Modern cities have been expanded rapidly and crowded with skyscrapers，which inevitably yields severe environmental pollution，resource shortage，traffic conjunction and exorbitant housing prices. These urban problems have significantly restricted the healthy development of urbanization. The 21st century is marked by the anthropogenic utilization of underground space，but the sustainable development is confined by the current passive and extensive underground exploitations in a single-function and disorderly manner. The mode of exploitation and utilization in the foreseeable future should be changed from the passive to an active manner with the features to be ecologically，integrated，deeper and informational. In this study，some key principles for underground space exploitation were proposed. The different stages for deep earth science from era 1.0–5.0，the corresponding top plan conception and strategic blueprint were presented. Taking the unique advantages of the deep space，such as the clean environment，sound and quake insolation，natural disaster prevention，low background radiation and constant temperature and humidity，the idea and associated subversive technology have also been proposed with the aim to utilize the underground space for self-balancing and multi-layered ecological city through the deep underground energy resource generation and recycling system，harmless treatment and storage system of wastes in deep underground circumstances. The deep underground city with the full-chain deep underground ecosystem will be constructed with the capacity for settlement，health-care，manufacturing and scientific research. These functions will realize the prospect of utilizing the space and resources from the underground. The idea of underground cities and ecosystems will fundamentally relieve the conflict between the rapid population growth and relative shortage of surface land resources，which will be an important step to realize the sustainable development of human society in the future.

Based upon the cutting cantilever beam theory and the construction experience in Ningtiaota coal mine，the mechanism of gob-side entry by roof cutting was analyzed and the key processes of this novel no-pillar mining method was proposed. A double blast-hole mechanical model was established to obtain the cutting-through criterion of adjacent holes. The key parameters for the cumulative blasting was obtained considering the roof lithology of mining face S1201. The stress distribution and development before and after the roof cutting in both the mining face and the entry were studied systematically by means of theoretical analysis，numerical simulation and field measurement. The results indicate that the mine pressure at the working face and retained entry changes a lot before and after the roof cutting，mainly because the cutting process alters the roof connection and prevents the stress propagation from the gob roof to the entry roof. The periodic pressure strength reduces while the periodic roof weighting pace increases to a certain extent within the area of roof cutting influence. Analysis also shows that the supporting role of the gangue filling body is the immediate reason for the pressure strength reduction，and the decrease of the effective loading acting on the key stratum is the substantial cause for the roof weighting pace to increase. The gob rock masses experience the caving，compacting and stabilizing processes due to the roof cutting. Fully utilization of the bearing capacity of hulking gangues and the collaborative support of surrounding rocks are the effective ways to reduce the supporting intensity and increase the stability of surrounding rocks.

The current indices used to evaluate the shale brittleness consider mostly the mechanical properties before or after the peak separately and cannot reflect the brittleness characteristics in the whole process of rock failure. In this paper，the variation of the various types of strain energy of rock materials in the process of plastic deformation to brittle fracturing was analysed based on the complete stress-strain curves. The levels of the pre-peak dissipation energy and the post-peak fracturing energy are the key factors to determine whether the brittle fracturing occurs. The brittleness estimation indices which represent comprehensively the mechanical properties of rock in pre-peak and post-peak periods were proposed by combining the pre-peak dissipation energy and the post-peak fracturing energy. The brittle characteristics of different rock materials under different confining pressures and the anisotropy of shale brittleness were evaluated with these brittleness indices. The results show that the proposed brittleness indices can simultaneously reflect the difficulty of brittle failure and the scale of brittleness and can evaluate the change of brittle characteristics under different mechanical conditions. The pre-peak dissipation energy and post-peak fracturing energy of different rock materials increase with the increase of the confining pressure. The brittleness decreases constantly with the increase of the confining pressure，but the decrease trends are different. The red sandstone and shale show the transformation of brittleness-plasticity at low and high confining pressures，while the granite has the strong brittleness in the whole process of the confining pressure increasing. The brittleness of shale is anisotropic. The brittleness of shale specimens with different inclination angles of bedding plane has significant difference. The shale brittleness shows a transition process of stable，increase to decrease as the inclination angle of bedding planes ? increases. When ? = 0°，the degree of brittleness of shale is stronger than that of ? = 90°. When ? = 60°，shale has the weakest brittleness and shows the plastic characteristic.

The strict grading requirements of rockfill materials in hydropower engineering cause the difficulty to predict the fragmentation distribution. The statistical results of primary joints and the simulation on blasting cracks were employed together with the field investigation，indoor experiment，numerical simulation and engineering test to investigate preliminarily the blasting fragmentation distribution of rockfill materials. A set of fragment-size prediction methods were established. Firstly，the distribution network of natural joints of the study area was drawn through field investigation，and a three-dimensional jointed rock mass model based on the statistical results of primary joints was established. Then，the dynamic parameters of the rocks under the impact load were obtained with SHPB test device，and the extension ranges of blasting cracks were simulated with Ansys/Ls-Dyna. A three-dimensional jointed rock mass model after blasting in the investigation area was established considering comprehensively the information of primary joints and simulation results of blasting cracks. The output data of line-area-volume from the three-dimensional jointed rock model were used for block calculation with Matlab. The fifth longest side of rock blocks was taken as a fragmentation prediction index，and finally the predicted grading curve was obtained. Engineering application shows that the gradation prediction method is in line with the engineering practice. The overall prediction error is 5.5% in Jiang Tsui quarry which is much better than that of index based on diameters of equal volume sphere.

The discrete element method based on the potential function has many deficiencies. The physical meaning of the potential function is not clear and the contact force calculation is inconsistent with the reality. A novel discrete element method based on the distance potential for the arbitral convex polygonal elements was thus proposed using the new definition of the distance potential function. This method describes the potential function as a normalized distance function between the contact couples. The distance potential function has the physical meaning and gives an accurate measurement for the embedded extent of the contact couples. Furthermore，the tangential vector is redefined and calculated in this approach. This method retains all the merits of the original potential method and remedies the problem in which the contact force calculation is affected by the element form. In addition，the method gets rid of the restrain of the triangular shape completely and can be applied to the arbitrary polygonal elements. It was illustrated with several examples that the method can accurately simulate the motion of the complex discontinuous media.

Tunnels contain radial cracks due to the blasting excavation，and these cracks affect the tunnel stability significantly. In order to study the dynamic fracture behavior of tunnels containing radial cracks under the impact loading，the medium and low speed impact experiment was carried out by using the sandstone tunnel models，and the finite difference code AUTODYN was used for the numerical simulation. The propagation path and the arrest of the crack under the impact loading were studied，and the crack initiation toughness and propagation speed were calculated with the experimental-numerical-analytical methods. The fracturing behaviors of surrounding rock under the static and dynamic loadings are quite different. The damage under the dynamic loading is only the crack initiation and propagation at the crack tips，whereas the damage under the static loading occurrs at the crack tip，arch shoulder，arch foot and sidewalls. The propagation path of the radial crack is along the original direction of the crack under the impact loading，and the crack arrest phenomena was observed clearly in the propagation path. The experimental-numerical-analytical method can be used to determinate the initiation and propagation speed quite well. The curves of the dynamic stress intensity factors of cracks versus the time were obtained by using the displacement extrapolation method. The dynamic initiation toughness was determined using the initiation time measured with the strain gauges.

The bedding rock mass is a common geological configuration in tunnel engineering. The seismic damage occurs frequently in the bedding strata，but there is no effective method of seismic response analysis. In this paper，a method of seismic wave input and a corresponding formula were established. The method combines the FEM with the analysis of the time-domain wave and adopts the visco-elastic artificial boundary. The transverse isotropic constitutive law of bedding rock mass is used with the consideration of the characteristics of polarization and phase velocity change of the seismic wave in rock mass. The method is applicable to the case of the oblique incidence direction of earthquake wave in parallel with the longitudinal section of the tunnel. In order to verify the feasibility of the method，the seismic response of a high-speed railway tunnel in a bedding rock mass was studied. The results show that，when the rock layer is horizontal or vertical，the qP wave causes the symmetric internal force envelope of lining. When the rock layer is inclined，the qP wave causes the asymmetric internal force envelope，and the amplitude of the asymmetry correlates to the dip angle of the rock layer. When the dip angles of rock layers are different，the difference of bending moments is larger. The maximum of hoop bending moment is located at the arch foot，while the maximum longitudinal bending moment is located at the vault and invert no matter the moment envelope is symmetrical or not. When the rock layer is simplified as the isotropic medium，the P wave causes the symmetric internal force envelope，which is close to the results when the rock layer is simplified as the transversely isotropic medium. The findings further verify the rationality and reliability of the method.

The first time fracturing of the main roof is often analyzed with the fixed boundary conditions at four edges which are difficult to achieve in practice. A mechanical model of elastic thin plate with the elastic boundary foundation condition was established. The influences of the elastic foundation coefficient k，the span L，the main roof thickness h，the elastic modulus E，Poisson?s ratio on the principal moments and initial fracture position of the main roof are calculated with the finite difference method. The first time fracturing of the main roof with the elastic foundation boundary calculated based on the fracture criterion of principal moments occurs in the middle or at the long side ahead of the coal wall. When the ratio of k/E or k/h3 or k/(Eh3) is constant，the fracture position of the main roof is not changed. When the ratio of k/E or k/h3 or k/(Eh3) is small，the middle of the main roof fractures firstly，namely，when the coal seam is soft and the thickness and elastic modulus of the main roof are large，the main roof fractures firstly in the middle. When the ratio of k/E or k/h3 or k/(Eh3) is large，the long side edge ahead of the coal wall fractures firstly，namely，when the coal seam is hard，and the thickness and elastic modulus of the main roof are small，the first fracturing position is at the long side edge ahead of the coal wall. The initial fracturing of the main roof with the elastic foundation boundary is determined by k，L and the stiffness D of the main roof.

Calculations of hydraulic fracturing are very essential for the exploration of shale gas. In this paper，the shale is approximated by a homogeneous porous medium. The seepage process in rock mass and the fluid motion in cracks are described by the dynamic Darcy-Biot and Poiseuille flows respectively. The crack propagation is tracked with the phase-field method and the simulation method for the dynamic hydraulic model is proposed. The method is implemented under an explicit finite element scheme. The accuracy of the method to calculate the dynamic displacement and pressure fields is illustrated by comparing the output with the one-dimensional analytical solution. A series of numerical examples indicate that the proposed method can not only simulate the typical characteristics of dynamic hydraulic fracturing，can also calculate the crack intersection，bifurcation and three-dimensional propagation.

In this research，two centrifuge shaking table model tests with the geometric scale of 1∶50 were conducted to study the seismic behaviours of lower bedrock deposit slopes before and after reinforced with stabilizing piles. 4-stage seismic waves(El Centro wave) with the increasing peak acceleration were applied from the bottom of each model. The acceleration response at slope surface and inside，the crest settlements，the distribution characteristics of static and dynamic bending moments were monitored in the process of tests. The recorded data and observations of the centrifuge models showed that the PGA amplification coefficient，the acceleration response spectra and the settlements at slope crest were decreased to some extent when the lower bedrock deposit slope was reinforced with the stabilizing piles. The stabilizing piles improved the seismic performance of upper deposit under earthquake conditions and in the meantime caused the seismic wave reflection effects in slope body，which make slope surface acceleration amplification factor increased along the pile-crest direction but decreased along the pile-toe direction. The relationships between the permanent displacements at slope crest and the Arias intensity of input seismic waves were linear. The changing amplitude of the dynamic bending moment of pile in the earthquake loading process was significantly larger than the increment of static bending moment after seismic excitations. Both the dynamic bending moment and static bending moment of pile reached their peak values near the bedrock surface，where the stabilizing piles most likely been damaged. These features should be fully considered in the aseismic design of stabilizing piles.

A new device was designed to study the failure characteristics of rock in complex stress state under excavation unloading. The hollow cylinder specimens with 49.84 mm in outer diameter and 20 mm in inner diameter were prepared and were tested under loading and unloading conditions on the system RMT–150C. The failure mechanism of the specimens subjected to the hole pressure unloading was discussed in detail. Owing to the existence of the stress difference，the hollow cylinders do not show the ductile behavior under the high confining pressure，the strengths of the hollow cylinders with hole pressures are greater than those of the hollow cylinders with no hole pressure at high confining pressure. The effect of the hole pressure unloading on the damage of hollow cylinder is great. The strengths of the hollow cylinders under the hole pressure unloading are lower than those of the hollow cylinders under the axial loading. The influence of the unloading on the strength is smaller when the stress difference at the failure is large. This indicates that the reason of the failure of the surrounding rock lies in the increase of the stress difference after the excavation unloading. The failure mode of most of the hollow specimens with a certain hole pressure is shearing. However，all specimens under hole pressure unloading conditions present the modes of tensile failure or tensile-shear failure，indicating that the stress paths have the great effect on the failure patterns of the hollow cylinders.

A method of slope stability analysis based on independent cover manifold method(ICMM) and vector sum method(VSM) was proposed in this paper. ICMM is employed to calculate the stress fields，particularly for slopes containing discontinuities(joint，faults etc.). This method avoids the complex pre-processing algorithm in the finite element and numerical manifold methods. To calculate the factor of safety，VSM is carried out with the real stress state and the vector sum algorithm. VSM possesses the merits of clear physical meaning and high efficiency without the time-consuming iterations involved in the strength reduction method. Besides，the simulated annealing genetic algorithm(SAGA) is used to determine the critical slip surface. With the above advantages，the factor of safety of complex slopes containing discontinuities could be calculated effectively and precisely by the proposed method. Four representative numerical examples and one engineering case validate the proposed method.

The dynamic response and energy-absorbing property of medium-fine grained granite under the actual temperature were studied using the modified split Hopkinson pressure bar(SHPB). The complete stress-strain curve of the granite displayed three notable stages of elastic，plastic and strain-softening in the range of 20 ℃–500 ℃. When the temperature rose to 700 ℃，the plastic yielding platform in the curve appears. A rise in the strain rate caused the increase of the compressive strength of granite，but the effect of the strain rate decreased gradually as the temperature increases. Neither the temperature nor the strain rate showed the influence patterns on the elastic modulus. The increase of strain rate raised the energy-absorbing capacity of per unit volume(Ev)，but the effects of strain rate on the value of Ev were quite diverse under the different temperatures. When the temperature was less than or equal to 500 ℃，the effects of strain-rate on the peak strain are relatively close，whereas the strain-rate sensitivity coefficient of the peak strain increased significantly at 700 ℃. Under the same loading pressure，the strain-rate ranges of the specimens treated under different temperatures differed widely，and the influence coefficients of the pressure were also distinct. The failure mode of specimen under the increasing strain rate at 500 ℃ and below changed from the axial splitting to fracturing. At the temperature of 700 ℃，all the specimens were pulverized.

A new pseudo three-dimensional analytic solution for stresses of horizontal borewell in transverse isotropic rock considering the hydrostatic pressure of borehole，the maximum and minimum horizontal principal in-situ stresses and the overburden stress was established based on the anisotropic linear elastic mechanics，coordinate transformation methods and the superposition principle. The distributions of three principal stresses of the horizontal borewells in shale and sandstone were analyzed. The results show that compared with the situation in mechanically isotropic formations，the anisotropy of rock mechanical properties does not affect the principal stress ，but affects the distribution of the principal stresses and . The greater the anisotropy is，the more affected the principal stress and . High mechanical anisotropy may increase the number of tensile broken points on borehole wall.

Different heating paths produce the different heating effects. The power and the heating time are the important parameters influencing the rock fragmentation. The microwave heating tests were conducted to the cubic and cylindrical basalt samples under three different heating paths and the P-wave velocity and UCS were measured before and after the microwave treatment. The sample burst into fragments when the thermal stress within the sample exceeds the ultimate strength of the rock. The sample was largely melt when the temperature in the sample exceeded the melting point. When a high microwave power was applied，the sample burst into fragments in shorter time and consumed low energy. The P-wave velocity and UCS had a significant reduction before the sample burst. The higher the power，the shorter the burst time and the faster the strength reduction. Therefore，the high power microwave can be used in rock fragmentation or assisted mechanical rock breakage with significantly decrease in energy consumption.

In the tunnel excavation，the deformation of the soil core in front of the surface of tunnel excavation may stimulate the arch effect in the surrounding soil ahead of the tunnel face. This kind of arch effect is different from the one produced behind the tunnel face and is called the incomplete arch effect. The performance of the incomplete arch effect is closely related to the pre-convergence deformation and extrusion. The formulas for calculating the soil pressure around the front soil core considering the incomplete arch effect are proposed and are different from Terzaghi formula，because in the proposed method，an angle between the fracture face and vertical direction is assumed and the effect of the pre-convergence deformation on the surrounding soil pressure and the non-vertical sliding surface effect of cohesive soils are taken into consideration. The results show that as the increase of the pre-convergence deformation，the earth pressure exhibits three stages：the rapid near-linear decrease，the slow decrease and the stable ones. The earth pressure decreases with the increase of internal friction angle，thickness-span ratio and cohesion. However，the earth pressure increases with the increase of the angle of rupture surface. The formula for calculating the reinforcement parameters of the front soil core based on ADECO-RS is deduced and its applicability is verified in a case study.

The stability of electric circuit，the digital techniques for the improvement of complete temperature compensation method and the application of in-situ equipment under complex environment were investigated with the technique of CSIRO cell in order to meet the demand of accurate measurement and long-term monitoring of in-situ stresses. The development of the collection system with the function of instantaneous data-logging and data-connection in power cut-off condition were discussed in this paper as well. The compromised techniques of temperature self-compensation transducers and a double circuit set for temperature compensation(twin temperature compensation) are involved in the realization of complete temperature compensation in the front-end digital CSIRO cell. The test results of lab and in-situ measurement show that the twin temperature compensation technique can improve the precision of measurement to 15%(compared with the results from the original temperature compensation method). Three groups of in-situ tests were also carried out with the new digital hollow cell，and the recorded curves of strain gauges correctly indicate the defects of rock core，the tectonic disturbance，the intense influence of temperature and the process of stress release. The modified values from the twin temperature compensation calculation of the last two in-situ measurement are 64 ?? and 86 ?? respectively and the stability of the data can still meet the standard of 5 ?? in 30 minutes under the intense disturbance of temperature. The new type of digital CSIRO cell shows good accuracy and stability both in laboratory experiments and in-situ tests.

Determination of over consolidation ration(OCR) from piezocone penetration tests(CPTU) can not only avoid the sample disturbance in laboratories but also provide the continuous profiles of OCR of soil with depth. The penetration of piezocone is taken as the ultimate internal pressure required in expanding a spherical cavity. Assuming the normal and shear stresses on the cone face to be the friction at the cone-soil interface and the ultimate expansion pressure respectively，a modified approach to determine the OCR from CPTU was proposed using the solution of a spherical cavity expansion described with the modified cam clay. Two CPTUs in lightly and heavily over-consolidated clays are selected to verify the general validity of the proposed method. Comparisons between the predicted and measured results show that the presented method is more reliable than the existing approaches because more factors such as the cone roughness and cone penetration rate are taken into account. The presented method is also applied to Lianyungang marine clay for OCR prediction，and the result shows that the layer is consolidated or lightly over consolidated.

The cyclic freezing-thawing is one of the main factors causing the performance deterioration of the subgrade filling material in cold regions. In order to identify the effect of the original compaction degree on the variation of mechanical properties of silty clay in Qinghai—Tibet Plateau，a series of triaxial tests were performed with different degrees of compaction under freezing-thawing cycles. The results show that the levels of original compaction degree affect considerably the freezing and thawing effect on soil mechanical properties. The forms of stress-strain relation of samples with different degrees of compaction are similar，changing from the strain softening to hardening after several freezing-thawing cycles. The water migration inside samples under the closed condition during the freezing and thawing lead to the partition of zones with the moisture content increase and decrease respectively. The sample with the lower compaction degree has a bigger zone with the moisture content increasing. The effect of freeze-thaw cycles on the failure strength decrease for the samples with high compaction degree，and increase for those with low compaction degree. The relationship between the shear strength and the moisture content can be expressed as a nonlinear function，and the redistribution of the moisture content inside the samples leads the change of overall shear strength. After the repeated cyclic freezing-thawing，the cohesion of samples with the high compaction degree decreases，while that with the low compaction degree increases. The internal angle of friction always increases after the redistribution of moisture content，and the lower compaction degree causes the higher increasing rate. Hence both the dry density and water redistribution affect the mechanical properties of samples，and their effects exist simultaneously during the freezing-thawing cycles. Which of these two factors played the leading role depends on the original compaction degree and the number of freezing-thawing cycles.

纤维增强塑料筋锚杆具有的高强度、耐腐蚀特性使其比传统钢锚杆更具应用前景，目前其相关研究尚处于起步阶段。锚固力学特征分析对其应用于锚固工程具有直接的指导意义，对此从纤维增强塑料筋锚杆拉拔试验所得P-s曲线出发，建立锚固段剪切滑移刚度沿程变化的界面黏结–滑移本构模型，该模型包含了对锚杆材料属性、岩土体性质、围岩应力状态以及接触面性质的综合反映。结合受力平衡方程和变形协调方程，以最小势能原理为约束条件，在边界条件下，通过离散迭代求解了端部锚固锚杆在拉拔荷载作用下锚固体轴向应力、侧阻力以及相对滑移的分布演化规律，并从能量角度推导端锚条件下锚杆临界锚固长度的计算模型。算例计算结果与实际工程所测得的规律和趋势相符，验证算法的合理性。该算法能够为纤维增强塑料筋锚杆锚固系统的分析和设计提供理论参考。

Several ground treatment methods were applied in the joint section of the island and the tunnel of Hong Kong-Zhuhai-Macau Bridge(HZMB) to reduce the deformation of the foundation below the tunnel. Part of the ground under the tunnel was treated with the preload and the high pressure jet grouting piles(JGP). There is more than 10 meters backfilled sand layer over the treated foundation. The current field tests such as the core bowling，the standard penetrate test(SPT) and plate test are not suitable for evaluating the reinforcement effect. A full scale load test based on the Boussinesq theory was designed with the heaped load method to simulate the additional stress distribution of the immersed tube tunnel foundation. The good settlement results were obtained utilizing a serial of pre-embedded high precision hydrostatic levelling systems(HLS). The tangent modulus method considering the impact of modulus nonlinearity was employed for calculating the nonlinear settlement of the soft ground. The calculated results were compared with the experimental data and the numerical simulation results. The results obtained using the calculation model are quite close to the field measured data.

Consolidated-undrained triaxial shear tests were conducted at different strain rates and confining pressures to study the effects of strain rates on the effective deviatoric stress and pore water pressure of thawed saturated Harbin clay(TSHC). The results show that the thawed saturated Harbin clay presents an over- consolidation characteristic when the confining pressure is less than 240 kPa，and normally or slightly over-consolidation characteristic under the confining pressure of 240 kPa. The strength of thawed saturated Harbin clay increases first and then decreases with the increase of the strain rate below 0.15 h－1，but continuously increase when the strain rate exceeds 0.15 h－1. The characteristics of pore water pressure-strain curves change from the softening type to the hardening type when the confining pressure increases，but the influence of strain rate effects on the development of pore water pressure is unclear. In addition，it was found that the generalized hyperbolic model described nicely the strain rate effects of thawed saturated Harbin clay.

In order to simulate realistically the characteristics of low amplitude and high vibration of the moving metro loads and to calculate accurately the long-term settlement of the soft soil foundation，a dynamic constitutive model was suggested to describe the creep behavior of soft soil under low stress levels. A time-dependent bounding surface model based on the theory of bounding surface model and Mesri creep model was established. In order to write the user-defined material subroutine in ABAQUS，the proposed model was deduced using the stress integration algorithm and further optimized using the prevent strain method. The model has advantages of shortening the computation intervals，increasing the total number of iterations and ultimately making the convergence much easier. The model was validated through the comparison of the simulation results with those from the GDS dynamic triaxial tests on normally consolidated Nanjing soft soil. Moreover，the 3D finite element analysis of a metro system incorporating the viscoelastic artificial boundaries and the proposed dynamic constitutive model was carried out. The results revealed that the optimization algorithm based on the prevent strain method is useful for the easier convergence of the simulation. The time-dependent bounding surface model is appropriate for describing the dynamic creep characteristics of soft soil and can predict effectively the accumulated settlement of soft soil under the moving metro loads of low amplitude.

The model tests of geogrid-reinforced soil retaining walls(GRSRW) subjected to the static and cyclic footing loadings were carried out to investigate the mechanism and deformation characteristics of GRSRW considering the factors such as the location of footing，the magnitude of the load，the frequency of load and the numbers of loading cycles. The optimum of offset，0.3H(H，height of wall)，was determined based on the analysis of ultimate bearing capacity of the footing on the top of the retaining wall. The settlement of the footing and the lateral deformation of geogrid-reinforced soil walls increase with the increase of the magnitude of loading，the frequency and the number of loading cycles. When the static load applied on the footing is less than the ultimate bearing capacity，the ratio of the settlement to the wall height is less than 2% and the ratio of the horizontal deformation to the wall height is always less than 1%. When the cyclic loading is applied on the top surface of retaining walls，the settlement and the horizontal deformation increase remarkably compared with those under the same level of static loads. With the increase of cyclic loads and frequency，the settlement and the horizontal deformation increase quickly at the very beginning and then the increasing slows down as the number of cycles increase. The strains in geogrids for the uppermost layer which are generally greater than those in the other layers，increase significantly when the higher cyclic loads with larger cyclic numbers are applied. The failure mode of the retaining walls under the static loading and lower cyclic loads with low frequency is that the top panel blocks is squeezed out. The failure surface occurs at the verge of foundation and then develops deeper when the offset of the footing increases continually. The blocks in the middle of retaining wall tend to be squeezed out when the cyclic loads and the loading frequency increase.

The stratum deformation caused by the quasi-rectangular shield tunneling is different from the circular shield tunneling and the limited research has been carried out to study the issue. The first time application of the quasi-rectangular shield tunnel in soft ground in China was studied and the surface deformation and layered settlement were monitored and analyzed to investigate the major pattern of the vertical stratum deformation. The suggestions for the construction controlling were presented in terms of the deformation mechanism. The results show that the maximum surface settlement is about 50 mm and the range of excavation influence is about 20 m ahead of the excavation face. The vertical displacement of the ground surface experiences four stages over the tunneling period，the slowly down(upward) stage，the rapid upward stage，the rapid down stage and the gently down stage. The surface settlement occurs mainly after the pass of the shield tail，which is caused by the consolidation of the disturbed soft stratum. The main factors for the vertical stratum deformation include the chamber pressure，synchronous grouting and shield posture. The shield posture caused the soil on two sides of the shield machine to move in the opposite directions. In addition，the influence of the shield posture to soil deformation is more significant than in the case of single circle shield tunneling.