a significant role in damage, while unloading confining pressure dominantly control the failure of marble. Rock fatigue cycles form hysteretic loops, and the areas of hysteretic loops change from sparse to dense. Loading and unloading curves of hysteretic loops coincide well with each other, and the modulus values at loading and unloading stages are approximately equal. After unloading confining pressure, the axial, radial and volumetric strains of marble increase in varying degrees, indicating that the strain is highly sensitive to the unloading confining pressure, and the sensitivity degrees of volumetric, radial and axial strains are from high to low. Due to the influence of fatigue cycle, both the drop of confining pressure caused by unloading confining pressure and the unloading period of confining pressure decrease with the increase of cycle number. To quantify the macroscopic deformation, the strain damage indices , and are obtained. The more the number of periodic cycles, the higher the strain damage index. The microscopic CT scan after rock failure reveals the internal mechanism of the effect of fatigue cycle on fracture morphology, and the crack density and size increase with the increase of fatigue number. The results can provide theoretical and model support for fatigue activity and unloading excavation of underground engineering.

Stress-type brittle failure of hard rock poses a serious threat to the surrounding rock mass stability of underground structures under high geo-stress. In order to study the deformation and failure characteristics of deeply-buried granite under the condition of high confining pressure cyclic loading and unloading, MTS815 is used to perform conventional triaxial and cyclic loading and unloading tests on the granite from an underground powerhouse under confining pressures of 10, 30, 40, 50 MPa. The corresponding stress-strain curves and deformation and failure characteristics are obtained. The following observations are made from the results: 1) Under the two stress paths, granite specimens under various confining pressures show obvious brittle failure characteristics. 2) Under the two stress paths, the peak strength and crack damage stress of the specimens increase linearly with the confining pressure; elastic modulus and cracking initiation stress increase first and then decrease with confining pressure. Poisson's ratio increases first and then remains unchanged or decreases with confining pressure. 3) Under the same confining pressure, the peak strength, crack initiation stress, crack damage stress and the Poisson's ratio of the specimen in cyclic loading and unloading tests are generally larger than those in conventional triaxial tests, while the unloading elastic modulus is smaller than that in conventional triaxial tests. 4) Under the two stress paths, the macroscopic failure of the specimens is primary shear failure. The deformation and failure rules of granite specimens revealed have significant reference for the selection of rock mass mechanical model, the evolution rules of mechanical parameters with damage variables, and the formulation of support countermeasures for the surrounding rock mass stability of deeply-buried underground structures.

To investigate the failure behavior of different graded coral sand cementations under static and dynamic loads, a series of impact tests is carried out on the coral sand cementations with different gradations through the drop hammer impact test facility. Combined with static compression tests, the mechanical behavior and failure modes of coral sand cementations are analyzed. The experimental results show that the wider the grading of the coral sand is, the greater the compressive strength of the cement test block is, the stronger the impact resistance is, the smaller the damage angle is, and the crushing angle decreases gradually. The coral sand cement blocks show different failure modes under different kinds of loads, which are obviously different from concrete blocks. Additionally, a 3D discrete element model is established and the paremeters are calibrated according to the the stress-strain curves of the experimental results, then the numerical impact tests are conducted. The numerical results show that, from the perspective of fracture distribution, as the gradation interval and the average particle size increase, the impact-induced micro-fractures that are uniform and dispersed will be more concertraded in a certain direction, leading to the reduction of the number of cracks and the damage degree. From the perspective of system adhesion, the cohesive force inside the block with narrow gradation range is small and distributed uniformly, while the cohesive force in the block with wide gradation size range is large and unevenly distributed.

This project planed to investigate the law of shear action in pile-rock interface of bored rock-socketed pile in reef limestone stratum. For this purpose, the shear test, physical and mechanic property test were performed on the four structure types of reef limestone core samples including framestone, bindstone, rudstone and bioclastic limestone which were sampled from a certain core reef in South China sea. In this way, the variation law of shear stress-shear displacement curve of pile-rock interface was explored. Meanwhile, shear test on the interface between red sandstone and concrete was also carried out to reveal the basic reason for the difference of shear strength between two different sedimentary types of rock and concrete bond surfaces. Based upon these, the investigation suggested that shear strength of reef limestone-concrete interface was affected by the structure type of reef limestone and the strength ratio of pile-rock interface. As a result of the diffusive filling effect of cement slurry in reef limestone, the cohesive force and internal friction angle of the interface between reef limestone and concrete were both larger than those of sandstone-concrete interface. The shear strength response of the strength ratio of pile-rock interface was influenced by the type of reef limestone structure. Cohesive force of the limestone-concrete interface of framestone and bindstone were both larger at a small strength ratio of pile-rock interface than that at a large strength ratio. Internal friction angle of the interface between framestone and concrete was bigger at a large strength ratio of pile-rock interface than that at a small strength ratio while this index changed little in the bindstone -concrete interface.

In order to understand the hydrothermal activity mechanism of active layers to rainfall in permafrost regions caused by humidification of climate, the differences of ground surface energy balance and hydrothermal activity in different types of shallow soil with the consideration of rainfall were discussed. Based on the meteorological data in 2013 observed at Beiluhe observation station of Tibet Plateau, three types of shallow ground soil (i.e., sandy soil, sandy loam and silty clay) were selected to compare the differences in the water content and energy balance at the ground surface, dynamic processes of water and energy transport in active layers and coupling mechanism under rainfall condition in the plateau using a coupled water-vapor-heat transport model. The results show that the increase of soil particle size leads to the increase of surface net radiation and latent heat of evaporation, but the decrease of soil heat flux. The difference of surface energy balance, especially the sensible heat flux and latent heat of evaporation, are larger in the warm season but smaller in the cold season. The liquid water transport under hydraulic gradient and the water-vapor transport under thermal gradient are obvious as the particle size in soil increases. However, the water-vapor flux under thermal gradient increases but the liquid water flux under hydraulic potential gradient decreases. As a result, the water content in shallow soil decreases accordingly but it increases slightly at the depth of 25 ~75 cm. Moreover, with the increase of soil particle size, the thermal conductivity of soil, convective heat transfer under rainfall and surface evaporation increase, but the soil heat conduction flux and soil temperature gradient decrease. Thus, soil temperature in sandy soil is much higher than that of sandy loam and silty clay at the same depth. The permafrost table declines with the increase of the thickness of active layer, which is unfavourable to permafrost stability. The results can provide theoretical reference for stability prediction and protection of permafrost caused by humidification of climate.

In the soft foundation treatment projects, the phenomenon that the spacing of vertical drains reduces when the consolidation efficiency of the foundation decreases often appears. Given this, the distribution function of horizontal permeability coefficient of soil in overlapping smear zones is established, and then the analytical solutions are obtained for the excess pore pressure and average degree of consolidation of vertical drains foundation with overlapping smear zones. Based on the analysis of the variation of the average degree of consolidation of the foundation with the spacing of the vertical drains for different cases, the reasons are explored when the spacing of the vertical drains reduces and the consolidation efficiency of the foundation decreases. Finally, we discussed the influence of the smear effect and well resistance effect on the minimum critical spacing of vertical drains. The results show that the overlapping of smear zones of adjacent vertical drains is the underlying reason for the minimum critical spacing of vertical drains in the foundation. The greater the smear effect is, the greater the minimum critical spacing of vertical drains is. The specific performance is that the minimum critical spacing of vertical drains increases with the increase of the disturbance degree of the foundation or the radius of the smear zones. The larger the well resistance is, the smaller the minimum critical spacing of vertical drains is. When the permeability coefficient of the vertical drain decreases, the length of the vertical drain increases or the radius of the vertical drain decreases, and the minimum critical spacing of vertical drains decreases accordingly.

Sludge is rich in a large number of organic matters, and with the action of microorganisms, organic matter can be gradually decomposed by humic acid. Meanwhile, humic acid affects not only the degradation of organic matter but also the sludge solidification. Thus, the sludge is immersed in a constant alkaline buffer solution environment (pH=9.0). The results show that the alkaline buffer solution can accelerate the decomposition of organic matter, consume humic acid and keep the solution alkaline. When the decomposition of organic matter is completed, humic acid is released, and the degradation process continues to approximate 28 days. By adding cement and lime solidified silt, it is found that the strength of solidified silt containing organic matter increases firstly and then decrease with curing time, but the strength of solidified silt containing pre-degraded organic matter does not decrease. It indicates that the durability of solidified soil can be improved by pre-degradation of silt organic matter by the alkaline buffer solution.

As one of the perfect geometries in nature, sphere is common in the daily and industrial life. The mechanical properties of sphere are of great significance to engineering safety and numerical simulation. Internal cracks or defects are inherent properties of materials, and have an important influence on the mechanical properties of materials. However, the internal crack of sphere is not considered in the current research due to the limit of technology. Thus, understanding of the propagation of internal cracks of brittle sphere is limited. In our study, internal cracks were created in glass sphere samples by 3D-ILC (3D-internal laser-engraved crack). Uniaxial compression tests were performed on samples with an internal crack at 60°. By comparing with results of samples without a 60° internal crack, the propagation of the internal crack, the load and the fractography were investigated. The distributions of KI, KII, KIII were calculated using M-integral. Results showed that: 1) the fracture patterns include wing cracks and primary crack. 2) Wing crack is composed of smooth zone (mode I-II fracture) and tear zone (mode I-II-III fracture). 3) The distributions of KI, KII, KIII around crack tips obtained by M-integral are consistent with the test results. 4) 3D-ILC can be successfully applied into the investigation of internal cracks of sphere and it provides experimental and theoretical basis for the study of 3D problem, internal cracks and mode I-II-III fracture in fracture mechanics of brittle materials.

At present, it is assumed that the consolidation coefficient of the soil remains constant for the nonlinear consolidation solutions of the double-layered soil considering the nonlinear compression and permeability of soil. There are few studies on the nonlinear consolidation solutions of double-layered soil considering the variation of consolidation coefficient. The classical e- and e- nonlinear relationships are introduced to describe the nonlinear compression and permeability characteristics of soil. Based on the assumption that the ratios of compression index and penetration index in both layers are the same and not equal to 1, the approximate solutions for one-dimensional nonlinear consolidation of the double-layered soil are obtained considering the variation of consolidation coefficient and time-dependent loading. Under the condition of 1, the solutions in this study can be degenerated to the existing one-dimensional nonlinear consolidation solutions of double-layered soil when 1. The influence of relative parameter ratios of the lower layer to the upper layer in double-layered soil on the nonlinear consolidation behavior finally is analyzed. The results show that, under the condition of single drainage, the nonlinear consolidation rate of the double-layered soil increases with the decreasing , the reducing relative compressibility, or the increasing relative permeability. When reduces or the thickness of the soil layer with low compressibility and high permeability increases, the consolidation rate of double-layered soil increases.

The study of dynamic-hydraulic characteristics and fine particle migration of sand-silt mixtures under load is the basis and key for analyzing the mesoscopic disaster-causing mechanism and evolution mechanism of natural or engineering disasters such as vibration liquefaction and mud pumping etc. The experimental study on fine particles migration mechanism of saturated sand-silt mixtures under combined dynamic-static train load was carried out by using the self-developed test system. The experimental results show that the axial deformation of the sample exhibits a “stepped” change trend. The total stress distribution shows an exponential decrease with increasing depth. The pore water pressure in the sample experiences the cyclic process of accumulation under dynamic loading and dissipation under static loading. In this process, the axial gradient of pore water pressure gradually forms a "pumping" effect on pore water, which causes the migration of fine particles and water. Furthermore, by analyzing the composition change of three particle size groups contents and effective diameter d10 of different layers of the sample, it is analyzed the combined dynamic-static loads affect fine particle migration in saturated sand-silt mixtures.

According to the specification of scale reduction, four different scale reduction methods, including scalping method, equal-weight replacement method, similar grading method and mixing method, are used to reduce the scale of a coarse-grained soil into a grading with smaller particles, namely 20 mm, 40 mm and 60 mm.. A number of the maximum dry density tests are conducted by the vibrating method. Based on the test results and fractal theory, a normalizing method is proposed to describe the relationship between maximum dry density, grading and content of fine grains. Based on the newly proposed normalizing method, the relationship of dry density versus fractal dimension before tests and the content of grains smaller than 5 mm and maximum particle size is found. According to the founded relation, the maximum dry density of the real gradation is determined. In addition, the effect of scale reduction method on the variation amplitude of grain size distribution curves of coarse-grained soil specimens before and after tests is studied. And the relationship of fractal dimension of particle breakage versus fractal dimension before tests coefficient, the content of grains smaller than 5 mm and the maximum particle size is found. Based on the newly summarized relation, the fractal dimension of particle breakage of the real gradation after filling can be determined.

The investigation of tunnel damage after strong earthquake shows that the seismic damage of tunnel entrance is quite serious, so it is necessary to further investigate the dynamic response of tunnel entrance slope. Taking the typical tunnel entrance slope in Wenchuan earthquake area as an example, the dynamic response characteristics of tunnel entrance slope under strong earthquake are studied using large centrifugal shaking table test. The experimental results show that: 1) The acceleration amplification on the slope and inside the slope has a significant elevation effect, the acceleration amplification coefficient of the tunnel arch roof is larger than that of the other parts of the tunnel, and the closer to the tunnel entrance the more obvious the acceleration amplification effect. 2) The acceleration amplification effect of the slope is very obvious for different amplitudes, and the acceleration response at low amplitude is larger than that at high amplitude. 3) Under the condition of maintaining 0.25g excitation, the acceleration amplification coefficient of slope under different centrifugal load grades is greater than 2.0, but the acceleration magnification factor is basically flat with the increase of centrifugal load. 4) With increasing slope elevation, the dynamic earth pressure decreases linearly, and the dynamic earth pressure response coefficient at the relative elevation of 0.48 (i.e., tunnel arch roof) is the largest. Research results can provide reference for the design and research of seismic mitigation for tunnel entrance in strong earthquake area.

Based on the research results of unsaturated porous medium, considering the influence of thermal effect and porosity fluid tortuosity, the propagation characteristics of thermoelastic wave in unsaturated soil are studied in this paper. The thermoelastic wave equations of the problem are established by the mass balance equation, seepage flow equations of continuity and momentum balance , and generalized non-Fourier heat conduction law of the solid-liquid-gas three-phase medium coupled with heat in unsaturated soil. By introducing the potential function, the dispersion characteristic equation of thermoelastic wave in unsaturated soil is theoretically derived. The variations of the wave velocity and attenuation coefficient of several types of thermoelastic waves with the thermophysical parameters such as tortuosity, thermal expansion coefficient and medium temperature, are analyzed in numerical examples. The results show that the increase of pore water tortuosity causes the decrease of wave velocity of P1 wave, P3 wave and S wave, while the increase of pore gas tortuosity only causes the decrease of wave velocity of P2 wave. The increase of thermal expansion coefficient causes the increase of P1 wave velocity and the decrease of thermal wave (T wave) velocity. The rise of medium temperature causes the increase of wave velocity of various thermoelastic waves. The variations of frequency, thermal expansion coefficient and medium temperature have a great influence on the attenuation coefficients of various thermoelastic waves, and these variations cannot be ignored.

To ensure better horizontal deformation resistance, the pile foundation of integral abutment jointless bridges (IAJBs) should be designed as flexible pile. However, the calculation algorithm of flexible pile in relevant codes in China is mainly applied to the laterally loaded pile, and whether it can be used to identify the flexible pile for IAJBs remains a tricky issue to be studied. Therefore, in order to study the aseismic performance and interaction mechanism of the single pile-soil system, three concrete model piles with different lengths were tested under horizontal low-cycle reciprocating displacement based on a specially designed pile deformation measurement method. The result shows that the earliest cracking position of concrete pile is between 3~6 times of pile diameter. The deeper the pile is buried, the better the effect of pile-soil interaction with a deeper location of the deformation characteristic point. Meanwhile, stiffness of pile-soil system, horizontal ultimate bearing capacity and aseismic performance is improved with burial depth increased. The result also indicates that, when the pile-soil system reach the elastoplastic stage, the flexible performance of the pile will gradually degenerate from the elastic pile to the rigid pile. Furthermore, the provisions in relevant codes in China are not safe enough when evaluating the flexural performance of the pile foundation of integral abutment jointless bridges. Hence, it is recommended to use the Broms method for the benchmarking calculation in practical engineering.

In order to study the creep characteristics of the sliding zone soil of the Huangtupo landslide under different consolidation stresses, the unidirectional load, load-unload, load-unload-reload tests were used to consolidate the sliding zone soil, and then the shear creep tests of the sliding zone soils in different consolidation states were carried out. The experimental results showed that the initial void ratio of the sliding zone soil was 0.49 and the compressibility coefficient a1-2 was between 0.37 and 0.45 MPa?1, belonging to the moderate compressibility soil. After unidirectional loading to the predetermined pressure, the void ratio of sliding zone soil reached to the maximum and the compression amount the minimum. After loading-unloading to the predetermined pressure, the void ratio of sliding zone soil was the minimum and the compression amount the maximum. The void ratio and compression amount after loading-unloading-reloading to the predetermined pressure was somewhere in the middle. For the same initial state sliding zone soil, after different loading-unloading consolidation states, under the same normal stress and shear stress level, the creep shear strain of unidirectional loading was the largest, but the creep shear strain of loading-unloading was the minimum. The creep shear characteristics of sliding zone soil were closely related with the loading state and the void ratio after loading. The Burgers model was used to fit the creep test data and the creep parameters of Maxwell model and Kelvin model were obtained. The fitting and test curves were in good agreement, which indicates that Burgers model can reflect the creep characteristics of sliding zone soil under different consolidation stresses.

In engineering practices, the vertical stress and horizontal stress in the subgrade soil unit constantly change, and the amplitude and direction of shear stress also constantly change, which lead to continuous rotation of the stress path in the soil. To investigate the influence of the confining pressure and the cyclic stress ratio(CSR) on strength, cumulative strain, resilient strain and softening of natural soft clay when the principal stress axis continuously rotates under pure axial compression of traffic load, the GDS hollow cylinder apparatus (HCA) is used to simulate the stress path under a laboratory-simulated traffic load, and tests of continuous rotation of the principal stress axis under different confining pressures and different cyclic stress ratios are carried out. The testing results show that with the accumulation of pore pressure, the samples of natural saturated soft clay gradually softened. The axial and torsional moduli decreased with increasing CSR and confining pressure and then reached a steady value after a certain number of cycles. When the cyclic stress ratio was relatively small, the axial and torsional stress-strain hysteretic curves were linear, and almost coincided with different cycles. With the increase of the number of revolving cycles of the principal stress axis, the axial and shear stress-strain hysteresis curves became more and more nonlinear. The axial and shear stress-strain hysteresis loops of the specimens no longer coincided with the rotating circles, and the hysteresis loops gradually tilted towards the x axis. With the increase of cyclic stress ratio, the axial and shear moduli quickly attenuated at the initial stage of loading and then reached a steady value. Moreover, when the axial and shear moduli of the specimen were stable, the corresponding number of revolving cycles of the principal stress axis increased with increasing confining pressure and cyclic stress ratio.

The shaking table test of buried pipelines under multi-point non-uniform excitation is carried out to investigate the nonlinear seismic response of site soil with the use of a nine sub-table array shaking table system in Beijing University of Technology. Through experiments, the macroscopic phenomena, the dynamic characteristics, and the acceleration response of site soil during vibration were observed. Also, the seismic response characteristics and variation of the soil under different earthquake motions and different seismic intensities were studied. The acceleration amplification factor of the free-field and non-free-field soils and the acceleration time history and Fourier spectrum of the same measuring point were compared. The results show that the seismic response of the soil is not only related to the ground motion record and the loading level, but also has a relationship with the buried structures. The damping ratio and the basic frequency of the non-free field are larger than the parameters of the free field. The seismic response of the pipeline is basically subordinate to the response of the soil under lower loading level, but with the increase of loading level, the restraint effect of soil decreases, and the acceleration of the pipeline is slightly larger than that of the soil. The existence of the buried pipeline has a certain influence on the dynamic characteristics of the soil within a certain range, but if the location is beyond that range, the impact will be rapidly weakened. The conclusions obtained are consistent with the macroscopic phenomena of seismic response obtained by the test, which corroborated each other's rationality. Furthermore, the conclusions support the analysis of seismic damage mechanisms of subsequent buried pipelines.

It is a practical and effective method to strengthen the slope using pre-stressed anchor cables. Complicated coupling effect exists between the anchorage force loss of anchor cable and creep of rock and soil. Two coupling models are established. The constitutive equations of the model and the formulas for the effective pre-stress are derived. Based on the pre-stress monitoring data in a practical engineering, the creep parameters of the slope are obtained by inverse analysis methods. The corresponding theoretical models are adopted after the division of the prediction stages. The comparison between theoretical calculation value and the actual monitoring value is used to verify the rationality and accuracy of the models. The results show that a single coupled model leads to an increase in prediction of error as time goes on. The curve of H-K model, which is made up of the elastic model and the generalized Kelvin model in parallel, declines quickly, so it is suitable for predicting the early pre-stress loss of anchor cable. H-2K model, elastomer parallel with generalized Kelvin body to consider the stress relaxation of anchor cable, can fit the late changes of anchor cable pre-stress better. Reasonable staged prediction can accurately evaluate the loss of anchor cable pre-stress, and thus to provide references for the prevention and treatment of landslides

Many construction risk factors and frequent collapse accidents are associated with deep foundation pits in metro stations, and there are limitations for the traditional methods to conduct risk analysis of such complex systems with multiple states. In this study, a method for evaluation of collapse possibility of deep foundation pit collapse based on multi-state fuzzy Bayesian network is proposed. The multi-state Bayesian network model was constructed via fault tree transformation, and fuzzy numbers were used to describe the fault state and the failure rate of root nodes, which overcomes the problem that the traditional methods cannot consider the influence of intermediate fault states and are difficult to obtain the accurate failure rate. Based on the forward reasoning of Bayesian network, the risk probability of foundation pit collapse can be calculated in two different ways including the fuzzy probability of root nodes and the actual fault state in construction. As a result, a real-time dynamic risk analysis during foundation pit construction can be achieved. Furthermore, the key risk factors can be identified for the guidance of risk control according to the sensitivity analysis results. In addition, the posterior probability of each root node can be obtained by backward reasoning to carry out fault diagnosis and further predict the system state. Two case studies show that the proposed method can scientifically and reasonably evaluate the collapse risk of foundation pit and determine the key risk factors, which can be used as a decision-making tool for safety risk management of foundation pit construction.

The circular sliding method is one of the most important methods for calculating safety factor of heave-resistant stability in China. Most commonly, the traditional methods assume the position of center of the slip arc are placed at the intersection of the bottom support and retaining wall, which means the support system will not be destroyed and the calculated result is obviously insecure. To solve this problem, the center of slip arc is not fixed in this paper. Through several calculations, the minimum safety value is adopted as the final safety factor of heave-resistant stability. Besides, a new method which considering the width of the foundation pit is also proposed in this paper. The analysis of the example shows that the center of slip arc may be located at the bottom support or above the bottom support for the insertion type of traditional subway foundation pit. It shows the stability of the support system has a significant impact on the safety factor. When the ultimate axial support force is large enough, the new method can be turned into the traditional circular slip method. Further analysis shows that the ultimate center of the slip arc is located inside of foundation pits. The proposed method is an important improvement to the traditional circular slip method, which is suitable for design and construction of foundation pit.

In order to quantitatively evaluate the stability of tunnel surrounding rock and guide the support design, the concept of critical stable section of tunnel and the stability analysis method of tunnel surrounding rock based on critical stable section are proposed. The main contents are as follows: 1) The critical stable section of a tunnel is the largest section with the same central buried depth and similar geometry as the designed excavation section, and the surrounding rock can be self stable without support. 2) When the design excavation section is smaller than the critical excavation section, the surrounding rock between the critical stability section and the design excavation section can be used as a support structure; and when the safety factor meets the design requirements, it is considered that the surrounding rock can be self-stable for a long time, except for local protection, no system support is required, otherwise supplementary engineering support measures are required. 3) When the design excavation section is larger than the critical stable section, the "artificial" support is required. 4) A method for calculating the design support force is proposed, in which, the surrounding rock in the damage area is considered to be loose, and the design support force should be able to maintain the stability of the loose body with a certain safety factor. This method is employed to analyze two typical sections of the critical stable sections of railway tunnels, and to calculate the self-bearing safety factor of surrounding rock and the required ‘artificial’ support force under the conditions of different surrounding rock grades and different burial depths.

The conventional static pile load testing methods include Kentledge, reaction piles and bi-directional methods, whereas each of these methods has inevitable disadvantages. A vacuum static load testing is developed to avoid the disadvantages of these traditional methods. A set of reaction devices is designed for vacuum negative-pressure static pile load test, which can be used in engineering practice. Pile foundation loading and vacuum negative-pressure static load tests were carried out. Vibrating wire rebar stress meters, earth pressure cells and displacement bar monitoring sensors are installed on the pile. The effective sealing reaction system is formed by referring to the measures of foundation vacuum preloading drainage preloading sealing system. The Q-s curve, s-lgt curve, the distribution of axial force, lateral resistance and terminal resistance in the loading process of the tested pile are analyzed. The tests show that the response of lateral friction of the pile is closely related to the vacuum pumping process. Due to the stiffness, pressure transfer and sealing effect of the negative pressure platform, there is a certain gap in the maximum loading magnitude between the vacuum negative-pressure and the related theoretical value. The corresponding solutions and improvement measures are proposed for the above problems.

The saturated hydraulic conductivity of rock and soil mass in colluvial landslide is uncertain, and it is an important parameter for the saturated-unsaturated seepage analysis. It is of great significance to carry out the seepage deformation analysis of reservoir bank landslide considering the spatial variability of saturated hydraulic conductivity. In this study, the Baishuihe landslide in the Three Gorges Reservoir Area is investigated as a case. The spatial variability characteristics of the hydraulic conductivity, which is obtained by the surface nuclear magnetic resonance technology (SNMR), are analyzed in detail. The vertical fluctuation range of the hydraulic conductivity is obtained by using the semi-variation function, and a non-stationary random field model of hydraulic conductivity is established. The non-intrusive stochastic finite element method is adopted to carry out the fluid-solid coupling simulation of the uncertain model and the deterministic model under the two working conditions of reservoir water level fluctuation. The seepage field, deformation characteristics and their differences between the two models are analyzed. The results show that, compared with the determinate model, the hysteresis of pore pressure change in the uncertain model is more obvious, and the overall deformation is greater under the condition of reservoir water falling. If the non-stationary spatial variation of the hydraulic conductivity of the sliding body is neglected, the actual deformation of the landslide will be underestimated.

Due to the extremely high sensitivity of tunnel boring mechine（TBM）performance to rock mass conditions and its huge early investment, it is of great value to evaluate the rock mass boreability and predict the TBM performance. In this study, about 300 sets of field data from China and Iran are collected, covering three different rock types and 5 TBM tunnels. FPI (field penetration index) is selected as the evaluation index of rock mass boreability. Specifically, the relationships between rock uniaxial compressive strength(UCS), rock mass integrity index , angle between main structural plane of rock mass and axis of the tunnel ?, tunnel diameter, D and rock mass boreability are systematically analyzed. In addition, a unified approach of rock mass parameters which is suitable for the study of rock mass boreability is discussed in detail, and an empirical prediction model of rock mass boreability with relatively high accuracy ( 0.768) is further established. Based on this model and supplemented by K-center clustering method, the boreability of rock mass are classified into 6 groups, which are then applied to the exploration of the distribution of average cutter thrust and cutterhead speed under various of rock mass boreability conditions. The findings in our work shed light on the evaluation of rock mass boreability, the selection of operational parameters as well as the arrangement of TBM tunnel construction schedule.

With the rapid development of asphalt concrete core rockfill dams, an unprecedented opportunity is coming for the construction of ultra-high asphalt concrete core rockfill dams. However, with the increase of dam height, the security challenges of core become very prominent. Based on the definition of stress level, an improved measure that reduces the high stress level of ultra-high asphalt concrete core is proposed. Depending on the sensitivity research of tress level of core, the value ranges of strength parameters (most sensitive material parameters) of core that can independently and comprehensively meet the yield shear failure control standard are calculated, respectively. The results show that the stress level of core increases sharply with increase of dam height and valley slope ratio. The failure ratio , cohesion c, and internal friction angle of core are the highest sensitivity parameters and the stress level of core can be reduced effectively by the increase of failure ratio , cohesion c, and internal friction angle of core. The recommended value ranges of failure ratio , cohesion c, and internal friction angle of core for the suitable construction of ultra-high asphalt concrete core rockfill dams are: 0.8, 0.4 MPa, and 31.5° (dam height 200 m), with the growth gradient adjusted by 5%/25 m, 15%/25 m, and 5%/25 m.

The methods of calculating seismic influence coefficient and dynamic magnification factor of seismic design code in different industries are compared, and the suitability of current nuclear safety guides to high slope anti-seismic stability assessment of nuclear safety grade is studied. Taking the typical anti dip layered soft rock high steep slope at a certain nuclear safety grade for example, this paper discusses the application of various methods to analyze the dynamic amplification effect, safety and seismic performance of retaining structures. Firstly, on the basis of typical two-dimensional calculation profile, the preliminary reinforcement design of slope is conducted by quasi-static method. Then, based on large-scale shaking table tests and numerical calculation, the dynamic amplification effect of the soft rock slope and the dynamic response characteristics of the retaining structure under different seismic loads are studied. Finally, the safety of the slope is evaluated by field engineering monitoring. The results show that under strong earthquake, it is feasible to design the nuclear safety slope according to the seismic parameters in other industry codes. The whole slope is stable and the seismic performance of the retaining structure is good by shaking table and numerical analysis. The research ideas and methods are reasonable and feasible, and a lot of engineering investment will be saved. The present research enriches the theory of high steep slope stability with nuclear safety grade and can provide technical support for seismic safety evaluation and engineering design of nuclear safety grade slopes.

In order to investigate the influence of temperature in deep coal mining area on coal seepage and pore fracture structure deformation, 3D CT reconstruction technology and ANSYS were used to simulate the process of conjugate heat transfer and thermal deformation of coal microstructure respectively. The conjugate heat transfer simulation results show that water that was initially injected into the 80℃ coal wall at 20℃ was heated to 37.13℃ when it flows out. The temperature of the coal gradually decreases along the wall facing the fluid center. Pore fracture structure has an important influence on the velocity and the temperature of the flow along the flow direction. When the connected cross-section porosity is large, the flow speed is slow, the fluid heats up quickly, and the solid temperature decreases. On the other hand, when the connected cross section porosity is small, the flow speed is fast, the fluid temperature rises slowly, and the solid temperature rises. The thermal deformation simulation results show that the deformation is proportional to the distance from the constraint surface. When the deformation near the constraint surface is small, and the direction is pointed to the pore fracture space. While if the deformation at a place that is far away from the constraint surface is large, the deformation direction is diverging outward. Moreover, the existence of the cracks will increase the deformation, the deformation difference between the different pore or crack structures will also increases with the increasing temperature.

In order to exploit geothermal energy in dry hot rock reservoirs, it is often necessary to conduct artificial hydraulic fracturing to form a penetrating heat transfer channel. However, convective heat transfer in thermal reservoir has an important influence on the heat extraction rate of dry hot rock. Artificially stimulated reservoirs will form fracture surfaces with different geometric shapes, while different roughness of fractures will cause significant differences in heat transfer performance. Hence, this study selects four Barton's classical rock fracture roughness profile to establishe a single-fracture convective heat transfer model under laboratory conditions, and to analyze the heat transfer characteristics of the hot working fluid in granite rough fracture in detail. The results show that the local convective heat transfer coefficient decreases gradually along the fracture length direction. The average convective heat transfer coefficient increases with the increase of joint roughness coefficient (JRC), which indicates that the heat transfer performance is better. The distribution of local convective heat transfer coefficient is well correlated with the geometric profile of JRC curve, that is, the variation trends of wave crest and trough of the two curves are consistent. Relative to temperature, the high flow velocity enlarges the local convective heat transfer coefficient, which indicates that the greater the velocity is, the greater the fluctuation of the local convective heat transfer coefficient is.

Thanks to the excellent damping capacity of Duxseal, a newly designed active isolating barrier-Duxseal-WIB is proposed to be used for vibration screening. This barrier is a special type of WIB (wave impeding block) with cylindrical holes and the holes are filled with Duxseal. To investigate the isolation characteristics of Duxseal, numerical studies are firstly performed using a three-dimensional semi-analytical boundary element method (BEM) combined with a thin layer method. Then, the vibration screening effectiveness of the proposed isolating barrier-Duxseal-WIB is verified by field tests. The results show that Duxseal can effectively reduce ground vibrations as an active barrier in the free field, and the effectiveness of vibration isolation at distances far away from the vibration source is relatively better than that near the vibration source. The values of soil parameters have a significant influence on the isolation effectiveness of Duxseal. The isolation effectiveness increases with the increase in diameter, thickness and embedded depth of Duxseal material within a certain range, and the embedded depth is the most critical factor affecting the isolation effectiveness of Duxseal. In addition, the isolation effectiveness at a distance away from the center of the vibration source is higher for Duxseal-WIB than traditional WIB. When we consider a distance of 12 m away from the vibration source as the representative measuring point, the vibration screenings of Duxseal-WIB along the X, Y, and Z directions achieve vibration isolation values of approximately 40%, 39%, and 51%, respectively, under a moving load at a high speed of 250 km/h.

During soil freezing and thawing, water migration, phase transition and heat transfer are a multi-field coupled process in which these factors affect each other. In this study, a mathematical model for the coupling process of water migration and heat transfer was constructed by solving a simultaneous equation group, which contains the basic equations of water migration and heat transfer, and the equilibrium equation of water phase change and temperature. In the mathematical model, the effects of water phase change on hydraulic and thermal parameters were considered, so was the effect of latent heat in water phase change. Also, a code for the coupled heat transfer and water migration simulation was developed based on the finite volume method for the spatial discretization and fully implicit backward difference scheme for the time discretization. The code supporting unstructured mesh can ensure the conservation of mass and energy. It also has a parallel function, which can be used for the calculation of complex problems. Furthermore, an indoor soil freezing tests with two different temperature boundary conditions were conducted, and the corresponding numerical calculations were subsequently conducted. The experimental results generally matched the calculated ones, so the developed numerical simulation program can well simulate the evolution characteristics of the temperature field and water field during the soil freezing process. Hence, the established OpenFOAM program is an effective method to simulate the coupling process of water migration and heat transfer for the frozen soil.

Based on Biot wave theory of porous media, a model was established for non-homogeneous saturated half-space, in which porosity, density, shear modulus and coefficient of permeability were coupled with each other and varied along the depth at the same time. A three-dimensional (3D) dynamic control equation with soil skeleton displacement and pore pressure as the fundamental unknowns is constructed in the cylindrical coordinate system. Operator operation and Hankel integral transformation are used to solving the control equation, and the product decomposition of the vibration response of the half-space under the action of simple harmonic concentrated forces is obtained. The results obtained in this paper are reduced to homogeneous saturated half-space and elastic half-space, respectively, and compared with the classical Lamb solution, the accuracy of results is also verified. Based on the existing results, the coupling relations among porosity, density, shear modulus and coefficient of permeability are given and substituted into the derived results for numerical calculation. The dynamic responses of water-saturated foundation and gas saturated foundation (dry soil) are analyzed respectively. The effect of non-uniform gradient on the calculated results is also investigated. The results show that the coupling of four parameters along the depth of the foundation has a certain influence on the dynamic response of the foundation, and the attenuation rate of vibration displacement and pore pressure in the formation is accelerated. Since the viscosity of water is much higher than that of gas, the vibration attenuation in the water-saturated ground is much faster. The higher the degree of non-uniformity, the more obvious the influence of coupling effect.