In order to assess the global stability of underground cavern group for energy reserves，deformation stability theory which considers the strength reduction approach of finite element method is developed. The global stability criterion of cavern group is established based on the K-?E relation，where K is the strength reduction factor and ?E is the plastic complementary energy norm. The plastic complementary energy norm is the norm of unbalanced force，whose magnitude indicates the global stability of cavern group. The unbalanced forces clearly exhibit the position and pattern of the unstable failure. The global stabilities and unstable failure evolution laws of the single cavern，double cavern，multi-cavern and Jintan oil-gas storage cavern group in salt deposit are studied. Multiple influencing factors such as cavern diameter，cavern spacing，weak intercalation，internal pressure，pressure loss and cavern layout are considered. As a result，the maximum cavern diameter，the minimum cavern spacing，the minimum stable internal pressure and the optimal layout mode of cavern group are determined. The results show that the deformation stability theory provides practical and effective theory and method for the global stability assessment and unstable failure analysis of cavern group.

The energy analysis for the stress field and displacement field of the locked slope body indicates that：in the case that the thickness of locked slope body bring up the rear is large and the slope body consists of solid rock，enormous shear deformation energy accumulates in the slope system under the action of huge thrust of middle and rear slope body，which makes that the shear deformation energy released by the slope system far exceeds the energy for failure of rock body of latent slide belt in the critical slide and sheared locked slope body. The superfluous deformation energy converts into kinetic energy of slide body in impulse condition，which leads to an acute-moving landslide. The curve of shear deformation energy change rate of locked slope body and its expression，which contains an abundance of information，are deduced. Through the shear deformation energy change rate curve and the load-deformation curve of latent slide belt of locked slope body bring up the rear，the shear deformation energy accumulation of the slope system and the relationship between the deformation energy releasing amount in critical slide and the starting impulse velocity of the landslide body are described in the forms of direct geometry way；and a calculating example about the impulse velocity of the acute-moving landslide is given.

A reasonable excavation procedure and contour blasting method is one of the key techniques for construction of deep underground powerhouse. Firstly，the excavation procedures and contour blasting methods adopted for the underground powerhouses of large-scale hydropower stations under building or completed are summarized and analyzed. Secondly，based on the analysis of the propagation of cracks driven by explosion gases during contour blasting，and taking into account the combined effects of initial in-situ stress of surrounding rock mass and the adjacent blast holes，the possibility of stable propagation of pre-split cracks under confinement of high lateral in-situ stress is demonstrated. The results show that the in-situ stress of surrounding rock mass is a main factor to control the crack propagation for pre-split blasting. When the lateral in-situ stress vertical to the axis of underground powerhouse is larger than 10–12 MPa，it is not feasible to employ an excavation procedure of pre-split first followed by the main rock excavation. Alternatively，an excavation procedure of middle cut blasting carried out first，followed by pre-split or smooth blasting is recommended.

By physical model test，the response of end-anchored rockbolt close to working face is studied under blasting loading in mass charge. The dynamic strain measured from strain gauges mounted on rockbolts are obtained considering gauge?s locations on rockbolts and distances from working face. And then，the measured data are analyzed. The results show that：(1) Rockbolts vibration approximately ceases after duration of 5 ms. And the initial wave is either tensile wave or compressive wave. (2) After blasting，the residual deformations exist on the rockbolts. The maximum residual strain appears on the free segment of rockbolts? tail，while the maximum dynamic tensile strain appears on the anchoring segment of rockbolts? middle. When the total strain is divided into axial strain and bending strain，it is found that：(1) The main deformation of rockbolt close to working face under blasting load is bending deformation；and the axial deformation is small relatively. (2) The rockbolts are bending after blasting. And the frequency and magnitude of bending strain wave apparently decrease with the increase of distance. Based on wavelet packet theory，vibration frequency distribution of rockbolt caused by blasting is analyzed. The analysis also proves the attenuation law of vibration frequency of rockbolt. Comparison with previous field test results indicates that the strain waves measured in model test reflect the dynamic response of engineering rockbolts on the whole

By analyzing the data of field measurement，simulation experiments and theoretical analysis of the first fully-mechanized mining face with 7.0 meters height supports in China，the key strata structural morphology of the fully-mechanized face with super-large mining height in Shendong mining area and its influence on strata behaviors as well as the reasonable working resistance of the support are deeply studied. The results show that because of the obviously increased mining height in the super-large mining height workface，the inferior key stratum 1 of overburden is easy to enter the caving zone and periodically breakage as“cantilever”structure but not the“voussoir beam”structure. In this condition，the continuous length of periodic weighting is close to the roof distance of the support，which is significantly larger than that under the action of the key strata as“voussoir beam”structure. In some conditions，the periodically breakage of the inferior key stratum 2 would cause the early breakage of the first one，which would lead to the periodic changes of one big and the other small for the roof weighing step and ground pressure strength. As a result，the determination method of the support?s working resistance is proposed with different key strata structural morphologies. Based on the method，the reasonable working resistance of the 7.0 m height support in working face 22303 of Bulianta Coal Mine should be 17 612 kN. And the existing rated working resistance of 16 800 kN is slightly small in some regions of the working face.

Lots of fractured shaft walls are analyzed by the code method，it is indicated that the results by code method are not consistent with the realities mostly. The temperature difference can cause the changes of strain and stress of shaft wall，while the temperature stress has not been considered in the code method，which may be the key reason leading the inaccurate result of code method. So，it is necessary to modify the code method and consider the influence of temperature stress. Based on the elastic theory，the calculation formula for design strength of shaft wall considering the influence of temperature stress is proposed. The mathematic characteristics of the formula is analyzed；and its uncertainty and modified idea are investigated. Considering the complexity of shaft wall design，in order to improve the scientificalness，rationality and validity of the code method，it is advised that further research and discussion should be brought out.

Both of MTS 815 testing system and acoustic emission (AE) monitoring system are used to measure the AE activities of single rock，single coal and coal-rock combined body under uniaxial compression test. We focus on finding the discrepancies of failure mechanisms of the three；and then it can provide guidance for microseismic monitoring in the field. The experimental results indicate that with the increase of load，the cumulative AE numbers of single rock，single coal and coal-rock combined bodies are increasing. In addition，the AE numbers of unit volume of single coal or coal-rock combined body is about 1 order of magnitude more than those of single rock. It can be attributed to the low coal strength and its internal fractured structure. Through comparison of the AE numbers of different periods，we find the essential characteristics among the three kinds of samples. With the increase of load，the AE number in a time interval gradually increases in rock，decreases in coal，and increases initially and then decreases in coal-rock combined body. In the three kinds of samples，single rock and coal have the maximum and the minimum failure strength，respectively. However，the failure strength of coal-rock combined body lies in between the single rock and coal. For the coal-rock combined body，the AE number accounts for about 10%–30% in rock，and about 70%–90% in coal. In addition，the spatial distribution of AE activity is mainly affected by the coal initial internal micro structure and the primary micro cracks.

The occurrences of breakage and water inrush disasters of working face floor under mining above aquifer are increasing with the mining depth in China. Taking the working face floor above deep aquifer in Jiulong Mine as the research object，by means of the core extraction，drill core logging and laboratory testing，the distribution laws of aquifers and mechanical parameters of each rock stratum of the working face floor above aquifer are obtained. Meanwhile，the reliability of parameters are ensured. The similar simulation test for fracture instability characteristics of working face roof and floor during the mining above aquifer are carried out by the self-designed confined water simulation equipment. And the stress variation laws of the roof and floor during working face mining are obtained. Using the noncontact optical measurement technology，the whole field displacement contours are measured. Base on the‘down three zones’theory，the maximum failure depth of working face floor，the raise height of confined water and the thickness of effective confining rock strata in deep region of Jiulong Mine are calculated. The simulation results show that：the‘three zones’appear in deep working face floor above aquifer in Jiulong Mine；and the new confined water simulation equipment can simulate the process of water pressure relief.

The modified rubber powder-cement mortar and glass fiber reinforced plastics (GFRP) are used to simulate the rock and bolt，respectively. The reinforced effect of bolt on rock mass with perforation joints is studied by laboratory uniaxial tension test. The experimental results show that: (1) Comparison with the failure shape of sample without bolts，the anchored samples present the plastic failure characteristic. (2) The bolts enhance the deformation modulus and uniaxial tensile strength of the jointed rock mass；and the deformation modulus and uniaxial tensile strength increase at first，then decrease with the increase of the anchoring angles. (3) The latter failure modes of reinforced samples change with the increase of anchoring angles，which is relative to the combined effect of bond performance and shear resistance properties.

Comprehensively considering the relationship of the rebound value and longitudinal wave velocity with the temperature，the change laws of the longitudinal wave velocity and mechanical characteristic with temperature of the sandstone after high temperature are studied by triaxial unloading test. The test results show that：(1) The longitudinal wave velocity of the sandstone becomes lower with the increase of baking temperature. And the velocity decreases more rapidly while the temperature becomes higher. (2) With the increase of baking temperature，the rebound value of the sandstone is not a simple monotone increase/decrease. (3) The mechanical properties of sandstone change under the interaction of friction characteristics and cement properties. The friction characteristics strengthen greatly after high temperature baking；and then，the strength of sandstone increases greatly under the high confining pressure. (4) The longitudinal wave velocity，rebound value and strength don?t have inexorable law after high temperature baking. (5) The unloading damage of natural air-dried rock samples under low confining pressure still shows a significant compression and shear failure mode. (6) By analysis of the test results，we believe that the tensile strength of rock samples decreases significantly after high temperature baking. The interior of sandstone produces the thermal stress after heat treatment. The thermal stress induces the thermal cracking of the surface and internal microcracks，which is the essential reason of the tensile strength decreasing.

Based on the notion of the new Austrian tunneling method，the field monitoring of secondary lining structure of central pump house in Zhuji Coal Mine is conducted by displacement convergence gauge and steel-string sensors. And the time-dependent variation laws of surface displacement，contact stress between primary support and secondary lining，reinforcement stress and concrete strain are obtained. The monitoring results show as follows：(1) The surface displacement rate is larger at the early stage and the displacement is convergent after about 100 days of secondary lining construction. (2) The contact between primary support and secondary lining is close，which indicates that the secondary lining bears the load of surrounding rock effectively. (3) The reinforcement stress changes enormously at initial several days，then increases and achieves a steady state eventually. (4) The concrete strain is stable after experiencing a transformation from initial compressive strain to tension strain. By analyzing the monitoring data，the conclusions can be drawn as follows：(1) The final values of all monitoring items are within safety limit，which demonstrates the reliability and security of secondary lining structure. (2) The steel string sensors are easily affected by the hydration heat generated in the process of concrete hardening. (3) The mechanical state of secondary lining is disturbed by excavation of adjecent caverns.

A self-made observation testing apparatus of micro- and meso-scopic mechanics and deformation of tailings is used to study the nonlinear characteristics of deformation evolution for meso-scopic structure of tailings under loading，including directionality of internal stress，variation rule of void ratio，fractal characteristics of meso-scopic pore structure，deformation evolution rule of pore structure under loading，etc. The results show as follows：(1) The internal stress of tailing specimen has obvious direction characteristics，because the vertical stress which is slightly lower than load increases nonlinearly and horizontal stress which is far lower than load increases linearly with the increase in load. (2) The void ratio of tailings，which changes a lot，decreases nonlinearly in different layers. The change in void ratio for lower layer lags behind that for upper layer；and both will finally reduce to the same value. (3) The concept of section void ratio of meso-scopic structure of tailings is put forward. For the same section，the section void ratio has linearly positive correlation with void ratio of the same layer. (4) The meso-scopic structure of tailings has obvious perimeter-area fractal characteristics. The fractal dimensions are 1.424–1.537；and its value has logarithmically negative correlation with section void ratio obviously. (5) The section void ratio decreases under the effect of loading despite tiny rebound，the fractal dimension of perimeter-area increases at stages under the effect of loading，followed by small amplitude reduction at each stage. The section void ratio and fractal dimension of perimeter-area describing the characteristics of meso-scopic structure of tailings are put forward，which is very important to quantitatively study meso-scopic structure characteristics and mechanical properties of tailings dams.

Based on in-situ stress measurement results in 5 mine areas of Huainan coal mine，Anhui province，by hydraulic fracturing method，the in-situ stress characteristics and the influence of lithology on it are revealed；the variation law of stress and plastic zone of surrounding rocks around tunnels after excavation are analyzed. The following preliminary results are obtained as follows：(1) The tectonic stress is dominant in these areas and the stress level is high. (2) The lithology has a great influence on the coefficient of lateral pressure. The obtained coefficients of sandstone are 1.52–1.87，and for mudstone，they are 1.08–1.18. (3) The lithology has a great influence on the plastic zone of surrounding rocks around tunnels. Because of the difference of lithology，the range of plastic zone in Panyi mine differs greatly from that of south part of Guqiao coal mine，though the maximum horizontal principal stresses of these two mines are close. In addition，the range of plastic zone in Liuzhuang coal mine which consists of calcilutyte is obviously greater than that of Panyi coal mine which consists of quartz-sandstone，though the maximum horizontal principal stresses at the measured depth in Liuzhuang coal mine is smaller than that of Panyi coal mine. The results can provide references for analysis of failure mechanism of surrounding rocks and reinforcement and support of tunnels of similar projects.

The surrounding rock of roadway in Tertiary thick coal seam in Qingshui coal mine of Shenyang is soft with high ground pressure. The tunnel had large deformation with 4 times reinforcement and much damaged support after excavation. The mechanisms of rock plastic flow，asymmetry deformation and failure and inharmonic deformation between support and rock are analyzed. The initial support with constant resistance and large deformation bolt can protect the support capacity of the anchorage zone. After the release of deformation energy by the extensional deformation of the constant resistance and large deformation bolt，the concentration stress is transferred to deep to utilize the strength of deep surrounding rock；then the stable loading plastic zone is formed. According to the characteristic of the mining roadway，the reinforced support is complementary with the strengthened roof，released stress sidewalls and supported side corner. The stability is dependent on the common load by support and surrounding rock. The new design containing anchor cable，constant resistance and large deformation bolt，steel band，injected pile is applied to successfully controlling the roadway at #205 working face in second mining area in southern mine. The theory is applied to controlling the stability of this kind of coal entry. The roof subsidence，sidewall shrinkage and floor heave reduced by 75%，60%，42%，respectively. The practice shows that the proposed method can control the deformation of the roadway with soft rock.

Two-dimensional scattering of incident Rayleigh waves by a lined tunnel in elastic half-space is solved and analyzed by the high-precision indirect boundary integral equation method(IBIEM). It is found that the scattering around the lined tunnel may be significantly different from that around the unlined tunnel；and the lining stiffness has a great effect on the wave scattering. The dynamic response and dynamic stress concentration depend considerably on the stiffness ratio of the lining to the surrounding soil，the embedded depth and the radius of the tunnel，the frequency of incident waves，etc. For the soft lining，there is a large displacement amplification for the case of shallow tunnel. While for the rigid lining，the dynamic stress concentration at the inner surface of the lining is very large. In the whole，the scattering of Rayleigh wave around the tunnel gradually weakens as the depth of tunnel increases.

Zhaolou coal mine is one of the deepest mines in China. Its geological structure is more complex because it is located in Caoxian—Yuncheng active fault. In order to master the distribution law of in-situ stress field in the mine，the in-situ stress measurement is carried out by means of the hydraulic fracturing in-situ stress measurement technique. The stress states are obtained for 16 measuring sections in 2 holes. The measurement results show that the maximum principal stress increases linearly as the depth increases；and the in-situ stresses are varied around the depth of 800 m. The maximum horizontal principal stresses are 28.45–45.75 MPa；and their directions are NEE. It reflects that the horizontal stress is dominant in the stress field of the mine area. The proposed measurement results provide scientific basis for the mine construction and mining design.

Due to the severe strata pressure characteristic of the gob-side entry driving in the island mining face and the difficulty in supporting roadway，if supporting parameters of the gob-side entry driving are improperly designed，and roadway support fails，the mining safety will be greatly affected. Taking the return airway of No. 1251(3) island mining face as project background，3-dimensional fast Lagrange analysis of continua (FLAC3D) is adopted to study the distribution characteristics of advance abutment pressure in the island mining face. The mechanical model of main roof of the gob-side entry driving in the island mining face is established. By the mechanical model，the calculating formula of roof convergence affected by the dynamic pressure is derived. The study results show that when the advance abutment pressure of the island mining face increases obviously，the surrounding rock deformation of gob-side entry driving in the island mining face increases dramatically，which adds to the difficulty in supporting roadway. Based upon the above study results，the supporting parameters of roadway during the periods of roadway driving and mining are separately designed. The engineering practices show that the combining support of bolting，cable，wire mesh，and grouting can effectively control the surrounding rock deformation of the gob-side entry driving in the island mining face. The results can be generalized for roadway support under similar conditions.

Tunnel boring machine(TBM)performance prediction has played an important role in the selection of construction method，project planning，construction planning and management. Headrace tunnels No.1 and No.3 of Jinping II Hydropower station were excavated respectively by two tunnel boring machines. On the base of the obtained information of rock masses conditions and rock masses environmental conditions，such as in-situ stress and groundwater condition along the tunnel alignments，the rock mass was sectioned according to the influence of key factors on TBM excavation. NTNU and rock mass characteristic TBM performance prediction models were used to predict the penetration rate. And NTNU cutter life mode and CAI value were used to predict the cutter wear. By comparing the results of in-situ TBM penetration tests with the prediction penetration rates，the applicability and errors of these penetration rate prediction models were discussed. During TBM construction process，the rock mass conditions，TBM operation parameters，TBM operation results were collected and analyzed. The actual rock mass conditions and excavation results were compared with the rock mass conditions obtained for TBM performance prediction and predicted TBM performance results. The reasons of making the difference were studied. Generally，the penetration rate prediction is reliable in most cases. But in the condition of high in-situ stress，these TBM penetration rate prediction models need to be modified. Due to the influence of the high in-situ stress and rock bursts，the abnormal cutter failure is too much. Thus，the predicted results for cutter life are not good.

The failure phenomena such as large deformation and collapse usually occur in weak surrounding rock of tunnels after excavation because of low strength，poor stability and long deformation period. The failure phenomena result in intense deformation and damage of the first stage support，which have a strong impact on construction and security of tunnels and become a major problem in the construction of tunnels. Mechanical characteristics of the support system are analyzed by monitoring axial force of rock bolts，pressure of surrounding rock and stress in the steel frames for Tianpingshan tunnel of Guizhou—Guangzhou Railway. It is concluded that，for the weak surrounding rock which has large deformation rate in the first stage of excavation，the axial force of rock bolts is often large in the middle and small in the ends；and its variation often lasts for a long period of time. The profile steel frame has larger surrounding rock pressure than the grid steel frame by 70%–90% under the same geologic conditions；the profile steel frame has more uniform stress distribution and better support effect than the grid steel frame.

Based on the stochastic granular discontinuous deformation(SGDD) method，a cohesive zone model is employed to simulate the breakage of coarse aggregates. In this model the cohesive interface elements are inserted into the region of coarse aggregates；and the constitutive response of cohesive element is governed by an energy-based damage evolution law. If the interface between these sub-particles breaks，the breakage will happen. By using this model，it is possible to study the influence of particle breakage on the macroscopic properties of the rockfill，such as volumetric strain，shear strength and dilatancy angle. The numerical simulation results reveal that the strength of the coarse-grained material can significantly decrease due to particle breakage. The mechanism of this phenomenon lies in the weakening effect of dilatation due to particle breakage. Along with particle breakage，the acoustic emission(AE) occurs；and the AE count under higher confining pressure is greater than that under lower confining pressure. In the shear process，the contact normal orientation between particles is inclining gradually from horizontal direction to vertical direction. Furthermore，the main direction of normal contact force is the same as the loading direction；and the average normal contact force between particles increases gradually.

Based on Biot theory，a semi-analytical approach is proposed to analyze the transient response of one-dimensional porous media；and the first typical boundary condition is adopted as an example. The dimensionless displacement governing equations with its initial and boundary conditions in matrix form are derived. A proper transform is applied to homogenizing the boundary condition；and the corresponding characteristic problem for the governing equations with viscous coupling omitted is solved to get a series of eigenvalues and characteristic functions，which are proved to be orthogonal. Using the orthogonality of characteristic functions，a series of ordinary differential equations and their initial conditions are derived. The ordinary differential equation system is only coupled in damping matrix and is solved by precise time-integration method when it is truncated as a finite ordinary differential equation system. Some examples are presented to demonstrate the influence of the dynamic permeability coefficient on propagation of waves. The method is valid for arbitrary non-homogeneous boundary conditions and suitable for problems considering inertia，viscous and mechanical couplings；and no limitation of compressibility of fluid and solid particles is required.

In order to study the action effect and mechanism of rock bolt in loess tunnel，the stresses of 48 rock bolts in 3 loess tunnels in Wubao—Zizhou Expressway in Shaanxi Province are measured by in-situ tests and statistically analyzed. It is shown that under the condition of steel arch support，the arch systematic rock bolts in loess tunnel are compressed and the stress is very small；the feet-lock bolts in arch foot are mainly subjected to tension and the stresses of feet-lock rock bolts are larger than those of arch systematic rock bolts. The mechanical state of arch systematic rock bolts in loess tunnel is analyzed from the deformation of soil and anchoring effect of rock bolt and soil. It is revealed as follows：(1) After tunnel excavation，the arch of shallow loess tunnel settles entirely；and there is no anchoring section in systematic rock bolts. (2) After tunnel excavation，there is a large part of plastic area in deep loess tunnel；and there is no anchoring section in systematic rock bolts. (3) The anchoring effect of rock bolt and soil by cement mortar and anchor agent is not very well；so the anchoring force of rock bolt in loess tunnel is small. (4) Rock bolt is anchored in the first lining and inserted into the soil，which can constrain the soil inside. After the construction of the first lining，the arch systematic rock bolts are subjected to downward frictional resistance from soil，corresponding to negative friction in pile；so the arch systematic rock bolts in loess tunnel are compressed. From the above analysis，it is shown that under the condition of steel arch support，the support effect of systematic rock bolts in loess tunnel is not obvious，which can be ignored. Engineering practice shows that ignoring systematic bolts under the condition of steel arch support can reduce construction procedure，making construction safe and improving the safety of support structure；it also can reduce the engineering cost and shorten the construction period. It will achieve obvious economic and social benefits.

24 groups of shear tests on remolded loess are conducted by using triaxial apparatus for unsaturated soils to study the wetting deformation laws of unsaturated embankment fill. The dry densities of specimens are 1.7 and 1.8 g/cm3，respectively；the cell pressures are chosen as 50，100 and 200 kPa；and the control suctions are chosen as 0，50，100 and 200 kPa. Based on the above，two simplified models and double-line method are used in the analysis of wetting deformation；and formulae for calculating the wetting deformation using the two models mentioned above and values of relevant parameters are proposed. Through the analysis，it is shown that the wetting deformation are greatly influenced by the dry density；and the wetting deformation could be effectively controlled through the enhancement of compaction of the roadbed.

The strength parameters of sliding zone soil are indispensable factors for stability evaluation and countermeasure design for landslides. Based on the previous study results，the shear tests on sliding zone soil derived from Xuecheng landslide，located along Zagunao river，Sichuan province，are conducted as follows：first the sliding zone soil is consolidated；then large displacement ring sheared，then consolidated again，and last ring sheared again；and the strength characteristics of sliding zone soil of the reactivated landslide are simulated and clarified. The method for determining and selecting the residual strength and recovered strength parameters depending on different effective vertical stresses is proposed and proved to be useful and rational for the reactivated landslide. The method may provide some important references for rationally choosing strength parameters of sliding zone soil of the reactivated landslide.

A series of direct shear tests were carried out to study the effect of stress history on shear behavior of interface between clay and concrete. The clay-concrete interfaces of different roughnesses(sawtooth height of 0，1 and 2 cm，respectively) were loaded to an initial normal stress，then unloaded to a normal stress before shearing according to the schemes of loading and unloading. Results are presented for interface shear behavior in forms of shear stress-shear strain curves，vertical strain-shear strain curves and shear strength parameters. Results show that the shape of shear stress-shear strain curves is hyperbolic；and no strain-softening phenomenon was observed in the tests. Higher initial normal stresses offer higher shear stress with the same horizontal displacement. The strength of interface still obeys the Mohr-Coulomb criterion；and the internal friction angle and cohesion can be obtained by fitting lineally. The effective parameters of friction and cohesion are employed to reflect interface strength normalized by the strength parameters of clay. The higher applied initial normal stress offers the lower effective parameter of friction. But the higher effective parameter of cohesion is received for higher applied initial normal stress. The dilation was observed during the process of shearing the interfaces of different roughnesses；the rougher interface offers the higher dilative displacement. Meanwhile，the effect of stress history on dilation law of interface is obvious. For the interface without experiencing normally unloading，it first exhibits a short contraction behavior before dilatation，while directly exhibits dilation for the interface experienced normally unloading. The more significant dilation was found for the higher initial normal stress.

The simple shear tests are conducted to study the shear properties of silty clay-concrete interface by using the improved cyclic simple shear testing system. Three kinds of interface roughnesses，i.e. smooth，general and rough，respectively，and two kinds of soil specimen thicknesses(10，20 mm) are selected with normal pressure varying from 5 to 200 kPa to probe into the effects of these factors on the shear properties of interface. Test results show that the interface exhibits mainly two kinds of shear failure modes，i.e. shear failure in soil nearby the interface and sliding failure at the interface. The shear strength of interface is equal to the lower limit value of these two failure modes；and the stress-strain relationship of interface is accordingly determined by which of the two failure modes happens，although it tends to be the former mode with the increasing interface roughness and normal pressure. The tested stress-strain curves are affected by the thickness of soil specimen that adopted in tests，although this effect decreases rapidly with the increasing interface roughness and normal pressure.