The Sichuan—Tibet Railway is of great significance and plays an important role in the long-term western development and the economic and social development of Tibet. However，as the most difficult railway project in the history of the world's railways，the Sichuan—Tibet railway is faced with many unique complex and urgent scientific and engineering problems during the construction and long-term safe operation in the future，especially geological security risks. Based on the concept of earth science system，in this paper，the engineering geological problems of the Qinghai—Tibet Plateau through which the Sichuan—Tibet Railway crosses are systematically analyzed. It is believed that，in the superficial crust of the region along Sichuan—Tibet railway，there is a loose change circle composed by tectonic deformation circle，rock loosening circle，surface freeze-thaw circle and engineering disturbance circle under the combined action of internal and external factors such as plate compression，plateau uplift，climate change and engineering disturbances. The loose change circle affects and restricts the stability of the regional geological body，engineering geological body，engineering rock-soil body and engineering structure of railway engineering，and causes and controls the occurrence and chain evolution of geo-hazards. It is proposed that the Sichuan-Tibet railway is faced with the top-ten challenges and the core scientific problem behind the project is the disaster-causing mechanisms of the interaction between the plate collision zone and the surface layer. Consequently，five key research directions，including the regional crustal stability and the dynamic mechanism of major disasters under plate compression，the stability of the engineering geological body and the chain evolution mechanism of major geohazards under the background of the Qinghai—Tibet Plateau uplift，the stability and importance of engineering rock and soil mass driven by climate change and the geohazard chain amplification mechanism，the engineering structure stability under special geological environment and the mutual-feedback geohzard response mechanism for major projects，and the major project disaster risk prediction and prevention under complex environment，are proposed. The Sichuan—Tibet Railway is a rare high-quality research base for exploring the scientific problems of engineering geology and geohazards of major green corridor projects and the theory of human-land coordination. The research results will play a leading role in the geological safety research of similar major projects around the world.

Nuclear-project-related slopes are natural or artificial slopes which locate around the structures or buildings classified as anti-seismic type I and type II referring to the Chinese code for seismic design of buildings. The seismic safety assessment of slopes involved in nuclear projects is one of the key components of the overall safety evaluation for the construction and operation of the nuclear power plants or military infrastructures. A review on seismic design codes for slopes of China and other countries，nuclear project regulations related to slope seismic inspection as well as current experiences on the design of nuclear-project-related slopes is presented. The procedures of slope seismic inspection based on static and dynamic analysis proposed in this paper could be suitable for the safety classification and design of nuclear-project-related slopes. A summary of the formulas evaluating comprehensive seismic coefficient is also provided. This study may be of significance for the development of association standard《Design Code for Nuclear-project-related slopes》of Nuclear Industry Exploration and Design(CNIDA).

In order to study the seepage characteristics of red sandstone under different confining pressures and damage degrees，water-force coupling tests of red sandstone under different confining pressures were carried out by Rock Top multi-field coupling apparatus. The results show that，with increasing the confining pressure at a constant gradient，the failure mode changes from single master crack splitting failure to multi-crack stacked dendritic failure and the failure surface is powdery under high confining pressure. Under the same deviator stress，the permeability decreases with increasing the confining pressure，showing that the confining pressure has a significant effect on seepage inhibition. When the gradient of the deviation stress grows，the permeability variation range decreases with increasing the confining pressure. With increasing the confining pressure as a constant gradient，the initial stress and damage stress of the rock sample increase gradually，but the change range decreases gradually. It was found by steady-state method and transient method that the permeability under different confining pressures experiences four stages of slow decline，approximate stable，slow increase and rapid growth before peak stress，corresponding to the stress-strain curve. Based on the test results，the relationship between the rock damage index and the permeability was deduced，and the evolution law of the permeability with the rock damage index was revealed.

During the development of shale gas fields，the surrounding rock is always in a three-way high-pressure state. After the completion of hydraulic fracturing，the pressures of the shale gas in the fracture and the fracturing fluid will decrease along with the backflow of the high-pressure fracturing fluid. The shale reservoir suffers long-term cyclic loading in the whole process. In order to explore the mechanical properties of shale under cyclic loading，triaxial variable upper and lower limit constant amplitude cyclic loading and unloading experiments on natural shale were performed under different confining pressures by using the RLW–2000 microcomputer servo rock triaxial testing machine，and the deformation characteristics，energy evolution mechanism and damping characteristics of shale were analyzed. The experimental results show that the deformation modulus and the Poisson¢s ratio fluctuate drastically in the few cycles near failure，indicating that the shale is about to fail. Under variable upper and lower limit constant amplitude cyclic loads，the stress reaching the stage of energy weakening at a low confining pressure is smaller than that at a high confining pressure，while the stress at the energy-strengthening stage does the opposite. The stress ratio can be used as the threshold point for energy conversion and distribution of the specimen to predict the energy strengthening and weakening process in the deformation and failure of the specimen. Finally，the relationship between the cumulative horizontal energy and the stress ratio of shale under variable upper and lower limit constant amplitude cyclic loads was clarified，and the evolution law of the damping ratio with the stress ratio and the number of cycles was revealed.

The strong excavation unloading under the high geo-stress conditions leads to damage or even failure of surrounding rock mass in deep underground engineering. As the main bearing structure of underground engineering，fracturing rock mass has significantly effect on engineering safety. It is necessary to study the energy dissipation characteristics of unloading damaged rock during reloading. Unloading damaged test was carried out by MTS815 test system. The unloading points were set as 70，80 and 90 MPa，and the unloading confining pressure rates were set as 0.1，0.5 and 1.0 MPa/s at each unloading point. Twenty-seven damaged specimens were obtained，on which uniaxial compress reloading test was performed. The unloading test results show that the dissipated energy density is positively correlated with the unloading point and negatively correlated with the unloading confining rate. The unloading point has greater influence on the dissipated energy density than unloading confining rate. The damage variable D increases with increasing the dissipative energy density. The uniaxial compress reloading test results show that the failure strain of specimens after unloading increases exponentially as D increases. The destruction and energy characteristics are divided into two stages with a threshold value of Dc = 0.10. When D＜Dc，the absorbed energy density，dissipated energy density and elastic energy density tend to be stable as the damage variable increases， and the failure mode of the unloading damaged sample is dominated by shear failure accompanied by a small amount of tensile cracks. When D> Dc，the proportion of the dissipated energy density increases sharply，while the elastic energy density and absorbed energy density decrease rapidly. The failure mode of the unloading damaged sample is mainly tensile failure. The fragment size is large and the quantity of fragments is small. This research is significant for the selection of mechanical parameters of surrounding rock and the optimization of support schemes in deep underground engineering.

In view of the complexity of the formation mechanism of rockbursts and the problem that it is difficult to prevent the occurrence of rockbursts accurately and effectively，rock mechanics experiments of rock samples with a filled cavity were performed to analyze the energy evolution mechanism and failure mode of the rock samples under different filling conditions and to reveal the energy regulation evolution mechanism of the hole filling of the rock samples with strong impact tendency. The results show that compared with undrilled intact rock samples，the mechanical parameters of rock samples with an unfilled，copper tube-filled(rigid filling) or  solidified body-filled(flexible filling) borehole are deteriorated. The energy evolution law of the rock samples under different filling conditions is roughly the same as that of the intact rock samples except for in the yield failure and failure stages. Due to the existence of boreholes，the initial damage of the rock samples is aggravated. Filling cooper pipe increases the total strain energy absorbed by the rock samples，while filling consolidation body not only improves the strength of the rock samples but also changes the strong and brittle characteristics of the rock samples. The filling modified energy conversion efficiency was constructed，and the energy regulation mechanism of“first release + then absorption”was further explained by calculating the energy conversion efficiency. Finally，the sequence of impact tendency of the rock samples under different filling conditions was compared and analyzed，and it was found that drilling filling copper pipe and solidified body can better reduce the degree of rock burst and the latter is better than the former. However，it is necessary to pay attention to strain increase behavior under the solidified body-filled condition，which possibly results in disasters under large deformation environment.

The static and dynamic mechanical responses of rock mass after grouting reinforcement are important for evaluating the safety and stability of rock engineering. In order to study the mechanical characteristics of grouting-reinforced rock under static and cyclic impact loads，the failure mechanism and damage evolution model of red sandstone samples of different grouting types were studied using the drop hammer impact test device. The test results show that specimens grouted by cement show poor reinforcement effect due to the low bonding performance and strength of the cement，while that resin grouting material can effectively improve the stress concentration caused by cracks and obtain a good reinforcement effect due to its high strength，toughness and good coordination with the rock. The maximum tension strain at the middle position of the cement grouting sample first increases rapidly and suddenly changes when the load reaches the peak value of the cement cracking load，while the strain changes of the specimens grouted by resin are smooth and there is no obvious mutation. All specimens，whether or not they are grouted，will be destroyed immediately when the impact energy is large enough. For both resin grouting specimens and un-cracked specimens，there is a clear double logarithmic linear relationship between the impact energy and the impact life，and the specimen will be damaged when the impact cumulative residual strain reaches the difference between the static peak strain and the dynamic peak strain. The damage evolution curve presenting an obvious three-stage change was obtained and verified by experiments of different grouting types and different impact energy. The damage evolution can better simulate the damage accumulation during the impact process.

With the extensive application of digital electronic detonator and hole-by-hole initiation technology in open pit mining，the stress wave interaction of adjacent double holes has become a research hotspot in the field of blasting technology. In this paper，a double-hole bench model with a proportion of 1/50 to typical full-scale bench is designed from granite，an experimental system of high-speed three-dimensional digital image correlation is established，and simultaneous initiation in double-hole bench model is studied based on full-field strain，high-speed photographic image and stress wave distribution characteristics. The preliminary experimental results show that the horizontal principal strain concentration area occurs prior to the vertical principal strain concentration area. The surface crack evolution process of the bench model is obtained based on the high-speed photographic images，and then a method to determine the initiation time and location of the horizontal crack is proposed. In order to investigate the influence of the out-of-plane movement of the bench surface on the deformation measurement，the analysis results of 3D-DIC and 2D-DIC are compared, and it is found that the maximum strain error at a single measuring point is about 3.6%. The charge affects the horizontal crack initiation time，the horizontal crack opening angle and the total number of cracks. Finally，the stress wave distribution of simultaneous initiation of double-hole bench model is analyzed.

As a common dynamic disaster of coal and rock，the prevention，monitoring and early warning of rockbursts are of great engineering significance. In order to improve the early warning ability of rockbursts in one working face，11 rockbursts occurred in the working face from May to August in 2018 were studied. Case study shows that，ten of the 11 rockbursts occurred in the roadway adjacent gob，that the rockbursts, affected by the static concentration stress generated by the superposition of the side pressure of the gob and the section coal pillar，occurred under the dynamic load disturbance caused by the large energy mine tremors，and that the microseismic(MS) energy and frequency can reflect the stress concentration degree and the dynamic load disturbance intensity and thus can be used for the monitoring and early warning of rockbursts. The evolution of the MS energy/frequency and their deviation values before and after the rockbursts was analyzed，and the time sequence law of MS precursors of rockbursts was obtained. It is shown that the MS energy and frequency before rockburst have obvious deviant trend characteristics with high deviation values，and the sum of the occurrence frequency of deviation high values of the MS energy and frequency in 7 days before a rockburst is at least two. A new quantity-trend rockburst risk early warning method based on daily MS maximum energy and the maximum occurrence frequency of deviation high values of the MS energy and frequency was then proposed. Specifically, the daily MS maximum energy is used for preliminary early warning，and then the final risk level is adjusted by the maximum of the occurrence frequency of deviation high values of the MS energy/frequency within 7 days. Comparative analysis of the early warning effectiveness between the new method and the original method used in the working face by R-score method shows that the R values by the two methods are respectively 0.673 and 0.072，which indicates that the new method is far superior to the original method. The new early warning method was applied to a mine in Xinjiang province and the R value reaches 0.652，which further verifies the effectiveness of the new method. The research results may provide some guidance for the monitoring and early warning of coal mine rockbursts.

The existing theoretical researches on the damage mechanisms of tunnel lining under high-speed train loads，which are generally based on the tensile and compressive characteristics of conventional concrete，seldom consider the tenacity and failure characteristics of fiber concrete，and very limited practice examples of fiber concrete applied to high speed railway are documented in literature. In this paper，a series of fiber concrete experiments with different fiber types，lengths，and volume ratios were conducted to obtain the tensile and compressive characteristics of fiber concrete，and the failure characteristics of different fiber concretes were observed by the DIC technology after the experiments. The concrete damage parameters were determined based upon the equal strain assumption and Najar¢s damage theory，and the effects of the type，length and volume ratio of fiber on the damage development of the tunnel lining under the excitation force caused by trains at different speeds were analyzed by utilizing the finite element method to simulate the rock mass and the tunnel structure. The results indicate that the fiber can effectively improve the damage resistance of concrete. Specifically，the fiber in concrete can alleviate the multi-step damage development under train excitation loads and greatly reduce the final damage of tunnel lining after train loading. When the volume ratio of the fiber with a shorter length is lower than 0.15%，the glass fiber achieves the greatest improvement in the damage resistance of concrete by 69.5% to 74.9%，followed by mixed fiber，and the improvement by the PVA fiber is only 42.6% to 48.8%. However，when the volume ratio is higher than 0.15%，the negative effect resulted from fiber clustering overweighs the positive effect caused by its bridging，resulting in a significant reduction in the peak strength of fiber concrete. The maximum reduction value of the PVA fiber is 94.3%，which makes the damage resistance of the fiber concrete inferior to that of the conventional concrete. In addition，it is observed that the performance enhancement in damage resistance of 6mm fiber is higher than that of 12 mm fiber. The train speed has a great influence on the final damage value of fiber concrete lining，and both the final damage value and the vertical peak displacement increase with increasing the train speed.

To improve the resilience of the rockfall protection system in remote mountain areas，a resilient steel canopy structure was proposed for rockfall protection in this paper. The correlation between system damping and resilience was analyzed，and a rockfall trajectory control model and an evaluation method of the impact force were established. Consequently，a mechanism model of the resilient steel canopy protection system was constructed. A full-scale impact test model composed of three units was conducted，and impact tests were carried out with impact energy of 150 and 500 kJ based on a large-scale impact test platform. The test data were collected by a high-speed camera and a dynamic data acquisition instrument，and the impact responses were analyzed. A dynamic nonlinear model was established，and the explicit dynamic analysis was carried out. The study shows that the impact response roughly experiences three stages such as large deflection with high tension，spring back and system recovery. According to the design method proposed in this paper，rocks¢ throwing out is controllable and the damage of the system can be reduced. The residual deflection of the net is 9.3%–16.8% of the initial deflection，which is significantly lower than the existing flexible protection system，showing very strong resilience. Compared to the analytical solution of the Hertz collision theory，the impact force is reduced by 99%. A calculation method for the impact force was proposed considering the influence of large deflection，and the errors are less than 6% compared with the test results.

In this paper，the distribution of dislocations on the fault plane is discussed，and a new type of dislocation distribution mode, taking into account the unevenness of the dislocations on the fault plane, is proposed based on the asperity model. This model is based on Somerville theory and empirical formulas to divide the distribution of asperity on the fault plane and to analyze the influence of fault dislocation on the co-seismic deformation. By solving the co-seismic deformation in the asperity dislocation distribution mode，the variation characteristics of the surface displacement field with the asperity position were obtained. Taking the Mw6.95 Loma Prieta earthquake in 1989 as an example，the calculation results of the asperity dislocation distribution mode were compared with the uniform distribution and the real distribution to verify the accuracy of the asperity distribution mode. Finally，the effect of dislocation distribution mode on the surface co-seismic deformation under different fault types is analyzed，which reveals the shortcomings of the uniform dislocation distribution mode. The research results can provide a guidance for the risk assessment of active faults.

The classical one-dimensional electro-osmosis consolidation theory cannot consider the attenuation of the effective potential，which exists objectively in the electro-osmotic process，and hence, overestimates the result of electro-osmosis. Aiming at this problem，theoretical and numerical studies are carried out. According to the idea of Riemann integral summation，the effective potential decay function is reduced to polymorphic form. Considering the uniformity of effective potential decay and pore pressure dissipation in the time dimension，one-dimensional electro-osmotic consolidation calculation under effective potential decay is transformed into iterative solution for a single state segment by inheritance of initial conditions. The governing equation is discretized by using the Crank-Nicolson form，and programming is implemented by using Python. The calculations under the three-segment numbers of 3，6，and 20 were carried out and compared with the classical theoretical results. The results show that the pore pressure amplitude considering the potential decay is significantly lower than that from the classical one-dimensional consolidation theory，and the developed method of polymorphic inheritance can effectively reflect the influence of the potential decay. The pore pressure curve will have a sudden change in amplitude at the segment points，while the mutation phenomenon gradually weakens gradually as the number of state segments increases. At the anode，the effect of the potential decay is most pronounced，and the reduction of the pore pressure is greatest. The method is clear and concise，and can provide good theoretical support for practical application of electro-osmotic drainage method.

In order to study the influence of power supply voltage，power-on time and drainage distance on the effect of electroosmotic composite foundation method improving soft soil，a model test rig was designed for electroosmotic composite foundation. According to the variable control，static loading test，direct shear test，and calculation between energy consumption and electroosmosis consolidation，the model test and corresponding parameter analysis were carried out for electroosmotic composite foundatiosn. The results show that，compared with the power-on time and the drainage distance，the voltage has the greatest impact on the drainage rate and the bearing capacity of the electroosmotic composite foundation，and that the electroosmotic energy consumption coefficient shows a significant increase trend as the power-on time exceeds 70 h and hence，it is recommended that the power-on time in the actual project should be controlled within 70 h. It is also shown that the increase of the voltage and the energization time will sharply increase the pile-soil interface resistance，which in turn reduces the effective potential，decreases the drainage rate and affects the increase of the electro-osmotic composite foundation.

In order to investigate the response spectrum characteristics of the dynamic soil pressure along the elevation and sliding surface of loess slopes under the action of earthquake，large-scale shaking table experiments were performed by progressively loading X-direction and Z-direction seismic waves until failure of the slope. The dynamic soil pressure curves of 5 sensors along the elevation and near the sliding surface were obtained，and the time-domain curve of the dynamic soil pressure was decomposed by using wavelet transform. The results show that，in the process of step loading through inputting EL-Centro wave，the response of the dynamic soil pressure at each measurement point is significant，and that the peak value of the dynamic soil pressure is increasing under the action of the inertial force while the dynamic soil pressure is decreasing along the elevation. The soil pressure is increasing from the foot to the inside of the slope along the sliding surface，The slope of the straight line between the measuring points S–1 and S–3 is greater than that between the measuring points S–3 and S–5，indicating that，in the loading process，the front of the landslide maintains compaction state while the S–5 point in the rear is more likely to be disturbed. The low-frequency seismic stress wave of the wavelet components of the first frequency band(0.1 to 6.26 Hz) and the second frequency band(6.26 to 12.51 Hz) has the most significant effect on the dynamic earth pressure，playing a leading role in the response of the earth pressure. The dynamic earth pressure curves under the first and second frequency bands of each channel are similar to the measured curves，while them are quite different from each other under the third and eighth frequency bands. The low-frequency wave plays a dominant role in the response to the soil pressure，and the loess slope has a "filtering effect" on the high-frequency part of the seismic wave moving along the elevation.

Loess has a loose structure and strong water sensitivity，and dry loess is easy to disintegrate and collapse when meeting water. The industrial by-product lignin is used as a modified material to effectively improve the water holding capacity and water stability of loess. Based on a series of soil-water characteristic tests and disintegration tests，the water holding capacity and water stability of lignin-modified loess were studied. Combined with the imagines obtained by scanning electron microscope tests，the microscopic mechanism of lignin improving water stability of loess was analyzed. The results show that the soil-water characteristic curves of the modified loess with a lignin content of 1%–2% are relatively smooth，and that，with increasing the matric suction，the volumetric water content loss is small and the water holding capacity is the strongest. Under different volumetric water contents，the matric suction of the modified loess increases first and then decreases with increasing the lignin content，and reaches the highest as the lignin content is equal to 1%，showing that the strength of the modified loess also increases first and then decreases. The water stability of the modified loess is not continuously enhanced with continuously increasing the lignin content，and the water stability of the modified loess with a lignin content of 1%–2% is the best. Based on these studies，the microscopic mechanism of lignin improving water holding capacity and water stability of loess，mainly represented by the effective filling of soil pores，cementing particles and hydrophobic repellence，was analyzed.