In this study，the longitudinal wave velocities of schist specimens with saturated and dry fractures under loading and unloading conditions were measured，so that the variations and characteristics of wave velocity of saturated schist with fractures in the whole process of compression were obtained and relationship between wave velocity with the rock damage and failure were established. The wave velocities of the saturated specimen without loading were found to be significantly higher than those of dry specimen. The wave velocities   parallel to cracks increased from 0.928% to 15.357% upon saturation，and the wave velocities   perpendicular to cracks increased from 20.042% to 113.362% upon saturation. The wave velocities   perpendicular to cracks were affected more evidently than those parallel to cracks. Under compression，the acoustic wave velocities perpendicular to cracks for both the schist specimens with the dry and saturated fractures were nonlinear in the elastic stage or the compression process and dropped drastically at the point of peak stress indicating the cracks were developed. While for dry specimens，the wave velocities   parallel to cracks were reduced suddenly only at the peak point. For the saturated specimens，the wave velocities   parallel to cracks undulated.

The mathematical relationship between the creep parameters and the degree of saturation of the low-grade metamorphic slate was established based on the experimental data of uniaxial creep under different moisture states. It is found that the higher the degree of saturation of the rock，the smaller the creep parameters. The instantaneous elastic modulus varies linearly with the degree of saturation. The viscous modulus and the coefficient of viscosity vary exponentially with the degree of saturation. The damage of the rock induced by water is considered as the damage of each creep parameter. The variables defining damage and the variation of damaging are determined according to the experimental results. Then creep equation for the low-grade metamorphic slate considering water damage is established. The constitutive model is incorporated into the software FLAC3D. The results from the compressive creep test and the numerical calculation verify the rationality of the model.

The node-to-segment approach using penalty method was widely applied in engineering field due to its great simplicity. To deal with the problem in which a large penalty factor may cause ill-condition，the degree of freedom relevant to contact is described by relative displacement in local coordinate system，which enlarges significantly the upper-limit of penalty factor and provides an efficient solution for large-scale contact problem without using any special preconditions. A general 3D contact smoothing method based on radial point interpolation is proposed to avoid probable projecting singularity and jump of contact force in node-to-segment. This method reproduces smooth surfaces which passes exactly through the surface nodes even for coarse or hybrid meshes. The doubly connected edge list is applied to the local searching for contact information and effectively reduces the computing cost. A nonlinear contact analysis program is written and the results of numerical examples indicate that the program effectively describes the phenomenon of displacement discontinuity，solve the contact nonlinear equation，and tackle the large-scale contact problems in underground engineering.

The joint fissures of a copper mine is very well developed with the fragmental surrounding rock and ore body. The success rate of drilling holes for explosive installation was low，so reinforcement was needed. The explosion resistant resin MP 364 for mine applications was selected for the chemical grouting test in-situ. The grouting pressure and the diffusion radius etc were determined experimentally. A grouting system was built based on the experimental results. After the application of the chemical grouting according to the recommended proportion of grouting materials，the rock mass strength was improved significantly，the success rate of drilling holes for explosive installation was increased by 25%，the exposed area of the stope roof was increased by 110 m2，the retention volume of the stope ore was reduced by about 10%，and the ore recovery ratio was increased by 23.3% .

After tunnel is excavated，the effect of seepage on the surrounding rock is very serious. So far，the differences of seepage are remarkable between the analytical results or numerical results and the practical seepage influence. While analyzing，the considered seepage area is the whole half-plan，not only the calculating load is enlarged，but also the surrounding rock is not influenced more seriously by the farther seepage. Aiming at the problems of the nonlinear seepage and the calculated watershed in surrounding rock，a simple and effective mathematical method is presented to derive the seepage force expression in the surrounding rock；and the effects of tunnel radius and embedded depth on the seepage action are also researched by the analytical expression。Comparisons between the analytical results and numerical results show that they coincide with each other very well，and that the mathematical method proposed is rational. Finally，the analytical expression is used to research the calculation seepage boundary，and a new theoretical method to calculate the seepage boundary is proposed. The results not only satisfy the seepage requirements，but also save the calculation load.

In order to investigate the fault F4–4 at the undersea tunnel in Jiaozhou Bay near Qingdao，an extendable testing system modeling water inrush in subsea tunnel overcoming the problems in the existing fluid-solid coupling model test was developed. The testing system composed of an extendable model bench，a water inflow acquisition and measurement device and an automatic water-level upgrading and loading device. The extendable model bench was made of high-strength steel and tempered glass. The steel structure members operated independently connecting with the glass room for observation，which made the testing process visible and the equipment attractive in appearance. The bench was made extendanle along the longitudinal dimension through the prefabricated bolt holes according to the test needs，achieving the simulation of different geological defects. The water inflow acquisition and measurement device was composed of the water inflow acquisition appliance，the aqueduct and the flow rate measurement sensors to monitor real-time water inflow. Meanwhile，two kinds of similar materials different in hydraulic property were developed according to the similarity conditions in fluid-solid coupling，and were proved to be suitable for simulating the fault and the normal surrounding rock. The information of multivariate precursors in real time water inrush tests such as the displacement，the stress and the seepage pressure was collected with the fiber grating sensors and the micro pressure cells. Model tests of water inrush in fault were carried out with the built model testing system. The variations of the displacement and the seepage of fault and surrounding rock mass were captured in the process of the water inrush and excavation process. Test results showed that the system was stable and reliable.

Determining the mechanical parameters of jointed rock mass is a critical problem in rock mechanics. The techniques to study the size effect and the spatial anisotropy of the mechanical parameters of jointed rock mass through three-dimensional distinct element simulations were discussed and the methods to solve the problems encountered in the simulation were proposed. The size effect on mechanical parameters of jointed rock mass was investigated on the basis of a three-dimensional fracture network model through a case study by considering the effect of model location. The normal and the shear constitutive models of actual joints were established according to the laboratory test results. These constitutive models were used to represent the mechanical property of joints via a program written with Fish language. The variation of the normalized rock block strength，the deformation modulus，the shear modulus and the bulk modulus with the location and block size were obtained and the representative elementary volume(REV) size was determined to be 18 m. Finally，the anisotropy of jointed rock mass in the studied area was revealed by rotating the REV block size of 18 m in every 45°in 3D to determine the mechanical parameters in different directions.

Collapse is one of the main risks during the construction of tunnels through soft ground in urban areas. Understanding the characteristics of tunnel collapsing helps the prevention of the problem in tunneling through the soft ground. Model tests were performed to study the collapsing characteristics of a deep tunnel and a shallow tunnel under the same soft ground condition respectively. The results showed that collapses of the tunnels in soft ground under different covering depths had two similar characteristics，the progressive failure of surrounding rock and the sudden occurrence of tunnel collapse. However，the characteristics of collapses in the deep tunnel were different from ones in the shallow tunnel in the following aspects：(1) The failures of surrounding rock around the deep tunnel did not spread to the ground surface. Collapses occurred several times and there was a short-time and stable collapsing arch during each collapse. The collapses did not stop until the formation of a stable collapsing arch. All the boundaries of collapsing arches were in the shapes of typical quadratic parabolas. (2) The failures of surrounding rock around the shallow tunnel spread to the ground surface，and eventually caused the ground surface to collapse. A short-time and stable collapsing arch was also observed to exist during the failures of surrounding rock，and its boundary was also in the shape of a typical quadratic parabola. (3) The failures first occurred on the two sides of the tunnel and then at the tunnel crown in the case of the deep tunnel，while the ruptures of the ground surface occurred earlier than the surrounding rock around the tunnel during the construction of the shallow tunnel. Therefore，the key measures of preventing the collapses should be taken in the tunnel for deep tunnels，and both in the tunnel and on the ground surface for shallow tunnels.

By using the pendulum hammer driven SHPB apparatus，the ideal incident waveform is generated by changing the shape and by controlling the impact velocity of the pendulum hammer. The compressive test and Brazilian test of sandstone specimens were conducted using the pendulum hammer driven split Hopkinson pressure bar(SHPB) apparatus，and the variation of dynamic compressive strength and dynamic tensile strength under different impact velocity of the pendulum hammer is examined. The strain rate ranging from 100/s to 102/s，which is generally considered as intermediate strain rate，is measured during the dynamic compression test，and the loading rate corresponding to the tensile stress at center of rock disc，ranging from 100 GPa/s to 400 GPa/s，are generated during the dynamic Brazilian test. The dynamic compressive strength and dynamic tensile strength of the sandstone samples increase with the impact velocity，showing an obvious strain-rate dependency. During the dynamic Brazilian test the sandstone samples were finally separated into two halves along the loading diameter. The V-shaped failure zone at the contact area between the incident and transmitted bars and the rock specimen becomes larger with the increasing impact velocity. The advantage of the pendulum hammer driven SHPB apparatus is that the ideal incident stress waveform can be excited by the pendulum hammer，and it can supply a feasible experimental method to measure the dynamic strength and failure process of the rock under the intermediate strain rate.

The catastrophic behavior of working face，the movement and development of debris flow，the stability control of the surrounding rock mass are the key scientific issues of tunnel construction in the debris flow strata. A test device capable of simulating the geological structural features of Qilianshan tunnel were developed for investigating the occurrence，the development and the mechanism of catastrophe of debris flow. A program of orthogonal tests was carried out to study the effects of the water pressure，the debris gravity and burial depths of debris strata，material compositions on the occurrence of debris flow. The instability model of tunnel face and the stability identification index of tunnel face under the lasting action of water pressure were investigated. The conditions of strata formation of debris flow such as the material structure，the groundwater and the tunnel excavation section were analyzed systematically according to the results of the model tests.

In order to understand the mechanism of the underground engineering disaster caused by sand and water loss in water-rich sand stratum，a new visualization experimental device was developed to investigate the leaking process of sand and water. Five types of sands with the coarser particle size D90 between 0.4 mm and 4.1 mm were experimentally studied. A critical width of gap in the leaking process of sand and water was discovered. Numerical simulation was performed using the particle flow code-comutational fluid dynamics(PFC-CFD) method in order to study the variation of the chains of contacted force and the structure load on both sides of the gap. The results showed that catastrophe failure occured when the gap width exceeds the critical gap width. The failure surface near the gap was found to be quadratic. With the increase of the gap width，the volumetric content of sand in the discharge increased. The leaking process of sand and water accompanied a continuous and variable process of soil arch formation and break. The fluctuation of structure load on both sides of the gap reflects the forming and breaking of soil arches.

Construction of crossing tunnels underground in urban area inevitably disturbs the surrounding ground，posing a series of problems on the environment，especially for the old Beijing city. In the construction of Subway Line 6 in Beijing，two tunnels cross each other one over the other in the section between Beihai north to Luoguxiang south，which is a first case of underground tunnel crossing in Beijing. Numerical simulation and field measurement were adopted to study the surface deformation characteristics of five typical sections under different excavation sequences，layouts and grouting methods. The maximum ground surface settlement and the width of settlement trough were smaller and the tunnels were more stable in the case of the lower tunnel excavated first than the ones the upper tunnel excavated first. The surface deformation was found to increase notably with the increase of the crossing angle of two tunnels. When the crossing angle was greater than 60 degrees，the maximum value of ground surface settlement exceeded 30 mm which was above the control standard. The stratum needed to be strengthened through grouting in this case. The maximum settlements at ground surface and tunnel crown decreased with the increase of the thickness of grouted layers. Having considered the economic costs and the unfavorable effects of grouting pressure，the thickness of grouted layers was suggested to be 1.5–2.0 m. The monitored field data showed that the ground surface settlements after grouting met the requirement of control standards and the grouting was an effective method to reduce the ground surface settlement and the width of settlement trough.

A peak shear strength model for cement filled rock joints was proposed based on the results of theoretical analysis and direct shear tests. Firstly，three-dimensional morphology parameters of the cement filled rock joints was obtained. Then，the peak shear strength of the cement filled rock joints was calculated using the proposed model and comparisons were made between the calculated and measured results. Finally，the errors between the predicted and the measured peak shear strengths were analyzed. The predicted results was close to the measured ones. The model was found to capture well the influence of the three-dimensional morphology characteristics，the percentage of cement filling and the strength ratio of joint rock wall to cement stone. Errors were mainly caused by the inaccuracy of the proposed model and the defect of bond between joint and cement stone.

In order to study the crack and stress evolutions caused by the directional focused energy blasting in deep borehole，an experiment system was constructed，and a series of laboratory and field experiments together with the field experiments of directional focused energy blasting were carried out. The results show that the energy of directional blasting mainly concentrated in focusing direction and then penetrated the coal sample with the cracks in focusing direction much longer than those in other directions. Because of the effect of directional focused energy blasting，the mechanical properties of the samples in focusing direction were changed much more significantly than in other directions. The permeability after directional focused energy blasting in coal seam was found increased. The maximum gas drainage volume was 10–40 times of the original one，with the effective radius of gas drainage reaching 7 meters. Besides，the directional focused energy blasting made little damage to the roof and floor of coal seam and the surround rock of roadway.

Conventional triaxial experiments and unloading experiments of marble were carried out. The forms of yielding functions on the meridian plane were discussed under different loading and unloading stress paths. According to the generalized theory of plastic mechanics，the mathematical expressions of the yielding surface of shearing in q direction and the volumetric yielding surface in p direction were given. Results show that the yielding surface for shearing was linear under the loading stress path, was a parabola under the unloading stress path. The volume of the marble samples dilated under both the loading and unloading stress paths. The volumetric yielding surface was divided into the compression stage and the expansion stage. The volumetric yielding surface of marble under the loading stress path made up by two linear segments and under the unloading stress path was a parabola. The yield function determined according to the test results reflected the impact of the stress path changes and the anisotropy of rock and avoided the disadvantages of assumed ones. The plastic shear strain and plastic volume strain increased faster under the unloading stress path than under the loading path. The subsequent yield surface developed to the limit yield surface very quickly. These results illustrate that the unloading failure occurring more suddenly.

Because of the complexity of the urban environment and the variability of the geological conditions，it is very important and difficult to predict the ground deformation accurately. The process and mechanism of ground deformation were analyzed systematically from three aspects，the materials，the meso-structures and the environment of ground layers. Three typical kinds of meso-structures were put forward to describe the characteristics of complex ground conditions and correspondingly the methods of stability analysis were established. According to the designated type of ground meso-structure and its spatial relation to tunnel，the quantitative relationship between the stability of the meso-structure and the macroscopic ground deformation was established，which predicted accurately the ground deformation and the surface subsidence caused by the instability of meso-structure. A model of calculating the ground deformation due to the water table fall and the loss of water and sand was established. Together with the elasto-plastic deformation of ground，the total ground deformations were thus be obtained and were found to agree very well with the measured data.

To overcome the deficiency of existing direct tension test device，axial positioning devices were developed，including an axial positioning device for bonding and an axial positioning device for tension. The two sets of axial positioning devices eliminated the bonding eccentricity and the tensile eccentricity respectively，ensuring that rock specimen be pulled in uniaxial tension state. The direct tension tests of rocks were then carried out using the axial positioning devices and the universal testing machine. The tensile strength，the ultimate tensile strain and the tensile elastic modulus of sandstone，limestone and granite were measured. In the direct tensile test，the standard rock specimen was used. The tensile stress-strain curves of these rocks were obtained. The failure surfaces of rock specimen were found to appear at the middle of specimen mostly. The most of the rock specimens displayed the mode of brittle failure. The fractures of rock influenced greatly the tensile properties of rock. In order to measure the tensile strength of rock accurately，the rock specimen should be selected strictly before testing.

Wind and snow erosion is due to the combined effect from the action of wind blowing，snow melting and temperature varying. The unprotected embankment filled with Aeolian sandy soil of the Inner Mongolia-Sue provincial highway located in the section of Sanggendalai in Xilingol League was studied in wind tunnel test. The characteristics of the soil porosity were analyzed using the optical microscope combined with the digital image method. The pore area ratio was defined and the quantitative analysis of porosity characteristics was conducted before and after the wind-snow erosion. The affected depths by the wind-snow erosion from the slope surface at the different testing layers were obtained. The relationships between the pore area ratio of each tested layer and the freeze-thaw erosion from the melt snow infiltration and the wind erosion were established. The measured results showed that the shoulder was most seriously affected，and the effect of wind-snow erosion decreased from the shoulder to the toe of the embankment. The maximum influenced depth at the embankment shoulder was found to be about 1/6 times of the model height. The pore area ratio at the embankment shoulder increased by 50.1% while the pore area ratio at the embankment toe increased only 30.7% after three cycles of wind-snow erosion. For the same erosion cycles，the structure damage due to the wind erosion on the embankment soil was shown more severe than the one due to the freeze-thaw erosion.

Cushion is one of the key parts of composite foundation with the thin-wall pipe piles made of cast-in-situ concrete(PCC) and makes the piles and soil to work together. The cushion is usually made of gravel with geogrid reinforcement in practice. The characteristics of cushion，such as the thickness，the reinforcement layers and types，affect the load sharing of piles and soil，which affect the load transfer mechanism of the composite foundation. A large model testing system of simulating the full scale pile foundations was developed and described in this paper. The load transfer mechanism of PCC pile composite foundation was studied with the full scale model tests. The effects of nine different types of cushions on the load transfer mechanism were studied，including the load-settlement curve，the pile-soil stress ratio，the axial force in piles，and the soil pressure and friction inside the pile wall. The testing results show that with the increase of the number of geogrid reinforcement layers，the pile-soil stress ratio，the pile axial force，and the soil pressure and friction inside the piles were all increased；and the settlement was decreased under the same amount of load. Piles always played a major role in load carrying in the composite foundation. The loads transferred to the pile heads were increased and the negative friction force onto the piles was decreased.

A series of unconfined compression tests were conducted on compacted loess samples with different structures at the same dry density and experimental water content. Based on the stress-strain curves of unsaturated and saturated compacted loess，the initial quantitative parameter was defined to describe the maximum overall structure potential before the start of the structural damage of the compacted loess. The influence of different structures caused by the change of molding water content on the stress-strain and strength characteristics as well as the structural parameter was investigated for the compacted loess with different experimental water contents. The results indicated that the molding water content affected the structure and the unconfined compressibility of unsaturated compacted loess，but had little influence on that of saturated compacted loess. The degree of influence decreased with the increase of water content. The plastic limit was found to be the critical value. When the experimental water content was smaller than the plastic limit，the influence was greater. The unconfined compressive strength and the initial structural parameter increased notably with the increase of the molding water content at the same experimental water content and decreased significantly with the increase of experimental water content at the same molding water content. The group of curves describing the relationships of the unconfined compressive strength versus the molding water content and the experimental water content was normalized into a nonlinear relationship with the initial structural parameter. The normalized nonlinear relationship described the influence of molding water content and experimental water content on the structure of compacted loess. Together with the grain size and the density，it described reasonably the mechanical properties of compacted soil.

To analyze the roadbed deformation distribution of high-speed railway(HSR) in seasonally frozen regions，thermo-elastic mathematical equations describing the stress and deformation of frozen roadbed were deduced considering ice and water phase transition. A finite element model was built，achieving continuous coupled calculation of geotemperature and deformation. Different frozen-heave ratios were adopted for the filling material along Harbin—Dalian HSR roadbed in deformation and stress analysis. The calculated vertical displacements，transverse deformation differences，horizontal displacements and tensile stress were found to increase with the frozen-heave ratios and frost depths. The calculated surface vertical displacements of roadbed are possible to exceed the allowed values of HSR standard. The calculated tensile failure occurrs in the section of roadbed shoulder and slope，indicating the possible occurrence of cracks. It is also indicated that the variation of the frozen-heave and the thaw-compression ratios caused by the water redistribution inside the roadbed under the action of geotemperature field are the main influencing factors to the deformation and stability of HSR roadbed.

The seepage deformation of soil dam(foundation) is a main cause of dam burst and failure，it is therefore necessary to study the seepage deformation of dam(foundation) soil and its types. The data of 472 tests of seepage deformation on noncohesive soil(crushed gravel soil and sandy soil) from 48 projects were collected and statistical analysis was made. The results show that the seepage deformation type of crushed gravel soil is piping；and the type of seepage deformation of sandy soil is soil shifting(flow). Further analysis is made on the distribution curve of grain sizes of the noncohesive soil with Cu≤5 and the seepage deformation type of crushed gravel soil with Cu≤5 was found to be piping.

In order to ensure the safety utilization of heavy metal contaminated ground，it is necessary to investigate the effect of carbonation on the performance of cement solidified heavy metal-contaminated soils. Artificial contaminated soils with three different lead contents were solidified using cement，and the electrical resistivity and pH values of the solidified samples before and after carbonation were tested. The carbonation led to an increase of the electrical resistivity of cement solidified lead-contaminated soils，but the electrical resistivity decreased with the increase of lead content，porosity and degree of saturation. A modified Archie?s electrical resistivity model was proposed by replacing the porosity with a parameter which represented the influence of carbonation time，cement content，and lead content on the electrical resistivity of cement solidified lead-contaminated soils. The Archie?s electrical resistivity model was extended to heavy metal contaminated soils. The results also showed that adding lead reduced slightly pH values of the solidified soils，and the pH values of the samples varied from 11–12 to 8–9 after carbonation. There is a nonlinear relationship between the electrical resistivity and the unconfined compression strength of solidified soils.

Large-scale model tests in laboratory were carried out to study the behaviors of geogrids reinforced retaining wall of wrapped face under the loading on top of the retaining wall. The vertical and horizontal soil pressures，the stress diffusion angle，the coefficient of lateral soil pressure，the lateral displacement and the vertical settlement of wall face and the tension strain of geogrids were measured. The distribution of the vertical soil pressure along the geogrid length was found to be nonlinear and the position of the maximum pressure was moved from the middle of geogrids to the position under the loading point. The distribution of the lateral soil pressure along the wall height near the wall face increased linearly along the wall depth due to gravitational stress before loading and decreased along the wall depth after the overhead loading. The values of the lateral soil pressure were always smaller than the active earth pressure. The measured stress diffusion angle was greater than that of soil mass without geogrids and the stable values of the stress diffusion angle was 50°. The coefficient of lateral soil pressure was in direct proportion to the overhead loading，and its distribution along the wall height was similar to that of horizontal soil pressure. The cumulative lateral displacement of wall face had a distribution curve of S-shape，and its maximum value was located in the lower middle. The strain distributions of geogrids along its length were the curves of single-peak or twin-peak and the horizontal distance from the position of peak strains to the wall foot decreased gradually along the wall height.

A series of one-dimensional electroosmotic consolidation experiments with the test tank built in-house were carried out on dredger filling. The current intensity，the drainage and the electric potential were monitored. The final water content，the shear strength，the coefficient of electroosmotic permeability，and some other indices were analyzed to investigate the influence of applying stepped voltages on electroosmotic consolidated dredge fillings. Test results showed that different programs of stepped voltage yielded quite different treatment efficiencies for dredge fillings；In comparison to applying 25 V constantly，the technique of stepped voltage reduced energy consumption，improved electroosmotic efficiency at later stage and raised water drainage，enhanced the soil shear strength near the cathode region effectively and reinforced the soil more homogeneous. Appropriately raising the initial voltage increased the water discharge of electroosmosis significantly. Very high initial voltage did not lead to further improvement in soil consolidation，but to more energy consumption.