To explore the chemical erosion phenomena, the chemical compositions of the spring water, seeping water and rainwater in Longmen Grottoes area are analyzed; and chemical solutions with different compositions are artificially made, which are in turn used to study the mechanical properties and the chemical solubility of Longmen Grottoes limestone under influences of different chemical solutions. The strength damage characteristics of the limestone are obtained based on the mechanical experiments with respect to different solutions and different erosion durations. A time-dependent corrosion equation of uniaxial compressive strength for limestone is developed under different chemical solutions. Based on the chemical kinetic tests on limestone under the effects of the different chemical solutions and for different erosion durations, the solubility of limestone eroded by different chemical solutions is addressed. The chemical dynamic erosion equations of limestone are developed. The analysis indicates that the strength of limestone decreases due to the dissolution of chemical solutions under chemical erosion. The salt effect and the common ion effect significantly influence the dissolution rate and strength of limestone. The salt effect can raise the dissolution rate, while the common ion effect can reduce the dissolution rate. When the composition and concentration of the solution are the same, the stronger the acidity, the larger the dissolution rate is. The dissolution rate of limestone increases with the increase of salt concentration when the composition and the pH value of the solution are the same.

The deformation of surrounding rock around a deep tunnel is a complex nonlinear mechanical problem. The creep in whole process and dilatation of the rock are two significant factors. Based on the Hoek-Brown criterion, the nonlinear stress solutions are obtained with and without the condition of the surface force around the tunnel, and dilatancy angle is introduced to consider the influence of the plastic volume change. Then an expression of viscoelastoplastic creep displacement is deduced under the nonlinear stress state using Hohai model which can describe the whole process of creep. Finally, the influence of the surface force around tunnel and dilatancy angle on the creep displacement of tunnel wall is discussed with different NVPB creep parameters and different material parameters m. The results show that under high ground stress the whole creep curve can be obtained by describing the creep problem of deep tunnel surrounding rock with the nonlinear creep model. In addition, the creep displacement of tunnel wall increases with the decrease of the surface force around tunnel and the value m, or the increase of the dilatancy angle, which is unfavorable to the long-term stability of surrounding rock. The results can be used to forecast the surrounding rock collapse of deep tunnels.

The laterite soil is widely distributed in Southern Hunan region. The soil has some special properties, such as a high natural water content, large void ratio and strong structural properties, etc., and can be used as special subgrade filling. To obtain the dynamic resilient performance of the soil, the dynamic triaxial tests are carried out to investigate the influence of deviatoric stress, confining stress and volumetric stress on the dynamic resilient modulus. Results show that the dynamic resilient modulus increases with the increase of confining stress and compaction degree and decreases with the increase of deviatoric stress. The dynamic resilient modulus is greatly affected by the water content and reaches a maximum value near the optimum water content. Based on the stress dependence of dynamic resilient modulus revealed with experiments, three typical prediction models for stress dependent dynamic resilient modulus are adopted to perform a regression analysis for experimental data; and then the best prediction model is selected from them. It is found from an error analysis that the prediction model considering confining stress and deviatoric stress provides a higher determination coefficient. That is to say it is the best prediction model of the dynamic resilient modulus for laterite soil in Southern Hunan. The test results and the selected prediction model can provide a basis of experiment and theory for subgrade design of laterite soil in Southern Hunan.

The Fenhe River-Weihe River Basin is one of the areas with the most developed ground fissures and related geohazards in China and even in the world. The effect of the rheological properties of loess during the long geological history is considered as the fracture extension mode of ground fissures. Applying stepwise loading and cyclic unloading, a series of consolidated undrained triaxial tests is conducted on Q3 intact loess sampled from Chang'an ground fissures belt in Xi'an region, to examine the rheological properties of the loess with different confining pressures. The loading and unloading creep curves, strain rate vs. time curves of Q3 intact loess within ground fissures are obtained. The experimental results show that the Q3 intact loess is featured with slow creep under low stress and slow creep or constant creep under high stress. Based on the unified rheological theory, a three-dimensional creep constitutive model which is suitable for Q3 intact loess within ground fissures belt in Xi'an region is established; and parameters of the model are obtained. The results lay a foundation for studying the fracture extension model of concealed ground fissures and the mechanism behind.

The freeze-thaw cycles change the structure of soils and influence their physical and mechanical properties, which can in turn be closely related to the pore water pressure change. However, measuring the pore water pressure of freezing soils has always been a challenge task. Here a new pore water pressure probe is developed and used to measure variations of pore water pressures of sand and silty clay during freeze-thaw cycles, from which the pore water pressures at three different depths of a cylindrical specimen are obtained. It is found that the frozen fringe and some ice lens occur in the silty clay samples during freezing; while no frozen fringe and ice lens form in sand samples. The pore water pressure is influenced by temperature, freezing rate, freeze-thaw cycles, soil types and others. The pore water pressure experiences a periodical change during the freeze-thaw cycles. The pore water pressure decreases and suction increases gradually during freezing, whereas the pore water pressure increases during thawing. The freezing rate, freeze-thaw cycles and soil types can primarily influence the amplitude of pore water pressure drop. In addition, the pore water pressure drop and suction increase near the freezing front are the major driving force of water migration from unfrozen zone to frozen zone. The above results show that the pore water pressure probe can be effectively used to measuring the pore water pressure of frozen soils.

Limit research effort has been made to explore the mechanism and settlement of high-speed railway bridge above goaf. With the pile group foundation of Guanshandi bridge in Hefei-Fuzhou high-speed railway as a prototype, a model test is carried out. According to the similarity theory, the similarity constants are derived and the similarity model materials are produced; and then the model setup is made. Based on multistage loading tests, three types of data are achieved including the internal forces of piles, stresses of soil among piles and the settlements of pile, pile caps, roof of goaf, the behaviors of piles and soils among piles as well as the settlement of goaf roof are determined. It can be found that the influence of goaf on the bearing capacity of pile is inversely proportional to the load. For all model piles, no negative skin friction is found to occur along pile shaft; and the center of the distributed skin friction in goaf descends significantly compared to those of the conventional piles. There is a critical value for the uneven settlement of pile group above goaf. If the settlement exceeds the critical value, the uneven settlement will stop growing. In addition, according to the test results and theoretical analysis, the equations for calculating bearing capacity and settlement of pile group above goaf are proposed based on the current code.

The piled beam-slab foundation is a new type of foundations for the wind turbine on land. The bearing capacity and the ability of deformation control of the piled beam-slab foundation are as good as those of the traditional pile-raft foundation. Compared with the traditional pile-raft foundation or the gravity foundation, it is popular for its great advantage in cost savings. Unfortunately, the piled beam-slab foundation is still designed according to the design method for traditional pile-raft foundation since now, which leads to a waste of money. In order to develop a reasonable design method for the piled beam-slab foundation, a large-scale model test is carried out to study the deformation characteristics and the mechanical property of the piled beam-slab foundation under vertical load. The study shows that the behavior of the piled beam-slab foundation system is elastic under the working load. A significant differential settlement occurs between the centre and the edge of the foundation. The pile-pile interaction and the pile-soil interaction which are not considered in the present design method have significant impacts on the behavior of the piled beam-slab foundation. Thus, it should be considered in the future design.

Considering the complex hydrogeology condition and the particularity of mineral composition of shallow brackish aquifers for energy storage, a controllable three-dimension infiltration experiment is conducted. Based on the theories of surface chemistry and colloid stability, the intrinsic connection between the variation of macro parameters of recharged solutions and the redistribution of micro-nano particles are analyzed from the mesoscopic standpoint. The spatial and temporal variations of the pore structure of brackish aquifer are analyzed; and the regions of low permeability curtain formed in different modes are determined. The results show that it is the variation of temperature and salinity of recharge solution that breaks equilibrium condition of forces between particles and induces the decrease of aquifer medium permeability. By fixing and switching the locations of pumping and injection well, the relative permeability of the whole aquifer medium k/k0 decrease to 63% and 57%, respectively, after one complete energy storage period, showing that the aquifer medium space structure variations are irreversible as result of micro-nano particles redistribution. Under the two working modes, low permeability curtain occurs in the 700-900 mm and the 500-700 mm seepage elements, respectively, due to their different formation mechanism.

By considering the effect of friction between the crack surfaces on the crack-tip stress field, the fracture angle value of the compression-shear combined crack is deduced by using the maximum circumferential stress criterion. According to the failure characteristics of the crack tip of rock subjected to biaxial stresses, a compression-shear combined fracture criterion is proposed by combining the maximum circumferential stress criterion with the modified Griffith strength theory. The frictional effect of the closed crack propagation is also considered in the criterion. The calculation results show that the fracture angle is influenced by the angle between the crack and the loading orientation, the friction coefficient of the crack surfaces and the lateral pressure coefficient. When the fracture angle of the compression-shear combined crack is one specific value, the ratio of the fracture toughness of the pure mode-II crack to that of pure mode-I crack is only influenced by the friction coefficient of the crack surfaces. This study is essential for the research on the failure models of fractured rock mass under the combined compression-shear stress.

A series of large-scale shaking table experiments was conducted on three-arch type underground structure in liquefiable ground subjected to the near field earthquake and the far field earthquake. Experimental results are discussed in items of pore water pressure, earthquake-induced ground settlement, acceleration response of soil and structure and the deformation of model structure. The measured data substantiate that, the buildup of pore water pressure mainly experiences two stages, at the first stage, the pore water pressure increases slowly, at the second stage, the pore water pressure rises sharply. Good agreement is found between the development of pore water pressure and Arias intensity. A larger peak of Arias intensity corresponds a higher peak of pore water pressure ratio. The distribution of pore water pressure field implies a lower degree of liquefaction at the bottom of model structure as result of a low intensity earthquake; while for the high intensity earthquake, the lower degree of liquefaction occurs at the bottom of ground. Subjected to the high intensity earthquake, the model structure generates an upward movement relative to the foundation. Both model structure and model soil present intense response to the ground motion with low frequency, the peak acceleration of ground motion in shallower fine sand layer shows some ‘spikes’ during the shallower liquefied soil cyclic mobility. Moreover, the low frequency components appear more at the upper soil than deeper soil. For the structure, the strain response of center column is larger than that of subarch, and the strain recorded at atrium arch is the smallest. With the increase of tensile strain amplitude, the natural frequency of the model structure decreases. The tensile strain recorded at the primary observation plane is distinctly different from that at secondary observation plane, implying that remarkable spatial effects of model structure.

An isotropic compression curve of the remolded clay always approaches to the normally consolidated line (NCL) from below on the void ratio vs. logarithmic mean stress plane. In the whole process, the tangent value of the compression curve increases monotonically. While for the structured clay, due to the existing of internal structure, the compression curve firstly rises above the NCL and then approaches to the NCL from above. In the whole process, the absolute tangent value of the compression curve increases firstly and then decreases. The difference in the tangent evolution between the structured clay and the remolded clay can be analytically described through increment function. For example, a horizontal line in the rectangular coordinate system is made as the reference and a function starting at the origin is formulated through the tangent that is decided by the function value difference between the formulated line and the reference line. The monotonicity of the formulated function tangent depends on whether or not the reference line is static. Inspired by this, a moving NCL (MNCL) on the void ratio vs. logarithmic mean stress plane is presented considering clay structure effects. Taking the MNCL instead of the NCL to be the reference line and incorporating the framework of the unified hardening model (UH model), behaviors of the structured clay in compression are well modelled.

A series of impact experiments were conducted on debris flow slurries and the mixtures of the debris flow slurry and large-sized particles with densities of 1 400-2 200 kg/m3, and 31 groups of impact experimental data at velocities of 2.4-5.2 m/s were obtained. The noise signals generated from device vibration and environmental interference are filtered out with the wavelet analysis method. Based on the results of the frequency spectral analysis using the fast Fourier transform method, a frequency threshold of 2 Hz is identified so that the low-frequency slurry impact force and the high-frequency large-sized particle impact force can be effectively separated. In the current hydrodynamic model the empirical coefficient α is generally difficult to determine. To resolve the issue, the functional dependence of the fluid Froude number Fr on coefficient α is developed based on 157 sets of debris flow monitoring data; and a formulation for calculating the slurry impact force is proposed, which represents different flow forms and the diminishing size effect. Compared to the smooth nature of slurry impact force, the large-sized particle impact force has more random characteristics. Both the number and frequency of particles impact on sensors increase when more particles are mixed in the flow. When mass ratio of particles increases from 0.05 to 0.21, the impact number increases from 1 305 to 2 838 times, and the impact frequency also increases from 82 to 195 times per second. The average particle impact force is about 60 kPa, which is about 3 times that of slurry. The frequency of particles detected by the upper sensors becomes larger than that detected by the bottom sensors as the particles content increases, demonstrating that the particles are prone to concentrate on the surface or at the head of debris.

Based on the results of triaxial experiments on rockfill materials, a dilatancy equation is derived by considering the nonlinear dependence of the dilatancy stress ratio on the stress ratio (i.e. the ratio of the deviatoric stress to the mean stress). This equation reveals the deformation characteristics of rockfill materials induced by dilatancy appearing at low confining pressure and by shear shrinkage appearing at high confining pressure. Within the framework of the generalized plasticity theory, the plastic flow direction vector and the loading direction vector are deduced. A compression index is determined in terms of compactness-dependent and mean stress-dependent effects. Then the plastic modulus is formulated as a function of the mean stress, the shear stress ratio and the compactness. On the basis of above studies, a new elastoplastic constitutive model is derived by considering the particle breakage of rockfill materials. The methods are addressed to determine ten material parameters of this model. Finally, the proposed model is used to simulate the triaxial tests on rockfill materials under different confining pressures and stress-paths, and the simulation results are good agreement with the experimental data.

Dynamic stiffness is an important index in pile dynamic measurement and analysis. In practice it is important to analyze and identify the factors that influence the dynamic stiffness of pile foundation. To analyze the dynamic stiffness of the intact and defected piles, an analytical model of admittance response under vertical harmonic loads is developed and solved. In this model, two variable cross sections are considered. The measured results show that the model can be effectively used to calculate the values of resonance frequency and dynamic stiffness. Moreover, 513 bridge piles of the same type are measured using mechanical impedance method. The dynamic stiffness for all piles is analyzed statistically. It is shown as follows. (1) the supporting stiffness of pile tip and the pile length significantly effect dynamic stiffness; the dynamic stiffness of end-bearing pile decreases with its length, whereas that of pure friction piles increases with the pile length. If friction pile has a longer length, its dynamic stiffness may exceed that of end-bearing pile. (2) For defected piles, the volumetric change has the positive relation with the variation of dynamic stiffness. (3) Dynamic stiffness is very sensitive to necking defection, which can be used to estimate the pile integrality and bearing capacity to some extent.

To explore the mechanisms underlying the compaction performance of sulfate saline soil, a series of light compaction tests is conducted on sulfate saline soils under various mixing conditions. The testing results show that the effect of salt content on the maximum dry density and the optimum moisture content of sulfate saline soil is complex; and it depends on the three states of sodium sulfate (sodium sulfate solution, anhydrous sodium sulfate and sodium sulfate decahydrate) and the relative amount of these three states of sodium sulfate. Both the maximum dry density and the optimum moisture content are inversely correlated to the relative amount of different states of sodium sulfate in the soil. The effects of the original moisture content and the curing times on the compaction are related to the salt content. The effect is trivial when the salt content is low (e.g. 1.5%), and very significant when the salt content is high (e.g. 5.0%). During the drying process, sulfate saline soil shows a false drying phenomenon. These experimental results provide a reference for evaluating the compaction characteristics and the degree of compaction of sulfate saline soils.

A loading device with the displacement rate control is developed for the model loading tests. Under the condition of displacement rate control, the indoor model loading tests are conducted on the TJ-1 lunar soil simulant by using a foot pad as footing. The average stress of the foot pad bottom is calculated with three different methods. The main conclusions from the analysis of the test results are as follows. The bearing capacity and deformation modulus under the foot pad increase approximately linearly with the loading rate. The bearing capacity calculated using the actual contact area between the bottom of foot pad and the TJ-1 lunar soil simulant is a little larger than that calculated using the maximum section area of the foot pad. The bearing capacity calculated using the maximum section area of the foot pad is recommended for the safety stock. The deformation modulus calculated using the actual contact area under the foot pad loading is between those calculated using the maximum and minimum section areas of the foot pad.

To analyze the effect of confining pressure on the stress intensity factors (SIFs) determined by the cracked Brazilian disk, the weight function method is employed to obtain the closed-form expressions of SIFs under various confining pressures; and the explicit expressions of the SIFs subjected to both the confining pressure and diametrical force are obtained. Based on the expressions of the SIFs, the effects of confining pressure on SIFs of the cracked Brazilian disk are analyzed. It is shown that the confining pressure has no effect on the SIF of mode II; and the crack subjected to pure confining pressure always tends to close up. The SIF of mode I decreases with the increase of confining pressure when the cracked Brazilian disk is subjected to the combined effect of confining pressure and diametrical force. By comparing the numerical results and theoretical results, it is found that two results are in good agreement, indicating the validity and reliability of the theoretical analysis. In addition, the effect of confining pressure on the loading conditions is also analyzed for pure mode II crack. The results show that the critical loading angle for pure mode II crack decreases with the increase of confining pressure, and gradually tends to 0 degrees. Therefore, the crack generated at about 0 degree of the loading angle is not always the pure mode I fracture at a high confining pressure.

Using the improved true triaxial testing system SPAX-2000, the static and dynamic drainage consolidation tests on muck are carried out. And then the mechanical responses of muck are investigated at different impact loading frequencies of 1 Hz, 8 Hz and 16 Hz and different confining pressures of 200 kPa, 250 kPa and 300 kPa. With combining the triaxial shear tests, this paper studies the undrained strength development of muck under different consolidation conditions. The experimental results are drawn as follows. (1) At the same impact loading frequency, the shearing strength of the specimen continuously increases as confining pressure increases. The increasing confining pressure also can result in an increase in the spherical stress and the volumetric strain increase, effectively promoting the specimen drainage consolidation. (2) Under the same confining pressure, there is a threshold of impact loading frequency. When the frequency is lower than the threshold, with the increase of impact load frequency, the axial strain gradually tends to become smaller, and vice versa. (3) At the instant of the impact, the volumetric strain is negative and characterized by volumetric expansion. The development law of volumetric strain is in agreement with that of pore water pressure at tamping moment in a field test. The fact is confirmed that a negative growth in pore water pressure would occur as the muck with high water content is subjected to the impact.

In Northwest China, loess is widely distributed and is the main material for landfill final cover. The gas permeability of loess will effect the landfill gas emission directly. In order to study the effect of the water content on the gas permeability characteristics of the loess cover in service, a device is developed to measure the gas permeability of unsaturated compacted loess specimens. The water content of the specimens after compaction is controlled using the osmotic technique. In addition, a one-dimensional steady-state model of gas migration in waste layers and final cover is established on the basis of the flow theory in porous media. The effects of gas permeability of the loess cover and gas extraction rate in the diffusion layer on landfill gas emission are investigated. The experiments demonstrate that the osmotic technique can effectively simulate the changing service water content of the loess cover. The measured gas permeability of loess specimens ranges from 10-17 m2 to 10-12 m2, and decreases with the increase of service water content; and the decrease is more significant for the high density specimens. The gas pressure at the bottom of the loess cover increases with the decrease of the gas permeability. Extracting landfill gas from the gas diffusion layer of the cover is able to reduce the gas pressure and the landfill gas emission rate.

A series of shear tests is carried out on the interfaces between concrete and silty clay, fine sand to study pile-soil interface shear behaviors of super-long bored pile using large-scale interfacial shear apparatus. Bentonite mudcake or bentonite mudcake and cement slurry are installed on the interfaces between fine sand and concrete to study the influence of mudcake and post grouting on the shear behavior of pile-soil interface. The results show that the shear stress increases nonlinearly with the increase of the shear displacement. After the shear stress reaches an ultimate value, the shear stress retains mainly a constant value or shows a softening tendency. The shear behaviors of the interface are significantly influenced by the soil type and the normal stress on the interface. The friction angle of interface between fine sand and concrete is close to the effective internal friction angle of the soil. The friction angle of the interface reduces 40% when the mudcake exists, showing that the lubrication action of the mudcake can greatly weaken the shear performance of interface. By grouting the cement slurry into the interface with mudcake, the friction angle of the interface increases nearly by one time that of the mudcake interface. It is shown that grouting not only can eliminate the adverse effects of mud cake, but also can further improve the shear properties of the interface. Furthermore, the relation between shear stress and shear deformation of the interface is closely related to mudcake and cement slurry. Due to the interface shear in the soils, a shear band is found to form gradually in soil near the interface. The phase of shear displacement gradually transforms into the phase of shear slipping during shear process. Moreover, there is great difference in the shear deformations of soils with different types of interface during shearing.

In this paper, we propose a simplified analytical method for computing the minimum safety thickness of water and mud inrush induced by filled-type karst water bearing structures. The theory of slice method widely used to analyze the slope stability is applied to investigate the stability of the karst filling material. A simplified computational model is established for the complex system which consists of tunnel, karst filling material and karst conduit. In this model, it assumes that the stress of filling material along the surface to reach the state of limit equilibrium and the failure of filling material along the sliding surface to obey Mohr-Coulomb failure criterion. An equation is derived by using the equilibrium of forces to calculate the minimum safety thickness of water and mud inrush induced by filled-type karst water bearing structures, in which it is used for the application of the practical engineering problems. The results calculated by the proposed method are in good agreement with numerical simulations. It indicates that this method is applicable for the determination of the minimum safe thickness of water and mud inrush, which also provides an efficient way to explore the mechanism of water and mud inrush in karst tunnels.

The phenomenon of sinkholes in soil stratum induced by subterranean cavity is the common geological hazards. However, there is limited research on the formation mechanisms of sinkholes due to its complicated reasons. In this paper, the formation models of sinkholes in soft and coarse-grained soil strata are firstly obtained by analyzing the formation causes and case studies. For the cylinder-shaped sinkhole in soft soil stratum, the equations of safety factor are derived using the plastic limit equilibrium theory, which are further used to characterize some relevant factors that influence the formation of sinkholes. For the funneled sinkhole in coarse-grained soil stratum, the equation of safety factor is also determined on the basis of the granular media flow theory. By analyzing the formation patterns of sinkholes, we propose a method to predict and assess the sinkhole occurrence based on the thickness of soil stratum and the maximum subsidence. Finally, the deformation characteristics of the soft and coursed-grained soil strata induced by sinkholes are analyzed by using numerical simulation, and two formation models of the sinkholes are further verified. This study is essential to understanding the formation mechanisms and prevention of sinkholes in soil stratum.

To analyze the deformation of the tunnel in weak loess, the surface settlement, crown settlement and horizontal convergence are in-situ monitored in the Dayoushan loess tunnel by using precision level and convergence gauges. The results show that the magnitude of crown settlement is much larger than that of the horizontal convergence. The deformation sustains for a longer time and the steady maximum crown settlement is 950.6 mm. The deformation of surrounding rock is larger when the buried depth of the tunnel is at the critical depth. The deformation rate of surrounding rock is larger at the stage of secondary lining construction. The deformation rate, which acts as the stability criterion for the surrounding rock-supporting system in the weak loess tunnel, should be raised moderately. The deformation of the surrounding rock follows an exponential law; and the exponential function can be used to predict the final deformation of surrounding rock. The deformation of weak loess tunnel can be divided into three stages: rapid deformation stage, sustained growth stage and slow growth stage; and finally, it tends to steady. The tunnel excavation significantly influences the surface deformation; and the maximum settlement of surface occurs along the central axis of tunnel; and the settlement gradually decreases with the increase of the distance from central axis transverse. The deformation allowance of weak loess tunnel should not be unified at different locations. For the weak loess tunnel in Xining area, the reserved deformation of grade Ⅴsurrounding rock is suggested to be 700-800 mm for the crown, and 300-350 mm for the side wall. The crown and side wall of tunnel should be connected by smooth curve.

Assuming that soil skeleton satisfies the constitutive relation of the standard linear viscoelastic solid, the transient dynamic responses of the coupled system of saturated viscoelastic soil-elastic lining of a deep circular tunnel subjected to a blasting load are studied. First, based on the Biot model of the saturated soil and the elasticity theory of the lining, with the boundary conditions as well as the continuity conditions on the interface between the saturated viscoelastic soil and elastic lining, the analytical solutions of the displacements and stresses as well as the pore water pressure of the saturated viscoelastic soil and elastic lining in the Laplace transformed domain are derived by means of the Laplace transform and potential functions. Then, the transient dynamic responses of the coupled system in the time domain are obtained with the Crump numerical inverse Laplace transform, and the radial displacements and circumferential stresses of the soil-lining coupled system as well as the pore water pressures of the saturated soil for different soil models are analyzed numerically. It is shown that, for the soil-lining coupled system with different soil models, their dynamic behaviors are almost the same under the blasting load, whereas their vibration periods and amplitudes are obviously different. Furthermore, for the system of saturated viscoelastic soil-elastic lining, the influences of the viscosity parameters on the soil radial displacement and the pore water pressure are remarkable; while the viscosity parameters have a little influence on the circumferential stress of soil.

The paper studies the collapsing height of overburden rockmass at metal mine with dimensional analysis. The collapsing height is closely related to such factors as mining techniques, thickness of ore body, mining depth, tectonic stress, size of goaf, lithology of overburden rockmass, lithological structure, fault structure and time, etc. The statistics and analysis of the influential factors are carried out. The functional relation and dimensional matrix are established combining the engineering practices and dimensional analysis. The quantitative relations are set up among collapsing height H and ore body thickness d, mining depth h, tectonic stress ? h , size of goaf s, unit weight of rock ? , coefficient of volumetric expansion of rock k and coefficient of hardness f . The prediction relation expression of collapsing height is verified with practical engineering. The computed results of collapsing height are consistent with the measured results at an error of about 5.8%, which satisfies the engineering requirements. This method provides references for mining parameter selection under the mine water body, mine rockburst control and selection of mining techniques.

Based on the theory of linear elastodynamics, and combined with the coordinate transformation, the dynamic governing equations for a half-plane inhomogeneous subgrade are developed. The dynamic response of a two-dimensional inhomogeneous subgrade subjected to moving loads is analyzed based on a semi-analytical method. Using Fourier series expansion, and assuming the series form of response function, the analytical expressions of various physical quantities are developed for the inhomogeneous subgrade subjected to moving loads, in which the shear modulus can arbitrarily change with depth. Assuming the shear modulus has an exponential distribution with the thickness, a parametric study is presented to illustrate the influence of the foundation soil inhomogeneity and load moving velocity as well as shear modulus at subgrade surface on the dynamical response of foundation soils. The calculated results are compared with the responses of a homogeneous subgrade, showing that the vertical displacement of soil decreases with the increase of the shear modulus at the surface of subgrade and the inhomogeneous gradient index, and increases with the increase of the load moving velocity. Under a moving load, the dynamic responses of inhomogeneous subgrade are significantly different from that of homogeneous subgrade.

Rockburst is a main geological disaster influencing underground constructions at the high ground stress area. The prediction of rockburst has become one of the worldwide difficulties in underground works. Formation lithology and the value of ground stress are two basic factors that affect the occurrence of rockburst; and the accurate discrimination of them is directly related to the success of rockburst prediction. According to the measured principal stress data of the engineering site, a numerical calculation model of the region is established by FLAC3D. Using radial basis function neural network, inverse analysis of the initial ground stress field is made. Then based on the rock mechanics in-situ experiments and TPS203 detection technology, formation lithology of the area with high rockburst risks is obtained. Finally, combining inverse analysis data and TSP detection results, the intensity of rockburst within a great distance of the region in front of tunnel face is precisely predicted. The case study shows that the proposed procedure is of high maneuverability; and the rockburst prediction results are well consistent with actual excavation conditions.

The hydraulic and mechanical properties of rock masses are affected significantly by the discontinuities, and thus it is vital to characterize the development of various discontinuities for the fundamental stability analysis of rock masses. The hydraulic and mechanical behaviors are different for the discontinuities with the same dip direction but different other parameters. Although the conventional method is widely used to classify the discontinuities by the dip direction, this approach is challenging to apply for those discontinuities having the same orientation but different other parameters. Therefore, we propose a new method based on quantum particle swarm optimization algorithm for partitioning multivariate discontinuities data. An objective function is established by the similarity measure of discontinuities. To search global optimal solution, quantum particle swarm optimization algorithm is employed. The newly proposed method classifies the discontinuities by their multivariate parameters, which is also validated by categorizing the simulated data into groups. Finally, the new method is applied to analysis the data of multivariate discontinuities collected from the Songta dam site on the NuJiang River, and there is good agreement with the in-situ measurement.

According to the long-term monitoring data of the Qinghai-Tibet Highway from 2004 to 2011, we systematically analyze the characteristics of permafrost embankment deformation and the reasons of roadbed disease. Our studies show that the thawing-sinking is the major deformation behavior of common fill embankment, and the settlement may be further increased in future. The types of deformation can be divided into uniform and non-uniform deformations in terms of the deformation rate differences of each part of embankment. The average deformation rate is in the range of 0.2-5.5 cm/a. The deformation rates of embankment are different in different regions. In river valley regions, the deformation rate is the maximum; it is followed in the mountain regions, and the minimum is in other regions. The types of deformation can also be divided into longitudinal and lateral embankment deformations depending on the deformation direction. The longitudinal embankment deformation has the greatest effects on the pavement and results in the wave-shaped pavement disease, which induces uncomfortable driving situations and the road traffic safety. The lateral embankment deformation results in longitudinal cracks in embankment, which causes the collapse towards to the severe deformation side, and thus influences its overall stability. Based on the investigation of the Qinghai-Tibet Highway roadbed diseases in 2012, it has been found that the proportions of embankment status grades of very good, good, fair, poor and very poor are 57.39%, 28.12%, 9.71%, 4.60% and 0.17%, respectively. This study provides a reference for maintaining the stability of Qinghai-Tibet Highway and a basis for route selection and engineering design in future.

This paper quantitatively investigates the viscous damping and numerical damping in the discontinuous deformation analysis (DDA) method. The motion equations of the block system are first developed based on the Newmark method; and the relationship among the viscous damping ratio, the dynamic coefficient and the time interval of each step in DDA is developed based on the kinetic theory of viscous damping. The constant acceleration integration scheme in DDA, the partitions and the damping ratio of the numerical damping are discussed; and the calculating formulations of the damping ratio for the combined damping are obtained. An example of the block vibration is analyzed under simple harmonic motions; and the proposed formulations are validated by comparing the DDA calculations to the theoretical solutions. The simulation results show that the viscous damping significantly affects the low frequencies; and the numerical damping can quickly eliminate the interference of the high frequencies. If the two dampings are combined, the frequency-dependence can be reduced. The study results provide a theoretical basis for the vibration and wave calculation using the DDA method.

A slope stability limit analysis based on the translational failure mechanism is presented under typical uniformly-distributed loading and seismic loading conditions. The sliding body of slope is divided into arbitrary discrete blocks with inclined interfaces. Based on the upper-bound limit analysis method and nonlinear Mohr-Coulomb failure criterion, a general expression for safety factor Fs in state of critical failure is developed based on the multipoint tangent method and strength reduction method. In this expression, the inhomogeneity of normal stress in rock mass is considered. The upper bound solutions of the slope safety factor are obtained by applying a nonlinear sequential quadratic programming (SQP). The contrastive analysis shows that agreement with the previous results can be achieved by a relative error less than 3.565%, demonstrating the rationality and reliability of the proposed method. Meanwhile, the slope stability safety factors Fs calculated by multipoint tangent inclined slices method are smaller than those obtained by traditional single tangent inclined slices method, showing that multipoint tangent inclined slices method is a conservative and effective method for slope stability analysis. Parametric analysis indicates that the uniformly distributed loading, seismic loading and nonlinear parameters have significant effects on safety factor and the potential critical slip surface of the slopes. This paper provides a new approach to analyzing the slope stability by introducing the multipoint tangent method into the nonlinear Mohr-Coulomb failure criterion.

Based on the consolidation data of deep fine-grained soils distributed along the Beijing-Shanghai high-speed railway, a simplified method is proposed for determining the compression modulus of the undisturbed normally consolidated foundation soils using standard compression modulus E1?2 and liquid limit wL, in which the composite function expression containing the segmental function of the e-lgp curve and the linear relationship between liquid limit and compression index are also adopted. It is shown that the Harris function can describe the e-lgp curve characters well, and E1?2 can reflect the secant slope of the low-pressure section of the compression curve, while wL can reflect the tangent one of the high pressure section. The compression modulus estimation method of foundation soil yields good results for all levels of pressure, namely, the average error is just 7.89% in the commonly used pressure section of 100-1 000 kPa, and in the high pressure section is about 13.70%, whereas significant error occurs only in the low pressure section. The study results provide a new approach to rapidly obtain the compression modulus of soil in the case that the e-lgp curve is lacking.

Based on Kelvin’s contact force calculation model, the conditions required for simulating the mechanical behavior of the porous materials consisting of spherical particles are analyzed, from which a new granular model construction method is proposed. In this model a seed position is stochastically generated in the complex solution domain; and then it is gradually expanded to fill the entire region. In the filling process a local Delaunay triangulation mesh control is used to generate new particles; and particle distance control in a complex geometry boundary is used to decide the relative position of a new generated particle. For particles near the model boundary, an optimized tolerance position and radius are calculated and filled, which enhances the coupling characteristic between boundary and the particles. Meanwhile, the pore position can be refilled to ensure that each particle is tangent with at least three particles in order to improve the coupling characteristic between model particles. Finally, arbitrary polygons are used to divide several materials. The model region will be simplified for judging whether the polygon point is in the polygon or not, which can simplify the setup process of complex model materials. The results show that the proposed method has small overlap between particles, high filling rate between particles, particle and boundary. The proposed method can decrease flying overflow phenomenon when the adhesive force between particles disappears, and can be used to model construction of random connected domain.

Based on the composite element method, we propose a composite element model associated with a three-dimensional heat conduction-convection equation and a “filled model” for the determination of the transient thermal field in fractured rock mass. Although the existence of fractures is not considered during mesh generation, it is explicitly treated in the mapping composite element by means of the composite element pre-processing work program. There is no restriction on the computational mesh generation. A self-adjoint process is made to adjust the heat conduction-convection equation. The composite element algorithm is deduced by applying the variational principle for solving transient thermal field in fractured rock mass. The proposed method is applied to calculate the respective temperature of rock sub-elements and fracture segments, in which it also takes into account the thermal exchange characteristics of the fluid in fracture and the adjacent rock blocks. The obtained numerical results are consistent well with the experimental data. The reliability and validity of the proposed numerical method are verified with the measured results, which show that the thermal conduction and convection and obviously occur between the fluid in fracture and the adjacent rock blocks.

The traditional theory of soil arch effect is developed on either cohesionless soil or saturated cohesive soil. In practice the unsaturated soils are commonly encountered, whose mechanical properties are influenced by natural environment transformation. Based on the Terzaghi’s assumption and the principle of principal stress axes rotation on soil arch effect, an analytical model is proposed to evaluate the loosening earth pressure of unsaturated soils considering matric suction. The analytical solutions of the loosening earth pressure and the lateral pressure coefficients are derived for uniform, trapezoidal, upright-triangular and reverse-triangular matric suction distributions respectively. A numerical model by FLAC is developed to verify the analytical model. The theoretical results are consistent well with the numerical results. The influences of such factors as saturation degree, thickness of overlying soil, Trapdoor width, groundwater level and rainfall, on loosening earth pressure are discussed. It is found that the loosening earth pressure decreases firstly and then increases with the saturation degree of soil increasing. The minimum loosening earth pressure is reached at the saturation degree corresponding to the air entry value of the soil.

In contrast to the high demands and fast development of shield tunnels, significant deficiencies exist in the shield tunneling techniques and theoretical researches for large-scale deep tunnels, and especially under hydraulic conditions, the issues related to the stability of the deep shield tunnel face become even more prominent. Based on the upper bound limit analysis and the unified parameters of water and earth pressures, the face stability of tunnel in the homogeneous soil is studied with considering the effect of water pressure. A three-dimensional log-spiral failure model of the deep shield tunnel face is designed; and then an equation for calculating the limit support pressure is developed. Based on the soil thickness-weighted average method, the developed theoretical procedure is applied to evaluate the face stability of tunnel in multilayered soils. The limit support pressure of the face in the Shanghai Yangtze River tunnel is determined with the proposed upper bound limit method of three-dimensional log-spiral failure mode. The calculated results are compared with the previous studies and the simulated results. Through this research, the calculation methods of the limit support pressure of deep shield tunnel face under hydraulic condition can be improved, providing a theoretical basis for the determination of the reasonable support pressure during the construction of shield tunnel.

The fuzzy point estimate method can simultaneously consider fuzzy and random uncertainty in slope stability analysis. To overcome the drawbacks of a great deal of computing existing in traditional fuzzy point estimate method, an improved fuzzy point estimate method is proposed on the basis of artificial neural network. Firstly, the Latin hypercube sampling method and radial basis function (RBF) neural network are adopted to establish a prediction model for determining safety factor of slopes. Secondly, fuzzy-random variables, i.e. cohesion and friction angle, are transformed into interval numbers by the λ cut set approach, and then combined at each cut set level. The corresponding safety factor of each variable combination is obtained with the established prediction model. Finally, reliability index of slope is calculated using the point estimate method. A practical example is analyzed, showing that the proposed method is convenient and reliable to evaluate slope stability, and can be further improved to increase the computational accuracy of slope reliability index by increasing the number of λ cut set levels. For those slopes with 2-4 fuzzy-random variables, as the proposed method is used to compute the reliabilty of a slope, the number of λ cut set levels is recommended to be 25.

Plane strain apparatus is an early-developed, relatively widely used, and yet immature experiment apparatus for soil testing. With the development of infrastructures, the plane strain tests and the related testing methods are applied to many project fields, showing their importance in engineering design and research. This paper reviews the historical development of plane strain apparatus at home and abroad, pointing out that it is necessary to explore a new kind of plane strain triaxial test apparatus for soil to achieve more reasonable and accurate plane strain data under complex stress loading conditions. For this purpose, by improving the structure of pressure chamber, loading system and control system, a new horizontal plane strain triaxial apparatus for soil has been developed. The results of the plane strain test are compared to those of the modified true triaxial test on remolded loess; and the strength parameters are determined using the new apparatus and compared with those of the conventional triaxial tests, showing the accuracy and reliability of the new horizontal plane strain triaxial apparatus. Finally, the failure characteristics determined by the new plane strain apparatus are compared to those obtained by the modified true triaxial apparatus, showing the applicability of the new plane strain apparatus in capturing the main features of soil localization.