Water-bearing state has an important influence on the damage evolution process of coal and rock samples. In order to study the l energy release law in the whole process of damage evolution of coal and rock samples with different water-bearing states under uniaxial compression，to pick up the AE signals of key pregnancy disasters based on the common criteria of energy contribution rate and ringing count contribution rate and hence to guide the application of AE technology in rock mass engineering monitoring and disaster early warning，uniaxial compression tests of coal and rock samples in different water-bearing states are carried out by using rock mechanics test system and full-information AE information analyzer. The mechanical properties，energy release law，failure modes and key parts of disaster AE signals of coal and rock samples under different water-bearing conditions are mainly analyzed. The test results show that the mechanical properties of coal and rock samples are different in different water-bearing states and the increase of water content can effectively weaken the strength of coal and rock samples. The energy release law of coal and rock samples in different water-bearing states is different. While water softens the coal-rock matrix，it also absorbs a large amount of elastic strain energy，which further leads to an increase of the proportion of the elastic strain energy and a rapid decrease of the dissipative strain energy in the loading yield stage of water-bearing coal and rock corresponding to the energy storage period (AE quiet period). When the pore water pressure increases to expand and penetrate the cracks，the sample immediately enters the failure stage. Under different water-bearing conditions，the uniaxial compression failure modes of coal and rock samples are in the form of shear，and the shear crack tends to be complex as the water content increases. The AE signal picking method based on the energy contribution rate and ring count contribution rate calculation criterion is verified to be feasible，and a corresponding relationship with other conventional AE parameters is established. The research results can provide reference for the specific analysis of precursory characteristics and disaster early warning.

To entirely understand main unfavorable geological conditions and engineering geological problems along Sichuan-Tibet railway，to offer scientific basis for route planning，selection and design and to ensure the safe construction or operation of railway，the existing research findings were summarized by literature review and geological survey. Main unfavorable geological conditions and engineering geologicla problems were analyzed，and research proposal was proposed for potential problems. The results indicate that the unfavorable geology conditions are well developed along Sichuan-Tibet railway and have seven significant characteristics named as “five high (high elevation，high earthquake intensity，high geostress，high hydraulic pressure and high geothermal)” and “two active (active fault belt，active frozen soil slope and freezing hazard)”. The active fault belts since Quaternary，which maybe trigger intensive earthquakes or geological hazard chains， are the severe challenges for railway construction. The distribution of surface hazards including rock fall，landslide and debris flow is controlled by the active fault belts and these hazards exhibit high-risk properties for a long period after earthquake. The frozen soil slope failure and debris flow triggered by glacier lake outburst are also typical engineering geology problems along the railway. The heat and freezing hazards can deteriorate the mechanical properties of rock or construction materials and reduce the service life of tunnels. Under the coupled high geostress，high geothermal，high seepage pressure and dynamic load condition，the mechanisms of water and mud inrush，collapse，large deformation of soft rock and rock burst hazards are special and complex，and the prevention methods need to be improved.

In this study，a uniaxial compression with acoustic emission，elastic wave velocity and SEM scanning test was conducted to study the failure mode，mechanism and precursory characteristics of deep buried granite in Southwest China.It is found that the granite in the tunnel has obvious “time-delayed type” and “immediate type” failure characteristics and the “time-delayed type” failure also has obvious “intermittent”characteristics. The sound，phenomenon，incubation time and duration of “time-delayed type”failure are obviously different from those of “immediate type”failure；The “time-delayed type”is dominated by shear failure，while the “immediate type”is dominated by tension-shear mixed failure. Before failure，lg(AF/RA)(characteristic parameters of acoustic emission that can represent failure types)of the “time-delayed type”increases obviously，while the change of the “immediate type” is not obvious. The wave velocity of the two types before failure decreases obviously，but compared to the “immediate type”，the precursor of the “time-delayed type” failure appears earlier and the amplitude of the decrease is larger. Besides，the main frequency bandwidth of the“time-delayed type” is larger while the mean value of main frequency of the“time-delayed type” is lower. Before the “time-delayed type” failure，the dominant frequency distribution between the bands of 170-260 kHz is strengthened with a trend of “nucleation”，but the precursory feature of “immediate type” failure is not obvious. The research results are of great significance to the recognition of occurrence mechanism，early warning and prevention of granite rockburst in Southwest China.

In this paper，starting from the interface bonding mechanism of “geological body—engineering body”binary media materials，the control indexes affecting the bonding performance of rock-concrete interface were explored，and the theoretical characterization of the interface bonding strength of binary media was constructed. Then，a bond strength freeze-thaw degradation model of rock-concrete interface was proposed through the internal cognition of the degradation process of the interface bonding performance under freeze-thaw. For further verifying the accuracy and evaluation effect of the proposed model，shear tests of interface-bonding performance with different interface roughness (JRC) and freeze-thaw cycles were carried out on granite-concrete binary samples，and it is shown that the test results are consistent with the theoretical calculations. The model comprehensively considers the interface apparent characteristics，concrete C-S-H group “root pile” effect and freeze-thaw damage deterioration characteristics，and provides a theoretical reference for understanding freeze-thaw deterioration of rock-concrete interface bond strength. Additionally，in order to thoroughly cognize the cause of the error between the freeze-thaw deterioration theoretical model of the interface bond properties and the measured values，further discusses were carried out about wall strength distribution coefficient，characteristics of interface failure morphology analysis，NMR layered microscopic analysis technology and coupling characteristics of interface bond strength freeze-thaw deterioration，which expands the cognitive depth of interface bond properties deterioration induced by freeze-thaw. The research results can provide theoretical and experimental basis for evaluating the deterioration of bond strength between rock and concrete caused by freeze-thaw.

Muzhailing tunnel，taken as the background of the research，has the worst geological condition in the whole line including  strong fault tectonism，high ground stress，large depth and rich groundwater. Aiming at the damage phenomena of Muzhailing tunnel after first support such as initial support cracking，arch damaging and surrounding rock seepage，NPR bolt-mesh-cable support was applied and the deformation was successfully controlled with a maximum of 240 mm. In order to reduce the construction cost and to improve the construction efficiency，in this paper，the optimum design of the cable-line spacing of NPR anchor net was carried out. A structural element of NPR anchor cable with high constant resistance and large deformation was established by using Fish language of Flac3D，and numerical simulations of different row spacing optimization schemes were implemented to compare the normal stress，shear stress and deformation nephogram under different schemes. Field tests were conducted，and the field test results were compared with the numerical solutions. It is shown that loose ring may be affected by small footage excavation and NPR anchor mesh cable support system. At last an optimal design direction of NPR anchor mesh cable support was proposed，which provides a theoretical and practical foundation for secondary optimization. The research gives a reference for the implementation of Sichuan—Tibet Railway.

In view of the evolution characteristics and stability of overlying rock structure in the upward mining of short distance coal seams with strong impact prone，taking B4–1 strong impact prone coal seam in Kuangou coal mine as the background，a mechanical model of the key layer structure of the inverted trapezoid overlying rock structure in the upper part of the strong impact prone coal seam and the critical position of the impact is established，and a analysis method of the minimum safe distance of the coal pillar is proposed. Based on the combination of physical material similarity simulation and numerical simulation， the evolution of the overburden structure， pressure behaviours and the characteristics of focal distribution are analyzed using pressure sensors and SOS microseismic monitoring system，and the impact risk is evaluated by analyzing the stability of the overburden structure. The results show that，during the upward mining of B4-1 strong impact prone coal seam，the upper overburden presents a dynamic evolution process from “double inverted ladder” structure with the key layer as the boundary to “single inverted ladder” structure after the centralized collapse of the upper layer of the key layer. When the size of the remaining coal is small，the upper inverted ladder overburden structure has a concentrated source with large energy，and the source in the active area of the goaf is scattered with small energy . Two rockburst risk indexes Im and In，for analyzing structural stability of the inverted trapezoid overburden structure and stresses of the key stratum at the critical position of impact respectively，are put forward，and the change trend of the rockburst risk indexes is analyzed quantitatively. B4–1 coal seam is divided into three parts including relatively stable area，periodic obvious damage area and impact risk area. The accuracy of the double peak stress superposition effect is verified by numerical simulation analysis of the floor stress. The residual size of coal pillar is determined as 39.2 m to ensure the upward mining of B4–1 coal seam with strong impact tendency in short distance by comprehensive analysis of three methods. The research results provide a scientific guidance for the study of the stability of the overburden structure in the upward mining of short distance strong impact prone coal seams.

Daguangbao(DGB) landslide，formed within a saturated bedding fault 400 m in depth，is the largest landslide triggered by the 2008 Wenchuan earthquake. To study pore and crack water pressures (i.e.，interstice water pressure) responses within weak layers，a series of shaking table tests were conducted on a geological model with a saturated weak interlayer. The results show that the excess interstice water pressure within the weak layer is much larger than that in both the upper and lower layers and that the excess water pressure of the weak layer is characterized by transient generation and gradual accumulation. It was proposed that compression-tension and shear behaviors of the model depending on uncoordinated deformation and dynamic damage depending on uncoordinated deformation within the weak layer respectively induce transient excess water pressure and accumulation of the excess water pressure. An effective stress model for earthquake-inducted landslides under both horizontal and vertical shaking conditions，containing the interstice water pressure ration rw and the effective area index of interstice water pressure η，was developed. For the DGB landslide，site investigations show that η is in the range of 0.7-0.9 and that the effective stress of the sliding zone decreases to zero while rw ranges from 0.73 to 1.04. The shaking table tests also show that the seismic parameters in the landslide area during the Wenchuan earthquake can make rw reach the above range. Finally，the failure mechanism of the DGB landslide mechanism from strong seismic action，damage and expansion of dislocation interface resulted from dynamic uncoordinated deformation，excitation of the excess interstitial water pressure to initiation of landslide was concluded.

To study the diffusion and migration pattern of grouts in rock mass fracture network，a visual fracture constant pressure grouting test system，consisting of pressure supply equipment，constant pressure pumping equipment，fracture simulation equipment and monitoring equipment，was developed. The system can design a specific fracture network according to test requirements to simulate the grout flow process under various parameters such as grouting pressure，grout viscosity and fracture aperture and to investigate the grout-water/gas displacement mechanism in fractured rock mass. The reliability of the test system was proved by the comparison of the test results with the single fracture grouting theory，and the grouting diffusion mechanism of random fracture network was studied. The results show that the pressure at the same point in the fracture increases with increasing the grouting pressure or decreasing the fracture aperture but is not affected by the change of the grout viscosity，and that，after the grout is dispersed into several branches in the fracture network，the pressure drops significantly and the flow velocity slows down. It is also shown that the pressure of each branch and the flow distribution coefficient are greatly affected by the angle of the bifurcation (intersection) fracture. The test system and the study results have certain reference for the grouting engineering.

Based on the Brazilian splitting test，three-dimensional scanning and 3D printing technology，a surrounding rock-lining contact surface model is produced, and surrounding rock-lining contact samples were prepared using simulation materials. By shear test of the surrounding rock-lining contact samples，the shear properties and failure mechanisms of the surrounding rock-lining contact surface were studied，the main affecting factors were analyzed，and the formula of the shear strength of the surrounding rock-lining contact surface was explored. The results show that the shear curves of the surrounding rock-lining contact samples have two types of failure including ductility and brittleness. The normal stress，the roughness of the contact surface and the mechanical properties of the materials on both sides affect the shear deformation，shear strength and the failure mode of the surrounding rock-lining contact surface. By comparison，the material properties on both sides of the contact surface effect more than the roughness of the contact surface. The shear properties and failure modes of the contact surface depend not only on the magnitudes of the affecting parameters but on the combinations of the parameters. Introducing adhesion theory into Barton empirical formula according to the damage characteristics of the contact surface, a shear strength formula which is suitable for surrounding rock-lining contact samples was proposed, which embodies the unity of strength characteristics and influencing factors. The research results provide a test reference for the study of surrounding rock-lining interaction under earthquake action.

Based on the rock slope engineering of the left bank of Baihetan hydropower station，Multi-fractal Detrended Fluctuation Analysis (MF-DFA) is used to estimate the multi-fractal spectrum of microseismic waveforms，and the pre-warning signs of rock slope deformation are pointed out on the basis of the time-varying response characteristics of multi-fractal time series of microseismic waveforms. The results show that the multi-fractal characteristics of rock microcracking and blasting waveform time series in the left bank slope are obvious，and that the multi-fractal spectrum width of the blasting waveform is much larger than that of the rock microcracking waveform. Before the slope cracks increase，the multi-fractal time-varying response characteristics of rock microcracking waveforms show strong regularity，which can be viewed as pre-warning signals for deformation. Before the deformation and failure of the rock mass，the multi-fractal spectrum width △α shows an increasing trend while the multi-fractal spectrum of microseismic waveforms △f(α) presents a decreasing trend，which can be regarded as precursor signals of deformation pre-warning. When deformation and failure occur，△α shows a decreasing trend while △f(α) presents an increasing trend，which can be regarded as a deformation failure period. After deformation and failure，both △α and △f(α) show a steady trend and △f(α) as a whole will be near the zero line，which can be regarded as a stable period.

The instability of karst filling medium induced by seepage-erosion process often causes serious water-mud inrush disasters，and the scientific evaluation of its grouting reinforcement effect of karst filling medium is an important prerequisite for ensuring the safety of underground construction. In this paper，seepage-erosion tests before and after grouting were conducted via a self-developed large-scale triaxial seepage-grouting multi-functional test platform，focusing on the key factors of grouting reinforcement effect including the initial porosity of the medium and grouting pressure.，and the changes of the medium porosity and the water outflow rate during the seepage process were monitored. The decline of the permeability coefficient，the evolution characteristics of each seepage stage and the delay amplitude of the critical point for flow transition were quantitatively analyzed，and then the reinforcement effect for the filling medium under specific existence conditions and particular grouting parameters were evaluated. The test results show that grouting improves the  seepage resistance stability of the filling medium and delays the rapid evolution of porosity as well as the occurrence of the "water inrush" stage，which systematically confirms the rationality of the "three-stage" seepage theory. The regression equations of the delay time of transition points I，II with the grouting pressure and the initial porosity of the samples not only quantitatively describe the influence of grouting on each seepage stage，but also provide a new evaluation perspective for the grouting reinforcement of the filling medium in karst cavities.

Mountain tunnels are typically located in complex geological environments，and the seismic performances of the tunnels are directly affected by the degradation of tunnel linings resulted from various erosions during the service life. The degradation laws of concrete and steel bars were determined by introducing the time-dependent concrete strength model and statistical characteristics of corrosion parameters of steel bars，and a time-dependent load carrying capacity formula of tunnel lining was established applying the load-bearing capacity equation of eccentric compression members and the time variable. According to the theory of seismic fragility analysis，an assessment process of seismic vulnerability of mountain tunnels considering lining degradation was proposed. A deep buried mountain tunnel in western China was taken as an example，a series of 2D dynamic time history calculations were carried out by using the incremental dynamic analysis method. An automatic extraction of the data and an automatic calculation of the maximum of damage index(DImax) during the seismic response process were implemented by using the Python programming language. Seismic vulnerability curves of tunnels with different service life were obtained considering the deterioration of concrete and the corrosion of steel bars. The results show that the vulnerability of the lining increases nonlinearly with increasing the service time. The damage probability of the lining increases slowly in the early stage of the service(0-50 years)，while increases rapidly in the late stage of the service(50-100 years)，showing that the longer the service time，the greater the effect of lining corrosion on seismic vulnerability of tunnels. Therefore，it is necessary to take into account the deterioration of linings for the risk assessment of operational tunnels. In addition，the shapes of the fragility curves of tunnels within the service time are similar for different surrounding rocks. The important effects of surrounding rocks and lining degradation on the vulnerability of tunnel structures are highlighted. The damage probability of the tunnel is larger for worse quality rock mass. The results can provide references for seismic vulnerability analysis and risk assessment of operational tunnels.

Compared with the wide foundation pit，the stability of the retaining wall of the narrow foundation pit is greatly improved due to its small excavation width. For narrow excavation engineering with a longitudinal length of several kilometers，optimization of the insertion depth of the retaining structure maybe bring significant economic benefits. Based on the narrow excavation of a cable tunnel in a city of Fujian province，the optimization of the insertion depth of the narrow excavation retaining structure was studied. The force and deformation characteristics of the retaining wall with different excavation widths were compared analytically. It is shown that with decreasing the excavation width，the horizontal additional load acting on the retaining wall，the internal force and deformation of the wall are greatly reduced. A new method for calculating the safety factor of anti-uplift stability of narrow excavation pits was put forward to improve the method proposed in the current specifications. The calculation results indicate that the safety factor obtained by the improved method is larger than that calculated by the current specification and that the insertion depth of the retaining wall calculated by the improved method can be reduced by 25%. For verification，centrifugal model tests were carried out. The test results show that，for narrow excavation pits，the calculation method of the critical insertion depth of the retaining structure provided by the code is indeed too conservative. Therefore，it is necessary to optimize the insertion depth of the retaining structure when designing a narrow excavation pit. The research can provide a theoretical basis for the optimal design of the retaining wall insertion depth of the narrow excavation pits.

Gaoshan tunnel of Qianjiang-Zhangjiajie-Changde railway goes through a huge karst cave with a long crossing distance (the affected area of the cave up to 124 m) and a large suspended height(the clearance under the tunnel floor up to 30–55 m)，and the cave has unfavorable conditions including large volume，complex structure，poor stability and high risk of falling rock，which makes the construction and treatment of the tunnel to be very difficult. In order to overcome the above-mentioned issues，a treatment scheme of “backfill with tunnel ballast + upper grouting” was proposed through comprehensive comparisons，and the settlement pattern of the backfill under static and dynamic loads was comprehensively studied by using field monitoring，numerical simulation and theoretical analysis. The monitoring results during the construction period show that the surface settlement of the super thick backfill-body is mainly affected by the gravity and the load of the upper structure and the convergence rate of the settlement is fast. The settlement is mainly resulted from the lower un-grouted backfill and the surface part of the deposit at the bottom of the karst cave. A 3D numerical simulation model was established based on finite element method to simulate the influence of the dynamical load of trains on the super thick backfill-body. The simulation results show that，due to that the transfer of the dynamical stress of the train to the super thick backfill is largely reduced because of the exist of the ballast track and the 3m-thick reinforced concrete subgrade and further blocked by the upper grouting layer of the backfill body，the un-grouted layer of the backfill body is nearly not affected by the dynamic load，that is，the dynamic load of the train will not cause an additional settlement value of the backfill. The engineering practice shows that the backfill treatment of the huge karst cave in Gaoshan tunnel of Qianjiang-Zhangjiajie-Changde railway is reliable，that the settlement after the construction is under control and meets the design requirements. The proposed technology can be adopted as a reference for other similar kind of projects.

In order to study the energy dissipation characteristics of micro steel tube pile-soil composite anti slide structure (hereinafter referred to as pile-soil composite structure) under earthquake action，a quasi-static direct shear test device for the soil-pile composite structure is designed，and three models of pile-soil composite structure with the same pile spacing and different pile diameters are tested under cyclic loading. The bearing capacity，hysteretic performance，stiffness degradation，ductility and energy dissipation capacity of the test models are compared and analyzed. The results show that the pile-soil composite structure can work together under low cyclic reciprocating load. When the distance between piles is about 10 times of the pile diameter，the pile-soil composite structure has better energy dissipation capacity. However，the energy dissipation capacity of the pile-soil composite structure decreases obviously when the ratio of the pile spacing to the pile diameter is less than 5.9. The model with a smaller pile diameter is closer in bearing capacity，hysteretic performance and energy dissipation capacity，and the hysteretic curve is fuller. When the pile diameter is large，the bearing capacity，hysteretic performance and energy dissipation capacity of the model decrease obviously.

The dynamic response rule of subgrades under dynamic loads is the basis for studying the long term dynamic stability of the subgrades. The self-developed separated variable frequency vibration exciter was used to carry out full-scale model tests to study the railway subgrade dynamic response. The dynamic response rules of the railway subgrade under different excitation frequencies and dynamic load levels were studied. The test results show that the resonance frequency of the railway subgrade which was filled with lime improved soil and silty clay is 25 Hz and the vibration acceleration and dynamic stress of the subgrade surface increase significantly with increasing the excitation frequency. The vibration acceleration and dynamic stress along the depth and horizontal direction were researched. It is revealed that the vibration acceleration and dynamic stress in the depth of 1.5m reduce by 90%，which indicates that the vibration acceleration and dynamic stress along the depth attenuates faster than those of the ballastless track subgrade. The changes of the vibration acceleration and dynamic stress  in the horizontal direction are affected by the stress diffusion effect. To be specific，the vibration acceleration and dynamic stress decay rapidly in the shallow horizontal plane while keep relatively stable in the depth of 0.7m. The research results reveal the spatial variation characteristics of the subgrade dynamic response.     

The excavation of the basement will break the original stress field of ground and hence has an unfavorable effect on the underlying tunnel. In this paper，a new simplified method is developed to evaluate the response of the existing tunnel duo to the unloading of the basement excavation. Firstly，the Euler Bernoulli beam resting on the Pasternak foundation was used to simulate the interaction between the existing tunnel and ground，and the coefficient of subgrade reaction considering the effect of the burial depth of the existing tunnel was adopted. Secondly，the ground displacement at the tunnel center induced by basement excavation was obtained with the application of Mindlins solution，. Then，a deformation control equation of tunnels was established based on the displacement coupling condition between the existing tunnel and the ground. Finally，the solution of the longitudinal response of the existing tunnel caused by adjacent excavation was obtained using the finite difference method. The accuracy and applicability of the proposed method were verified by comparison with the three-dimensional finite element method analysis and theoretical solutions published in other literature，and the influence of different factors on tunnel response was analyzed including the tunnel buried depth，relative space position between the basement and the existing tunnel，the excavation depth of the basement，the geometry of the basement，the relative rigidity between the existing tunnel and the ground，etc. Finally，a simplified formula for predicting the maximum vertical displacement of the tunnel induced by excavation was presented. The results could provide some theoretical support for similar projects.