For a long period of time in the future，there will be a demand for the construction of a large number of tunnels in China?s water conservancy，hydropower，and road and railway industries. Large deformation of the surrounding rock mass is one of the most difficult disasters to control during the construction of tunnels. Focusing on the large deformation of surrounding rock masses of tunnel，this paper firstly systematically analyses the origin and evolution of the large deformation concept，and considers that the large deformation of surrounding rock masses should be defined from the effect of rock deformation and its engineering significance，and then identifies the occurrence conditions and mechanical mechanism through the classification process of large deformation. By systematically sorting out cases at home and abroad，as well as typical tunnel cases which were encountered with large deformation issue by the author's team，a total of 48 tunnel projects containing 241 tunnel sections were collected. Based on these materials，the factors and occurrence conditions of surrounding rock mass large deformation are discussed in detail，and eight generation mechanisms for large deformation based on the combined or individual effects of the occurrence environmental conditions(geo-stress，groundwater) and the surrounding rock mass conditions(lithology，water-rock interaction effect，rock mass structure) are clarified，thus revealing the essential causes for each generation mechanism. The idea of classifying surrounding rock mass large deformation based on the causes of deformation is proposed to classifying the large deformation into four types：squeezing type，expansive type，loosening type，and composite type. The characteristics of each type of large deformation and their differences are discussed. Then，for the squeezing type large deformation，the related domestic and foreign criteria are summarized and analyzed，and the threshold value based on the strength-stress ratio method，the stress criterion for large deformation considering the lateral pressure coefficient of geo-stress，and the improved prediction method for squeezing deformation are proposed. Finally，the proposed criteria and prediction method are applied to the identification and prediction of the squeezing deformation of surrounding rock mass in a tunnel section with large overburden depth of Xianglushan Tunnel of the Central Yunnan Water Diversion Project to verify the reliability of the proposed method.

Under the action of the periodic rise and fall of the reservoir water level，the jointed rock mass in the hydro-fluctuation belt of a bank slope has been in a state of soaking-air-drying cycle for a long time. In order to study the damage and deterioration characteristics of the jointed rock mass in the hydro-fluctuation belt，the typical jointed rock mass of a bank slope in the Three Gorges Reservoir area was selected as the research object. In this paper，a water-rock interaction test considering the water pressure fluctuation and soaking-air-drying cycle process is carried out，and the shear mechanical properties and the microstructure damage evolution law of the jointed rock mass are systematically analyzed. The results show that：(1) the shear strength of jointed rock mass under water-rock interaction shows a deterioration trend from steep to slow，which can be divided into three stages. Among them，the degradation range of the shear strength parameters of joint surface caused by the first six water-rock interaction cycles accounts for about 90% of the total degradation range，and the total degradation degree of the shear strength of joint surfaces is about 30% after 10 water-rock interaction cycles. (2) The microstructure damage of the joint surface is significantly deteriorated under water-rock interaction. It gradually changes from a dense state to a loose and porous state. The three morphological parameters of the joint surface，such as the average fluctuation angle，the average relative fluctuation amplitude and the area expansion rate，show a trend of first steep and then slow deterioration. Macroscopically，the roughness coefficient JRC of the joint surface and the strength of the rock wall are reduced，and the coincidence degree of the upper and lower walls of the joint surface is reduced，which leads to the gradual deterioration of the shear properties of jointed rock mass under water-rock interaction. (3) Based on the Clough-Duncan hyperbolic model，a shear constitutive model of jointed rock mass considering the damage of water-rock interaction is established. The verification analysis shows that the model can better reflect the deterioration law of shear mechanical properties of jointed rock mass under water-rock interaction. The relevant research methods and conclusions can provide a theoretical basis for the long-term deformation and stability analysis of reservoir bank slope.

To improve the early warning accuracy of rainfall-induced landslides，the Qinba Mountains region in southern Shaanxi province is taken as an example. At first，artificial neural network(ANN) and logistic regression model(LR) were used to establish the landslide susceptibility model，and the established susceptibility model was tested and corrected by frequency ratio model(FR) to express the spatial probability of landslide occurrence；Secondly，sensitivity analysis method was employed to select the optimal rainfall variables and the attenuation coefficient K，and then，two-dimensional Bayesian approach was be used to establish probabilistic threshold model，which can be used to calculate the temporal probability of landslide. The model was tested by the rainfall data from 2016 to 2020；Then，the spatial probability and temporal probability of rainfall-induced landslides were coupled base on Bayesian formula，and a probabilistic early warning model for rainfall-induced landslide(PLEWM) was proposed. To test the performance advantages of PLEWM，PLEWM and traditional early warning model were separately used to issue warning information day-by-day for the rainy season(July to September) from 2016 to 2020. It is proposed to use the investment of operating LEWM(Invest)，losses caused by landslides (Loss)，correct alert rate，missed alert rate and false alert rate as warning model performance indicators，to compare the performance differences between the PLEWM and traditional early warning model. The results show that：(1) EE-D is the optimal combination for rainfall threshold model in the study area，and the optimal attenuation coefficient K is 0.816. (2) Probabilistic threshold model predicts that 213.71 triggering rainfalls will occur from 2016 to 2020，and 201 actually recorded，with a cumulative error of 10.07%，the predicted triggering rainfall and the actual recorded in each probability intervals are distributed along a diagonal line with a slope of 1. (3) According to the statistics of the warning information issued in the rainy season from 2016 to 2020，The Invest and Loss of the PLEWM are 62.86% and 63.48% of traditional early warning model，respectively. The correct alert rate，missed alert rate and false alert rate are 63.99%，34.71% and 1.3% respectively，which are better than the traditional warning model；During the condition of long-lasting and high-intensity rainfall，the performance of PLEWM is significantly higher than traditional warning model.

The freezing of pore water is the root of frost heave damage of rock mass in cold regions. Studying the evolution law of unfrozen water content is of great significance to understand the freezing process of pore water and to reveal the damage mechanism of frozen rock mass. Taking intact and double fractured sandstone as the research object，the cyclic freeze-thaw tests were carried out at different freezing temperatures(－2 ℃，－5 ℃，－10 ℃，－15 ℃，－20 ℃)，and the changes of the unfrozen water content were detected by nuclear magnetic resonance(NMR) system. By analyzing the influence of freezing temperature，freeze-thaw times and cracks on unfrozen water，the relationship between the unfrozen water content and the sandstone meso damage is explored. The results show that：(1) The unfrozen water content of rock samples decreases exponentially with the decrease of the temperature. Under the action of the temperature gradient，the freezing rate of capillary water is the fastest，followed by free water，and the freezing rate of bound water is the slowest. (2) The unfrozen water content has a linear negative correlation with the number of freeze-thaw cycles. When the freezing temperature is lower than －20 ℃，the influence of the number of freeze-thaw on the unfrozen water content is weakened，but the existence of accelerates the freezing rate of free water in the early stage of freezing and thawing，and the freezing of combined water in the middle and late stages. Compared with the complete rock sample，the unfrozen water content of fractured rock sample is reduced by 5%. (3) The pore volume and permeability of rock are positively correlated with ice content. The freeze-thaw damage of fractured rock is mainly caused by the in-situ freezing of free water in the early stage of freeze-thaw，the continuous freezing of bound water in the later stage and the migration of capillary water. This study is helpful to understand the freeze-thaw characteristics of fractured rocks，and provides a theoretical basis for the safe construction and operation of rock mass engineering in cold regions.

The stability coefficient of the falling dangerous rock mass is controlled by the depth of the trailing edge crack，and the conventional static calculation method cannot track the dynamic change of the crack depth in real time. How to obtain the current stability coefficient of the dangerous rock in real time is still an urgent problem to be solved. The dynamic equation of a rock beam is established based on the modified Timoshenko beam theory，and the relationship between the bedrock and the dangerous rock mass is compared to the relationship between the Semi-infinite space foundation bed and the foundation. The dynamic constraint boundary of the bedrock to the dangerous rock mass was obtained based on the semi-space theory of the dynamic foundation. Combined with the constraint boundary conditions and the general solution of the dynamic equation，the analytical solution of the natural frequency of the dangerous rock mass is derived，and the quantitative relationship between the natural frequency and the fracture depth of the trailing edge of the dangerous rock mass is established. In order to verify the correctness of the algorithm，the theoretical calculation value is compared with the laboratory test value. The maximum error of the first-order natural frequency under different crack depths is 3.3%，which fully demonstrates the rationality and effectiveness of the natural frequency algorithm of dangerous rock mass. The algorithm is applied to Baoquan Pumped Storage Power Station，and the natural frequency of the dangerous rock mass is successfully obtained through the measurement of constant time fretting. After calculation，the fracture depth of the rear edge of the current dangerous rock mass is obtained，and the stability coefficient of the current dangerous rock mass is calculated. Practice has proved that the natural frequency of the dangerous rock mass is measurable，which provides a theoretical reference for the realization of automatic monitoring of collapse and has theoretical and market prospective.

To explore the characteristics of the infrared radiation response of coal bodies under the action of gas and stress，the self-developed experimental system for detecting the temperature change of gas-bearing coal rock rupture was used to analyze the mechanical properties and infrared radiation characteristics of coal samples from Pingcoal Mine 11th under different gas pressures，and to compare the time-varying characteristics of differential maximum radiation temperature ΔTMIR，cumulative differential temperature ΣΔTMIR and thermal image evolution under different gas pressures. The comparative analysis of the time-varying properties of differential maximum radiation temperature ΔTMIR，cumulative differential temperature ΣΔTMIR and thermal evolution at different gas pressures were carried out. The results show that，with the increase of the gas pressure，the damage pattern of the specimens changes from single-slope shear damage to shear-tension instability damage，and the damage development increases significantly. The peak compressive strength and the elastic modulus of the specimens decrease with the increase of the gas pressure，and the peak strain shows an increase and then a rapid decrease. The specimens show an overall warming trend at different gas pressures，with a warming precursor before rupture at low gas pressures(0–0.4 MPa) and a cooling precursor at high gas pressures(0.6 and 0.8 MPa). The low-temperature anomalous stripes and high-temperature anomalous regions appear during loading of the specimens and are consistent with the macroscopic crack orientation and location. The response mechanisms of infrared radiation from coal rocks under the influence of gas are revealed，including thermoelastic effect，frictional heat effect，gas expansion heat absorption effect，and adsorbed gas desorption heat absorption effect，with different degrees of influence of the thermal effect at different loading stages. The results of the study explain the causes of abnormal temperature variations of coal rock gas dynamic disasters and clarify the characteristics of infrared warning precursors under different gas pressures，which can be used for targeted disaster monitoring and warning according to the magnitude of gas pressure in mines.

Concrete shed slab is the main disaster-bearing project for rockfall prevention. In the existing theoreties，the contact model is elastic or elastic-plastic contact，and the shed slab is simplified as a beam or a thin plate element，which leads to underevaluate the impact resistance of shed slabs. Considering the damping characteristics in the contact process between the rockfall and the shed and combining viscoelastic contact theory and orthotropic plates，a mechanical model of rockfall impact shed slab is built up，and then the dynamic control equation of rockfall impacting on shed slab is obtained. According to the different initial conditions，such as the displacement，velocity and acceleration of rockfall，the corresponding theoretical solutions of the characteristic parameters about the impact process are obtained with the differential equation algorithm. In order to verify the correctness of the theoretical solutions，the impact processes of rockfall and shed slabs are simulated by the numerical method. It is shown that the linear elastic model can only approximately describe the rockfall impact process，while the theoretical solution based on the viscoelastic contact model with the initial condition combinations of velocity and acceleration is more similar with the numerical solution. The viscoelastic contact model can consider comprehensively the deformation of the shed slab and the energy loss of rockfall during the impact，which is closer to the actual. The sensitivity of rockfall parameters is analyzed，and the maximum impact force，the time of the maximum impact force and the impact duration of the rockfall are proportional to the rockfall mass. With increasing the rockfall mass，the rockfall impact parameters increase significantly，and the damage to the shed slab would be greater. The proposed theoretical solution in this paper is in good agreement with the experimental results，it provides the guidance for the actual shed protection design.

In order to solve the problem of low resource recovery rate of traditional double entry driving and tight replacement of gob-side entry driving，taking the 11502 working face of the first mining area of Lower group coal mine in Zhaizhen Coal Mine as the engineering test object，this paper innovatively put forward an arrangement method of double entry driving with a narrow coal pillar in the middle，and constructed a narrow coal pillar high-strength composite reinforcement support technology. By adopting comprehensive research methods such as theoretical analysis，experimental test combined with numerical simulation，the arrangement principle of double entry driving with a narrow coal pillar and a narrow coal pillar reinforcement support technology are deeply   researched and explored. The results show that the technology of double entry driving with a narrow coal pillar can realize the sequential succession of working faces and effectively improve the recovery rate in the mining area. The technology of narrow coal pillar composite reinforcement support is mainly based on advanced broken roof and relieved pressure，the improvement the bearing capacity of the narrow coal column side by anchor cable through coal pillar，and the high-strength composite reinforcement support of the concrete-filled steel tubular columns，which prevents the narrow coal pillars from prematurely entering a plastic state and then losing overall stability，and can effectively maintain long-term stability. Based on the combined structure theory of overburden rock，a coal pillar-roof structural mechanics model was established，the distribution law and magnitude of the abutment pressure above the coal pillar were studied，and a design method for the double entry driving with a narrow coal pillar reinforcement support was established. The numerical simulation proves that compared with the traditional gob-side entry driving，this technology can better control the deformation of surrounding rock of roadway，and the deformation of coal pillar body and roadway have been effectively reduced.  

At present，there are relatively few studies on the fracture depth and evolution process of multi-level failure of slopes. In order to solve such problems，the limit equilibrium theory of the cantilever beam is used on the basis of the existing failure boundary model to deduce the fracture depth of the multi-level failure boundary of slopes，a calculation model of the fracture depth of the multi-level failure boundary is established，and the reliability and applicability of the model are verified through large-scale centrifugal simulation tests and engineering examples. The results show that the evolution process of the multi-level failure boundary shown by the centrifugal simulation test is consistent with the proposed calculation model. According to calculation results by the proposed model，the fracture depth of the secondary failure boundary is 215.35 mm，and the fracture depth of the third-level failure boundary is 87.39 mm，which are consistent with the centrifuge test results. Calculation results of an anti-dip rock slope on the left bank of the Lancang River in Yunnan Province buy using the calculation model show that the fracture depth of the first-level failure boundary is 8.06 m and the third-level failure boundary is 2.34 m. The field measurements of the second-level and third-level failure boundaries are 6–10 m and 0.5–2 m respectively. The calculated results are consistent with the actual measuring values. The research results have theoretical guiding significance for the analysis of the stability and failure mechanism of the anti-dip layered rock slope.

This paper aims to establish a damage constitutive model that can accurately characterize the mechanical properties of the evolution process of microscopic crack propagation in rocks. Firstly，based on phenomenological theory，the rock mesostructure is generalized into three parts：complete rock micro-elements，crack propagation damage micro-elements and pores. Using the static equilibrium relationship between these three parts，a mesoscopic force model of fractured rock is constructed. Secondly，according to the crack propagation characteristics of rock，a bio-blocking growth model is proposed to characterize the crack propagation length. Based on the geometric damage theory，the quantitative relationship between crack growth length and damage is established，and the damage evolution equation of crack propagation of rock is established. Thirdly，the actual stress of crack propagation damage element is solved by fracture mechanics. Then，by introducing the damage variable of crack propagation and the actual stress of crack propagation damage microelement into the mesostatic equilibrium equation of rock，and considering the influence of nonlinear deformation in the compaction stage of soft rock，a damage constitutive model of rock considering the microscopic crack propagation evolution is established. Finally，a method determining the model parameters is proposed，and the influence of model parameters on the mechanical properties of the rock is discussed. The results show that the model can better characterize the stress-strain characteristics the crack propagation process of rock，which is in good agreement with the test results，and the physical meaning of the model parameters is clear.

In view of the limitations of borehole optical image information in reflecting the borehole contour characteristics，and at the same time，in order to enrich the source of borehole texture and geometric contour information，this paper proposes a 3D visualization method of geological boreholes based on photo-acoustic combination measurement，which visually presents the 3D morphological characteristics of the borehole wall by integrating the circumferential and axial texture images and scanning contour information of the borehole. The method can solve a series of problems，such as borehole wall optical image reconstruction，contour curve reconstruction，3D modeling and data visualization optimization based on the synchronous fusion of optical image information and acoustic scanning data. Firstly，based on the principle of optical image and sound scanning synchronous measurement technology，which can realize the borehole fine measurement，a method of borehole wall optical image and contour curve reconstruction is proposed，which can realize the stitching of borehole wall texture images at different depths and the modeling of borehole wall 3D contour. Then，based on the borehole wall surface texture and geometric contour，the mapping relationship and fusion mechanism between the photo-acoustic combined measurement data are established，and a 3D visualization system of geological boreholes based on photo-acoustic combined measurement is formed. Finally，combined with a specific case，the 3D visualization and morphological feature analysis of geological borehole are completed，and the feasibility and superiority of this method are verified. The research shows that the borehole data obtained by the combined measurement of optical image and sound scanning is more abundant，and the 3D visualization model of geological borehole can effectively improve the accuracy and objectivity interpretation of geological borehole wall data，which can provide a new idea and method for the fine detection and research of geological borehole rock mass structure.

Deformation measurement is the basis of rock mechanics theory research and engineering practice. Digital image correlation algorithm has been widely used in rock deformation measurement，but there are some problems in practical application，such as poor convergence of displacement cloud edge detection and few quantitative characterization parameters. Based on this，this paper introduces the target tracking method into the field of rock deformation measurement，and proposes a rock surface deformation measurement method based on target tracking algorithm. This method obtains the position of key feature points in the image through Harris corner detection，and then uses KLT algorithm to calculate the corresponding position of tracking points in the deformed image，so as to determine the whole field displacement of rock surface. In order to verify the reliability of the algorithm，indoor rock shear experiments are carried out，and the experimental results of target tracking algorithm and digital image correlation algorithm are compared and analyzed. The results show that the target tracking algorithm can realize the non-contact displacement measurement of rock surface，and the accuracy and stability are improved compared with the digital image correlation algorithm. The target tracking algorithm solves the problems of non convergence and poor stability of the digital image correlation algorithm in the calculation of deformation at the rock edge，and truly realizes the pickup of the whole field displacement within the calculable range. Using information entropy to quantitatively describe the evolution characteristics of rock deformation field in the process of failure is helpful to analyze the mechanical behavior of rock under various complex external loads more comprehensively and accurately. In this study，a new measurement method of rock surface deformation field is proposed，which not only provides an effective technical means for the visual study of rock surface deformation evolution law and damage characteristics，but also provides a certain reference for non-contact deformation measurement in the field of geotechnical engineering.

To investigate the transformed effect of nano-pores structure and its control on gas transport in coal under different pressures of CO2 phase transition fracturing(CO2-PTF)，the experiments of coal induced with CO2-PTF were carried out under the fracturing pressures of 120，150 and 185 MPa. The structure evolution characteristics of macro-pores(＞50 nm)，meso-pores(2–50 nm) and micro-pores(＜2 nm) were analyzed by the comprehensive measurements of high-pressure mercury injection，low-temperature liquid nitrogen adsorption and low-temperature CO2 adsorption. The results show that CO2-PTF has pore-enlarging effect for macro-pores and meso-pores. The average pore size and pore volume of macro-pores increase significantly，while the pore surface area decreases. The average pore size of meso-pores increases，while the pore surface area decreases obviously. The pore connectivity improves greatly. It is hard to transform the micro-pores with chemical properties by the declined fracturing pressure of CO2-PTF due to the fracturing pressure expanding preferentially from fractures and large-scale pores in the short duration. The pore enlarging effect of CO2-PTF for macro-pores and meso-pores enhanced with the fracturing pressure. The distribution of macro-pores，meso-pores and micro-pores is obvious differences in coals with different metamorphic and deformation degrees. Therefore，the research of “high fracturing pressure-long action duration - high energy” CO2-PTF device will contribute to further enhance the pore enlarging effect，improve the gas transport channel with nano-scale and promote the gas drainage efficiency. The research results provide a scientific basis for the optimization and improvement of CO2-PTF technology.

It is a crucial work in the research of landslide deformation status and hazard assessment to predict the displacement of step-type landslides. Generally，the research of step prediction is stationary fluctuation signal. The deformation rate decomposition method based on the step motion characteristics of landslide provides a new idea of step landslide signal decomposition in nonlinear deformation stage. Taking Gapa landslide as an example，the deformation rate data is obtained by signal differential and smoothing method of discrete wavelet transform(DWT). Based on the step motion characteristics of landslide，the deformation rate data is decomposed into small-scale fluctuation items determined by external inducers and large-scale trend items determined by internal control factors，in which the deformation rate trend signal is predicted by Inverse logistic function model(ILF) with added oscillation function. The deformation state of landslide is judged by curvature extreme value method. Deformation rate fluctuation term signals were predicted by constructing nonlinear mapping models using long short term memory LSTM，with rainfall and water level as evoked inputs，and the prediction results of trend term as control inputs. The prediction results show that the decomposition model based on the rate of deformation is more accurate than the traditional displacement fitting decomposition model for the non-linear process data of the Gapa Landslide，and its ability to map external factors is stronger. Therefore，deformation rate decomposition is an effective idea for prediction based on step motion mechanism，which solve the problem of step landslide prediction in nonlinear deformation stage.

Wire-ring nets，consisted of discrete wire bundles，are commonly used for flexible protection system in the field of rockfall disaster protection. The wire-ring nets? numerical models in existing research simplify the discrete wire-bundle section into a circular section with equivalent area，which can?t realize the equivalent tensile-bending stiffness of the ring section and is still difficult to accurately predict the failure of wire-ring nets. In this paper，a tensile-bending coordinated model was hereby established by introducing the tensile，bending stiffness correction factors and tensile-bending stiffness coordinated factor of the ring?s discrete wire-bundle section. The tensile tests of single rings and ring chains were carried out to determine the model parameters，and the failure mechanism of the wire-rings in contact area was revealed. The nets impact tests were further carried out，and the key indexes such as impact displacement，impact forces and ultimate bearing energy were analyzed，with relative error 3.0%，6.6% and 5.9% respectively. Compared to the existing area equivalent model，the ultimate capacity prediction accuracy of the new model can be increased by 20.4% in average. The tensile-bending coordinated model can predict the loading stiffness and failure accurately，which improves the design accuracy of flexible rockfall protection system.

The anchoring eccentricity of cable bolts is a common in geotechnical and underground support engineering，which has a certain adverse effect on the working performance of the anchoring system. Through theoretical analysis and laboratory experiments，the influence mechanism of the anchoring eccentricity problem was preliminarily explored，and the influence characteristics of the eccentricity on the anchorage performance of the cable bolt were clarified. Based on the self-developed pushing and limiting device of resin cartridges，the control method of the anchoring eccentricity problem of the cable bolt was effectively explored. The results show that the shear stress and displacement distribution at the interface of resin-surrounding rock are unbalanced when the cable bolt is anchored eccentrically. It is easy to cause the failure of the resin-surrounding rock interface area on the near side of the cable bolt because the shear stress and displacement bearing limit are reached，thereby weakening the bearing performance of the cable bolt anchoring system. The anchoring eccentricity degree is negatively correlated with the pull-out resistance of the cable bolt anchored specimen as a whole，and the anchoring eccentricity will have a more significant impact when it is severe. The pushing and limiting device of resin cartridges can provide effective restraint for the cable bolt during the stirring stage of the resin，so that the cable bolt can be kept approximately in the central area of the borehole，thereby ensuring that the cable bolt has a good centering effect after anchoring. The actual working effect of the device has been effectively verified by laboratory experiments. The research increases the understanding of the influence mechanism of the anchoring eccentricity problem of the cable bolt，and conducts innovative attempts to solve the problem，which is helpful to further ensure and improve the resin anchoring effect of the cable bolt.

For the purpose of rapid drainage of surrounding rock before excavation of water-rich loess tunnels，a method of electro-osmosis combined with vacuum is proposed，and the theoretical analysis and experimental research on the drainage consolidation process are carried out. Firstly，based on the theory of porous media and the principle of unsaturated soil mechanics，a mathematical model of mutual coupling of electric field，pore pressure field and displacement field under the combined action of electro-osmosis and vacuum is established. Then，the drainage consolidation law of soil under the combined action of electro-osmosis and vacuum is deeply analyzed by using the finite element method. Combined with the indoor model test，the application effect of this method in the rapid drainage of water rich loess is further analyzed. The results show that the combined action of electro-osmosis and vacuum can effectively improve the drainage efficiency of soil，but when the initial permeability is large，the phenomenon of “pore pressure reversal” will appear in the later stage of combined drainage，which will lead to the low drainage efficiency in the later stage of combined drainage，which explains that increasing the voltage in the later stage of combined drainage can not improve the drainage efficiency. The electrode spacing mainly has a great influence on the change of pore water pressure in the later stage of electro-osmosis combined with vacuum preloading drainage，and when the anode potential is constant，the pore water pressure does not change monotonically with the electrode spacing.

Experimental model is conducted to explore the deformation characteristics of shield tunnels when subjected to the ground surface surcharge. In this paper，the 3D printing technology is applied to manufacture the shield tunnel model. The 3D printed shield tunnel model veritably reflects the structural features of shield tunnel linings，which overcomes the difficulty of manufacturing elaborate shield tunnel models. The concentrated load test is first carried out to investigate the characteristics of the longitudinal equivalent bending stiffness efficiency of shield tunnel. The ground surface surcharge test is then conducted to study the stress and deformation characteristics of shield tunnel induced by the ground surface surcharge. The results from the experiment test show that the longitudinal equivalent bending stiffness efficiency is not a constant，but decreases with the increase of load. Its value varies from 0.176 to 0.044 in the test. It is observed that normal distribution curve is observed in the tunnel crown when subjected to the ground surface surcharge. The main settlement range is within the width of surcharge. Moreover，the distribution characteristics of the earth pressure on the tunnel crown has a similar pattern as the settlement of the tunnel crown. With the increase of surcharge，the induced earth pressure on the tunnel crow is greatest，followed by the tunnel invert and the induced earth pressure on the tunnel waist is smallest according to the measurement around the middle ring of the tunnel. The shield tunnel lining occurs “horizontal egg”-like convergence induced by the ground surface surcharge. It is found the displacement in the tunnel crown is largest，followed by the tunnel waist and the smallest displacement is observed in the tunnel invert. The experimental tests reveal the deformation characteristics of the shield tunnel and the interaction between the shield tunnel and the surrounding soil layers. It will provide valuable references for protection of existing tunnel when subjected to the sudden ground surface surcharge.

In order to explore the influence of interface form and filling state on the lateral friction resistance play coefficient of reef limestone-cast-in-place piles，the reef limestone in the area of China-Malaysia Friendship Bridge was used as the research object，and the reef limestone-concrete interface shear test was carried out with a large direct shear instrument to study the strength play mechanism of coral reef limestone-concrete interface in the intact rock state，and the lateral resistance play factor of coral reef limestone layer - cast-in-place pile in the fractured and more fractured rock state was studied in combination with the field self-balancing pile test. The results show that：(1) when the interface between reef limestone and concrete is not filled or filled with mud skin，the interface damage is sliding friction，and when concrete is poured directly with reef limestone，the interface damage is controlled by the internal defects of reef limestone；(2) When the reef limestone and the cast-in-place pile are not cemented，the shear strength of the saw tooth interface is higher than that of the straight pile interface，about 77%；(3) When the reef limestone is cemented with the cast-in-place pile，due to the diffusion and filling of the cement slurry，the reef limestone-concrete interface forms an interface reinforcement. The failure surface of reef limestone-concrete specimens is controlled by the internal defects of the reef limestone. The interface form does not significantly improve the shear strength of the interface；(4) Combined with the field self-balancing test pile test，it is determined that the coefficient of lateral friction resistance of the rock-socketed section of the rock-socketed pile in the reef limestone stratum with the broken rock of clear water pore-forming process is 0.053–0.108，which is more than 2 times higher than that of the land source rock. The above results demonstrate that the clear-water pore-forming cast-in-place pile can give full play to the bearing performance of reef limestone strata，and can provide reference for the design and construction of large-scale engineering infrastructure on islands and reefs.

To study the environmental effect with hot and rainy feature to the structural characteristics of granite residual soil under multiple dry-wet cycles，the triaxial consolidation undrained(CU)，computer tomography(CT)，nuclear magnetic resonance(NMR) and scanning electron microscope(SEM) tests were performed. Then，a multi-scale study from microscopic，mesoscopic，and macroscopic perspective about the damage mechanism of the soil. The test results show that the wetting-drying effect shows a change in particle and pore structure at microscopic scale，an expansion of fractures at mesoscopic scale，and a decrease in strength at macroscopic scale. The effective cohesion decreases exponentially with the increase of the wetting-drying cycles and the effective internal friction angle decays in a small range. The development process of meso-fractures can be divided into three phrases，which are the germination stage(0 to 1 cycle)，the development stage(2 to 5 cycles)，and the stable stage(5 to 8 cycles). The pore volume distribution curves of granite residual soil show a bimodal shape. The pores can be divided into four types according to pore size. With the increasing number of wetting-drying cycles，the volumetric proportion of microscopic pores decreased，while that of medium pores and large pores increased drastically. During the wetting-drying process，the clay particles gradually loose and the intergranular pores expand and connect to form connected cracks. Due to the wetting-drying effect，the hydrophilic clay minerals expand during a humidifying process，the microscopic tensile stress increases during a drying process，and the cemented materials decompose and lose. The three factors jointly drive the expansion and connectivity of fractures and cause fatigue damage to the soil structure，leading to the attenuation of mechanical properties of soil. This study provides a useful reference for the understanding of mechanical properties and structural damage rules of granite residual soil in hot and rainy climate.

The water content of silty clay stratum varies widely and greatly affects the mechanical properties. The water content of silty clay stratum has great influence on tunnel stability. Thus，based on Dayingpo tunnel of Yangliu-Xuanwei expressway，the influence of water content change on the stability of tunnels in silty clay stratum was studied. Firstly，the deformation characteristics and deformation mechanism of the unstable section of Dayingpo tunnel were analyzed. The mechanical parameters of silty clay with different water content were obtained by triaxial compression test. Secondly，based on the experimental data，the influence mechanism of silty clay water content change on tunnel stability was studied by numerical calculation method. Finally，the criterion for determining the instability of silty clay tunnel was proposed. The results show that：(1) the silty clay in this area has strong water sensitivity，and its mechanical properties deteriorate significantly with the increase of water content. When the water content reaches 40%，its shear strength and elastic modulus are only 10%–20% of that when water content is 15%. The increase of water content causes the overall settlement of the tunnel，and the maximum settlement of dayingpo tunnel is 76.7 cm. (2) According to the water content，the stability of silty clay tunnel can be divided into four stages：stable stage(15%–25%)，early warning stage(25%–27.5%)，alarm stage(27.5%–wcr) and unstable stage(＞wcr). (3) The increase of water content of surrounding earth in the arch foot area leads to insufficient foundation bearing capacity and insufficient support resistance，which is the main reason for overall subsidence，misplacement and serious intrusion of initial support.