Deep earth science is the basic of deep resource exploitation. One critical challenge is to ascertain the physical and mechanical behaviours of rocks from different depths under in situ geological conditions. Rock mechanical experiments and theoretical studies suitable for shallow resource mining are difficult to consider the effects of deep in situ geological conditions of different buried depths on the rock physical and mechanical characteristics and engineering. This paper puts forward the concept and research content of“deep in situ rock mechanics”. Using rock cores collected from 10 different depths(1 000 m to 6 400 m) of Songke second well，the different characteristics of rock mechanical behaviors at different buried depths are studied. An in situ stress restoration and reconstruction method is proposed to approximately simulate the influence of in situ geostress on rock physical and mechanical parameters. Uniaxial compression tests indicate that rock mechanical parameters increase nonlinearly with increasing the buried depth and hence，cannot be treated as constants. Triaxial compression experimental results manifest that rock mechanical parameters vary more obviously with the buried depth due to the geostress，which is different from those under uniaxial compression. Rock mechanical tests retaining the in situ geological condition suggest that the rock mechanical parameters can present more obvious nonlinear behaviors with increasing the buried depth in the case of geostress restoration and reconstruction. The peak strength and Young¢s modulus in the in situ stress restoration and reconstruction tests，showing a logarithmic function relationship with the buried depth，are larger than the results in the triaxial compression tests. Also，the post peak strain softening behavior in the in situ stress restoration and reconstruction tests is more obvious than that in the triaxial compression tests. Especially，when the burial depth exceeds 4 800 m，the influences of in situ stress restoration and reconstruction on Poisson¢s ratio，strain hardening modulus and post peak are more remarkable. This research can provide support for exploring deep scientific laws and improving deep resource acquisition capabilities.

The geological repository of nuclear waste is in a variety of complex environments for a long time，and the safe，stable and efficient construction and operation of the geological repository usually need to consider the long-term coupling effect of thermo-hydro-mechanical(T-H-M) fields. Based on the long-term mechanical properties of clay rocks under multi-field coupling，this paper first summarizes the long-term mechanical test results and shortcomings of clay rocks under the thermo-hydro-mechanical coupling condition at home and abroad，mainly including the influence of HM and THM coupling on the permeability properties of clay rocks，and TM and THM coupling long-term mechanical properties of clay rocks. In the second place，the influence mechanism of temperature on the micro structure characteristics of clay rocks is discussed starting from the micro phenomena. Based on the above understanding，the THM coupling creep mechanical model of clay rocks and its applicability are proposed. In the meantime，the research results of the authors' team on the long-term mechanical properties of THM coupling of clay rocks are introduced. It is pointed out that the long-term mechanical properties of Boom Clay are regulated by temperature，pore pressure，stress and anisotropy，etc. Finally，the future research directions of clay rocks THM coupling that should be focused on are discussed.

To establish brittleness index of sandstone at different buried depths，the uniaxial compression test was carried out on the rock samples from different depths in Buertai coal mine. According to the stress-strain curve characteristics of rock samples at different buried depths，an energy evolution model of the stress-strain curve at different buried depths was constructed based on the positive and negative correlation of stress and strain. Based on the energy release rate，the brittleness index of rock samples at different buried depths was established and verified theoretically. The results show that rock samples at different buried depths correspond to four types of curves. Types I and IV curves are located at the shallowest and deepest buried depths，101.6–203.2 m and 509.8–589.3 m respectively. Type II curve is distributed at various depths，and type III curve is mainly distributed at 406.4–589.3 m. Different curve shapes at different depths correspond to four energy evolution models. The total strain energy increases in a“S”shape，and the elastic energy evolution curve is similar to the stress-strain curve. The dissipation energy of types II and III curves increases step by step with increasing the strain，and the dissipation energy of type IV curve increases in a“L” shape with increasing the strain，in which both surface energy and released elastic energy alternate with plastic energy while the strain increases. The brittleness index increases with increasing the buried depth, showing a quadratic function relationship. The corresponding average values are 0.77，1.01，0.93，3.66，9.94 and 11.55 respectively. The maximum energy release rate and brittleness index of type IV curve with average values of 555.27 and 30.98 respectively are much higher than those of the other three curves. In addition，brittleness index partitions of sandstones from different buried depths are quite different. The sandstone layer is weak brittleness when the buried depths are 101.6 m and 317.3 m，medium brittleness for 203.24 m depth and strong brittleness at the buried depths of 406.42 m and 589.35 m.

The surrounding rock mass of underground engineering generally contains a large amount of irregular and multi-scale cracks or fissures，making seepage problems extremely complicated. Therefore，it is of great practical significance to study the seepage characteristics and flow distribution of fractured rock mass for the maintenance of engineering safety and the utilization of deep resources. In this paper，the online analysis and imaging system of NMR rock seepage process was used to carry out seepage tests on sandstone samples with different fracture characteristics，and the parameters such as volumetric moisture content，T2 spectrum and permeability coefficient in the seepage process were analyzed. The results show that the permeability of fractured samples is related to the angle and quantity of fractures，fracture initiation and propagation are affected by the seepage pressure，and the permeability coefficient of the samples presents a trend of slow growth and then stabilization. The permeability coefficient decreases with increasing the confining pressure，while the sensitivity of the permeability coefficient decreases when the confining pressure exceeds 10 MPa. The T2 spectrum indicates that the fluid diffuses through the micro pores and then accumulates in the main fractures，gradually forming a complete seepage channel. The formula for calculating the permeability coefficient derived from the cubic law can well reflect the test results，which provides a more safe and reliable method for calculating the permeability coefficient of fractured rock mass under low confining pressures in practical engineering. Finally，nuclear magnetic resonance imaging(MRI) was carried out for the seepage process to intuitively obtain the law of fluid distribution inside the fractured samples，which can accurately describe the flow state of fluids in the fractured rock samples and provide meaningful guidance for the seepage problems of fractured rock mass in practical engineering.

To simulate the rockburst process of deep high stress circular tunnel sidewalls under internal unloading conditions，100 mm×100 mm×100 mm cube specimens from red sandstone with moderate rock burst tendency were prepared，and rockburst simulation tests under the condition of loading first and then drilling unloading were conducted using TRW–3000 rock true triaxial electro-hydraulic servo mutagenesis test system to simulate the two-dimensional stress state of 500 m depth. Firstly，the specimens were loaded to the set initial stress state，and then a self-developed drilling unloading test device(25 mm hole diameter) was used for rock internal unloading. Subsequently，the loading was applied in the vertical direction until the failure of the hole wall，and the active unloading was applied after the simulation effect was achieved. The rockburst process of the hole sidewall was monitored and recorded using a micro-camera during the tests. In order to compare the effect of unloading，rockburst simulation test was carried out on the same size red sandstone specimens with a prefabricated hole (25 mm hole diameter). The test results show that the rockburst process can be reproduced under these two test conditions. The whole test process can be divided into calm，particle ejection and rock fragment exfoliation stages. Finally，V-shaped notches were found on both sidewalls. Compared with the first drilling and then loading test，the initial failure stress of the hole sidewall in the loading first and then holing test is lower and the hole sidewall is more likely to be damaged. The test results indicate that the internal unloading of high stress rock will cause damage to the surrounding rock in a certain extent and range，and induce obvious strength-weakening effect to the surrounding rock.

In order to study the inoculation law and acoustic emission characteristics of rock fracture process zones，straight-crack disc sandstone samples were used for the split loading test on the GCTS rock test system，the real-time monitoring was performed with the help of digital image correlation method(DICM) and acoustic emission(AE) instrument，and the lengths of sample fracture process zones were obtained according to the change of the horizontal displacement of measuring lines near crack tips and the AE event locations. The theoretical value of the fracture process zone length was determined based on the high-order term of Williams series expansion as well as the revised maximum tangential stress criterion，and the failure morphology of the specimens was discussed. The results show that the average values of the fracture process zone length determined by DICM and theoretical calculation are respectively 9.07 mm and 5.19 mm，and the difference between them is due to that the theory method fails to consider the influence of the microscopic characteristics of the rock and the loading method. The load corresponding to the maximal incubation degree in the fracture process is very closer to the plastic yield point load，about 92.19%–95.47% of the peak load. The inoculation and development process of the micro-cracks of the specimen crack tips during loading is reflected by the acoustic emission signals，and the length of the specimen fracture process zone determined by the acoustic emission positioning point has good consistency with DICM. The research work is helpful to understand in depth the inoculation law of rock fracture process zones.

Based on the GNSS monitoring data of Jiuxianping landslide in the Three Gorges Reservoir area from June 2016 to August 2018，comprehensive multi-factor dynamic process analysis and quantitative analysis are performed to analyze the response characteristics and the inducing mechanisms of landslide deformation under seven different changing processes of reservoir water level(RWL). The research results show that the falling of the RWL is the main inducing factor for the deformation of Jiuxianping landslide. In general，the greater the rate of the RWL decline，the worse the stability of the landslide. Landslide deformation can be promoted by intense rainfall including short-term heavy rainfall，continuous heavy rainfall and intermittent heavy rainfall during the falling period and the 145 m maintaining period of RWL，while it can hardly be promoted by any type of intense rainfall in the RWL rapid rising period(＞0.5 m/d). For inducing landslide deformation，heavy rainfall can compensate with the RWL decline rate. In other words，generally speaking，the greater the RWL decline rate，the smaller the threshold of the precipitation which could induce the landslide deformation. That is to say，for a reservoir wading landslide，the rainfall threshold is not fixed but varies greatly with the process of the RWL change. As the direction of the seepage pressure points into the inside of the slope during the RWL rising-falling transition period，neither of the intense rainfall nor the RWL falling rate can induce the landslide deformation for about a few days to more than ten days. During the period of high frequency and low amplitude fluctuations of the RWL，the direction of the total seepage pressure generally points into the inside of the slope，therefore，the apparent landslide deformation cannot be induced by the RWL decline in this period. These research results are meaningful for the deformation inducing mechanism analysis，dynamic risk management，emergency treatment，and early warning criteria of monitoring for the reservoir wading landslide.

Salt cavern is an ideal shielding rock for deep storage of oil，natural gas and high-level radioactive nuclear waste. Considering the combined influence of temperature and volume-stress in deep，a damage variable is proposed based on the Weibull distribution of random failure of meso-scale element. The Drucker-Prager criterion is used to describe the brittle failure in the linear deformation at meso-scale，and the generalized Hook's Law considering the plastic damage is introduced to describe the sample-scale damage. As a result，a static constitutive model under triaxial compression is effectively established. Furthermore，introducing both the static constitutive model and the nonlinear fractional viscosity dashpot into Burgers model，a fractional Burgers model with creep damage considering the temperature and the volume stress is effectively established. The results show that the new model，sensitive to the temperature and the volume stress，can well simulate the creep deformation in whole evolution，especially for the accelerated creep deformation.

The inverse grading of high-speed and long-runout landslide deposits and its forming mechanisms are hot research topics currently. To further explore these issues，a series of experiments and numerical simulations were conducted to investigate the grain size distribution of the deposits and the corresponding segregation process of granular flows with different fractal dimensions based on the fractal particle size distribution of the deposits. The results show that with increasing the fractal dimension and the enrichment of the fine particles，the segregation process in the granular flow is weakened，resulting in a lower degree of inverse grading in the deposits. For granular flows with different compositions，the leading and tailing edges are highly dispersed，while the main bodies are densely packed with limited dispersion of particles on the flow surface. The formation of the inverse grading in the deposits is attributed to various segregation mechanisms. Based on the analysis，the requirements for segregation cannot be fully satisfied in the emplacement of high-speed and long-runout landslides except for local segregation process.

Regarding Zheduoshan tunnel，a control engineering of Sichuan-Tibet railway，as the research object，a dynamic time history analysis model is established. Combined with the site ground motion design response spectrum，the near-fault pulse-type ground motions and far-field ground motions are selected for the incremental dynamic analysis of the seismic performance of the tunnel engineering structure. Then，a preliminary discussion of the seismic intensity index IM applicable to the tunnel structure is carried out，and the damage degree of the tunnel structure at different key locations is presented. Afterward，the seismic vulnerability probabilities of the tunnel structure under the actions of the near-fault pulse-type ground motions and the far-field ground motions are compared and analyzed，and the failure probability of the tunnel structure under the actions of the two ground motions at the three-level fortification level is further presented. The results show that PGA is a suitable IM index for the tunnel structure. The lining on the left and right side walls of the tunnel is vulnerable to earthquake damage，which can be regarded as the weak parts for the seismic design. Under the level of VIII-degree frequent earthquakes，there is a high probability that the tunnel structure will only be slightly damaged or even remain intact and undamaged，while there is a greater probability that the tunnel structure will be serious damage to life and safety under the level of VIII-degree rare and extremely rare earthquakes. Under the same intensity of ground motions，near-fault pulse-type ground motions are more likely to cause more serious damage to the tunnel structure and have stronger destructiveness. Therefore，In the seismic design of tunnels，the impact of the velocity pulse effect of near-fault ground motions on the seismic performance of tunnel structures cannot be ignored.

For mines or natural soil and rock slopes，most landslide forecast methods are based on the three-stage creep theory of slope deformation，and the prediction of the sliding time is carried out according to the displacement after the onset of the acceleration before sliding. In this paper，after analyzing the displacement continuously monitored by S-SAR slope radar，it is found that the sliding time predicted by using OOA as the starting point of the inverse velocity method has a lag to some extent. Based on the normal distribution characteristics of the deformation velocity random variable in the uniform deformation phase of the slope，a method for dynamic identification of the SP position using the confidence interval of normal distribution is proposed. By converting the S-t coordinate system to the T-t coordinate system，a T-lgt prediction model is established，which can effectively improve the accuracy of landslide prediction time by applying the displacement data after the SP in some case.

Counter-tilt rock slopes are a kind of rock slopes in the construction of large-scale water conservancy projects，highway(railway) projects and mine projects in China. In this paper，the whole process of deformation and failure of a rock slope with a set of joints orthogonal to the stratums is studied by means of the base friction model test. The slope deformation characteristics such as macro deformation，rock displacement，rock bending angle are analyzed to reveal the failure mechanism and the spatial force evolution law of the failure process，and the deformation zones of the counter-tilt rock slopes with layered cataclastic structure are divided. The test results show that the failure modes of the counter-tilt rock slopes with layered cataclastic structure include tensile-toppling，tensile-slip toppling and flexural tensile-(slip) toppling according to deformation and failure characterizes. The slope is divided into stable，(flexural-)tensile-toppling，compression cracking and (slippling-) toppling，and shear-slippling zones. When the slope angle or the dip angle is large，the shear-slipping zone does not exist. With increasing the slope angle，the failure of the slope body is gradually rapid，the first broken part transfers from the middle to the top of the slope，and the flexural characteristics of the rock stratums gradually decrease during the failure process；Models with a certain slope angle and a smaller dip angle are easier to deform and prone to slip along the fracture planes，while those with a larger slope angle or a larger dip angle are prone to tensile toppling failure. The deformation of the rock stratums in different parts of the slope are out-of-step，and the deformation rule conforms with the three-stage development of creep characteristics. The deformation rate is basically in horizontal orientation when the tensile deformation begins and then becomes apparent in vertical orientation after the topping failure happens，which can be taken as a judgment of the initial deformation stage. The maximum bending angle of the rock stratums which are dominated by tensile-toppling failure is obviously smaller，and the fracture planes are ladder-like. The maximum bending angle and the failure depth of the rock stratums dominated by flexural tensile-(slip) toppling are obviously larger，and the fracture planes are mostly straight line or irregular broken line.

In response to the problems of runway settlement monitoring and early warning during the construction of shield tunnels underneath airport runways，the force and deformation characteristics of the airport runway structure are analyzed based on mechanics method and，combined with the Peck settlement trough modified calculation formula and the first strength theory of material mechanics，a calculation method and the corresponding flow of the limit value of the soil settlement trough under the runway and the reference value of the vault control are put forward. The research shows that the stiffness of the airport concrete runway surface is quite different from that of the lower soil layers. The runway surface can be simplified as an elastic foundation beam to obtain the maximum values of the bending moment，the deflection and the shear force of the airport runway. Due to the greater stiffness of the runway surface，the method of modifying Peck formula based on the stiffness of the building is used to consider the influence of the runway surface stiffness on the Peck theoretical calculation formula. Combined with the first strength theory，the calculation method and flow of the reference value of the deformation control of the soil and the vault under the runway are proposed. Taking Xianxia West Road underpassing the Hongqiao Airport bypass slide project as an example，the limit of the soil settlement trough under the runway is 5.74 mm calculated by the proposed method，and the lower and upper limits of the tunnel vault settlement control benchmark are respectively 17.39 mm and 13.67 mm according to the relationship between the runway settlement and the vault settlement.

Scaling off is a common disease of earthen sites with dual structure characteristics in arid areas，and conventional infiltration methods are not ideal for scaling off reinforcement. Using electroosmosis as a reference，an electroosmosis equipment was developed and penetration and reinforcement tests of atmospheric dripping and electroosmosis grouting were carried out. It is found that electroosmosis grouting can uniformly penetrate the radius and expand the penetration depth. On this basis，electroosmosis grouting penetration tests with sodium silicate solution were carried out under different electrode layouts. Regular hexagon was selected as the optimal layout by analyzing the changes in current，grouting volume and energy consumption coefficient during the test. Then，the field reinforcement tests of electroosmosis grouting of three kinds of reinforcement solutions and the related property test of the reinforced soil were carried out with the optimal layout. It is shown that glutinous rice slurry and sodium silicate solution are not suitable for electroosmosis grouting reinforcement，while that，after electroosmosis grouting by SH solution，the bonding between the scaling off layers is tight，and the penetration resistance，hardness，wave speed，wind erosion resistance and disintegration resistance of the soil in the reinforced area are significantly improved compared with the unreinforced soil.

Assembled multi-step cantilever retaining wall is one of new types of light retaining structures suitable for high fill earthworks. In order to determine seismic responses of the wall­slope system，horizontally shaking table model tests of assembled three­step cantilever retaining walls supporting a fill slope were conducted with geometry，gravity and time similarity ratios of 1∶10，1∶1 and 1∶3.162 respectively. The results show that the acceleration of the wall-slope system has obviously nonlinear amplification effect upwards along the wall. Both static and dynamic earth pressures on the walls are generally distributed in a trimodal model. Except for the highest-step wall，there is reduction effect of the earth pressure at each wall top due to the shielding action of the nearby heel plates inserted in the filling soil. Distribution of the dynamic earth pressure is commonly multi-segment polyline. At the moment of the peak acceleration of input seismic waves，wall displacements are sharply rising and almost close to their permanent values. During the process of strong seismic action，deformation development of the wall-slope system can be divided into 3 stages including slight deformation of each wall under PGA≤0.4 g，visibly horizontal movement of the lowest-step wall under 0.4 g＜PGA＜1 g，as well as seriously high displacements of all walls under PGA≥1 g. Correspondingly，the failure mode of the wall-slope system can be classified as three types covering horizontally sliding failure of the lowest-step wall along its bottom，shear-tension failure of the filling soil behind the lower walls，together with overall slide failure of the wall-slope system. Based on the overall failure mode determined by the tests，stability analysis of the wall-slope system was carried out according to the pseudo-static approach. Analysis results of a practical example indicate that the factors of safety under various earthquakes by simplified Bishop method and transfer coefficient method are almost equal to each other and about 3%–13% higher than that obtained by Fellenius method. The difference is increasing with rising PGA.

The tortuosity effect of porous media has an important influence on penetration diffusion and grouting effect. A seepage equation of power-law fluid considering tortuosity effect of porous media was established，and the column penetration grouting mechanism was analyzed. Based on computer programming technologies，a three-dimensional numerical simulation program for column penetration grouting of power-law fluid considering tortuosity effect of porous media was developed by using secondary development with COMSOL multiphysics platform and Darcy¢s law，and numerical simulation of penetration grouting process of power-law cement grouts with different water-cement-ratios into gravel soils was carried out. Finally，comparisons among theoretical analysis，model experiments and numerical simulations were performed. Research results show that theoretical calculation values and numerical simulation values of the diffusion radius considering the tortuosity effect of porous media are closer to the model experiment values than those without considering the tortuosity effect，indicating that the developed equation better reflects column penetration grouting diffusion laws of power-law fluid into porous media. Research achievements can provide theoretical support and technical guidance for design and construction of practical grouting engineering in porous media stratums.

This study focuses on the three-dimensional effect and defect quantitative analysis method of large-diameter piles in low strain integrity test. A coupling vibration model of variable cross-section piles and surrounding layered soil was proposed. A frequency-domain analytical solution of the longitudinal vibration response at any position of the pile，considering the three-dimensional fluctuation of the pile body，was obtained by establishing a recurrence relationship between the layers，and a semi-analytical solution in time domain was deduced with inverse Fourier transform. Then the amplitude attenuation and travel time of the incident velocity wave along radial or longitudinal directions of the pile under different conditions were discussed. Finally，a field test was carried out to investigate the longitudinal vibration response at different positions of a concrete pile，and the rationality of the analytical solutions was verified. The results show that the three-dimensional effect of a large-diameter pile in low strain integrity test is significant and the influence depth is related to the action area and duration of the excitation force on the pile top. The longitudinal attenuation characteristics of the velocity wave can well reflect the integrity of the pile body and the surrounding soil resistance. The research work provides a new method for testing the integrity of piles and has certain engineering application value.