The uniaxial compression and Brazilian splitting tests on the argillaceous anhydrite from the interlayers of the mine at Yunying were conducted with the different time lengths of immersion in order to reveal the mechanical characteristics (such as the softening) of the insoluble interlayer upon brine immersion and to provide the theoretical guide for the prediction and control of the interlayer destruction during the process of the cavity building inside the rock salt. It was found that the mechanical strengths of interlayer deteriorated significantly with the increasing of the time length of brine immersion. The relationships of the uniaxial compressive strength，the elastic modulus and Poisson?s ratio with the time lengths of brine immersion were fit well with DoseResp function. While the relationship between the tensile strength and the time length of brine immersion was fit with Slogistic1 function. The failure modes of the specimens in the uniaxial compression and Brazilian split tests were gradually changed from the tension failure to the shear failure as the time length of immersion was increased. It was found from the results of the test that the softening effect of brine was closely related with the soluble content of interlayer，the heterogeneity of hydraulic swelling of the interlayer ingredients，the lubrication of brine and the softening effect on the crystal bonding of minerals. An equation of the damage evolution with the time of immersion for interlayers was derived according to the experimental data and a model for softened depth of interlayer in the axial and radial directions was established. The model was applied to determine the softened range of the insoluble interlayer during the process of cavity building in rock salt. In addition，a criterion of maximum tensile stress was presented for the determination and prediction of the local softening damage of interlayers based on the relationship between the tensile strengths and the time lengths of brine immersion.

The existence of bedding planes is the fundamental cause of the anisotropy of the mechanical behaviors，the strength and the failure modes of shale formations and is also one of the main reasons for borehole instability of horizontal wells. In order to analyze the mechanical properties of bedding planes and the anisotropy of shear strength，direct shear tests on shale sample with different bedding angles were carried out. The causes for the anisotropy of shear strength were analyzed based on the anisotropy of the mechanisms of shear failure and the concentration factor of shear stresses. (1) The cohesion and the internal friction angle of bedding planes were found to be significantly smaller than those of the matrix of shale；the bedding planes are weak ones in shale formations and have the smallest shear strength. The shear stress-shear displacement curves do not exhibit the characteristic of slip-weakening when shear failure occurs along bedding planes and the residual friction is even slightly higher than the shear strength of the bedding planes. (2) The largest shear strength occurred if the angle ? between the bedding planes and the normal stress is 60°among the four angles of ? = 0°，30°，60°and 90°. The shear stress-shear displacement curves exhibit the characteristic of slip-weakening when the shear failure occurs for the shale samples with ? = 0°，30°and 60°. (3) The failure mechanism of shale is divided into three types: the shear failure across matrix，the sliding across matrix together with the tensile splitting of the weak planes, and the sliding along the bedding planes. The anisotropy of shear strength of shale is governed by the anisotropy of shear failure mechanism. (4) To some extent，the shear stress concentration factor can reflect the shear strength of rock, and it can be used to analyze the anisotropy of shear strength of shale. In the direct shear tests of shale，the shear stress concentration factor is related to the elastic modulus in shear direction and the thickness of shear layers. Under the same normal stress，the shear stress concentration factor is the largest with ? = 90° and the smallest with ? = 60°. But the shear strength of shale is the smallest with ? = 90°  and the largest with ? = 60°.

The mechanical behaviors of key blocks and characteristics of force transfer of landslides were analyzed. The interactions among forces of sliding，friction and thrust were investigated assuming the anti-sliding forces were not reduced. The slice is at the critical stress state if the sliding force is equal to the friction. Representative characteristics of thrust between the analyzed slices were studied. The difference of the thrust between slices defines the different stress states. If the stresses of slices are between the residual stress state and the peak stress state，the trust change decrease or increase gradually(the measured values of the thrusts can be negative or positive). If the stresses of slices have not reached the peak state，the thrust increases gradually(the measured values of the thrusts can only be positive). A relationship between the coefficients of stability considering the different stress states was derived. The coefficient of stability calculated with the conventional stability analyses in terms of the critical stress state of landslides was not the smallest one, while that calculated in terms of the residual stress state turned out to be the smallest one，considering three different stress state(the critical stress state，the failure stress state，the residual stress state and the mixed stress state).

The triaxial unloading tests on the precasted rock samples of a single joint with different dip angles were conducted to investigate the anisotropic mechanical behaviour of jointed rock masses under excavation including the stress-strain curves，the deformation and strength characteristics and the failure modes. (1) The stress-strain curves of jointed samples with dip angles of 0°，30° and 90°         had a yield phase，a softening phase and a residual phase upon unloading，while the samples with dip angles of 45°  and 60°had a yield phase only. (2) The variation of the deformation moduli versus the angles of joint inclination is in U-shape and the deformation modulus of the sample with the dip angle of 60°is the smallest. The differences of the deformation characteristics of different samples decreased gradually with the increasing of the confining pressure. (3) The compressive strengths of the samples with dip angles of 0°，30°and 90°were reduced，and those of the samples with dip angles of 45°and 60°were changed little. The cohesion versus the angle of joint inclination is in U-shape. The cohesion of the sample with the dip angle of 60°is also the smallest. The internal angle of friction increased with increase of the angle of joint inclination. (4) The failure modes of the samples with dip angles of 0°，30°and 90° were all shear failure across the joint surface and were not effected by the joint. The samples with dip angles of 45°and 60° were sliding failure along the joint surface. (5) It was revealed that the unloading mechanical characteristics of the jointed rock masses were controlled by the strengths of both rocks and joint surfaces.

The deformation of the longitudinal joint with a complex structure in shield tunnel is closely related to its internal force and highly nonlinear under eccentric compression. A reasonable value of the bending stiffness of joint is vital for the design of the segment ring of shield tunnels with the beam-spring model. The analytical formulas of calculating the deformations at different deforming modes based on the existed model were presented for the double-padded longitudinal joints under a constant axial force. The angles of rotations measured in the joint bending tests were compared with the calculated results with a good agreement. A non-linear equation system for the joints stiffness was derived considering the stiffness difference between the joints and the segment and using the formulas for the internal force of the segment ring and the one for different deformation modes of the joints. The non-linear equation system was solved with the fix-point iteration programme utilizing the software Maple. Reasonable stiffness values of the joints were obtained after several trial calculations with the iteration programme.

The forward and the inverse numerical simulations on the computed tomography of cross-hole resistivity was carried out based on the finite element and the least squares methods for the better geological prediction in urban subway engineering to avoid the potential geological disasters and ensure the construction safety. Three geoelectric models describing the water-filled karst cave，the water-filled fault and the bedrock surface were established respectively. The models were used to analyze the response characteristics and the behaviour and to verify the feasibility of the computed tomography of cross-hole resistivity. Meanwhile，it was pointed out that the computed tomography of cross-hole resistivity could be applied to the other type of cases in the urban subway geological prediction. Three types of layouts of the surveying lines and a 3D slice method of interpretation were presented to resolve the complexity of geological environment of the urban subway. Further case studies showed that the computed tomography of cross-hole resistivity had a high precision of detection and was flexible in implementation and did not interfere with the tunnel excavation.

Salt rocks are layering distributed containing multiple interlayers and with big difference in burial depths across China. The shape control of salt cavern is critical for its stability and safe operation. A testing device for salt cavern simulation and morphology control was developed for determining the optimal construction process and the control parameters of morphology of the salt cavern in laboratory. The test device was designed according to the similarity principles. It is composed of a reaction framework，a coupled multi-field system，an injection cycle system，a dynamic parameter measurement and control system of the injection cycle and a system for salt cavern shape measuring，etc. The reaction framework is the modularized main structure. The coupled multi-field system can simulate the ground temperature and stress fields. The injection cycle system can simulate the injection  of water and the control of oil pad. The dynamic parameter measurement and control system of injection cycle can achieve a good control of the pipe heights inside and outside and the height and angle of the probes. The system for salt cavern shape measuring can provide a video-visualization and a real-time shape measurement in the construction process of salt caverns. The device was tested on the constructions of caverns of different sizes inside the salt samples and was confirmed to be capable of providing the visual simulation of the cavern construction and the shape evolution of the embedded salt rock under the condition of the coupled multi-fields with different construction technologies and parameters.

Rocks are heterogeneous and have scattered test results for strengths due to the differences among specimens. The strength criterion fitted to test data describes merely an average effect of the confining pressure on the rock’s strengths. The experimental results within the confining pressure of 100 MPa revealed that the dispersion of the strengths resulted from the fissures or cracks in the specimens decreased as the increasing of the confining pressure. The two parameters in the exponential criterion to describe the effect of confining pressure on strengths were found to be material-dependent and not influenced by the other factors of specimens. The uniaxial compression strengths(UCS) of specimens may be calculated from the triaxial strength under confining pressure using the exponential criterion. The strengths of the granite specimen of small size under the high confining pressure were scattered greatly because the respective contents of the quartz，the feldspar and the mica were different in each specimen. Besides，the ends effect of friction affected the strengths of the granite specimen due to the occurrence of large lateral deformations under the high confining pressure.

Several groups of Brazilian split tests on heterogeneous gneiss considering the effects of different bedding orientations were conducted in order to investigate the influences of anisotropy and heterogeneity on failure behavior of rocks. The tensile strengths of gneiss with bedding structures of different orientations were obtained. The tensile strengths obtained can be considered as the one between the weak beddings of the minerals if the bedding orientation paralleling to the loading direction. If the bedding orientation is perpendicular to the loading direction，the obtained tensile strengths can be considered as the equivalent one of mineral grains of gneiss. But for other cases，the tensile strength is due to the combining effect of the tensile and shear failures，which deserves careful consideration in applications. A discrete numerical model was set up using UDEC. The bedding structures were modeled through assigning random distributed aggregates of deformable blocks and setting contacts between the bedding interfaces and the mineral grains. The numerical results have a good agreement with the experimental data，which explains the mechanism of fracturing failure modes. The study revealed that the failure of rocks was a self-organizing process of microcracks which was strongly affected by the microstructures of rocks.

The existing tunnels deform inevitably due to the excavation of a new tunnel nearby in the urban underground engineering construction. Correctly analyzing and predicting the deformation of the existing tunnel has been an important issue in underground engineering. Peck equation is one of the most popular used methods to predict the soft ground movement induced by the shallow tunneling. 23 sets of measured data from 10 projects in Beijing were found to fit well with Peck equation. The ground loss ratios fit by Peck equation are from 0.116% to 1.183%，and the width parameters of the settlement trough are from 0.93 to 6.76. The effects of the construction method of new tunnels，the auxiliary construction method of new tunnels，the burial depths of both the new tunnels and the existing tunnels，the flexural rigidity of the existing tunnels，the distance between two new tunnels and the position of the deformation joints of the existing tunnels on the fitting parameters were analyzed. Empirical formulae of fitting parameters were thus derived. Combining Peck equation with the empirical formulae of parameters，a simple and convenient method of prediction on the deformation of the exiting tunnels in Beijing area was obtained. The validity of the method was confirmed in an engineering case study.

The columnar jointed rock mass is a typical structural rock mass. Due to the columnar joints，the deformation and the strength of columnar jointed rock mass exhibit remarkable anisotropy. In order to investigate the mechanical anisotropy of columnar jointed rock mass，the mixtures of plaster，cement and water were used to make cylindrical columnar jointed specimens with different dip angles ranging from 0°to 90° for uniaxial compression tests. The deformation modulus and uniaxial compression strength of the columnar jointed specimens with different dip angles were obtained. The anisotropy curves of deformation and strength with different dip angles ? were plotted and the anisotropic characteristics of deformation and strength were analyzed. The shape of the anisotropy curves of deformation and strength resembles the letter“U”. Both the deformation modulus and uniaxial compression strength have the minimum value at ? =30°，and reach the maximum value at ? = 90°. The anisotropy ratio of the strength is as high as 1.5，which indicates a high anisotropy. The deformation modulus of columnar jointed rock mass reaches the minimum value when ? is between 30°and 60°，and the corresponding lateral strain ratio become greater than 0.5. Furthermore，the columnar jointed specimen have four types of failure modes under uniaxial compression and the failure mechanisms were discussed.

There were usually two drawbacks in calculating the long-term strength through isochronal curves. One was that the inflection point of the isochronal curve was generally not so apparent leading to the determination of the long-term strength with uncertainties. The other was that the testing time was usually short with only few loading steps，so the test results were not accurate enough. Therefore, the creep test to the salt rock from Jianghan in Hubei province in this study was carried out for about five months long. There was an obvious inflection point on the isochronal curve plotted according the test data and the long-term strength was thus determined without uncertainty. The longer testing time and the more loading steps were proved to be the vital measure to guarantee the credibility of the test results. A new fractional viscoelastic-plastic creep model was established according to the experimental results together with the improvements in two aspects. The proposed model was proved to be simpler and more reasonable in terms of the process of derivation，the outcome of test data fitting and the results of theoretical analysis.

The geomechanical model test is an effective method to study the global stability of arch dams. The geomechanical model test on the arch dam with foundation reinforcement at Dagangshan in the similar scale of 250∶1 was conducted. The deformation and strength of jointed rock mass，the discontinuous structural surfaces and the reinforcement measures were simulated through the masonry technique of small blocks. The water load imposed on the dam surface was controlled by the hydraulic jacks. The strains and displacements were collected and saved automatically and effectively with a data acquisition system of high accuracy. The high water pressure method was employed for the overload failure test. The stress and displacement distributions of the scaled dam were obtained and the failure processes of the scaled dam and the abutment were explored. Three factors of the global overload safety K1，K2 and K3，were used to evaluate the global stability of dams. The comparative analysis between the geomechanical model test and the numerical simulation based on the deformation reinforcement theory indicated that the global stability of the arch dam at Dagangshan was relatively high. The weak areas controlling the global stability of the arch dam was located.

The time-dependent propagation of cracks was observed from the failure of field surrounding rock and the monitored data of the water diversion tunnels in Jinping and became the dominating factor of the long-term stability of the tunnel. A long-term loading test was conducted on the marble from Jinping leading to the establishment of a fitted formula for the time-dependent behavior and a threshold ratio of driving stresses. A numerical specimen based on CPM model was set up considering the transitional characteristics from brittle-ductile-plastic and a numerical test of long-term loading was performed. A full scale PFC-based model was constructed for the water diversion tunnel and the long-term stability of the tunnel with various depths and rock types was assessed. It was found that in the test the failure time varied with the loading level exponentially. The subcritical crack began to expand if only a threshold of stress level, termed as the critical ratio of driving stresses, was reached. The ratio is 0.492 for Jinping marbles. The CPM-based numerical specimen reproduced nicely the triaxial behavior and the effect of confining pressure. The growth trend of the crack numbers was notable under the lower confining stress，but less noticeable under the higher confining stress. The number of the tensile cracks remained unchanged under the higher confining stress. During the numerical test of long-term loading，the axial strain and the growth of the number of cracks were in accordance with the three stage curve of creep. As the ratios of the driving stresses decreased，the strains due to creep increased. The development of the cracks due to the stress corrosion was also in accordance with the three stage curve of creep. A smaller ratio of driving stress led to a linear growth of the number of cracks of stress-corrosion but an exponentially decreased rate of growth of it. The results of the full scale PFC simulation suggested that after 100 years，the fracture zone of the tunnel would be with the range of 2.1–3.1 m for the class II marble and 3.3–4.5 m for the class III marble. It was thus confirmed that the long-term stability of the water diversion tunnel could be guaranteed.

The bolted and unbolted jointed rock mass specimens with cross-cracks were simulated by similar materials. The angles between the primary cracks and the secondary cracks，the positions of the bolts and the angles between the bolts and the loading directions were taken as the control parameters of the specimens leading to the total of 32 groups of specimens of similar material be produced. The uniaxial compression tests of the specimens were carried out to obtain the bolting effect and the failure modes of the jointed rock masses with cross-cracks. The test results showed that：(1) The strengths of the specimen reached the maximum values if the bolting position was above or under the crossing points of the cross-cracks for the group of specimens with the same angle between the primary and secondary cracks. When the bolting position went through the crossing points of the cross-cracks，the strengths of the specimens did not reach the maximum values but its after peak values were stable. (2) The majority peak strength values of the bolted rock masses with joints and cross-cracks are higher than those of the ones with a single crack. (3) The angles between the primary and the secondary cracks affected the mechanical properties of jointed rock masses with bolting. The jointed rock mass had the best bolting effect when the angle between the primary crack and the secondary crack was about 30°. (4) The bolt increased the ability of the jointed rock mass to resist the cross-crack propagation and reduced the possibility of jointed rock masses to a sudden failure.

A hazard forecasting system of landslide was developed using WEBGIS and an integrated technique of four databases on the basis of the previous research results in aspects of geological hazard stability，hazardous zonation，risk evaluation and landslide prediction of in the area of Three Gorges Reservoir. The data utilized in the system including the compiled geological maps，the landslide prediction models and the forecasting criterion in professional monitoring，the weather，the fluctuation of the water level in the reservoir，the human activities and the monitored results of landslides. The system has a main function module including the hazard assessment of regional landslide，the temporal forecasting of the individual landslide，the calculation of the landslide surge， and the real time information release. It integrated more than twenty models describing the landslide development of the geological environment in the area of the reservoir. The four databases integrated include a model base，a method base，a data warehouse and a knowledge base. The governing model base calls the method base to extract data from the warehouse base, solves the problems designated and finally deposits the expert’s decision as the source of knowledge in the knowledge base. Good results were achieved in the trial runs of the system in the cases of New Badong County，Bazimen landslide and Baishuihe landslide.

Field observation，theoretical analysis and in-situ tests and monitoring were carried out in order to tackle the problem of large deformation and roof caving of roadways with super-large cross-sections and soft and weak coal roofs. The reasons of the problem were found to be the weak supporting structure of the roof，the weak connections between the roof and the two side walls of the roadway，and the occurrence of large tensile stress in the middle span of the roof. It was therefore proposed that the cross section of roadway to be equally divided into two parts for excavation one after another with multiple supporting structure(MSS) to strengthen the roof and roof-sidewall connection and reduce the deformation of the roof. A total of 10 factors were found to be vital to evaluate the roof safety. The proposed method was successfully applied to the coal mine at Wujiagou.

The shaking table model test was used to simulate the seismic response of the ground with fissures in the region of Xi?an where metro tunnels often penetrate through the active ground fissures. It was found that the hidden fissures inside the soil body grew to appear on the surface after a while during the test and continue to expand to form through fissure lines crossing the surface. As the dynamic test continues，the secondary fissures were developed at the upper soil layer joining with the main ones. The loose soil fillings inside the fissures moved upward along the fissures. The uneven settlements occurred on the surface during the test and the largest difference of the settlements occurred just on the two sides of the fissures. The uneven settlements induced a tension between the two sides of fissures，which made ground fissures to expand its width, length and height and gradually expose to the surface. The measured accelerations at the upper layer are greater than those at the bottom layer. The results of the test may provide a guide line for the seismic design of structures in the areas of ground with fissures.

In order to study the behaviour of high loess slope excavated and supported with different reinforcement modes，a series of centrifuge tests were conducted to simulate the high loess slope at the entrance of Guanyintang tunnel，considering the excavations without the reinforcement，with the full-section soil nailing，and with the soil nailing at the upper part and the pre-installed stabilizing pile at the lower part(pile-soil nailing structure) respectively. The pile-soil nailing structure was found to improve greatly the stability of the high loess slope in the tests. The soil nails at the upper part mobilized effectively a much wider area of loess slope to deform. The inward migration of the potential sliding surface led the toe of potential sliding surface be lowered to the position below the top of the pre-installed stabilizing piles. As such，the pre- installed stabilizing piles at the lower part can effectively bear the thrust force exerted by soil slope and guarantee the stability of loess slope during excavation. The stability of the loess slope was improved to certain degrees in the case of the full-section soil-nailing. However，when potential sliding surface surpass the reinforcement region of the soil nailing，the soil slope collapses eventually. Therefore，the combined structure of pile-soil nailing is better than the full-section soil nailing for the reinforcement of high loess slope.

On 11th of January，2013，a catastrophic landslide with an estimated volume of 250 000 m3 occurred in Zhenxiong County，Southwestern China. The geological surveying，the landslide mapping，the soil sampling and the laboratory tests were carried out afterwards to study the catastrophic causes and mechanisms of the landslide. It was found that there was an abundant precipitation even in the dry season of January due to the effects of the vertical climate and the micro geomorphology. The late Triassic colluvium of Feixianguan formation(T1f) in the stratum of the slope was found to have a high porosity and to be easily saturated which was very likely prone to landsliding. The initiation of the fluidization of the saturated soil of high porosity and the liquefaction due to the movement were found to be the mechanisms of the sudden occurring and the long range movement of the landslide. The mining activity on the deeply buried coal seam over 300 m away from the landslide were excluded to be the cause of the landslide based on the facts that there were no mine disasters and no mine collapses when landslide occurred.

The soil arch effect of the open cut tunnel and the variations of the earth pressure with the heights of the filled soils under the different load reduction schemes were studied with the model tests of reduced scales. The experimental results showed that the earth pressures on the top of open cut tunnel increased nonlinearly and the soil arch effect occurred when the filled height was up to a certain level. The soil arch effect was not stable and the soil stresses measured at the crest of the tunnel were smaller than the calculated ones. A single layer of geogrid was thus proposed to be placed above the tunnel and a corresponding method of calculation of the earth pressures at the top of the geogrid，under the geogrid and on the crest of the open cut tunnel was presented on the basis of Rankine?s theory of earth pressure. In addition，an expression of earth pressures for multiple layers of geogrid was also derived. The field experiment of an open cut tunnel demonstrated that the load reduction by geogrid was effective and the calculation method was appropriate.

The in-situ soaking tests on loess collapsibility upon deadweight with the thickness greater than 36.6 m were carried out including a deep layer soaking test on a foundation treated with compaction piles of different lengths，a soaking test on a foundation treated with the deep dynamic compaction inside holes and a soaking test on a foundation buried with TDR moisture meters without water injection holes. The significant foundation subsidence occurred due to deep soaking when the thick deadweight collapsible loess foundation was treated 6 to 12 m in depths upon. When the depths of treatment were from 15 to 20 m，the ground settlement upon deep soaking was small. When the treatment depth was more than 20 m，the settlements of the foundation can be ignored. When the water pit of soaking test was 22.5 to 25.0 m in depth，the soil moisture content increased rapidly and even reached saturation，while if the water pit was deeper，the moisture content increased slowly with little collapse of loess. So 22.5 to 25 m can be viewed as the critical depth of foundation treatment and collapsibility evaluation for thick deadweight collapsible loess. The collapsibility in different regions and soil microstructures should be evaluated adopting different coefficients of collapsibility.