Taking a typical deep soft rock roadway of Xinhu coal mine as the engineering background，the bearing structure of the surrounding rock is divided into fluid，plastic softening，plastic hardening and elastic layers according to the variations of stress and strength of the surrounding rock，and the plastic softening and hardening layers form a plastic bearing zone. A dynamic reinforcement support scheme is proposed which includes the first support of anchor net spray and the second reinforcement of shallow and deep hole grouting jointed bolts and cables，and a mechanical model of the layer-double arch bearing structure is proposed in combination with the characteristics of the support scheme. Under the limit equilibrium condition，the forces acting at the layer-double arch bearing structure are analyzed and a formula for calculating the ultimate bearing strength is obtained. The engineering calculation shows that the ultimate bearing capacity of the air returning cross-cut of Xinhu coal mine reaches 29.30 MPa after the surrounding rock is reinforced by the proposed support scheme and that the support scheme is reliable. The on-site monitoring results show that，after the dynamic reinforcement support，the surrounding rock deformation of the roadway tends to be stable with only 36 mm of the subsidence of the roadway roof and 67 mm of the displacement of roadway's two side walls，and that the roadway can maintain long-term stability.

Deformation memory effect(DME)，as one of basic properties of rocks，has time features. The influence of the loading time(Tc) on DME is one of time effects. Sandstone and two kinds of granite materials were selected to carry out physical experiments under different Tc. The accuracy of memory formation and the magnitude of strain difference were analyzed. Based on the viscoelastic frictional sliding theory of multi-microstructural planes in rocks，a basic memory theoretical model was constructed by using three elements of rocks，and the DME mechanical theory under different Tc was studied. The results show that，with increasing Tc，the accuracy of memory formation of granite and sandstone is obviously improved and the amplitude of strain difference decreases gradually，and that both the accuracy of memory and the amplitude of strain difference tend to remain unchanged when Tc increases to a certain extent. It is put forward that Tc is the optimum creep time when the amplitude of strain difference keeps stable. The variations of the memory formation accuracy and the strain difference amplitude obtained from the proposed theoretical model are consistent with physical experiment results，which means the proposed model based on multi-microstructural planes can describe the macroscopic behaviors of rock DME under different Tc. The research provides an experimental and theoretical basis for the study of rock DME.

The engineering properties of semi-diagenetic rock are poor，especially for the mechanical properties which are greatly affected by the water content. Taking the semi-diagenetic rock of the Xigeda formation as the research object，the deformation characteristics and failure mechanisms of semi-diagenetic rocks are studied by triaxial tests in laboratory，and a damage constitutive model reflecting the total stress-strain process of semi-diagenetic rocks is established by introducing the damage theory. The results show that，with increasing the confining pressure，the peak and residual strengths of semi-diagenetic rocks increase，and the axial strain corresponding to the peak strength and the fluctuation of the stress-strain curve in the softened stage increase. With increasing the water content(from 17.79% to 30.83%)，however，the peak strength of semi-diagenetic rocks decreases rapidly，the residual strength decreases in a less range，and the axial strain corresponding to the peak strength increases. When the water content is low，the peak point is sharp and the post-peak stress falls rapidly to the residual strength，which shows softening characteristics. When the water content is high，the peak point collapses and the slope of the stress curve after the peak is slower，showing a trend from strain softening to strain hardening similar to soils. The peak and residual strengths obey Mohr-Coulomb criteria in the range of experimental water content，and all strength indexes decrease approximately linearly with increasing the water content with a more sensitivity of the peak cohesion and the peak friction angle to the water content than that of the residual cohesion and the residual friction angle. It is also indicated that the developed model with a simple form and less parameters can well describe the strength and deformation variations of semi-diagenetic rocks affected by the water content and the model curve is consistent with the experimental results. The research results can provide experimental basis and mechanism understanding for the analysis of mechanical properties and engineering application of semi-diagenetic rocks.

The local averaging value of the random field of soil strength parameters on the slope slip surface is the main factor that controls the reliability of a slope. Based on the theory of random field，a formula of the local averaging variance is derived by one-dimensional local averaging of two-dimensional random field on the arc curve，and then，a simple reliability analysis method for homogeneous undisturbed slopes is proposed. The method first estimates the limit state curve through a few deterministic finite element analysis，then calculates the statistical index of the slope strength parameters by the one-dimensional local average variance formula，and finally obtains the probability of slope instability by integrating the area of the distribution function of the strength parameters on the dangerous side of the limit state curve. Comparison between the developed method and Monte Carlo stochastic finite element method shows that the proposed method is reliable and can provide a new idea for slope reliability analysis.

To illuminate the long-time failure mechanisms for in-seam boreholes influenced by mining disturbances，the model experiment tests under a cyclic vertical stress were carried out by employing a independently-developed bi-direction loading device. Results show that the shrinkage of the borehole has obvious time effect at the constant stress stage and increases at the boost stress stage，which can be described well by the introduced borehole shrinkage model. Cycle loading makes the borehole shrink but the shrinkage rate decreases with increasing the cycle number. At the initial stage after drilling，the surrounding rock damages intensely with tiny fractures accompanied by no obvious cracks on the hole wall，which mainly causes borehole shrinkage. At the constant stress stage at the first cycle，the damage of the surrounding rock continues and tends to be stable，and the damage on the hole wall is enhanced. At the boost stress stage，the damage on the hole wall increases further and the damage range is enlarged，which raises the possibility of rock peeling from the hole wall. Meanwhile，the influence of stress boosting to the damage of the surrounding rock decreases with increasing the cycle number of loading. After repeatedly loading cycles，the damage of the surrounding rock accumulates and fractures propagate and link，inducing serious instability of the hole.

Rainfall-induced landslides are the most frequent and catastrophic geological disasters，while the accurately early warning of precipitate landslides in response to intense rainfall is still challenging. Understanding the rainfall-induced mechanism of landslides is the prerequisite for the early warning. In the study，a typical post-earthquake landslide in Dujiangyan County was selected as a real-time monitoring site，and the stability and failure mechanism of the slope were investigated in a long period by combining the real-time monitoring data of five hydrological years and hydro-mechanical coupling theory. A landslide warning model with multi-parameter thresholds including rainfall intensity-probability threshold(I-P)，saturation，matric suction，inclination and slope stability，was proposed based on the unsaturated slope stability calculation and the long-term monitoring data analysis. The proposed method was successfully implemented in early warning at Yindongzi gulley in Aug. 2017 and Jun. 2018 and proved reliable and practicable. The research provides a reference for early warning of rainfall-induced landslides.

The thermal damage capacity for granite is different under different cooling modes，and the microfracture degree and macroscopic mechanical properties are also different. Comparative tests of the uniaxial compressive strength and surface cooling law of granite were carried out under two cooling modes of natural cooling in 20 ℃ air and cooling in thermostatic water of 20 ℃，and a heat transfer numerical simulation method under different cooling medium environments was established by introducing a thermal shock factor which can describe the damage ability of heat to rocks. Strength degradation mechanisms of granite with different cooling media were discussed from the perspective of heat transfer，and quantitative classification of thermal damage capacity is made according to the thermal shock factor. The results show that，due to that the heat transfer coefficient of thermal shock sharp cooling mode is much higher than that of natural cooling，the values of the thermal shock factor and the dynamic thermal stress under the former mode are larger than those under the later mode，which results in more serious cracking，larger density of cracks and worse deterioration of the mechanical strength of the specimen. In the thermal shock cooling mode in constant temperature water of 20 ℃，the compressive strength of granite is only 85%–90% of that in the natural cooling mode in 20 ℃ air. For different cooling modes，the evolution process and law of temperature gradient，thermal shock factor and dynamic thermal stress formed inside the granite specimen are consistent，and the maximum values always occur near the surface of the specimen. The thermal shock factor can well characterize the thermal damage ability，and the uniaxial compressive strength of granite has a good correlation with the maximum thermal shock factor. According to the evolution law of the thermal shock factor，the specific time of the most serious internal fracture of granite specimens can be determined，and the thermal shock factor can realize the quantitative classification of thermal damage capacity.

The mechanical parameters and structural characteristics of rock masses are the basis of stability analysis of underground engineering，and real-time obtaining surrounding rock parameters are very important for support design. Complex geological conditions such as high stress and extremely soft rock，resulting in loose and broken surrounding rock，are often encountered during underground engineering construction，and bolt-grouting support is an effective method to control the fractured surrounding rock. The mechanical property of the surrounding rock before and after grouting is the basis for the design of bolt-grouting parameters. The digital drilling test technique provides a new way to real-time obtain the surrounding rock parameters and to quantitatively evaluate the bolt-grouting effect. Based on the previous drilling theory of rock mechanics，the development of multi-function true triaxial rock drilling test system(indoor TRD system) and a large number of indoor tests，an intrinsically safe surrounding rock digital drilling test system of underground engineering(Site SDT system) is developed，and digital drilling tests on layered rock masses composed of different combinations of intact，fractured and grouted rock layers are conducted based on site SDT system. The test results show that the site SDT system has an excellent controlling and monitoring performance and highly matches with the indoor TRD system. The response of the drilling parameters at rock layer interfaces is obvious，and the average values of difference value ratios of equivalent uniaxial compressive strength，cohesion and internal friction angle obtained from site SDT system test and indoor rock mechanics test are less than 15%. The equivalent uniaxial compressive strength of fractured rock stratum after grouting is 3.5 times of that before grouting obtained by site SDT system test. Site SDT system can accurately identify rock layer interfaces，test equivalent rock mechanical parameters in real time and quantitatively evaluate the grouting effect of fractured rock masses.

In order to study the influence of water saturation on the strength parameters，deformation characteristics and energy evolution of Badong formation mudstone as well as the internal relation among the mechanical properties，energy evolution and microcrack development，uniaxial compression tests of mudstone under natural and saturated states are carried out，and the characteristic strength is determined by strain curve method. Through the quantitative comparative analysis of the deterioration law of the characteristic strength and the numerical difference of energy parameters as well as in-depth exploration of energy transformation characteristics in the process of water-rock interaction，the energy explanation of mudstone saturation softening mechanism is given. It is found that the effect of saturation on the mechanical properties of mudstone is manifested by reduction of the characteristic strength，weakening of the brittle deformation，enhancement of the plastic deformation and difference among deformation stages. Meanwhile，the influence of saturation on the energy evolution presents weakening of energy absorption and release properties，enhancement of energy dissipation properties and different energy distribution rules of each stage after saturation. On the basis of the experimental data，the numerical compression tests under the same water conditions are performed by means of particle flow code software，and the interaction between the development characteristics of micro-cracks and energy evolution of samples is analyzed to reveal the micro-mechanism of mudstone energy evolution. The results show that the particle flow theory is superior in explaining the damage mechanism of rocks from the perspective of meso-mechanics and provides a new means for the micro-study of rock heterogeneity.

Currently，the continuous upheaval deformation of high-speed railway subgrade during operation period in the region of red-bed soft rock mass has become a key factor to hinder the development of high-speed railways in China. In order to reveal time-dependent upheaval mechanisms of red-bed rock subgrade，and taking the typical upheaval of a deep cut red-bed soft rock subgrade in Southwest China as the research object，the in-situ engineering geology and hydrogeology conditions and the crustal stresses were surveyed，and the swelling and creep tests of red-bed soft rock mass under different hydraulic conditions were conducted. A layered deformation model of red-bed rock subgrade was built based on the time-dependent swelling and hydro-mechanical coupling characteristics，and the upheaval deformation mechanism and characteristics of the subgrade in short，medium and long terms were systematically analyzed. The results show that the red-bed mudstone inter-bedded with thin sandstone in the upheaval subgrade presents sub-horizontal，that the excavation normal unloading leads to the relaxation of micro-cracks in the shallow rock mass while the deep rock mass keeps intact，and that the horizontal stress of the subgrade increases obviously，resulting in significant structure effect of the subgrade deformation. Under the condition of lateral constraint and axial unconstraint，the time-dependent water-absorption deformation of the red-bed mudstone is related to its lithology and structural characteristics. It is also shown that the red-bed mudstone presents a three-phase creep characteristic under low stress condition and the creep strain ratio increases with decreasing the axial stress. Under the hydro-mechanical coupling condition，the creep property of the red-bed mudstone is more significant，and both the creep upheaval strain and the duration time increase more obviously for large unloading. The creep time lasts longer while the total creep strain decreases under the moisture-mechanical coupling condition. Based on the deformation mechanisms of different layered rock masses，the red-bed soft rock subgrade is divided into atmospheric influence layer(C1)，moisture-mechanical coupling deformation layer(C2)，hydro-mechanical coupling deformation layer(C3) and hydro-mechanical coupling confining layer(C4). The short-term，medium-term and long-term deformations of the subgrade are mainly contributed by C1，C3 and C4，and C2 respectively. The results can provide theoretical foundation and reference for risk assessment and forecast and the design of engineering control measures of time-dependent upheaval deformation of high-speed railway subgrade in the region of red-bed soft rock mass.

A mechanical model of space-time evolution of strata behaviors in compact filling is established and analyzed. Similar material simulation method is used to study the space-time evolution law of strata behaviors in stope under filling mining conditions，and the filling practice of a mine in Xingtai is illustrated as an engineering example. The results show that，during the active period of roof subsidence，the force acting at the filling body is positively correlated with the filling step and the advancing time. In the physical simulation of backfill mining，the stress of roof measuring points generally experiences a process of stress rising，rapid pressure relief，slow pressure rise and stabilization，and the peak stress of the roof in front of the working face and the force of the coal pillar increase with increasing the filling step. During advancing of the working face，the force of filling body increases continually and finally tends to be stable，and the roof stress and the force of the filling body after stabilization are less than the original rock stress. In the static stage after stopping mining，the roof of the filling area still subsides slowly with time. The measured results of the mine show that the pressures of the filling 15 and 40 m from the cut-hole are respectively 3.5 and 5.5 MPa and that the roof subsidence and overburden separation show regular changes with increasing the filling distance and the advance of the filling time.

The prediction of rockbursts during the construction of underground caverns is of great significance to ensure the safety of construction workers and to arrange the construction progress rationally. In this paper，a rockburst prediction method combining rock mass structure analysis and electromagnetic emission monitoring is proposed. In the process of implementation，the possibility of rockburst is preliminarily judged by the observation of the excavation face and its nearby rock mass structure，the potential rockburst area is then monitored by using portable electromagnetic emission meter，and finally the possibility and intensity of rockburst can be further predicted based on the changes of the electromagnetic emission energy and pulse. The developed method，comprehensively considering the rock mass structure conditions of rockburst occurrence as well as the energy conversion and rock micro-fracture frequency during the process of rockburst，is easy to be mastered and applied by field technicians，and has proved to feasible for rockburst prediction during the construction of underground caverns. Taking the Central Asia's longest tunnel—Uzbekistan Kamchik tunnel as an example，the rockburst prediction method，including rock mass structural conditions of rockburst，key monitoring positions and method of electromagnetic emission，the electromagnetic emission interpretation indexes and reference value of rockburst，is systematically introduced.

In order to systematically study the unloading deformation mechanisms of soft base waste dumps，taking the waste dump with a silty clay base of Dagushan Iron Mine as the research background，the deformation and failure processes of the waste dump under natural(hard base) and saturated(soft base) conditions are compared，and the displacement distribution and evolution law of the waste dump are acquired by speckle analysis and point tracking. The test results indicate that the stability of the soft base waste dump is obviously worse than that of the hard base waste dump. The deformation failure of the hard base waste dump shows a collapse-traction-push pattern，developing from the low-grade slope towards the high-grade slope，while due to the uneven unloading settlement between the front and back parts of the waste dump，the deformation failure of the soft base waste dump mainly controlled by the soft base presents a cycle of subsidence，breakage and slip until the failure of the whole slope above the soft base. Tension cracks in the hard base waste dump are caused by the uneven horizontal deformation while dislocation cracks in the soft base waste dump results from the uneven unloading settlement. It is suggested that dynamic consolidation and borehole grouting methods should be adopted to reinforce the soft base of the waste dump and，at the same time，a perfect drainage system should be built to reduce the softening of the base soil. The research results can provide reference for the research and treatment of unloading deformation of soft base dumps.

A small-scale vertical cyclic loading system for model tests of pile foundations，consisting of a loading system，a pressure chamber，a lifting device，model piles and a data acquisition system，is introduced. The model pile top is vertically loaded through a rotating roller screw driven by a coupler which is controlled by a servo motor，and soils samples are exerted with the confining pressure by hydraulic loading in order to simulate the in suit stress and consolidation of soil layers at different depths. The small-scale vertical cyclic loading system can be applied to carry out model tests of different pile foundations under vertical cycle loading in saturated soft soil，general clay，silty soil，sandy soil and other homogeneous or heterogeneous soils. Model tests of single pile under vertical cyclic loading are carried out and numerical simulation is performed for verification. Results show that the dynamic load amplitude and the consolidation pressure have great influence on the bearing capacity of the pile foundation. When the dynamic load amplitude is small，the bearing capacity of the pile foundation hardly weakens. When the consolidation pressure of the foundation soil increases，the bearing capacity of the pile foundation will be significantly enhanced，and the weakening will slow down. With increasing the cycle number and the amplitude，the axial force of the pile top gradually weakens to the residual value. During the cyclic loading，the degradation of the soil around the pile leads to a negative friction resistance of the pile foundation，and the bearing capacity of the pile foundation is weakened significantly. The test results are in good agreement with those obtained by the numerical simulation. Preliminary application proves that the test system can make up for the deficiency of low confining pressure in conventional 1 g small scale model test and that the nonlinear relationship between the load and the displacement of the pile top and that the cyclic degradation of the bearing capacity can be well reflected. This test system can output accurate load waveform，has high sensitivity and good stability in measurement and can be used to study the vertical cyclic loading characteristics of pile foundations under multiple working conditions.

To study the effective thermal conductivity(ETC) of composite-porous granular geomaterials，an improved mesoscopic cylindrical unit cell containing three phases of solid，liquid and gas，was established based on particle geometric characteristics. The relationship between ETC of the unit cell and the thermal conductivity of each component as well as structure parameters such as porosity and degree of saturation was then obtained by using thermal-electrical analogy lumped parameter method. Taking the saturation degree as a linkage，an unified evolution conceptual model of soil-water-thermal conductivity characteristic curve(SWTCC) was further proposed via analogy analysis on soil-water characteristic curve(SWCC). The results demonstrate that the developed predicting model of ETC based on multi-scale homogenization theory not only has clear physical meaning without any empirical constant but also appears significant improvement in the coincidence degree with sandy soil experimental test results. The average ratio of the experimental value to the theoretical value decreases from 1.58 to 1.27 and can be further controlled within 1.03–1.16 through linear correction. It is also illustrated that ETC is affected by the distribution pattern and physical mechanism of pore water in geomaterials，and the shift evolution of proposed conceptual model of SWTCC can effectively explain the ETC increases in a concave and convex trend(sigmoid function) with increasing the saturation for geomaterimals with different fines contents or cementation degrees，indicating that this conceptual model is a valid tool to unify most of ETC prediction models for different geomaterials.

In order to explore the influence of the thickness ratio of weak interlayer on uniaxial compression parameters and failure modes of cement soil samples，cement soil samples with a single interlayer of different thickness ratios were prepared by using the sample preparation method of single interlayer salt rock，and uniaxial compression tests at room temperature and frozen state were carried out. The uniaxial compression of cemented soil was simulated by PFC2D，and the micromechanical response mechanism of the specimen after loading was analyzed. An uniaxial compression damage constitutive model of cement soil under the coupling of weak interlayer and load was established，and the influence of the thickness ratio of the weak interlayer on the evolution of damage variables was investigated. The results show that the uniaxial compressive strength and elastic modulus of cement soil samples decrease negatively exponentially with increasing the thickness ratio of the weak interlayer at room temperature or frozen state，and that the failure strain changes parabolically with enhancing the thickness ratio of the weak interlayer. The uniaxial compression mechanical parameters and failure modes of the cement soil samples with different weak interlayer thickness ratios obtained by PFC2D simulation are in good agreement with the results of laboratory tests. Both numerical simulations and laboratory tests show that the thickness of the weak interlayer has a great influence on the failure mode of the sample. The developed damage constitutive model of weak interlayer and load coupling can well describe the stress-strain relationship of cement soil samples with a weak interlayer under uniaxial compression load at room temperature or freezing state. The weak interlayer makes the damage degree of the specimens obviously different in the process of deformation. The larger the thickness ratio of the weak interlayer is，the larger the total damage variable of the sample will be when the axial strain is small，and more quickly the sample breaks.

To investigate the horizontal dynamic response of defective large-diameter piles embedded in layered saturated soils，a horizontal coupling dynamic simplified model of the defective large-diameter pile-saturated soil is established based on Biot's theory and strict plane strain assumptions. The potential function，operator decomposition method and variable separation method are introduced herein to obtain the horizontal force of the soil acting on the pile shaft，and then，the complex impedance of the pile top is derived by employing the coupling condition of the pile-soil contact interface and the stiffness matrix transfer method. The reliability of the obtained solution is verified by model comparison and degradation comparison. The results show that the enlarging segments of the pile contribute little to the increase of the complex impedance while the necking defects can significantly decrease the complex impedance. The dynamic stiffness of the pile top is more sensitive to the radius and length of the defect than the dynamic damping，and the necking defects near the pile head can more seriously reduce the complex impedance in comparison with those in the middle of the pile shaft or near the pile tip.

As a special material of bank soil composition，riparian plant roots play an important role in adjusting mechanical properties of soils. In-situ tensile tests of two types of vegetation community root-soil composites were carried out by the hollowing method at three sites at the river bank of the source region of the Yellow River covered by alpine meadow，and the reinforcement effect of the root system of meadow vegetation on the tensile strength of soils of the river bank was analyzed. The collapse width of the meadow-covered bank is 0.52–0.70 m and obviously larger than that of the cohesive soil bank，and the collapse width of the native meadow bank is higher than that of the moderately degraded meadow bank. The average single root tensile strength of Blysmus sinocompressus，a dominant species of native alpine meadow，is 31.67 MPa，which is 15.52 MPa higher than that of the moderately degraded meadow dominant species Elymus nutans. The root area ratio of the former is about 2–3 times higher than that of the later. It is shown that the root system of riparian meadow has an inhibition effect on bank collapse process. The tensile strengths of vegetation root-soil composites in the three sites calculated by the critical equilibrium formula of bank collapse are 66.86，21.29 and 22.63 kPa，respectively. It is also indicated that the tensile strength of a single root and the root area ratio have a positive effect on enhancing the tensile strength of the soil-root composite. The tensile strength of the soil-root composite obtained by the critical equilibrium formula is in good agreement with that by Wu-Waldron root system model with a correction coefficient and the relative error is between 2.12%–9.21%. This test method is of importance to the in-situ measurement of the soil-root composite at riparian banks and provides field data for the theoretical study on bank collapse mechanisms in this region.