Investigations of the influence of correlative factors on deformation and fracture characteristics of roadways/tunnels surrounding rocks can provide theoretical support for the supporting design of roadways/tunnels. A test system for excavation and unloading of surrounding rock specimens was developed，and a series of tests with different unloading rates under different initial confining pressures were carried out on the surrounding rock specimens made of cement mortar. The test results show that the influence of excavation unloading on the deformation and failure of surrounding rock exists not only in the unloading stage but also in the stage after unloading，and the influence in the stage after unloading is more obvious with increasing the initial confining pressure. Both the tangential and axial strain rates during the unloading stage increase firstly and then decrease. The peak of the rapid-speed unloading strain rate appears earlier than that of the slow-speed unloading strain rate. When the initial confining pressure is same，the higher the unloading speed is，the faster the deformation rate in the unloading stage is and at the same time，the smaller the total deformation is. When the unloading speed is same，the higher the initial confining pressure is，the faster the deformation rate in the unloading stage is and the larger the total deformation is. It is observed that，when the surrounding rock specimen is destroyed in the slow-speed unloading test，the outer wall of the specimen is intact but the inner wall near the bottom flakes，and that，in the rapid-speed unloading test，annular cracks occur along the outer wall of the specimen accompanied by a small amount of vertical micro-fractures，the inner diameter is reduced obviously and the rock on the inner wall falls. The research is helpful to further study the influence of relevant factors on surrounding rock deformation law and surrounding rock rupture form.

In order to study the fracture characteristics of sandstones under blasting loads，blast tests were carried out on three kinds of sandstone specimens. By X-ray diffraction analysis and scanning electron microscope，the composition of the sandstones and the microstructure of the propagation fracture surface of pre-cracks were studied respectively. A numerical calculation model was established by ABAQUS code and the parameters of mode I crack such as the crack propagation speed and the dynamic fracture toughness were obtained by using experimental-numerical method. The test results show that the main failure mode of the sandstone around the borehole is plastic failure，that the main failure mode of the crack propagation section is brittle fracture and that the different compositions of the three sandstones result in different failure modes of microcrystal，different crack propagation speeds and different fracture toughnesses. The propagation speed of the dynamic crack is not a constant，and the propagation speed and the dynamic initiation toughness of the black sandstone are higher than those of the red and green sandstones. It is also shown that the dynamic propagation toughness is inversely proportional to the propagation speed.

Rock masses in the frozen wall are subjected to coupling actions of the temperature and the crustal stress during the construction of mine shafts using the artificial freezing technology. To investigate the mechanical properties of Cretaceous red sandstone after freezing under the coupling action of the crustal stress and the temperature，triaxial compression tests with frozen samples were carried out under different temperatures of 20 ℃，－5 ℃，－10 ℃ and －15 ℃ and different confining pressures of 0，2，4，6 and 8 MPa，and the influence of the confining pressure and the temperature on the mechanical properties of red sandstone during freezing process was discussed. Test results demonstrate that the confining pressure during the freezing process enhances the freezing effect modestly，namely，compared with the case without the confining pressure during the freezing process，the strength and the elastic modulus of the red sandstone increase while Poisson?s ratio decreases. With decreasing the temperature，the cohesion，the internal friction angle，the crack initiation and  dilatation stresses of the red sandstone increase，and the cohesion has a higher sensibility to the temperature. It is also revealed that，after freezing，the red sandstone has a comparative longer elastic stage and the reserve capacity for plastic deformation is not adequate. The crustal stress enhances the restraining capacity of pores so as to resist the damage caused by the frost heaving force，which makes the freezing action develop to the secondary micro-cracks. The study results help for the design of the thickness of the frozen wall and the section height of mine shafts in Western China.

In order to study the influence of the initial confining pressure and the unloading rate on permeability evolution of sandstone during unloading process，triaxial unloading seepage tests were carried out under different high initial confining pressures(10，20，30 MPa) and different unloading rates(0.1，0.5，1.0，1.5 MPa/min). The results show that the sandstone occurs brittle failure and that the lateral deformation and the volume expansion increase significantly with increasing the initial confining pressure or the unloading rate. The permeability evolution is closely related to the unloading stress and strain characteristics. The permeability increases slowly at the elastic deformation stage，rapidly at the yield deformation stage and sharply at the stress dropping stage，and eventually decreases to a stable value at the residual strength stage. The initial confining pressure and the unloading rate have a significant influence on the permeability evolution of sandstone. With increasing the initial confining pressure，the variation of the unloading pressure from the beginning of unloading to the moment of failure increases while the ratio between the final and initial confining pressures decreases. With ascending the unloading rate，the variation of the unloading pressure increases and the peak value of the permeability increases due to a lower confining pressure at failure. The results could provide a good reference for permeability and safety evaluation of surrounding rocks in deep underground rock engineering.

In order to achieve safe and efficient underground mining of extremely thick coal seam above 20 m，a fully mechanized top-coal caving mining method after extracting the middle slice in extremely thick coal seam was creatively proposed. The similar simulation test with a large scale of 60∶1 was performed to study breaking and moving characteristics of top-coal，displacement and vector fields of top-coal，and support load effects of the fully mechanized top-coal caving mining after extracting the middle slice in extremely thick coal seam above 20 m. The results show that，during the stage of pressure relief mining，the top-coal collapse shape is approximately trapezoidal，the breaking and instability of the stepped top-coal cantilever beam structure above the support have a periodic effect，the displacements of the upper，the median and the lower of the top-coal decrease in turn，and cutting top press support accident occurs after the first weighting of the main roof. During the fully mechanized top-coal caving mining stage，the short cantilever beam structure is finally broken into a loose structure and the total displacement of the median top-coal is greater than that of the upper top-coal. Due to supporting effect of the support structure，vertical cracks occur obviously in the lower top-coal，and the thickness of the top-coal affected by the support is approximately 10 cm. The evolution characteristics of the displacement and vector fields of the top-coal are in consistent with the experimental results. The research results lay a theoretical foundation for the development of mining technology of extra-thick coal seams above 20 m in China.

To study the meso-damage characteristics of sedimentary rocks，compression tests were carried out on sandstones under specific high confining pressures using the triaxial compression equipment. Scanning electron microscopy and energy spectrum analyzer were used to investigate micro behaviours of samples after compression，and the image-processing technique was adopted to analyze the meso-damage information of sandstones. The results indicate that，in the case of 30 MPa of the confining pressure，the stress-strain curves exhibit no evident yielding，and the plastic deformation and the meso-damage factor continue to increase and the sandstone strength gradually deteriorates with increasing the axial stress prior to exceeding the uniaxial compressive strength. The meso-damage factor obeys the Gauss function distribution，and the meso-damage gradually propagates from the edge of the surface to the center with increasing the axial stress. The three meso-structures within sandstone samples mainly exhibit as two forms of meso-morphology，e.g. sand and cement，and the damage of the sample begins from the cement and then transfers to the sand. Three components of sandstone including oxygen，silicon and aluminum respectively distribute throughout the sample，in the high-strength area and in the low-strength area.

Aiming at the practical problem of frequent rock burst in deep mining after large area goaf in shallow coal seam under huge thick hard magmatic rock beds，the induced mechanism of rock bursts by the fracture movement of magmatic beds was studied based on theoretical analysis，numerical simulation，field measurement and engineering practice. A triangular cantilever beam model of the hard magmatic rock roof above the large area goaf was established，and stress and energy characteristics of the roof were analyzed theoretically. A criterion for the fracture movement of the magmatic rock roof was proposed，and a mechanical model for rock bursts induced by the fracture movement of the roof was established. By considering the surface cracking and underground appearance，the large area overhanging of the hard magmatic rock roof above the shallow goaf and the local strong intrusion zone constitute the static action，and the extrusion of the magmatic rock roof“Rotary”movement and the mining disturbance of the working face constitute the dynamic action. The dynamic action plays a dominant role in rock burst induced by magmatic rock roof during deep coal mining. Analysis of field microseismic monitoring data indicates that the dynamic and static loads，resulted from the fracture movement of the hard magmatic rock roof，are the key factors inducing rock bursts. From two aspects of improving the anti-seismic ability of the roadway itself and keeping the high-energy micro-earthquake event away from the roadway，measures of deep-hole blasting at the floor and strengthening support were put forward，which were proven effective through practices

The electrokinetic effect(EKE) of rock and fluid is applied more and more in exploitation of underground resources such as enhancing oil and gas recovery，reinforcing soft rock in roadway and strengthening fluid flow in mine，et al. However，the blindness of engineering design and parameter selection reflects the lag of the theory. The researches of EKE were systematically summarized from three aspects，namely，the transport characteristics of the media，physical property and structural changes. Four main problems were pointed out including unclear transport process of multi-phase media，few researches of multi-field coupling，indistinct microscopic response mechanism of physical properties and unformed interface control concept of adsorption fluid，and the theoretical basis of double electric layers was clarified. On this basis，the concept of electrokinetic dynamics(EKD) of coal rock and fluid was proposed，which reveals the move rule of gas and liquid ions and the interactions with the external environment. The theory frame，taking double electric layers theory as the core，focusing on the electrokinetic effects such as electroosmosis，electrophoresis and electromigration and considering the outside physical and chemical field，was built. Five main research directions and four key techniques of EKD theory were summarized. The theory is suitable for the rocks with a larger specific surface area such as coal,mudstone and shale，and provides an effective method for many problems existing in exploitation of deep resources including difficult flooding in coal seam，blockage injury of coal power，slow desorption rate of methane，difficult support of soft swelling rock，slow dewatering of colloid filling and serious pollution of heavy metal in coal gangue，etc. The research also provides a new idea for revealing the mechanisms of fluid dynamic disasters of rock under the action of deep geoelectric field.

In order to investigate the evolution characteristics of relevant variable fields of uniform and non-uniform specimens under tensile loads，the correlation coefficient field of image gray，the strain field in y-direction and their characteristic variables of PMMA and mortar specimens with bilateral prefabricated cracks under tension loads were analyzed and compared using the digital speckle correlation method. The results show that there exist temporal and spatial corresponding relations between the surface characteristic variable and the localization of specimens. The evolution characteristics of the correlation coefficient field of the image gray can reflect the deformation localization area of the specimen，and the uniform and non-uniform deformation stages can be distinguished by the evolution of the characteristics variable of the correlation coefficient. In the non-uniform deformation stage where strain localization‘competes’intensely，the characteristics variable of the gray correlation coefficient of images fluctuates with time and increases sharply on the whole，which signifies the  failure precursor of the specimen with bilateral prefabricated cracks. The evolution characteristics of the strain field in y-direction can reflect the strain localization area，and the positions of strain localization‘competition’and crack initiation. The evolution process of the characteristic variable of the strain field in y-direction is related to the change of the load over time，and the heterogeneity of the specimen results in continuous fluctuation of the characteristic variable，which can be used to distinguish homogeneity and heterogeneity specimens.

Aiming at the problem of the external load determination of the vertical shaft in water-bearing bedrock layers in Cretaceous-Jurassic deep-buried coal-bearing strata in Western China，and based on the generalized effective stress principle and the seepage theory，an analysis model of the external loads on the shaft wall was established considering the joint action of the surrounding rock and the shaft wall，and the analytic solutions of the external loads on the shaft lining were obtained. The stress conditions of the attached and separated walls were proposed，and the formation mechanism of the external loads of the shaft lining was discussed. Combined with the characteristics of deep-buried water-bearing bedrock in western China，the value ranges of the reduction factors of the external loads and the water pressure were discussed. The results show that the water pressure reduction factor on the outside of the shaft wall， ，directly proportional to the ratio of the permeabilities of the surrounding rock and the shaft lining，is in the range of 0.5–0.9 in most cases，that the reduction factors of the external loads of the shaft wall for the attached and separated walls respectively vary from 0.496 to 0.963 and from 0.5 to 1.0，and that the single layer shaft wall is only suitable for the weak water-bearing deep-buried Cretaceous-Jurassic coal-bearing strata while the double-layer reinforced concrete shaft lining structure should be adopted in the water-enriched strata.

Cutting blasting is the key to the driving speed of the rock roadway. According to the characteristics of straight-hole and wedge shaped cutting technology，a multi-step cutting technology was developed to overcome the problem of poor blasting effect of the deep hole cutting. Taking the two-step cutting as an object，analysis of cavity theory was carried out. The result shows that two-step cutting changes the cutting blasting into one deep and one shallow cutting，which changes the order of the energy release of the explosive in the cutting area. The clamping force of the second cut blasting becomes smaller，at the same time，the pre-cracking effect of the central hole is beneficial to improve the blasting effect of the second cut hole. The cavity resistance and dynamic formula were obtained through model analysis. Based on the determination of the condition that the cavity formation should be satisfied，it was analyzed that the first cutting and the first blasting of the central hole are more favorable for blasting cavity from the point of overcoming the frictional resistance and the tensile resistance of the cavity wall during cutting. The volume relationship formulas of the first and second cuttings were established，and the formula for determining two-step cutting parameters was proposed. The ranges of the cutting parameters under different lithology conditions were determined，which provides a reference for determining the parameters of the cut blast hole. The practice shows that two-step cutting is obviously better than the ordinary wedge cutting technology in the technical parameters such as the blasting footage and the utilization of blast hole，and has good applicability.

Centrifuge model tests were performed to investigate the settlement of high loess-filled foundations in a valley during construction stage and in post-construction stage，and the influence factors on the settlement were discussed. Results illustrate that the settlement of the high loess-filled foundation is significantly affected by some factors such as the filling rate，filling height，valley shape，degree of compaction and time，and mainly occurs in the construction stage with a small proportion in the post-construction stage. The settlement in the post-construction stage increases linearly with the filling height and logarithmically with the time，while the post-construction settlement rate decreases exponentially with the time. Compared to the filled foundation in a U-shaped valley，the deformation of the loess-filled foundation in a narrow valley is evidently confined and as a result，the settlement is smaller and the time required to reach the stable state is shorter. A high compaction degree，a slow construction rate or a small filling height can reduce the settlement. Furthermore，the improvement of the compaction degree will be more significant for the settlement control of a thick filling body，the change of the construction rate directly affects the settlement of filled foundations in the construction stage，and there is a relatively stable positive correlation between the long-term post-construction settlement and the filling height.

To study active failure modes and the limit supporting pressure of a slurry shield tunnel face through sand，a stability control model test system of a slurry-shield tunnel face was designed，which can imitate the slurry pressure imbalance across a slurry shield tunnel face by reducing the water pressure of a flexible pressure chamber and can simulate the failure of the tunnel face based on the displacement and the shear strain field collected by the PIV system and the water pressure monitored using a hydraulic gauge. A series of model tests were carried out to investigate the failure modes of the tunnel face and the limit supporting pressure with three different cover-to-diameter ratios of 0.5，1.0 and 2.0. The test results show that the deformation of the face can be divided into four phases as the support slurry pressure is reduced. At the end of the third phase，the tunnel face is in the limit equilibrium state and the corresponding slurry supporting pressure is the limit slurry supporting pressure. As the slurry support pressure decreases，the deformation in front of the face would gradually expand to the ground surface. It is also observed that，when the covered depth is relatively small(C/D = 0.5)，the critical failure zone reaches the ground，and that，while the covered depth is greater(C/D = 1.0 or 2.0)，the critical failure zone remains underground. The failure modes and the limit supporting pressure calculated by Soubra’s and Mollon’s theoretical models are closer to those obtained from the model tests.

Investigations on the thermo-mechanical behaviors of precast high strength concrete(PHC) pipe piles，especially surrounded by multi-layer strata，are relatively few. Based on in-situ prototype tests，piezocone penetration tests and drill sampling method，the thermal and mechanical responses of a full-scale PHC energy pile in layered soil were analyzed. The results show that the temperature of piles distributes relatively uniform with an average increase of 20.0 ℃. The temperature of the pile near the ends or high conductive soil layers is lower，indicating obvious influence of inhomogeneous heat transfer ability of layered soils on the temperature of the pile. The compressive stress is generated in the pile body. The maximum stress is 4.70 MPa p and the stress at the bottom of the pile is 3.77 MPa. The neutral point locates at 16.3 m depth which is about 2/3 of the pile length，and the position keeps stable during the test. Compared with other field tests，it was found that the additional stress of the pile body is related to the strength of the surrounding soil and the pile type. The negative shaft friction develops in the upper part of the pile and positive shaft friction occurs in the lower part. The negative shaft friction is larger than the positive，which may be due to the difference between the pile-soil relative displacements of both ends of the pile. According to the results，a simplified distribution of pile-soil relative displacement and pile body stress was proposed.

Composite soil nail-anchor supporting walls have been widely used in practice because of their flexibility，strong supporting capacity，short construction period and low cost. However，researches of composite soil nail-anchor supporting walls leg engineering practices and the working mechanisms are not fully understood， which may lead to some uncertainties in design. Combining three-dimensional(3D) discrete element method (DEM) and experimental model test，displacement field，motion trace，porosity and shear stress of sand particles as well as anchorage resistance during the process of pulling anchor were investigated at the mesoscopic level. The results reveal that the larger the diameter of the anchorage plate，the larger the vertical influence range，and that the displacement field has a convergent bell-mouth shape. During the process of anchor-pulling，sand particles between anchors and soil nails tending to rotate or slide can be divided into three zones with different particle movements for each zone. When the anchor spacing is twice the diameter of the anchorage plate，the composite soil nailing method can achieve an optimum result. Meanwhile，dilatation and contraction occur in sand. The change of the porosity can be described by sinusoidal wave curve and the minimum porosity appears around the nails. Sand particles are squeezed together and blocked by the soil nails，which enhances the synergistic effect of composite soil nail-anchor supporting system. The results presented in this study may provide useful references for upgrading current design methodology of composite soil nail-prestressed anchor supporting system.

For the design and assessment of municipal and submarine pipelines，it is vital to solve the problems of the anisotropy and determination of the soil resistance coefficients around buried pipelines. Vertical and horizontal resistance coefficients were obtained by using transfer matrix method and analogy method，considering partial or complete embedment of the pipeline and change of the pipe-soil stiffness ratio，and axial resistance coefficient was solved by using shear displacement method and image method respectively corresponding to partially buried and completely buried cases. The rationality of the method for calculating the resistance coefficients was verified via numerical examples，and the differences in the values of the resistance coefficients caused by the change of parameters were analyzed for three typical foundation distribution forms. The results show that the resistance coefficients in three directions increase with increasing the buried depth-diameter ratio and tend to be stable with the buried depth-diameter ratio reaching 20，and that the vertical and horizontal resistance coefficients decrease with rising the pipe-soil stiffness ratio. In homogeneous semi-infinite soil，the axial resistance coefficient is less than the vertical resistance coefficient. The ratio of the horizontal resistance coefficient to the vertical resistance coefficient is less than 1 for the partially buried pipeline，but，for the completely buried pipeline，more than 1 and approaches 1 with a buried depth-diameter ratio of 20. The finite compression characteristic of soil under the pipeline has obvious influence on the vertical and horizontal resistance coefficients，and the influence on the former is more significance. The vertical and horizontal resistance coefficients obtained by simplified homogenization method are obviously different from the stratified solutions proposed in this paper. Corresponding to the cases of an upper-soft and lower-hard stratum and an upper-hard and lower-soft stratum，the simplified homogeneous values of the resistance coefficients are respectively bigger or smaller than the stratified solutions.

Aiming to solve the difficulties in the construction of deep foundation pits such as narrow construction site，unconsolidated backfill and loose soil area，a combined retaining structure of frame prestressed anchors and micro steel pipe piles was put forward，and the composition and working mechanism of the structure were discussed in detail. Based on the theory of Winkel?s elastic foundation beam，an interaction model between the combining retaining structure and the soil under the tensioning stage and the normal working stage was established，which can be solved by the displacement method and the finite difference method. The supporting effects and mechanical properties of the combined retaining structure were analyzed by the finite element software of ADINA，and comparisons between theoretical and simulation values were performed. The results show that the theoretical calculation results are basically consistent with the numerical simulation results，which verifies the rationality of the calculation model and the analysis method. Compared with the results obtained by the proposed method，the internal forces of the frame column and the micro steel pipe pile calculated without considering the inter-structure implicating effect are respectively smaller and larger，which means the former unsafe while the latter conservative. It is also shown that，compared with the pile anchor support structure or underground continuous wall support structure，the combined retaining structure can effectively control the deformation of foundation pits and the internal force distribution is more reasonable，which reflects good support performance of the combined retaining structure. The research can provide a theoretical basis and reference for the design of similar deep foundation pit support structure.

A method for calculating ground vertical displacements of double-layor elastic system due to shield tunneling was proposed combining the stiffness equivalent method with the Mindlin solution，which can simultaneously consider the unbalanced force at the tunnel face，the friction between the shield skin and the soil，the grouting pressure of the shield tail，the secondary grouting pressure，the additional load during tunnelling and the volume loss，and can also reflect the influence of the stiff difference of adjacent layers on ground displacements. The results show that the calculated ground vertical displacement induced by tunnelling in double-layer soil is different from that in single-layer soil while the overburden thickness is shallower，and close to the average value of the ground displacements calculated in soft and hard layers when the overburden thickness is getting deeper. It is also shown that the ground heave value first increases，then decreases and finally goes to zero with the secondary grouting ranging from the full face to the ungrouted zone and that the optimal grouting range is within the upper half. Comparisons between the ground vertical displacements of the field measurement and the theoretical calculation of Qinghuayuan Tunnel of the Jing-Zhang High Speed Railway indicate that the proposed double-layer model can describe the pattern of soil heave ahead of the tunnel face and settle-heave-stabilization behind of the tunnel face and that the calculated value of the ground vertical displacement by the model is much closer to the measured value than that calculated using single-layer model and the calculation error is reduced by 11.08%. The research results can provide a theoretical support for predicting ground vertical displacements caused by shield tunnelling both in single-layer soil and double-layer soil.