In order to study the global stability of underground storages and the laws of failure and damage，a method for stability analysis of underground energy storage group was developed based on the deformation stability theory. The relation curve of plastic complementary energy versus strength reduction factor served as the global stability and failure criterion of underground storage group，while the unbalanced force was used to indicate the location and pattern of failure. With the yield function as control variable of damage，an analytical method for salt rock was established and applied to study of the relation between the unbalanced force and displacement. The critical cavern spacing，failure patterns and buried-depth of double caverns were presented. Meanwhile，the effect of rock damage around a single cavern on the unbalanced force was studied. The results show that the unbalanced force and plastic complementary energy are suitable for quantitatively evaluating the stability of underground storage group；and the damage analysis based on the yield function provides a new approach to investigate the mechanical behavior of rock in plastic state.

The main cause of surface subsidence above salt rock gas storage is the creep contraction of salt cavern volume during operation period. Assuming that the surface subsidence caused by equivalent elastic deformation of cavern volume contraction is a first-order approximate quantity of actual subsidence induced by creep contraction，the salt cavern is transformed as the sphere cavern with the same depth and volume，bearing uniform contractive elastic equivalent surface force. Therefore，the subsidence prediction is similar to the problem of boundary deformation of the sphere cavern with shrinkage force in elastic half infinite space. The Mogi model is introduced to get the elastic analytical solution of the surface vertical and horizontal deformations，which is the most successful method to predict the deformation above volcanoes eruption. The subsidence above the salt rock gas storage could be obtained directly with the volume shrinkage，which is the main superiority of Mogi model；and the prediction result has a good approximate effect to the numerical result under the same condition. It indicates that the Mogi model has enough feasibility in salt cavern subsidence prediction. Finally，the direction and recommendation about the further research are given.

Based on the dimensional analysis method of similarity theory，the similar experimental model was established to simulate the cavity building using the molded salt rock instead of natural salt. By experiments，a kind of molded salt rock that can be used for cavity building was found. Using the self-developed mould，a kind of large-size molded salt rock was obtained，which has a diameter of 300 mm and a maximum height of 500 mm. Three groups of experiments with different kinds of solution mining techniques were conducted，and a method for measuring the cavity shape by saturated brine for its electrical properties was proposed. The study shows that the cavity shape and the cavity building efficiency are affected by the washing techniques，and main factors include the location of casing pipes，location of oil cushion，time of cavity building and water flow. The step-by-step expansion method for cavity building can induce higher cavity building efficiency，and the cavity is an inverted pear-shaped chamber with a volume of 4 200 cm3，the maximum diameter of 24 cm，the average diameter of 20 cm，and the height of 27 cm. The brine concentration is about 22%，which reaches the demand of salt mining. Based on the similarity criteria in the similar experimental model，relationship between model and prototype parameters was developed. It provides a guidance about the design and control of cavity building.

A special split Hopkinson pressure bar(SHPB) under confining pressure and temperature，triaxial static confining pressure and temperature split Hopkinson pressure bar(TSCPT-SHPB)，is designed. The uniaxial dynamic mechanical performances of salt rock with the confining pressures ranging from 5 to 25 MPa were studied experimentally and numerically. The salt rock under the condition of temperature ranging from 40 ℃ to 80 ℃ and the confining pressure from 0.0 to 0.5 MPa was also tested with the TSCPT-SHPB. The influences of the confining pressure and strain rate on the dynamic increasing factor(DIF) of axial compressive strength of salt rock and the effects of the temperature and confining pressure on the dynamic mechanical properties of salt rock were analyzed. It is demonstrated that：(1) The effect of confining pressure on the ductility of salt rock is tremendous under dynamic loading. (2) The salt rock is a rate-dependent and temperature sensitive material；and its maximum dynamic compressive strength increases as the strain rate increases；while the peak dynamic compressive strength of salt rock decreases as the temperature increases under the high strain rate of 400 s－1. It is noted that the increase of the maximum dynamic compressive strength under low confining pressures is more obvious than that under high confining pressures. (3) The approximate expression for the effect of confining pressure and strain rate on DIF of salt rock was presented；and the relationship between peak confining strength and temperature under the high strain rate of 400 s－1 was also obtained from the test data. The experimental results by the TSCP-SHPB were validated by numerical simulation，in which the modified Drucker-Prager model and its experiment-based parameters were used.

It is a key problem for reducing the width of railway safety belt reasonably according to the evaluation result of railway roadbed subsidence and deformation，which determines the feasibility of Hubei Yunying salt cavern gas storage group. The creep contraction of salt cavern volume during operation period is the main cause of ground subsidence. Based on the hypothesis that the subsidence basin volume approximately has a relation of direct ratio with the creep contraction volume，the ground subsidence curve could be fitted as a Gauss function. Two key parameters of volume transfer coefficient and impact angle were introduced；and the formula for ground subsidence above a single cavern was deduced under condition of a certain volume shrinkage. The formula was used in the ground subsidence prediction of planned Hubei Yunying salt cavern storage. Finally，the ground subsidence above the salt cavern gas storage group was forecasted by superposition method. To solve the conflict of railway safety belt and planned salt cavern site，according to different roadbed deformation standards and salt cavern gas storage group ground subsidence above prediction results，the suggestion of reducing width of railway safety belt is given，as well as the control method to reduce the ground subsidence above salt cavern gas storage group and the roadbed subsidence effect.

The projects of oil/gas storage in deep salt mine are being massively planned and constructed in China. It has been a technical problem to be solved urgently that how to realize safe and efficient leaching of storage cavern. Combining engineering practices and theoretical results，five key problems should be paid close attention to，i. e. typical distribution characteristics of salt mine in China；corrosion and mechanical property weakening of interbed in leaching environment；mechanism，failure mode and discrimination of interbed collapse；dynamic characteristics of tubing string and their influential factors；control technology of solution mining and its field application. By summarizing the main progresses in above problems，it is found that some major breakthroughs in mechanism of interbed collapse and control technology of solution mining have been made. Based on the breakthroughs，some engineering problems have been solved or explained. The results provide technological support for salt cavern storage. However，the researches are far from in-depth and comprehensive on corrosion property of different interbeds，dynamic instability model of leaching tubing under various factors，and laboratory simulation of cavern leaching design. Finally，several works that should be carried out further are listed.

In order to study the influence of different interlayer characteristics on mechanical properties of molded salt rock with weak interlayer，regularly molded layered salt rock was made by pressing the molded salt rock，and uniaxial and triaxial compression tests were carried out，considering that samples are not easy to be obtained by coring in field. The results show that the mechanical parameters，such as strength，elastic modulus，and Poisson?s ratio and the formation and failure characteristics of molded salt rock with weak interlayer change regularly to a certain extent as the interlayer?s thickness ratio and distribution characteristics change regularly. The following experimental results can be drawn. (1) The uniaxial compressive strength and elastic modulus of molded salt rock with weak interlayer decline with the increase in interlayer?s thickness ratio. (2) When the interlayer?s thickness remains unchanged，the strength of molded salt rock with three interlayers is higher than that of molded salt rock with one or two interlayers. As the distance between interlayers increases，the strength and elastic modulus of molded salt rock with weak interlayer decrease gradually. (3) The pure salt rock with high strength has stronger radial strain than the interlayer with low strength，and the failure surface is always generated from the pure salt rock. Generally speaking，these results can provide a new method for analysis of mechanical properties of layered salt rock and stability of underground salt rock storage.

How to decrease the effective volume loss of salt cavern gas storages during their operation period to increase their service life is the concerned problem of operation and management departments. The influence of formation parameters，design parameters and operation parameters on cavern shrinkage risk of salt cavern gas storages was analyzed from the macroscopic angle. The inductive seven factors were analyzed and forecasted aiming at their effects on volume shrinkage of salt cavern gas storages. Then，the single-parameter sensitivity analysis method was used to calculate the seven factors? sensitivity coefficients to volume shrinkage ratio. Finally，a new method of forecasting the cavern?s volume shrinkage ratio was put forward based on the factors? sensitivity coefficient when the operation parameters were changed. The following conclusions are drawn. Besides the creep parameters of salt rock，the running mode of neighboring caverns，low pressure runtime in a cycle period and ratio of height to diameter of cavern are the sensitive factors for cavern shrinkage risk. Therefore，the cavern shrinkage can be decreased effectively by injecting and producing simultaneously with neighboring caverns，reducing low pressure runtime and controlling the cavern shape during construction and operation periods.

Considering the geological formation characteristics of salt mines in China，a series of physical simulation experiments were carried out to simulate the soft and hard interbedded salt rocks. The influences of dip angle，interlayers and interfaces on the deformation and failure mechanism of soft and hard interbedded salt rocks were discussed. The test results and theoretical analysis show that：(1) As the dip angle changes，the uniaxial compressive strength curve of soft and hard interbedded salt rocks presents U-shape. (2) When the dip angle θ＜30°，the failure mode is structural failure dominantly controlled by the hard interlayers；when 45°＜θ＜75°，the failure mode is shear or sliding failure dominantly controlled by weak interlayers or weak interfaces；when 85°＜θ＜90°，the failure mode is splitting failure at hard layers or partial shear failure at weak layers. (3) Shear or sliding failure along weak interlayers or weak interfaces is the internal cause that the uniaxial compressive strength curve of soft and hard interbedded salt rocks shows U-shape. Therefore，when setting the range of internal pressures，more attention should be paid to the shear strength of weak interlayers and weak interfaces，in particular those at the haunches of storages，to prevent these interlayers and interfaces from being damaged and to avoid potential leakage of gas.

Monitoring the ground deformation concerns the safety of gas storages much. The ground deformation in salt cavern gas storage area is characterized by spatial diversity and temporal nonlinearity owing to the spatial distribution of salt caverns and the cyclic variation of stress environment. A technique with high spatial and temporal monitoring density is therefore needed to fully reveal the spatial and temporal characteristics of the ground deformation in salt cavern gas storage area. Based on permanent scattered interferometry(PSI) technique，the ground deformation history in Jintan salt cavern gas storage area from 2007 to 2010 was retrieved using PALSAR data. Compared with GPS data，the PSI results are found to have higher accuracy in both reflecting the general trend and the nonlinear process of ground deformation，and to have higher monitoring density in both spatial and temporal domains. The ground deformation in Jintan gas storage area presents obvious spatial patterns. Area with high settlement velocity corresponds to the area with intense human engineering activities. In addition，nonlinear behaviors were found in the ground deformation history in Jintan gas storage area；and this deformation history could be divided into three stages of settlement and two stages of uplifts. However，owing to insufficiency of relevant data，the problem that whether this fluctuation between settlement and uplift is attributed to human activities requires further research.

The progressive failure of rock can be divided into five stages，including crack closure stage，elastic stage，crack initiation and stable growth stage，and accelerated crack growth and post-peak stage. The characteristic stresses in the progressive failure process of rock under different strain rates were studied by using the dynamic mechanical system of rock with changing frequencies. The results show that：(1) When the strain rate  5×10－4 s－1，rock strength is slightly dependent on the strain rate；when  5×10－4 s－1，the rock strength is significantly dependent on strain rate. (2) The ratios of crack initial stress and dilatancy stress to the peak strength and the ratio of crack initial stress to dilatancy stress are 50%–60%，70%–80% and 80%–90%，respectively，showing no evident dependence of strain rate. Based on the energy conservation law，the energy characteristics and energy mechanism in the process of rock failure were analyzed. Some conclusions are dram as follows. (1) Both of the total absorbed strain energy and the elastic strain energy increase with the growth of strain rate；but the damage strain energy increases firstly and then decreases. (2) When  5×10－4 s－1，the absorbed energy and the elastic energy are slightly dependent on strain rate；when  5×10－4 s－1，the absorbed energy and the elastic energy are significantly dependent on strain rate. (3) If the strain rate is fixed，the strain energy absorbed by rock is stored mainly in the form of elastic strain energy，but the damage strain energy remains nearly unchanged，which only increases near the peak strength. Once the peak strength is reached，the strain energy stored in the rock is quickly released.

By uniaxial tests on salt rock specimens under different temperatures，it is shown that the uniaxial compressive strength of salt rock drops significantly and the peak strain increases gradually with the increase of temperature. Through the cyclic loading test under different temperatures，in which the upper and lower limit stresses are chosen according to the uniaxial compressive strength under different temperatures，it is found that：(1) The fatigue life of salt rock under the same stress ratio becomes longer as the temperature rises. (2) The fatigue damage development mode of salt rock under different temperatures all includes three stages：slow damage stage，uniform damage stage and accelerated damage stage. (3) The proportion of uniform damage stage increases as the temperature becomes higher. (4) The curve of volumetric strain shows the three stages more obviously than the axial strain curve. Finally，the fatigue damage of salt rock is analyzed by using the analytical formulas for elastoplastic material damage. It is indicated that the development mode of salt rock fatigue damage is matched with that of the volumetric strain. Therefore，the volumetric strain is more appropriate for describing the fatigue damage of salt rock.

To improve working security of underground gas storages in salt rock，a model for calculating the gas leakage rate at steady state was established；and a method for consequence analysis of thermal radiation from jet fire was presented based on probability equation and consequence evaluation model. The hazard distance estimated by the proposed method was then compared with the area of burn in the observation of the actual accidents. It is found that the estimated hazard distance agrees well with the observed value；and the maximum deviation by the proposed method is less than 20%. Furthermore，the main factors that influence the hazard range associated with jet fire accident from underground gas storages in salt rock were discussed. The results indicate that the hazard distance increases with the increase of operating pressure(or buried-depth) and pipeline diameter when a jet fire accident from the underground gas storages in salt rock happens. The quantitative assessment model will provide reference for quantitative hazard analysis of jet fire caused by gas leakage from underground gas storages in salt rock.

By using the triaxial servo-controlled seepage equipment for thermo-fluid-solid coupling of coal containing methane，permeability under conditions of different confining pressures and temperatures were determined. Studying the migration law of coalbed methane and taking appropriate measures to coalbed methane can prevent coal and gas outburst，or reasonably use the methane in the coalbed methane reservoir. It is of practical significance for mine construction and coalbed methane mining. The experimental results show that：(1) Under different experimental conditions，the change of seepage velocity lags behind the change of strain and stress of coal under triaxial compression；and the lagging amount of the minimum volumetric strain is large. (2) The lagging amount of the minimum volumetric strain and the peak stress both decrease with the increase of temperature. (3) The confining pressure hinders the gas seepage through the changes of internal structure caused by compression effect of confining pressure；and the lagging of the minimum volume increases with the increase of confining pressure.

The constitutive model of non-Darcy flow was established based on the laboratory data of high velocity non-Darcy flow through a single smooth parallel-plate fracture，and the determination method of non-Darcy flow influence coefficient was introduced. Generalized constitutive equation for both Darcy and non-Darcy flows was developed. The finite element method based on the generalized Darcy and non-Darcy flows constitutive equation was presented；and the basic iteration steps of non-Darcy flow analysis were performed according to conjugate gradient iterative method. Finally，the above theory and method were applied to the prediction of water inflow in a tunnel. By comparison of the two different calculation results for Darcy and non-Darcy flow theories，the necessity of adopting non-Darcy flow theory was explained. It is also found that the aperture of a big fracture and location of cross point of multiple faults have considerable influences on water inflow in the tunnel.

To study the aperture evolution of single fracture in granite under stresses and chemical solution seepage，seepage tests using different chemical solutions were carried out on granite with a single fracture under constant triaxial compressive stress. Ion concentrations of solutions were measured during the seepage tests. Analysis results show that under compression，three processes have effects on the evolution of fracture aperture，i.e. mineral dissolution at fracture contact area，mineral dissolution on free surface and mineral precipitation. The relationship between aperture evolution and contact area ratio was obtained using the 3D scanning data of fracture surface. Based on this，the aperture evolution model of granite with a single fracture under both acid and alkaline solutions seepage was established. Simulation results show good accordance with testing results. The established model can well describe the fracture aperture evolution under chemical solution seepage and stress. It shows that under acid solution seepage，the process of mineral dissolution at fracture contact area dominates aperture evolution；while under alkaline solution，the mineral precipitation also plays an important role.

Failure types of landslides generally include thrust load-caused type，retrogressive type and combined type. Stress field and displacement field were obtained based on numerical analysis and variable modulus elastoplastic strength reduction method. According to the numerical results，it is found that in thrust load-caused landslide，the displacement and the stress level of the upper region are higher than those of the lower region；while in retrogressive landslide，the displacement and the stress level of the lower region are higher than those of the upper region；and the combined landslide is the combination of those two failure types. Therefore，the failure type of a landslide can be clearly identified by its stress field and displacement field obtained from numerical method. Furthermore，anti-sliding piles were set at different sites of landslide to study the relationships between factor of safety and stress field and displacement field of landslide. It is found that setting the anti-sliding piles at the site of higher stress level and larger displacement can lead to higher factor of safety than at other places. Thus，the optimal reinforcement site is the upper region for the thrust load-caused landslide，while the lower region for the retrogressive landslide. As for the combined landslide，the optimal reinforcement site is the one of higher stress level and displacement. As a result，the optimal reinforcement site can be determined by the stress field and displacement field. These conclusions can offer more clear and reasonable reinforcement sites for engineering treatment，beneficial for the landslide treatment. At last，some typical landslides were analyzed. The results show that the above method is reasonable and feasible.

It is important to investigate the mechanical behavior of rock subjected to cyclic loading for both the basic theory of rock mechanics and the construction of geotechnical facilities. A series of triaxial compression tests under cyclic loading were performed to study the fatigue behavior of granite；and hereby a constitutive model was proposed to describe its fatigue behavior. In the tests，the following conclusions can be drawn. (1) The relation between residual strain and cycle number is influenced by the volumetric deformation behavior of granite，and so the relation between deformation modulus and cycle number is. (2) The fatigue behavior of granite could be divided into three domains in the stress-strain space，and the micro mechanism in one domain is different from that in another domain. (3) The threshold for fatigue failure of granite could be the peak deviatoric stress corresponding to the point transferring from volumetric contraction to volumetric dilation. (4) The potential of fatigue deformation is different from that of monotonic plastic deformation，while the granite exhibits a higher resistance to volumetric deformation under cyclic loading than that under monotonic plastic loading. (5) An internal variable fatigue constitutive model was proposed for the rock；and the fact that the predicted fatigue behavior is consistent with that observed in tests，so as to show that the constitutive model is capable of describing the fatigue behavior of rocks.

A kind of random weight particle swarm optimization(RandWPSO)-least squares support vector machine (LSSVM) prediction model of limit displacement of large underground cavern is established and applied to limit displacement prediction and analysis of large surge shaft of Nuozhadu hydropower station. The reliability of the model is validated by a case study. Through comparing with the results of numerical calculation，the surrounding rock stability of engineering area is evaluated comprehensively. The results show that the maximum relative error of limit displacement obtained by RandWPSO-LSSVM prediction model to the real value is 6.72%. The prediction error is quite less；and the prediction effect is well and meets the engineering requirements. The maximum displacement and tensile stress obtained by numerical calculation under condition of design support parameters are 19.45 mm and 0.54 MPa，respectively，mainly located at the five-tunnel area sidewall. The maximum tensile stress is far less than the tensile strength of little weathering rock mass；and the plastic zone distribution is less. The maximum displacement obtained by numerical calculation is less than the predication value obtained by RandWPSO-LSSVM prediction model. The surrounding rock of engineering area is stable. The results have great significance for estimating the stability of large underground cavern and will provide important guidance for making construction decisions reasonably.

The environment is very special at Galongla extra-long tunnel of Zhamu—Motuo highway in Tibet. The terrain，geology，earthquake and meteorological conditions in this region are representative compared with other cold plateau tunnels. The survey and design of this tunnel are combined with satellite remote sensing，in-situ survey，laboratory and field tests，theoretical analysis，numerical simulation，real-time monitoring and so on. From the idea of environmental protection，ecological balance and green development，several key techniques are proposed，that is，(1) frost heave mechanism and insulation technology in cold region tunnel；and (2) earthquake damage mechanism and aseismic technology in high intensity earthquake zone. These proposed key techniques have great significance for tunnel construction in Qinghai—Tibet Plateau with modern glacier.

The rebound deformation of foundation pits has significant influence on their stability. Nowadays，there are several calculation methods for rebound deformation，such as traditional method，empirical formula，residual stress method and so on. But there were always obvious errors between calculation results and measured values. According to the residual stress equal to the weight of removed soil，the larger unloading stress can be modified by residual stress. The corresponding rebound modulus can be gotten through the ordinary compression tests or empirical formulas. A new practical calculation method for rebound deformation was proposed. The conception of the method is easier to be understood and to be put into effect. The rebound deformation at any depth below the ground surface can be calculated by the method. By comparing the calculating results to the measured values，the method was proved to be feasible and advanced. It is of great significance to improve the design theories of foundation pits.

A two-dimensional numerical model was established for a reinforced soil retaining wall on soft soil foundation. The settlements，horizontal displacements，earth pressures of retaining wall and axial strains of geogrid were simulated under the condition of step loading. The computed results were found to basically agree with the measurements. The stability and location of slip surface of the reinforced soil retaining wall computed by the finite element strength reduction method coincide with the observed results，indicating a deep-seated failure. The maximum computed and measured strains of each geogrid layer appear at the position 4 to 6 m away from the wall，which is very different from the Rankine failure surface stated by current design theory for reinforced soil retaining walls. The reason is that the current design theory for reinforced soil retaining walls is based on the hypothesis of rigidity foundation and does not consider the effect of foundation deformation on the strain distributions and stability of reinforced soil retaining walls. The effect of lengthening the bottom reinforcements on the stability of the reinforced soil retaining wall was further analyzed using the numerical model. It is indicated that the lengthening values and reinforcement-lengthening numbers apparently affect the stability of the reinforced soil retaining wall on soft soil foundation. The obtained curves of factor of safety versus reinforcement- lengthening number for various lengthening values were considered to be significant for design of reinforced soil retaining walls on soft soil foundation.

Indoor experiments were carried out on models with geometric similarity of 1∶20 to study h-shaped anti-sliding piles mechanism. The load was applied in steps by a jack，and the moment and deformation patterns of three h-shaped anti-sliding piles with different row spacings and different beam positions were obtained. The pile-soil interaction model of h-shaped anti-sliding pile was established by finite element software ABAQUS；and several design parameters of pile were analyzed and optimized. The results show that the optimal pile row spacing is 5 times pile diameter；the optimal stiffness of connecting beam is 1.5 times of pile；the optimal embedded depth of pile is 3/8 of the length of front row pile. Finally，the conclusions were successfully applied to treatment of an actual landslide in Nanning.