Faults and fractured zones are common unfavorable geological phenomena encountered in the process of tunnel excavation. It is also the place where the surrounding rock is unstable and prone to accidents. In this paper，the weak rock mass of grade IV commonly found in mountain tunnels was selected as the reference object，and geomechanical model test and numerical simulation were carried out to study the progressive failure process as well as the stress and deformation characteristics of the surrounding rock of fault-crossing tunnel. After tunnel excavation，the rock mass of fault footwall located above tunnel arch was in the cantilevered state，and tensile cracks were found near the fault region. Tunnel excavation made the overburden load be transferred to the two sides of tunnel，which often led to the shear failure of rock mass below tunnel waist，especially for the rock mass close to fault footwall. Tunnel excavation caused stress redistribution around surrounding rock. Once the redistributed stress exceeded the ultimate strength of rock，the surrounding rock collapsed into the arch shape. At the same time，the tangential stress in rock mass located within the collapse scope dropped sharply. This feature can be used to determine the range of collapsed rock mass. When tunnel was excavated，due to the barrier effect of fault，the rock mass stress within the hanging wall and footwall of fault presented the characteristics of discontinuous and nonlinear distribution.

In order to simulate the complete process of water-inrush and to reveal the mechanism of water-inrush in mines，two principal properties of water-inrush such as the high-speed non-Darcy flow and the unity of dynamic flow field were considered. A non-Darcy flow model for water-inrush in mines was established based on the conservation of mass and the pressure equilibrium. The corresponding model with the coupled relation of Darcy，Forchheimer and Navier-Stokes equations established the connection of water source in aquifer，water-inrush channel and the exit of tunnel in a uniform flow field. A numerical model was developed based on the coupled integral equations between the week form of the finite element method and the finite volume method. Using the software of Finite element program generator(FEPG)，the FORTRAN source programs were compiled and applied to simulate the complete flowing process of water-inrush. By comparison of the results for Darcy and non-Darcy flow models，the necessity of adopting non-Darcy model for water-inrush in mines was explained. It was also found that the fractured rock mass was the channel connecting the confined aquifer and tunnel. The inertia effect of the high-speed flow in the channel was the main cause leading to the water-inrush through the fractured rock mass.

Based on the structure feature and behavior subject to disturbance，a structural model was established for complicated surrounding rock in tunnel engineering. The model specified the structure stability and calculation method of load effect，and realized the coupling of the load-structure model with the stratum-structure model. After excavation，the initial stress is released and the pressure is transferred，usually in a form of pressure arch. The failure of surrounding rock shows a progressive character. The concept of deep buried and shallow buried surrounding rock was put forward according to the stability. The different structure features among rock groups resulted in the discontinuous and phase-dependent character of the failure of deep buried surrounding rock. Surrounding rock in the same group move synchronously and its simultaneous failure gives rise to the outside rock formation to sustain the stability of the exterior rock，that is，a composite arch structure varied with time and space. Each deep buried rock group consists of structure layer and load layer. For rocks in the structure layer，they usually own larger thickness，strength and stiffness，so as to maintain the stability of the rocks in this group. In contrast，rocks with small thickness，strength and stiffness are classified as load layer，exerting on the structure layer. The instability mechanism of structure layer was revealed and the corresponding criterion was presented. The load effect of complicated surrounding rock in tunnel engineering is composed of the given pressure of shallow buried surrounding rock and deformation pressure of the deep buried surrounding rock. The former depends on the scope and character of the shallow buried surrounding rock and the latter depends on the controlled state and stiffness of theforce transfer layer.

The rock burst-prone tunnel section in Jinping II hydropower station was studied using micro-seismic monitoring technology as a means of monitoring and early warning of rock burst. The spatial and temporal variations of mirco-seismic events and rock burst were revealed by comparing the actual conditions and monitored micro-seismic results. The relationships among the magnitude，frequency and energy for micro-seismic events contour were revealed through the extraction of micro-seismic monitoring events by the corresponding characteristics of rock damage process. The four criterions of rock burst were presented based on 3S principle in seismology to determine rock burst. The in-situ results of the study showed that the regularity of the temporal，spatial and intensity distribution of rock burst in deep tunnels existed. Micro-seismic activities always occurred ahead of rock burst，while the locations of them coincided with rock burst. The criterion of rock burst can be used to make accurate early-warning，and provide evidence for rock burst forcasting and micro-seismic monitoring early-warning.

Considering soil-structure interaction，few analytical solutions of lateral internal forces in tunnel lining due to Rayleigh wave(R wave) have been obtained at present. In this paper，the closed-form analytical solutions for internal forces in circular tunnel lining due to R wave at any propagation angle were derived based on mechanics of underground structure and theory of elastic waves using the pseudo-static method. Two ultimate contact conditions，i.e.，the full-slippage and no-slippage along the soil-lining interface，were considered respectively. A numerical example showed that the lateral internal forces in circular tunnel lining reached the maximum values if the propagation of R wave was perpendicular to the tunnel axis and the internal force differences between two contact conditions were minor. In addition，the internal forces resulted from R wave were much higher than those from SV wave，especially the lateral axial force which was induced mainly by the component P wave contained in R wave. In seismic design of shallow tunnels，the lateral internal forces in the lining caused by R wave should be paid adequate attentions.

The study of minimum thickness of waterproof slab in long and deep tunnels is very significant in the process of engineering design and construction. A three-dimensional model test system for simulation of water inrush geohazards was developed. The test system has a three-dimensional model test device，a sample molding device and a device simulating tunnel excavation and unloading，so that the initial in-situ stress，water environment and process of tunnel excavation and unloading can be simulated. The test system is convenient and easy to operate and has the characteristics of short testing period and good loading stability. The system can carry out tests of large number of samples for statistical analysis and accurately simulate the process of excavation of the tunnel. Model tests were performed to simulate the water inrush geohazards at Longmen mountain tunnel of Chengdu to Lanzhou railway line. The confining and axial pressures of the test were both set as 0.6 MPa and the water pressure was 0.2 MPa. In this case，the minimum thickness of waterproof slab was 47 mm. The test results were used to guide the design and construction of the projects.

Brittleness is one of the most important mechanical properties of rock. The fragmentation efficiency of rock is closely related to the rock brittleness. No unified brittleness index of rock is confirmed in evaluating rock fragmentation efficiency by disc cutter. The existing 35 different brittleness indices were summarized and classified into seven categories with respect to strength，strain，strain energy，hardness，Mohr envelope，special tests，etc. In order to study the relations between the rock brittleness and the rock fragmentation efficiency by disc cutter，the normalized specific energy concept was introduced after carrying out the indentation tests with disc cutter，and a new index of rock brittleness was proposed. In addition，the relations between the normalized specific energy and brittleness indexes based on strength and indentation test were mainly studied. The results show that it is more difficult to penetrate into the rock of high strength for disc cutter. The relationships between the normalized specific energy and brittleness indexes B2 and B4 were found to be exponential. With the increasing of brittleness indexes B2 and B4，the normalized specific energy decreased but the rock fragmentation efficiency increased. Therefore，the brittleness index B2 can be firstly used for evaluating the rock fragmentation efficiency，followed with the brittleness index B4. The uniaxial compressive strength of about 20 MPa can be defined as the transitional uniaxial compressive strength，and disc cutter may be not suitable for cutting the soft rock with uniaxial compressive strength less than 20 MPa.

3D numerical simulation with FLAC3D，was carried out to investigate the interaction between double shield TBM and composite ground. The real TBM geometry and the non-uniform annulus gap between ground and TBM shield were considered. The characteristics of surrounding rock deformation，the contact force and the frictional resistance acted on the shield of TBM in composite ground were studied at the following conditions：(1) weak rock layer occurs along the ground depth；(2) soft rock occurs along the axial direction of tunnel；and (3) different lengths of soft and hard rock alternating in the longitudinal direction. Meanwhile，the non-uniform annulus gap was introduced to the calculation of contact force acting on the shield as a function. In case (1)，the curve of longitudinal displacement profile of surrounding rock came into contact with the TBM shield successively from bottom to top，which affected by the non-uniform annulus gap. The contact zone was mainly situated on the sidewall and below and the contact force was largely concentrated on the middle and tail end of both front shield and rear shield. The maximum magnitude of contact force occurred in the end of front shield. In case (2)，the frictional resistance acting on the shield was increased and finally kept in steady state with the increasing length of soft rock. In case (3)，the magnitude of the contact force acting on the shield was in periodic fluctuation and was basically in accordance with the variation of displacement. Moreover，the shapes of longitudinal displacement profile(LDP) curve in composite ground in cases (2) and (3) were absolutely different from that in homogeneous rock mass.

The selection of blasting borehole parameters is a key to eliminate the blasting blank area and to improve effects of blasting antireflection and gas extraction. In the process of liquid CO2 blasting，the curve of pressure-time process in the main pipe blasting was monitored. The principle of liquid CO2 blasting was studied and a FLAC3D numerical model was established. The results showed that the effective radius of single hole blasting was 6 m and 4 m along and normal to the direction of the vent hole in the horizontal bedding respectively. The control hole increased obviously the range of fracturing area under multi hole continuous blasting. Mathematical calculations and numerical simulation were adapted to identify optimal borehole parameters of multi hole continuous blasting. The spacing of blasting device and the blast hole spacing were determined as 5 m and 7.5 m respectively. The results of experiment on liquid CO2 blasting underground indicated that the permeability of coal seam increased by 17.49–22.76 times，and that the gas extraction concentration and mixed flux increased by 3.16 times and 1.71 times respectively. Optimal selection for borehole parameters of liquid CO2 blasting helped to save cost and achieve the best effect of blasting.

A new numerical method simulating the support of partially grouted bolts with pre-tightening force was proposed on the previous researches of indirect boundary element method of 3D-FSM?DDM. According to that the displacement difference between the two ends of the bolt hole is the same as the deformation of anchor bolt at the relative section from the axis direction，the induced displacement equations about the bolt hole and the bolt were established. With the stress equilibrium equations in the original system，all the unknown quantities about the fictitious stresses can be solved. Finally，the stress，displacement and stability at an arbitrary point of rock around roadway can be computed. The correctness of the method was proved by comparing with the numerical simulation results with FLAC3D. The numerical simulation system of boundary element developed can be widely applied in the stability analysis of large scale geotechnical engineering such as mine，tunnel，etc.

Vibration monitoring and acoustic detecting to rock slopes under blasting excavation at the altitude of 834.0–770.0 m on the left bank abutment slot of Baihetan hydropower project were carried out and the vibration attenuation of the first to the sixth bench was analyzed. The relationships between the peak particle velocity(PPV) and the damage depth at different distances to the blast center were obtained with the method of regression analysis. These relationships were applied to predict the damage depth of the seventh bench using the results of vibration monitoring. When the lithology of the slope was uniform and there was no large structural plane in the rock mass，the PPV at certain distance to the slope had a high correlation with damage depth. Predicting the damage zone using the correlations between vibration attenuation of pre-splitting blasting and damage depth of reserved rock mass was simple and convenient，thus greatly reducing the massive acoustic detection workload of rock slopes. Taking the geological conditions and physiognomy changes induced by excavation into consideration，other factors needed to be involved in regression analysis or acoustic detection points of key positions are supplemented to promote the prediction accuracy of damage depth.

The similar materials representing the softening feature of the soft rock in water were prepared and the similar model for the thick red-bed soft rock slope was built in order to study the disaster caused by the failure of the thick soft rock under the rain condition in Southern China. The softening process was monitored and its mechanisms were studied under different rainfall patterns，including the medium-weak(Id＜25 mm，Id is intensity of rainfall)，heavy(25 mm≤Id＜50 mm) and torrential rainfall(50 mm≤Id＜100 mm). The failure of the slope was found to be closely related to the rainfall patterns. Heavy and the torrential rains tended to soften rocks on the slope. At first，the bottom of the slope was saturated and then the initial cracks were generated. Along with the expansion of cracks，local failure occurred due to the influence of the gravity and seepage forces，caused the collapses of the upper part and finally resulted in the pull-type landslide. The infiltrating process of rain water includes three main steps，i. e. the unconfined seepage，the confined seepage and the saturated seepage. The cracks on the surface of the slope were mainly generated during the unconfined seepage and gradually expanded during the confined seepage. The failure of the slope occurred during the saturated seepage. The accumulation and dissipation of the excess pore water pressure in the thick red-bed rock layer slope changed the distribution of the effective stress field during the raining process and caused the movement of the slope. The response of effective stress and water pressure in pores was more sensitive than displacement，displacement rate and other parameters to the failure of slopes near the sliding stage. The safety precaution in terms of slope disaster was proposed on the basis of the effective stress and water pressure in pores.

The landslides induced by the rainfall have the characteristics of regional and multiple occurrence，which can cause great catastrophic losses in a short period of time. Thus，a method considering the effects of different rainfall periods to evaluate the regional landslide hazard was proposed. The grid-based regional slope-stability analysis model was based on the transient rainfall infiltration. The landslide hazard was defined as the probability of the instability of the each grid unit in a period of a certain duration. The uncertainty of the physical and mechanical parameters of rock and soil was used to solve the instability probability of each grid unit. A regional landslide dynamic hazard assessment tool was developed based on the ArcGIS software. Wanzhou central district by Three Gorges Reservoir in Chongqing City was studied as an example using the hazard assessment tool with the comprehensive data processing procedure and parameter selection method. The calculated results under two different rainfall conditions were compared. Comparison and statistical analysis between the site investigation of slope stability and simulation results showed that the landslide hazard distribution was basically the same as the real slope stability status，which partly reflected the temporal and spatial distribution characteristics of slope stability in the studied area and tested and verified the validity of the evaluation tool.

In order to explore the creep hardening characters of filling paste，a series of experiments were launched with specific compositions，including the water content and density determination experiments，the uniaxial compression experiment and creep experiment and the scanning electron microscopy. The results show that water content and density of the samples comply with the normal distribution with small discrepancy. The water content and density have no correlation with the strength of filling paste. The strain rate at the elastic stage decreases and the instantaneous deformation moduli of specimens increase with the increasing of stress level. The instantaneous deformation moduli under loading period of 2，4 and 8 h are 1.17×105%，1.21×105% and 1.23×105% respectively，and the average growth rate is 1.20×105%. The enhancing factors of effective moduli are respectively 0.813 9，0.873 7 and 0.911 8 under 2，4 and 8 h loading，and the average enhancing factor of effective moduli is 0.866 5 which is 1.14 times of the factor in uniaxial compressive experiment. The internal structure of filling paste specimens becomes well-distributed and dense under slowly loading process. The adjustment of internal structure of filling paste occurs and there are triangular strengthening cracks inside under long-term bearing，leading to the increasing of loading capacity. The adjustment of internal structure becomes more obvious with longer loading period. The creep coefficients of filling paste under 2，4 and 8 h loading are 1.06，1.16 and 1.20 respectively，and the average creep coefficient is 1.14.

A yielding technology of segment lining combined with compressible crushed stone was proposed， which was suitable for deep inclined shaft construction using TBM method under high in-situ stress. The long distance inclined shaft constructed with TBM in Taigemiao mine area was investigated. The yield effect of compressible crushed stone was analyzed from several respects of the plastic zone development of surrounding rock，radial contact force behind segment lining，bending moment and axial force in segment lining. The yield mechanism of compressible crushed stone was revealed from the compressive deformation path and movement characteristics. The results showed that the in-situ stress distribution and compactness of crushed stone affected the yield result. The compactness affected the value of contact force while the in-situ stress condition affected the shape of the contact force，which affected the distributions and values of internal forces in segment lining eventually. The yield mechanism of crushed stone layer consists of two parts：mutual wedging action and dislocation displacement effect. The effects of the two parts varied with the compactness of crushed stone layer and the in-situ stress value and distribution，which caused the difference of the compressive deformation path，so that led to the different yield effect eventually.

With Fourier-Bessel function expansion，the dynamic stress concentration factor of the cylindrical composite-lining cavity subjected to vertically incident plane SV waves was derived for an half elastic space with double lining and buffer layer，named as rock-buffer layer-lining. The factors affecting the dynamic stress characteristic of the lining structure such as the incident wave frequency，elastic modulus and thickness of the buffer layer were discussed. The damping mechanism of the buffer layer was studied with the solution and the numerical simulation. The results showed that the frequency of the incident SV waves played an important role in the dynamic stress concentration factor of the combined-lined cavity，and the dynamic stress concentration factor of the lining decreased effectively with the buffer layer subjected to low incident frequency waves. Because of the low shear modulus of the damping layer，the shear deformation of surrounding rock and tunnel was generated， so that the normal force on the lining decreased and the dynamic stress concentration factor of the inner lining decreased. But the tangential stresses in the wall rock and outer part of the lining increased with buffer layer. With the lower elastic modulus and lager thickness of the buffer layer，the dynamic stress concentration factor of the secondary lining decreased. The optimum elastic modulus ratio of the buffer layer to surrounding rock was proposed to below 1/10–1/20，and there is an optimal thickness of the buffer layer for one specific elastic modulus. Then the shaking table tests were accomplished based on a road tunnel，and the results showed that the dynamic internal forces of the tunnel decreased and the crack number of the lining reduced with buffer layers.

Stepped wetting tests were performed on collapsible loess under null stress and net vertical stress by using refitted direct shear apparatus for unsaturated soils. The variation of deformation and suction were measured during wetting. The influences of void ratio at the beginning of wetting(null stress) and net vertical stress on deformation and water retention behaviour of collapsible loess were analyzed during wetting. The wetting water retention behaviour under null stress was compared with that under net vertical stress. The models describing the relation of void ratio versus the suction and the water retention behaviour on the degree of saturation versus the suction were proposed under hydro-mechanical coupling. Having considered hydro-mechanical coupling，the relationship of void ratio and normalized suction was described by a logarithmic function and the influence of net vertical stresses on the water retention behaviour was reflected by the variation of void ratio. The relationship of the suction and degree of saturation under hydro-mechanical coupling was the same as that under null stress for the same void ratio. When the suction was less than a certain threshold value，the variations of the void ratio either at the beginning of wetting or induced by hydro-mechanical coupling had great influence on the relationship of suction and water content. A modified V-G model considering the variations of the void ratio was put forward. The model described the wetting water retention behaviour under null stress and net vertical stresses. The predicted results were in good agreement with the test results.

To improve the accuracy and effectiveness in calculating the deformations and internal forces of piles with large exposure lengths under horizontal and vertical loads，a finite difference solution was established based on the composite stiffness principle and the bi-parameter method. A computation program was compiled by means of MATLAB. The reliability of this approach was verified through comparisons with the measured data from model tests or the calculated results of an engineering example with the existing methods. The comparisons showed that the approach was more convenient and faster than the link finite element method based on the same principle. It was also showed that，for piles with large exposure lengths under vertical loads，the gravity second-order effect must not be ignored and the vertical loads increased not only the bending moments of piles but also the shear forces. The influence of vertical loads on shear forces was not reflected in the current methods，which tended to be unsafe and should be noted in design calculations of vertical and horizontal bending piles.

Based on the consolidated drained triaxial test on silty sand after freeze-thaw cycles，a constitutive model with double yielding surfaces was established by introducing the residual ratio of shear modulus and the numbers of freeze-thaw cycles. The experimental results showed that the stress-strain relationships exhibited strain hardening properties while the volumetric strain appeared shear contraction during the shearing process. The elastic shear modulus increased with the confining pressure but decreased firstly and then increased with the numbers of freeze-thaw cycles. The shear modulus dropped about 36% compared with the unfrozen silty sand. The shear yielding surface was expressed as a linear function cross the origin，while the volumetric one was represented as an elliptic curve. The shear and volumetric hardening parameters were related to the plastic strain and the numbers of freeze-thaw cycles and the non-associated flow rule was adopted. The proposed constitutive model with double yielding surfaces was verified by comparing the modeling results with the triaxial test results. The stress-strain curves predicted by the proposed model agreed well with the experimental results for both the unfrozen silty sand and the samples experiencing freeze-thaw cycles.

Vane shear tests on Tianjin soft clay were performed to obtain the strength of disturbed clay. The test results indicated that the strength change exhibited the positive thixotropy. The strength had a gain of 3.0 kPa after 100 minutes，then increased 1.8 kPa after 1 year. It would take 4 years at least for the disturbed clay to recover completely. The electrostatic force abiding the minimum-energy principle， the existence of the iron oxide (a significant component of cementing material) in Tianjin clay，the non-reversible grain cracking and the good drainage condition were found to promote the strength increasing. The direct shear tests showed that，as the normal pressure rised，the strength increment increased while the increment of thixotropic ratio decreased. The water content had little influence on thixotropic ratio.

Along the Gonghe—Yushu highway，three typical permafrost embankments，namely insulated board embankment，block-stone embankment and ventilated embankment were utilized. In order to study the process of variation of the underlying permafrost and to compare three measures，the temperature variations of the shallow layer(0–4 m) and deep layer(below 4 m) were analyzed. The chosen sections have a similar underlying permafrost conditions. The results showed that all three measures were confronted with the thermal asymmetry from the shady to sunny slope and the thermal asymmetry damaged the embankment stability. The deep temperature showed a continuous trend of increase. At the same depth，insulated embankment had the largest rate of increase，followed by the crushed-rock embankment，and the ventilated embankment had the smallest one. There was an uplift of artificial permafrost table for all three measures and still showing a continuous uplifting trend. The preliminary monitoring results showed that all three measures were effective in protecting permafrost from thawing. However，it has just been a short period since the construction of the highway，whether the measures are efficient to protect permafrost in the future is unknown，and further study is still ongoing.