The traditional theory of spatial Mohr stress circle was analyzed in this paper and was found unable to fully reflect the stress state of geo-friction materials under loading in two directions(when consider the medium principle stress). The tests of the geo-friction materials including concrete rock and soil indicated that the compressive strength under biaxial compression was larger than that under uniaxial compression. The bearing capacity of two main shear planes under loading in two directions was suggested to be larger than that of one main shear plane under unidirectional loading. The reason is that the normal stress in the biaxial stress state is larger than the one in the uniaxial stress state，which leads to the friction strength and cohesion to increase. ?1(compression is positive) becomes larger with increasing of ?2，and the Mohr circle becomes larger correspondingly too. Not only the two limit stress circles were changed，but also the three limit stress circles were enlarged when ?2 was increased from ?2 = ?3 = 0 to ?2 = ?1. Therefore，the spatial Mohr circle theory of geo-friction materials adapted to bi-directional loading was established. An energy strength criterion based on traditional spatial Mohr stress circle was developed from the constant strength to variable strength criterion，which reflected the strength characteristics of geo-friction materials under bi-directional loading.

For staggered zones revealed in Baihetan underground powerhouse with complex mechanical response behavior，a series of undrained triaxial conventional and unloading tests under different stress levels and paths were carried out to study the mechanical properties of staggered zones under loading and unloading in high stress conditions. In the unloading process，the unloading stress-strain curves were related to the initial confining pressure，deformation rebounded in the direction of unloading and strong dilation occurred from the start of unloading. The lateral expansion in the course of the unloading of the axial and confining pressure was more significant than that in the course of loading axially and unloading of confining pressure. The tensile-shear cracks appeared in the surface of the staggered zone samples. For the stress unloading path，the deformation modulus was degraded with the decrease of confining pressure，which was described with a cubic polynomial. The bulk modulus was decreased exponentially with the increasing of volumetric strain. The Poisson?s ratios of interlayer zone samples increased gradually with a parabola trend. In comparison to the loading conditions，the failure stress was decreased and the internal friction angle was increased and the cohesion was reduced significantly. The degradation in the course of unloading of axial and confining pressure was more significant than that in course of loading axially and unloading of confining pressure.

The contact problem is one of the key mechanical problems in the discontinuous medium such as rock. Based on the physical meaning of 3D contact problem，the equivalent complementary models were established in normal and tangential directions，respectively. A new approximating smooth function was proposed for the nonlinear property of the complementary model. The approximating function is equivalent to the complementary model when the parameter tends to 0+. Since the approximation function is C1 continuous，the corresponding Jacobian matrix is nonsingular under any condition which enables the successful solution for the conventional Newton algorithm. By introducing the direction vector，the constraint function method proposed in 2D frictional contact problems was extended to 3D ones. Hence the stability problem caused by the periodicity of the direction angle in 3D contact problems was resolved. Then，the 3D point-surface contact for finite element model was established. At last，the validity of the proposed method was verified with several classical cases.

The strain energy evolution of penetrative rock joints under shear loading was investigated to better understand the mechanical behavior of rock mass. To effectively investigate the stability of rock mass，laboratory direct shear tests and numerical simulation on rock joint samples collected from the Jiweishan landslide at Wulong  in Chongqing were conducted to obtain the strain energy evolution during the shear failure. Energy accumulation was found to mainly occur on the surface of penetrative rock joints，wherein the areas within rock joints facing the shear direction had higher strain energy and contributed more to the resistance of shear failure. Energy absorption happened with the increasing of elastic strain energy before the shear stress reaching the peak value. When the peak shear stress was reached，those tiny contacting places were damaged and the energy accumulated was translated into the energy liberation associated with the decreasing of the elastic strain energy. Additionally，the energy evolution varied from places to places. The friction may occur repeatedly in the center of the rock joint，accordingly，the energy absorption and liberation may take place alternately. Numerical simulated results matched well with the temperature distribution obtained through infrared thermal imaging，which indicated that the numerical simulation method used to estimate the energy evolution in this paper was accurate and reliable.

Multiple solutions may be resulted from the inversion of 3D electrical resistivity and the calculation is time-consuming，which restricts the application of resistivity detection. An idea is presented to solve this problem，with the inequality constraints to the inversion equations and the parallel algorithms being applied. Based on the traditional smooth constraints，the relaxed variables were introduced to apply the inequality constraints to the inverse equations，which carry the upper and lower limits information of subsurface media. A new objective function was obtained using the primal dual interior point method. The resistivity values in the function were defined within the inequality constrains range，and the parameters were optimized within the feasible region defined by the constraints. The method theoretically suppressed the multiplicity of inverse solution. The parallel calculation algorithm for partial derivative matrix and the parallel algorithm for Cholesky decomposition to the overall coefficient matrix were designed，which speeds the inversion more than fifty percent. Based on the above research，the parallel 3D electrical resistivity inversion method with inequality constraint based on relax variables was developed，and numerical tests and engineering application were carried out. Results showed that the above method made full use of the inequality constrains and removed the false anomalies，suppressed the multiplicity and improved the accuracy and calculation efficiency.

It is important to investigate the damage threshold of critical broken rock mass for the classification of different broken states and the scope of excavated zone in rock blasting. The broken states of the remaining rock mass under blasting loading were analyzed through the study of fragmentation process and the mechanism of rock mass breakage. The idea that the interface between the remaining rock mass and the excavated rock mass is in a critical broken state was put forward. According to the rock damage theory，the damage variable combined with the acoustic velocity in rock was used to indicate the broken states of rock mass. Rock damage was divided into the initial damage and the blast induced damage. Rock broken states were validated with a large quantity of acoustic tests in the blasting excavation zone at Baihetan power station，and the results showed that the damage variable of critical broken rock mass was about 0.8. Finally，some more engineering experiments were collected to ascertain that the statistic damage threshold was in the range of 0.75–0.85.

Brittleness is one of the important mechanical properties for rock mass and is also the key index in hydraulic fracturing，rock breakage and rock burst prediction. The calculation methods of brittleness indexes of rock in China and abroad were therefore summarized and their applicability was discussed. In order to evaluate the brittleness of rock mass reasonably，a new index was proposed based on the stress dropping rate after peak stress of stress-strain curve and the ratio of elastic energy release at the point of rock failure to total energy that stored before the peak stress. Then laboratory tests under different confining pressures were carried out using rock cores collected from the isolated and reservoir layers in Shengli oil field. Through the analysis of test results，the validity and superiority of the new brittleness index were verified. In addition，the jump of brittleness index of reservoir core under the confining pressure of 15 MPa illustrated that internal defects of brittle rock mass should be given much attention in practical work.

An analytical method is presented using the blind data theory considering a variety of uncertainties of parameters of rock and soil in slope engineering. The blind data safety factor of the slope with the reliability of minimum safety requirement is firstly presented as the comprehensive index to evaluate slope stability. Firstly，the limit state equation of the slope is solved by using the response surface method and the strength reduction method of FEM，the blind data model of safety factor is established based on the blind data theory，and the blind data solution is derived. Secondly，the expressions of blind data safety factor of the slope and reliability of minimum safety requirement are established. The blind data safety factor of the slope and reliability of minimum safety requirement obtained were smaller in comparison with ones from the traditional methods. Thus，it will be safer for engineering assessment.

Bedding planes are of significant importance for the stability of layered rock mass. In order to perform detailed stability analysis for underground excavations in layered rock mass，it is necessary to gain sufficient knowledge of shear behavior and strength of bedding planes. Due to the complex physical and chemical processes involved during diagenesis，bedding planes exhibiting different geological features(cementation，roughness，etc) are often seen in a specific engineering site. In order to better characterize the shear behavior of these bedding planes，two types of shear tests，namely the constant normal stress tests and the post-peak stepwise-decreasing normal stress tests，were conducted using the cemented bedding plane samples obtained from underground caverns of Wudongde hydropower station. Test results showed that obviously different shear behavior corresponded to different geological features. The curves of shear displacement-shear stress were mainly divided into two groups according to their peak and residual behavior. The roughness and surface materials of groups with clear peak shear stress were different from the ones without peak. Direct relationship existed between the normal stiffness and normal stress，however，no obvious correlation was found between the normal stiffness and bedding plane types. Dilation behavior and the corresponding dilation angles of different kinds were also observed. The shear strength of cemented bedding planes is higher than the one of the separated bedding planes and lower than the one of the intact rock，which weakens the whole rock mass. A deeper understanding of rock mass behavior can be achieved when the geological variety of bedding planes is properly considered.

Seismic dynamic responses of the fiber reinforced concrete tunnel lining were studied with large scale shaking table model tests and by comparing with the plain concrete tunnel lining. The damage characteristics，dynamic strain，internal force and compressive deformation were analyzed. The cracking occurred in the invert at first，then in the haunch under the horizontal seismic load and rock-soil pressure for two kinds of tunnel lining. The failure modes are cracking，peeling and attrition crushing in cracks. Cracking damage appeared early and the penetrating cracks occurred easily in the plain concrete lining. The crack opening displacement was large in the loading process. Cracking damage appeared relevantly late in the fiber reinforced concrete lining and the crack opening displacement was small in the loading process，and the cracks presented an extrusion damage state. Fiber prevented the appearing and developing of cracks effectively. The maximum strains and crack width in plain concrete lining increased with the peak acceleration of seismic waves，while those in fiber reinforced concrete lining increased slowly in a certain range and then increased rapidly. The final maximum strains and crack width of two kinds of tunnel lining were almost the same. So it was certain that the fiber reinforced concrete effectively avoided cracking and reduced the crack width within a certain seismic load. The fiber reinforced concrete lining had the low extreme bending moments and a well-distributed stress when the input acceleration peak values were 0.1 g and 0.4 g，and it had small compressive deformation rate in the tests，which indicated that fiber reinforced concrete tunnel lining can resist seismic load effectively.

In order to study the fracturing characteristics of the rock with a single crack，mechanical test was carried out to the rock specimen with a single pre-existing crack inclined at 45° using the MTS815.03 electrohydraulic servo controlled rock pressure testing machine. The confining pressure of 0，5，10 MPa were separately applied to the rock specimen and the effect on the crack propagation as well as the fracturing mode was analysed. A crack propagation model was established and the secondary cracking angle was obtained based on the maximum radial shearing stress criterion. The obvious precursory information occurred before the initial crack and the obvious stress drop was shown on the stress-strain curve. Wing cracks，secondary coplanar cracks and secondary anti-wing cracks were observed in tests. The initiation angle of wing cracks are about 68°–73°，the inclined anti-wing crack angles are about －119°–－125°.. The calculated theoretical crack angles are 0°，70.5° and －123.8°respectively which are consistent with the test results. The initiation stress is 90%–95% of the peak stress. The compressive strength and the confining pressure of fine sandstone have a good linear relationship of ?c = 2.69?3+61.9 with R2 = 0.97. The confining pressure affected fracturing. The fracturing modes are wing crack and anti-wing crack under no confining pressure，anti-wing crack under 5 MPa of confining pressure，anti-wing crack and secondary coplanar crack under 10 MPa of confining pressure.

In order to explore the characteristics of rockburst acoustic signals，laboratory experiment was conducted to simulate the process of granite rockburst using the true-triaxial rockburst test system developed in-house. The acoustic signals were monitored during the rockburst process. The characteristics of waveform，spectrum and fractal of acoustic signals of rockburst process were studied. The results showed that the variation characteristics of waveform reflected the main failure process of rockburst. In the rockburst process，a relatively quiet period of the acoustic signals，i.e.，the amplitude of waveform becoming quite low close to the moment of rockbursting was discovered. Furthermore，the value of time fractal dimension of amplitude declined continuously to the lowest value after increased to a peak during a period of time can be regarded as an indication of rockburst. During the process of rockburst，different failure phenomena have different spectrum features，the main frequency value of acoustic signals has a tendency of changing from high to low，the spectrum form experience an alternating process of multimodal and unimodal. In conclusion，acoustic signals in rockburst process have distinct characteristics and inner evolution laws on waveform，time fractal dimension of amplitude and frequency spectrum. Therefore，the acoustic signals can be regarded as the precursor information for rockburst prediction.

The geo-environmental effects caused by shield tunneling have been a key issue in urban metro construction. However，few investigations have been carried on the impacts of interaction between tunnel liner and soils. Particularly，the stress analysis of the liner is not conducted. A calculation method for soil displacements affected by tunneling with liner was proposed considering the non-uniform convergence deformation. The Airy stress function analytical solution of tunnel liner was established considering the compatibility of non-uniform convergence deformation between liner and soils. The stratum subsidence and horizontal displacement curves of soils from calculation were compared with the monitoring data. The influence of the material properties of soil and liner，the geometry and depth of tunnel and other main parameters on ground deformation and liner stress induced by tunneling were obtained through the parameter analysis. The non-uniform deformation mode was found to significantly affect the ground displacements. The soil settlements and horizontal displacement curves were in good agreements with the measured values. The maximum value of the surface settlement is close to the actual one. The tunnel radius and soil hardness have greater effects on the maximum subsidence of soils. Soil subsidence was reduced significantly by decreasing the radius and hardening soil. Change of the geometric parameters of liner has little effects on the soil settlements. The axial force and bending moment of liner are strictly symmetrical to axis of 90°/270° or tunnel vertical axes. The distribution of axial force along the circumference has the shape of 8. The shape of bending moment distribution was changed from 8 to 0 along the circumference with the increase of parameter k. The maximum axial stress and maximum negative moment occur in the position of arch lumbar. The values of lateral earth pressure coefficient k affect significantly the axial forces and bending moments of liners.

36 sets of orthogonal model tests on the ultimate bearing capacity of the pre-support system of tunnels with pipe roof in soft surrounding rock were carried out. The pre-supporting system with pipe roof was found to effectively prevent the collapse when cross-cover ratio H/D = 1. The 120° arrangement of pipe shed advanced support reduced 59.5%(H/D = 2) and 64.8%(H/D = 3) of the maximum surface settlement. The 150° arranged pipe roof reduced 63.2%(H/D = 2) and 76.8%(H/D = 3) surface maximum settlement. The recommended range of width parameter K of Peck formula was given by fitting the experimental data. K increased with the density of pipe roof，and increased about 0.13 in 120° pipe arrangement，about 0.19 in 150° pipe arrangement. The limit bearing capacity of supported surrounding rocks was approximately doubled in the ultimate load tests，and the destruction form was changed from the dome collapse into the sidewall squeezing in the process of the tunneling and loading.

During the high-speed movement of landslide-debris avalanches，the effect of erosion on the substrate material increases greatly the sliding volume and expands the disastrous zone. The effect of the particle size and volume of slide materials and the effect of the particle size and the thickness of substrate materials on entrainment process were studied with the physical model tests. A high frequency camera of the type of MotionPro-Y3–S1 was used to observe the process of substrate entrainment. The test results revealed that the sliding materials of high-speed movement impacted and eroded the substrate strongly and make the substrate splash with great velocity and move forward after being sheared. The entrainment distance increased with the growth of volume and grain size of slide materials as well as the particle size of the substrate materials while decreased with the growth of erodible substrate thickness. The impact failure was shown at the front of the debris avalanches，which damaged the substrate and brought entrainment due to impacting force. The shear movement at the middle and rear part caused the shear failure of substrate materials due to the shearing force.

In order to obtain the movement and subsidence of overlying strata under stripe mining with underground coal gasification(UCG)，a multi-layer elastic foundation beam model with temperature field for Huating coal mine was established. The direct and indirect influence of the temperature field on rock beam deflection was theoretically analyzed based on Fourier analysis of overlying strata during gasification process. The analytical solution of rock beam deflection with the damaged elastic foundation was obtained by introducing the coal burnt damage factor and determining the damaged ranges. The deflection，bending moment，shear force and transient loading of rock beam were theoretically analyzed. The temperature field was found to form the additional bending moment and thermal stress in rock beam in vertical direction and horizontal direction respectively，which increased first and then decreased with time in the immediate roof while increased continuously in the main roof during the gasification process. The deflection，bending moment，shear force and load of the rock beam were larger than that at normal temperature，and the values increased first and then decreased with time. The model was proved to be reasonable by comparing with the field measured subsidence curve.

The energy dissipater of ring-type brake for falling rock protection was studied to investigate the  load-displacement curves and the energy dissipation formula. Firstly，the working mechanism of the energy dissipater of ring-type brake was described. The main factors of influence，such as the pretension，the length of aluminum sleeves，the thickness of the steel pipe and the diameter of steel pipe were obtained. Secondly，the full-scale tests and finite element analysis for verification were carried out and the results were in good agreement with each other. Thirdly，the load-displacement curves and the energy dissipation characteristics under the action of the main influence factors were further studied based on the finite element simulation of the engineering examples. The starting force of the energy dissipater of ring-type brake was found to increase with the increasing of the length of the aluminum sleeves and the decreasing of the diameter of steel pipe. The energy dissipation changed significantly with the length of the aluminum sleeves in a certain range，while the diameter of steel pipe had a little effect on its energy dissipation. The staring force and energy dissipation of the energy dissipater of ring-type brake were increased gradually with the increasing of pretension or thickness of the steel pipe. The proposed tri-linear analysis model reflected well the characteristic of the load-displacement curves with three stages and the presented energy dissipation formula facilitated the design and engineering application of the energy dissipater of ring-type brake. The energy dissipater of ring-type brake enhanced the flexibility of the passive flexible protection and prolong the impacting time，also reduced significantly the energy consumption of the tension anchor rope and the supporting rope.

Brazilian disc(BD) and semi-circular bending(SCB) tests were carried out to investigate the characteristics of tensile strength and fracture properties of coal under quasi-static loading. The SCB specimens with notches of various depths were tested to analyse the fracture properties of coal. The KIC fracture toughness and J-intergral fracture toughness of coal were calculated. The effects of notch depth on the fracture toughness were also discussed. The strain gauges were utilized to monitor the deformation features of specimens. The computed tomography scanning was also carried out on the failure specimens to figure out the crack distribution. Results show that SCB method is more suitable to obtain the tensile strength of coals than BD test. In the current testing situation，the coefficient of variation(CV) of KIC fracture toughness is the smallest as the dimensionless notch depth equal to 0.28. The KIC fracture toughness is easily affected by the notch depth and the dimensionless stress intensity factor(SIF). The results also indicate that the J-intergral fracture toughness is more suitable for evaluating the fracture properties of coals.

Model tests were carried out using a lateral cyclic loading device developed in-house. The lateral cyclic deformation and the displacement prediction model of a caisson-piles composite foundation and a caisson foundation were investigated under one-way and two-way cycling loading in symmetric and asymmetric forms. The model tests with approximately 10 000 cycles revealed that the cyclic cumulative displacement of the foundation behaved with two characteristic phases, firstly increasing rapidly with the increase of cycles and then gradually being stable. The magnitude of cyclic cumulative displacement was significantly affected by the cyclic loading path. Compared with the caisson foundation，the caisson-piles composite foundation improved significantly the ability of the foundation in resisting the lateral cyclic deformations. Finally，the prediction model of cyclic cumulative displacement was established on the basis of regression analysis of the model tests results. It was shown that the prediction model predict effectively the cyclic cumulative displacement under different cyclic loading paths.

The triaxial creep tests considering different confining pressures and geotextile reinforced layers were conducted using the large scale triaxial creep apparatus developed in-house. The creep properties and reinforcement mechanism under different deviatoric stresses and reinforced layers were obtained. The proposed PH model for reinforced soil described the relationship among stress，strain and time and the parameters of the PH model under different influence factors were obtained. Finally，the coefficient of reinforcement effect was established to evaluate the impact of stiffness under different reinforced layers. The results showed that the reinforcement effect was improved linearly as the increase of the reinforced layers. In comparing with the increasing compaction degree of the high fill，the reinforced materials reduce the post-construction deformation more effectively.

From the perspective of nonlinear vibration mechanics，the vertical free vibration characteristics of a single pile with cushion cap embedded in layered foundation were studied based on renormalization method. The form of the spring coupled with the unit block was taken to discretize the pile body and its surrounding soil. The generalized Voigt series were used to describe the friction effect of the viscoelastic soil layers. A vertical vibration model for the nonlinear system of cushion cap-single pile-soil with multiple degrees of freedom was established. The vertical vibration frequency of the coupled model was given through the coordinate transformation principle of renormalization and the distribution coefficient of pile quality was introduced to represent different equations of vibration frequency under different conditions. The correctness and accuracy of the renormalization method for vibration frequency equations were verified. The influential factors including the pile quality，the material stiffnessthe cap quality and the friction resistance were investigated.

The present method of vacuum preloading has low efficiency of vacuum transfer and the drainage plates are easily clogged，so the deep soil is poorly consolidated and the hydraulically filled mud needs a long construction period. A new kind of vacuum preloading combined with flocculant method was proposed. A type of inorganic flocculant was added into the dredged slurry before the vacuum preloading. The effective chemical flocculation led to the aggregation of small particles into lager clusters. Meanwhile，the viscosity was decreased and the permeability was increased，leading to the improved drainage of the soil after the flocculation. A series of model tests of vacuum preloading combined with different dosages of flocculants were carried out. The test results showed that the degree of vacuum in the deep soil was increased significantly. Both the pore water pressure dissipation and the process of soil consolidation were accelerated. The overall vane strength was improved obviously and with low decrement along the depth. The test proved that vacuum preloading combined with flocculant method achieved better effect of reinforcement. An optimal value of the percentage of the added flocculant exists. The best dosage of the flocculant was 1.5% for the slurry in Wenzhou(water content is 300%).