The double-sided shear model experiment was applied to study the friction and sliding of granite specimens. The experimental image gathering system was constructed with CCD camera. Meanwhile，by using the digital speckle correlation method，the evolution characteristics of the displacement field，sliding displacement on the sliding surface and deformation energy density of specimens during friction and sliding were studied. The results of the study show that：in the initial slow growth phase of shear stress，the non-uniform spatial distribution of displacement field in the sliding rock is caused by the random defects in the specimen and the deformation of the concave and convex body randomly distributed on the sliding surface. The displacement is mainly the elastic deformation of specimen. In the linear growth phase of shear stress，a certain part of the specimen is in sliding state. The spatial distribution of the displacement field is dominated by sliding surface，and the whole displacement field of the specimen shows a characteristic of regular distribution. In the nonlinear growth phase of shear stress，the sliding surface has strong and weak sections spatially. The displacement contour lines of the weak section on the sliding surface display uniformly，approximately in straight and parallel. While in the strong section on the sliding surface，the displacement contour lines are non-uniformly distributed curves. The strong and weak sections change with loading process. The factor affecting the distribution of the strong section on the sliding surface is the hindrance of the concave and convex bodies. The hindrance of the concave and convex body is not only related to its own strength，but also related to the degree of occlusion on the sliding surfaces in this area. The horizontal displacement is controlled by the sliding condition of the strong section on the sliding surface. The horizontal displacement curve has a good correspondence with the loading curve. In the nonlinear growth phase of shear stress，static friction and sliding appear alternately on the strong section of sliding surface. The sliding velocity on the sliding surface varies drastically. Meanwhile，the deformation energy density begins to accumulate and release in this phase.

In order to deal with the failure of primary lining in large deformation tunnel，a kind of lining element named support resistant limiting damper(SRLD) was developed through theoretical analysis and test verification. SRLD helps to limit the internal stress of lining and to release the strain energy stored in rockmass by using its post-peak performance. Through laboratory test and engineering practice，design parameters of SRLD were optimized，and design and construction schemes of energy-dissipating lining based on SRLD were formulated. From the engineering practice of SRLD，the following conclusions were obtained：(1) Traditional lining with large rigidity and small deformation ability is not suitable for large deformation tunnel. The primary lining should be designed to accommodate large deformation and to dissipate strain energy. (2) The traditional rigid support can be converted to the “rigid-flexible-rigid” support and possess large-deformation and energy-releasing capability by tangentially embedding SRLD into it. This type of energy-dissipating support has successfully prevented the cracking of primary lining of tunnels deep buried in old loess and of tunnels with high horizontal geo-stress，showing that SRLD is a feasible and effective supporting element. (3) The energy dissipating support based on SRLD guarantees the structural integrity and safety. SRLD is easy to be processed and installed in construction activities. SRLD enhances the construction safety and reduces cost.

The issues of landslide dam and dam break are the focus of current research. Landslide dam is remarkably different from man-made earth-rockfill dam because of its special formation process，inhomogeneous material composition，complex internal structure and various geometrical shapes. Currently，there is still lack of in-depth research in the analysis of entire lifecycle and the reliable method to assess rapidly the stability of landslide dam. On the basis of systematical reviews of the forming conditions，stability analysis methods，overtopping and piping collapse mechanisms，dam break floods and geological disaster chain of landslide dams，a database which contains 1 328 cases of landslide dams is built according to the bibliography compilation. Then，the triggering factors，causes，volumes distribution，morphological characteristics and lifetime of landslide dams，and the relationships between them are analyzed. According to the principle of logistic regression，a prediction model with three parameters，the length and width of landslide dam and the reservoir capacity of barrier lake，is established，and a method to rapidly evaluate the stability of landslide dam is proposed. Finally，from the perspective of disaster chain，the main problems existing in current research and the future key development directions of the whole process of river-blocking disaster are pointed out. The research results indicate that the volumes，lifetime and stability of landslide dam are closely related to the triggering factors and causes of landslide dam. The three-parameter rapid assessment method predicts the stability of landslide dam accurately. The process simulation of the whole lifecycle and development of disaster warning system for landslide dam are the key development directions in the future.

To evaluate the safety of rock around the excavation front of roadway in mine or mountain ridge， tests on griotte under different loadings and unloadings of principal stress were conducted using true triaxial system. The variation of cohesion c，internal friction angle ，and Lode parameter of griotte were discussed in detail according to the Mohr-Coulomb and Drucker-Prager criterions. The maximum attenuation path was obtained and the double attenuation coefficient of the cohesion c and internal friction angle  was calculated. The results indicate that the condition for calculating the fracture strength based on M-C and D-P criterion is that the principal stress is loaded symmetrically. Under the condition of single sided unloading in the direction of minimum principal stress，the fracture strength calculated with the criterion is higher. The fracture strength value calculated with the double attenuation coefficient method based on M-C criterion is lower. The calculated fracture strength value using the D-P criterion that is modified by the strength reduction method based on the M-C criterion is closer to the actual situation.

Neat epoxy resin(EP) and Dibutyl phthalate(DBP) modified epoxy resin were proposed and applied to grout the cracked rock for reinforcement. The cumulative damages of the neat EP grouted samples and DBP modified EP grouted samples under high-frequency three-point fatigue load were compared. The test results showed that the strength，the deflection，and the fatigue performance of cracked rock were obviously increased after grouting. In addition，the grouting effect and the fatigue resistance of the samples with toughened EP were much stronger than that of neat EP. The strain and the damage of samples after grouting reinforcement also exhibited the three-phase behavior(initial damage phase，stability phase，and acceleration phase). The double logarithmic fatigue life equation was established，which has an excellent correlation with the experimental results. Moreover，the damage of toughened EP grouted specimens was less significant than the neat EP grouted samples at the same cycle ratio. Stress level is one of the most important factors affecting the fatigue life.

To investigate the influence of loading rate on the strength and deformation of rock，we analyzed the fracturing characteristics of rock containing cracks with various inclination angles under various loading rates. Uniaxial compression tests under various loading rates on the prefabricated rock specimens，containing cracks with various inclination angles，were conducted using the testing system RMT–150B. The results show that the peak strains correlate negatively to the loading rates when the static load is applied. For the samples with the same inclination angle，the rock strength increases nonlinearly with the increasing of loading rate. For the samples under the same loading rate，the inclination angle affects the peak strength，and the sample having the crack with the inclination angle of 15° has the lowest strength. The elastic modulus increases nonlinearly firstly with the increasing in the loading rate and inclination angle，then，the elastic modulus remains constant. To monitor the micro patterns of the cracks，numerical modelling of the laboratory tests was carried out with the Flat-jointed bond contact elements in PFC2D. The deformation and damage data of intact specimens were used to determine the values of parameters for numerical analysis. The numerical results of cracked samples agree well with the ones from laboratory tests. The numerical results show that high stress concentration occurs at the crack tips of the sample with the inclination angle of crack of 15°.

The deformation failure mode of fractured rock slope is actually determined by the potential paths controlled by the structural characteristics of rock mass. In the complex fractured rock slopes，the intersections of structural planes with different types，sizes and dip angles make the damage paths more uncertain. The method of synthetic rock mass(SRM) can achieve effectively the structurally controlled sliding damage. A complex fractured high rock slope at a hydropower station in southwest China is studied in this paper with the method. The SRM developed with the Particle Discrete Element PFC software is adopted to solve a series of technical problems，including the construction of a complex discrete fracture network model in different sizes and dip angles based on the non-uniform distribution of homogeneous zones，the construction of rock material models with different geological properties considering the range of particle size effects，and the calculation of the potential failure paths of fractured rocky high slope simulated by SRM and combined with the weight increasing method. The results indicate that the potential failure paths of the slopes are mainly step-shaped and formed due to steep-dip faults，dykes，or joints，and gentle-to-middle dip joints. The potential failure paths are dominated by the shallow local shear-tension instability mode.

Fully grouted bolts are widely applied in rock slope and tunnel engineering. Due to the structural effect of rock masses，the sliding of the unstable block along the joint plane causes the combined action of axial and shear forces in the bolt. The bolting theory of jointed rock mass is essentially different from the pull rod model which takes the bolt as a pure tension element in many respects such as geological features，mechanical mechanism，failure mode and evaluating method. In the past decades，in order to reveal the bolting mechanism of fully grouted bolts in jointed rock mass and then to develop the bolting theory and design method，laboratory tests and theoretical analysis were performed with respect to the stress and deformation performance of jointed rock bolts，interaction between rock/grout and bolts，failure mechanism of bolts and theoretical approaches. From the viewpoint of rock structure controlling the stability，the engineering background and scientific interest of jointed rock bolting were presented，and the mechanical behavior and deformation response of jointed rock bolts due to the combined action of tension and shear were investigated in this paper. The bolting mechanism of fully grouted bolts in jointed rock masses was explored and comparisons between the elastic ground beam model and the structural mechanic model were carried out. Finally，on the basis of a detailed summary of existing researches，key problems and development tendency of bolting theory of jointed rock mass were pointed out. The work presented is to attempted to provide a reference for the understanding of bolting mechanism of jointed rock mass，the development of bolting theories and the practice of bolting engineering.

In the bedded salt cavern reservoir，the insoluble interbed collapsed under natural conditions is uncontrollable and brings potential danger to the cavern making with water solution and to the operation of storage. Controlled blasting can promote the steerable collapse of the insoluble interbed and speed up the construction of cavity. In order to analyze the effect of the insoluble interbed collapse，a simplified mechanical model for two cases with placing explosives in the interbed and on the interbed plate respectively were established on the basis of the theory of elasticity. The expressions of stress component in the insoluble interbed under blasting loading were derived. Besides，the effect of the interbed collapse under blasting loading was analyzed. In the light of the strength failure criterion of the material，the radii of the broken zones under two kinds of  explosive locations were obtained. Theoretical analysis to the interbed collapse in a salt cavern under blasting loading was carried out with the derived formula. The results show that when the explosive is placed in the interbed，the range of decoupling coefficient is between 1.0 to 2.0，the radius of crush zone is 2–4 times of the borehole radius，the radius of rupture zone is 6–9 times of the borehole radius. When the explosive is placed on the interbed plate，the lower part of damage range is larger than the upper part，and tensile failure will occur on the upper edge of the interbed.

To study the mechanism of secondary diagenesis of the weak and broken rock，the compaction device developed in-house was used to investigate the factors affecting the secondary diagenesis and the mechanical behavior of the specimen after diagenesis. The results show that the secondary diagenesis process has a compaction-broken stage and a consolidation diagenesis stage. The eccentric core extrusion and the core extrusion are two main mechanisms at the compaction-broken stage，whereas，the self-cementation and the bonding among coarse blocks are the main diagenesis mechanisms at the consolidation stage. The breakage and consolidation indexes were proposed to characterize the level of difficulty in rock breaking and the degree of the consolidation diagenesis respectively. The statistical results show that，for the rock with large size，the large irregularity coefficients result in greater difficulty in compaction. In addition，the secondary diagenesis is affected by the water content. The compaction of the rock powder with the particle size smaller than 1 mm can be fulfilled when the water content is higher than 4.76%. The uniaxial compressive strength of secondary diagenetic specimens decreases linearly with the increasing in particle size. The triaxial compressive strength of the secondary diagenetic specimen increases with the water content in a relationship of cubic polynomial，increases linearly with the compaction stress but decreases with the increasing of particle size in a cubic polynomial manner.

Hydraulic fracturing is an important technique to increase the production of oil and gas reservoirs. The prediction of breakdown pressure accurately is the key to the success of hydraulic fracturing. The current prediction model of breakdown pressure assumes that the wellbore is circular，but the wellbore is actually elliptical according to the log data. The complex function theory and the theory of elasticity are therefore used to derive the analytical stress field around the elliptical wellbore and a prediction model for the breakdown pressure of an elliptical wellbore is established. The correctness of the model is verified through formula deduction and numerical calculation. The influence of the ratio of major axis to minor axis and the difference of in-situ stress on the breakdown pressure are analyzed. A well in western China was studied as an example. The error of breakdown pressure calculated with this model is within 4%. The stress concentration due to the influence of wellbore shape occurs in the direction of minimum horizontal stress and fractures initiate along this direction. When the ratio of major axis to minor axis is large，fractures initiate along the direction of minimum horizontal stress and fracture bending occur near the wellbore. When the ratio is small，the collapse of small area of well wall leads to drastic increasing in breakdown pressure. The equilibrium curve has an expression of . When the point of the parameter falls in zone I，the breakdown pressure is greatly influenced by the difference of in-situ stress，and the wellbore fractures initiate along the direction of maximum horizontal stress. When it falls in zone II，the breakdown pressure is greatly influenced by the shape of the wellbore，and the wellbore fractures initiate along the direction of minimum horizontal stress. When it falls on the balance line and its adjacent area，the breakdown pressure is close in different directions of the wellbore，and the multiple fractures initiate in the wellbore at the same time.

The interfacial transition zone(ITZ) is considered to be the “weakest link” of concrete structures. To study the effect of different strain rates，aspect ratios，and surface roughness of the aggregate on the dynamic tensile properties of the mortar-granite ITZ，a large-diameter(? 75 mm) split Hopkinson tensile bar(SHTB) device was applied in dynamic direct tensile tests to mortar-granite composite specimens. Experimental results showed that the tensile strength of ITZ increased with the growth of strain rate. The tensile strength of ITZ is strain rate sensitive，which is closely related to the surface roughness of aggregates. The average tensile strength of ITZ decreased with the increasing of surface roughness of aggregates. Under the same loading pressure，the average tensile strength of ITZ declined significantly with the growth of aspect ratio，and the descent range was diminished with the increasing of aggregate surface roughness.

Triaxial consolidated and drained shear tests under different freeze-thaw cycles were carried out to study the evolution of the yield surface and the stress-strain relationship of cinder improved soil. The optimal amount of cinder and the evolution of the yield surface were obtained. The evolution of the yield surface after several freeze-thaw cycles were described by introducing the influence factors of freeze-thaw cycles. The elasto-plastic constitutive relation was established according to the test results. The results showed that the strength of the improved soil increases firstly and then decreases with the gradual increasing of cinder content. The maximum shear strength was obtained when the cinder content was 15%. The yield surface for shear shrinking and shear dilation shrinks gradually towards the origin of coordinates with the increasing of freeze-thaw cycles. The effect of the first 5 freeze-thaw cycles was more obvious，then the change of the yield surface decreased gradually. The constitutive model was established based on the influence factors of freeze-thaw cycles which described the stress-strain relationship of the improved soil well.

In order to investigate the microscopic shear mechanisms of soft soil(muck)，the nuclear magnetic resonance test are conducted on the undisturbed and disturbed Nansha muck before and after triaxial test. The evolutions of size，distribution，and structural characteristic of pore under true triaxial consolidated-undrained shearing are analyzed. The results show that the pores of muck are mainly concentrated in the range of 1 μm to 20 μm，and the main peak amplitude of T2 spectrum is more than 99%，indicating that the pores of muck are of small size and narrow distributed. The water content decreases by 8.79%–17.73%，and the porosity decreases after triaxial test. The percentage of small pore decreases and the medium and large pore rises with the increasing of the strain rate. The percentage of small pore rises and the large pore decreases with the increasing of the strain when the vertical strain is less than the threshold of vertical strain(about 4%). This behavior reverses after the threshold. The pore size and pore structure parameters( ) can be directly measured with NMR，so the relationship between the microstructure parameters and macroscopic mechanical properties (generalized shear stress and generalized shear strain ) can be analyzed.

The strength and dilation behavior of unsaturated compacted soils was investigated via low-stress direct shear and direct tensile tests over a wide range of water contents. The results show that the unsaturated soils with the water content below the plastic limit exhibit the characteristics of strain softening and shear dilation. The peak shear strength，the minimum dilation rate and the uniaxial tensile strength of unsaturated soils over a wide range of water contents increase and then decrease with the increasing of water content similarly. A modified Mohr-Coulomb strength envelope in tensile stress regime for unsaturated soils is proposed based on the test results. It is verified that the revised Bishop's shear strength model predicts the effect of suction on the shear strength poorly，and the reason why this model is popular is analyzed. Finally，it is suggested that the contribution of suction on the peak shear strength can be described in terms of the effect of suction on interparticle tensile stress and shear dilation，in which the suction is the sum of capillary and adsorptive processes，and the interparticle tensile stress is approximated by the uniaxial tensile strength.

Stochastic medium theory is a practical method in ground settlement prediction. It is generally assumed that the cross section of tunnel is uniformly converged. A parameterized non-uniform tunnel deformation mode containing three different modes is proposed in this paper. A model for predicting ground surface settlement is established by combining the stochastic medium theory. The formulae of settlement，slope and curvature are deduced in terms of relative tunnel deformation parameters. The influence of the tunnel deformation parameters on settlement trough is considered. Back analysis on the tunnel section from Dahongmen Bridge Station to Heyi Station in Beijing is presented. The results show that the settlement trough of non-uniform tunnel deformation is narrower and deeper. The predicted settlement trough calculated with the deformation mode in this paper is better than the other two. The empirical values of the parameters，the angle of influence zone of ground surface settlement β，the relative convergence ε，the relative ovalization δ，the relative vertical movement λ，are 34.65°–37.61°，0.81%–0.97%，0.41%–0.53%，0.26%–0.38%，respectively. The case study confirmed the soundness of the prediction model.

The relationship between particle crushing and grain group transformation under different loading conditions and stress levels of coral calcareous sand(CCS) from Xisha islands is investigated in this study. A series of tests were carried out，such as the oedometer test，triaxial compression test，simple shear test and cyclic shear test. The growth rate of particle crushing is adopted to analyze the crushing behavior of particles. The results indicate that the crushing growth rate of CCS decreases rapidly to zero with the increasing of loading cycles. The increasing of stress level accelerates the reduction of the growth rate of particle crushing，and arrives at the stable state of crushing sooner. It is proposed according to the test results that the particle crushing reaches its limit when the particle crushing growth rate is less than a small value. The limit value can be used in engineering practice. The mechanical parameters of the CCS corresponding to the limit value can be used as the extreme value in the design for the most unfavorable or most favorable situation in real project. Samples with higher contact force but insufficient relative motion between particles are lack of regularity in particle group transformation after crushing，while the samples with full relative motion between particles have the particle group transformation with obvious similarity and good regularity. The particle size of 0.25 mm is a critical point where the grain group content will be changed from variation to a stable growth state. The distribution of particle crushing can be divided into domains of particle size increasing and particle size losing. The particle size losing domain is correspond to the inflection interval of particle distribution curve under the same coordinate model of particle size.

In order to study the deformation and strength characteristics of GMZ bentonite under high temperature and high pressure，undrained triaxial shearing tests were conducted to 81specimens with the high-pressure triaxial apparatus with temperature control. The influences of dry density，confining pressure，temperature and water content on deformation and strength characteristics of GMZ bentonite were investigated. The results show that the failure forms of GMZ bentonite were significantly influenced by confining pressure and dry density. The specimens tested under unconfined conditions were all in brittle failure. The specimens with low dry density under high confining pressure exhibited largely the plastic failure，while those with high dry density exhibited brittle failure. The strength of GMZ bentonite specimens decreases with the increasing of water content. The influence of temperature and dry density on strength is complex. The position of deviator stress-axial strain curves rises with the increasing of temperature for specimens with low dry density，but it behave oppositely for specimens with high dry density. The initial Young’s modulus of the specimen with low dry density also rises with the increasing of temperature，but it?s opposite for specimens with high dry density. The initial Young’s modulus of specimens generally decreases with the increasing of water content. Poisson?s ratio gradually decreases with the increasing of confining pressure for specimens with low dry density，but this tendency is not obvious for specimens with high dry density. Poisson?s ratio is less influenced by temperature and water content. The formulae of cohesion and internal friction angle changing with dry density，water content and temperature were established for GMZ bentonite specimens.

The inter-particle contact of coarse-grained soils consist of limestone is simplified as point-surface contact. The particle contact models of coarse-grained soils are obtained through experimental investigation on the normal and tangential contact properties. The large shear tests of coarse-grained soils are simulated numerically with the discrete element method(PFC) using proposed micro contact models. The contact models and micro parameters are verified by comparing simulated results with measured data. The contact behaviors and contact models of coarse-grained soils are further discussed. The results show that the relationship between contact forces and displacements are fitted with power functions with an exponent less than 1. In order to measure the tangential contact stiffness，the tangential force corresponding to the tangential displacement of 5mm is defined as the tangential contact strength，particularly，the peak tangential force is defined as the contact strength if a peak value occurs. Comparing the simulated results of large shear tests with measured data shows that the calculation errors are really small for soils with large particle diameters(2–5，1–2 cm). For the grading samples with smaller granules，the calculation errors are larger.