The occurrence and development of piping is the process that skeleton solids translate into fluidized-solids under the action of seepage; then flow with fluid in the pore channel and outflow the soil; Finally, during the process, seepage and erosion coupled and promoted each other, water and soil mutual effected as well; this means that the piping process is a highly nonlinear dynamic process during which multifield coupling and multiphase coupling. The experimental result of piping shows that only when the hydraulic gradient is bigger than the starting hydraulic gradient will the fluidized-solids outflow the soil with the fluid; then piping occurrence ，and there exists a corresponding relation between the porosity (stable porosity) and the hydraulic gradient in the stable phase of piping. This paper proposes the concept of stable porosity, revises the traditional constitutive law of seepage and erosion, establishes a modified governing equation for the three-phase coupling piping in porous media considering the experiment result. Finally, a soil sample in specific stress state is chosen to build the relation between the porosity (stable porosity) and the hydraulic gradient, a finite element program is designed to simulate the process of piping for this sample in axisymmetric cases based on the Galerkin finite element scheme. The results show that, the modified governing equations can describe the occurrence and development untill stable phases of piping than before.

The multiscale model for brittle granular materials generally involves three scales: elementary particles at the microscale, grains at the mesoscale, and grain piles at the macroscale. The multiscale model was created based on the discrete element method (DEM). To apply it to dynamic loading, parameters for two contact models and two bonding models were firstly analyzed, and connections between the micro and meso model parameters and the macro material constants were also discussed. Then, the dynamic multiscale model for quartz sand was created with the Hertz-Mindlin contact model and the parallel-bond model. Through selecting appropriate strength and local damping parameters, it is observed that the dynamic compression properties of the simulated sand agree well with the experimental results on quartz sand at both the meso and macro scale. With the calibrated model, the influence of the local damping mechanism which is closely related to dynamic loading, on the dynamic responses of the multiscale model was investigated. Results show that a higher damping level results in a stronger wave-attenuation ability of brittle granular materials. However, excessively high damping will result in an aberrant loading-velocity effect at both the meso and macro scale (the latter is actually the micro inertial effect induced by high damping). In addition, high damping can attenuate the waves emitted during the particle breakage process and reduce the breakage extent. At last, the multi-scale model was slightly modified and used to study the dynamic particle breakage property of brittle granular materials. The modified model can yield grain-size-distribution curves consistent with the experimental ones. Moreover, it can reveal the heterogeneous distribution of particle breakage at the space scale, which refers to the clustering phenomenon of microcracks caused by the interactions between the wave-producing and wave-attenuation mechanism in the particle breakage process.

The mechanical response of the saturated local inhomogeneous media under the cyclic loading has always been the rsearch difficulty in the soil dynamic field. How to describe the local structure of the inhomogeneous soil, weighting the influence of which on the macroscopic pore-pressure; all of them remain undetermined. In this paper, a model that can describe the influence of the local structures on the growth and dissipation of the pore pressure is established; basing on which, the analytical solution of the pore pressure is attained in the one-dimensional saturated soil layer bearing periodic load. Taking the relaxation time and the load frequency as variables, the influence trends of which on the pore pressure are analysed quantitatively; and the sensitive range of them are determined. Basing on the analysis, the relation curves between the relaxation time and load frequency are proposed when the pore pressure reaches maximum. All conclusions will contribute to the academic and engineering application in the research field of inhomogeneous media soil.

Crack propagation under compression of rocks and cracks in the rock are mainly tensile. Shear band can be formed as the result of interaction of tensile cracks; and shear failure finally occurs with propagation and interaction of cracks in the rock. It has been found that progressive failure process of rocks is affected by mineralogical composition, grain size, texture and foliation, etc. External factors such as the confining pressure and excavation disturbance also have great effect on progressive failure process of rocks. The influence of water pressure on crack propagation of sandstone is studied. Feature of each stage in progressive failure process of sandstone is researched; and stress thresholds—crack initiation stress and crack damage stress are summarized. Then the influence of water pressure on progressive failure process of sandstone is studied experimentally. It is indicated that with increase of water pressure at both ends of the rock sample, crack initiation stress has a tendency to increase and crack damage stress and peak stress decrease gradually. With increase of the confining pressure, stress thresholds during progressive failure process of sandstone decrease gradually.

Crushability evaluation on shale reservoir is to evaluate the difficult degree of generating fracture network; in other words, is to demonstrate the SRV(stimulated reservoir volume) can whether or not be effectively implemented. It is a key of the whole fracturing work. At present, there is no unified reference standard and evaluation method at home and abroad. A new evaluation method is developed in this paper. For 10 kinds of cores, their rock mechanical parameters are tested firstly; and the commonly used three kinds of shale brittle evaluation methods are comparatively analysed. The fracture is characterized quantitatively by using fractal dimension of trace of fracture structure surface and areal density; and the caving clastic mass after fracturing is analysed. The results show that the accuracy of Young’s modulus and Poisson’s ratio discriminance and plastic coefficient discriminance used to evaluate shale brittleness, are higher. The characteristics of high Young’s modulus, or(and) low Poisson’s ratio are usually presented for the brittle rock; but there is no corresponding relation between brittleness and uniaxial compressive strength, tensile strength and indentation hardness. Fracture distribution after fracturing has fractal structure with statistical sense of self-similar. The fractal dimension can be used for quantitative evaluation of fracture network complexity. The higher the rock hardness, the smaller the fracture density after fracturing. The stronger the brittleness, the larger the fracture density after fracturing. The new method is the integrated embodiment of characteristics of rock hardness, brittleness and natural fractures system(and sedimentary structure). It is not only visual and reliable, but also simple and effective to evaluate the ability of forming fracture network after fracturing on shale reservoir; and as a result, it illustrates a good prospect of application and extension in oilfield. This work is very significant for evaluation and development of shale reservoir.

Soil-water characteristic curves (SWCCs) of saline silt with different salt contents were measured by the filter paper and pressure plate methods. The influence of salt contents on the SWCCs was discussed. It was concluded from the experimental results that the variation in salt content in silt has little effect on matric suction; the difference between total and matric suctions measured by the filter paper increases with increasing salt content; and the difference is greater than osmotic suction of the pure saline solution with the same salt concentration due to the adsorption of the surface of soil grains to the solution; and the matric SWCC measured by the filter paper method is between the drying curve and the wetting curve. The calibration curve of Whatman No.42 filter paper was measured by the vapor equilibrium method for total suction at the high suction range; and thus the measured accuracy of total suction is improved at that range.

Reasonable determination for limit supporting pressure calculation and stability assessment of shield tunnel surface, it is basic and difficult to determine the unstable soil shape of shield tunnel surface. A numerical model is established to simulate the process of losing stability. According to the Mohr-Coulomb failure criterion, the Handy soil arching theory is used to get the calculation method determine the position and shape of unstable soil. The results show that the horizontal pressure arch is generated due to supporting effect of tunnel left and right sides in the horizontal direction, which causes that the unstable soil has a limit boundary. Catenary minimum principal stress arch is generated due to vertical soil movement in the limit boundary, the shape of unstable soil is similar to the shell-shaped. Taking the tunneling project of Nanjing Metro Puzhulu-Binjianglu section for example, theoretical calculation and numerical simulation results of the project are in good agreement.

The classification as three types is proposed for the load-displacement relation curve of the rock-soil mass at first; a criterion of high earth pressure is defined. A new constitutive theory is at first proposed; the complete-process relation of stress-strain can be described under different normal stresses (or different confining pressures) by this theory. There only exist three mechanical parameters describing the geomaterial and stress state. It describes not only the mechanical behavior of geomaterial, but also of the complex material and of the surface between different media, the arbitrary deformation can be obtained. The relationship of stress-strain for the different rock-soil masses and the surface between rock-soil layer and pile are described by the proposed constitutive theory. The testing data of pile foundation of Changshawan bridge are simulated; the results show: that the mechanical properties of different rock-soil masses and interlayer between rock-soil mass and pile can be presented by this constitutive theory.

Traffic loading from trains or vehicles will cause damages in transportation infrastructure constructed on silt soil, and consequently result in reduction of transportation infrastructure’s availability. In order to investigate cumulative deformation and dynamic behaviors of silt soil under large cycles of traffic loading, a series of dynamic triaxial tests have been conducted on Qiantang River silt soil. Effect of soil’s physical properties, such as relative compaction(RC), water content and loading features, and loading frequency, confining pressure and cyclic stress ratio(CSR) on soil’s axial strain, dynamic modulus, damping ratio have been discussed based on the test data. The results show that the critical cyclic stress ratio(CSR) of Qiantang River silt soil is about 0.11. When the applied dynamic stress is below the critical dynamic stress, silt soil’s dynamic modulus shows very little reduction; and the cumulative axial strain is very small. When dynamic stress exceeds the critical dynamic stress, soil’s dynamic modulus reduces quickly, and the residual dynamic modulus can reach about 20% of the initial elastic modulus. Meanwhile, the dynamic modulus and damping ratio change significantly with the axial strain. The test data on silt soil’s dynamic modulus and damping ratio show a uniform conclusion after normalization on the data. Silt soil’s dynamic modulus almost keeps constant when the axial strain (or the normalized cycle number) is less than a threshold value, and decreases exponentially when beyond it and reaches a stable value ultimately. The damping ratio develops exponentially with the axial strain (or the normalized cyclic number).

Study of stress relaxation properties of soft rock is an important aspect of long-term mechanical property, which is very important to keep soft rock tunnel long-term stability. The stress relaxation test of red silty mudstone under triaxial compression with confining pressure of 30 MPa is carried out on TLW-2000 triaxial rheological machine. The test results show that: with the deterioration of material properties and relaxation damage evolution, the process of stress relaxation is nonlinear. By analyzing the damage energy dissipation during stress relaxation, a new relaxation damage equation is established. And, a nonlinear relaxation model is established by introducing the damage factor into Nishihara model. The fitting results of stress relaxation test show that the stress relaxation properties are well reflect by this model. The research results provide a scientific basis for long-term stability analysis of soft rock tunnel for Yichang-Badong Expressway.

Regarding the soil profile in seismic liquefied deposits as being composed of a non-liquefied crust layer at the ground surface, a liquefied layer in the middle of the deposit and a non-liquefied base layer, and based on the theory of saturated porous media and Novak’s thin layer method, the dynamic behavior of an end-bearing pile in liquefied viscoelastic under axial force soil layer is investigated. The horizontal dynamic impedance of liquefied soil was obtained using Helmholtz decomposition. The analytical expressions of the harmonic vibration and dynamic complex stiffnesses of the end-bearing pile in liquefied soil under axial force are obtained with the transfer-matrix method. A parametric study was conducted to analyze the influences of the axial force, the slenderness ratio of the pile, pile-soil modulus ratio and the coupled coefficient of fluid and solid phase on the dynamic stiffnesses and dampings. It is shown that, with different slenderness ratio of the pile, pile-soil modulus ratio, coupled coefficient, the absolute values of the dynamic stiffness of pile with axial force are smaller than those of pile without axial force; and the change tendency with frequency are the same. The influence of the axial force on the dynamic impedance of the horizontal vibration pile is remarkable. The absolute values of the dynamic stiffness factors of the horizontal vibration of pile are approaching to zero; and the pile will buckle with the axial force increasing. Furthermore, the influences of the slenderness ratio of the pile and the pile-soil modulus ratio on the dynamic impedances of pile are notable; and the influence of coupled coefficient of fluid and solid phase is trivial.

For the urban construction, the method of “Central island by bottom-up and peripheral part by top-down” has been used more and more in large deep excavation of foundation pit. In the help of this method, construction cost and project time can be saved a lot. However, there is a lack of simple and reasonable calculation method for it. Central island distribution pattern of passive earth pressure are put forward in this article which is based on and Rankine's earth pressure theory. In the condition of single soil, the pattern was described in 3 polygonal lines with the corresponding depth. The practical method for central island method of retaining structures is proposed according to the above-mentioned distribution pattern and the design method of cantilever structure from excavation engineering handbook, and a case was given. It is proved by the example that the method was simple and practical, and convenient for using to the engineer.

Regarding the soil skeleton as a viscoelastic medium with fractional derivative constitutive relation, the governing equations of the steady state vibration of the saturated fractional derivative viscoelastic soil embedded a spherical cavity are established based on the Biot’s theory. The analytical expressions of the displacements, stresses and pore water pressure of the saturated fractional derivative viscoelastic soil with a spherical cavity are obtained with the introduction help of potential functions in case of spherical symmetry. The influences of the parameters of fractional derivative model and saturated soil on the vibration characteristics of the soil are examined; and the numerical results show that the fluid compressibility has a great influence on the dynamic characteristics; while the influences of the soil skeleton compressibility and fluid-solid coupling coefficient are trivial. The influence of the fractional derivative order on the dynamic behavior of the soil depends on the values of material parameter ratio. Furthermore, the dynamic responses of the saturated soil with undrained boundary condition are greater than those with the drained boundary condition.

Permeability is one of the most important parameters required for reservoir evaluation, well production calculation and developing a reasonable development program. Obtaining the accurate permeability is helpful for effectively exploiting tight petroleum reservoirs. Due to the shortcomings of conventional steady-state permeability measurement method such as long experimental process and easily affected by the environmental temperature, this paper has conducted comparative study of permeability of 39 block rocks of tight reservoir using both steady-state and unsteady-state techniques. Meanwhile, those factors which affecting experimental results accuracy have also analyzed including permeability, experimental operation method and the way of combination of effective stress. The experimental results show that the unsteady-state pulse transient decay technique consistently underestimates the steady-state Klinkenberg-corrected permeability. Pulse decay permeability is only about 47.26% of the steady-state permeability in average. The difference between the above two different kinds of permeability increase with the decrease of the rock samples permeability. Error analysis suggests that the high effective about 9 MPa loaded on the rock sample before the pulse decay permeability measurement and the combination of high confining stress and high pore pressure can induce a portion of experimental error, but still not fully explain the overall error between the pulse decay permeability and the steady-state Klinkenberg-corrected permeability. Finally, mathematical fitting result shows that the relative error and the pulse decay permeability has a good logarithm function.

Numerous wading landslides formed after dams were completed. In order to study the impact of the wading landslide’s stability induced by water level fluctuation. Based on the classification of significant wading landslide, in light of landslide of buoyancy weight loss, applying the self-made landslide model test system, and establishing the landslide model of buoyancy weight loss, the reservoir water level fluctuation test is carried out. The test results indicate that the effective stresses of the landslide model decrease with the reservoir water level increasing and increase with the water level lowering. For the model test, Geo-studio software is used to model the process of seepage and calculate the stability. By comparing the results of experiment and numerical simulation, it is shown that the changes of seepage simulation of earth and pore water pressure are basically consistent with changes of test results. The stability coefficient decreases with the reservoir water level increasing and rise with the water level lowering. The law of reservoir water level fluctuation on the buoyancy weight loss landslide stability is drawn as follows; that effective stresses of the landslide decrease with the reservoir water level increasing, resulting in lower landslide stability; effective stresses of the landslide increase with the reservoir water level lowering, so as to make the landslide stability increase.

Rock salt sample dissolution tests under on the condition of triaxial stress with self-designed triaxial testing machine, rock salt dissolution rate orthogonal experiment under the mutual coupling of concentration, temperature, flow and deviatoric stress under the condition of triaxial stress, are carried out. Various factors influencing rock salt dissolution rate are studied. Any two factors are the binary linear regression, the relative importance ratio according to the standardized regression coefficients for rock salt dissolution rate to build judgment matrix; analytic hierarchy process is used to calculate weights of various factors. The results show that: Rock salt dissolution rate decreased rapidly with the concentration increasing. Dissolution rate increases with the temperature rising. Dissolution rate increases slowly with the flow increasing and did not change significantly. Dissolution rate decreases first and then slowly increases with increasing deviatoric stress. Range analysis and weights calculation show that primary and secondary factors affecting the rock salt dissolution rate are concentration, temperature, flow and the deviatoric stress. The weights of concentration, temperature, flow and the equivalent stress affecting the dissolution rate are 0.570, 0.384, 0.048, 0.005 respectively; the weights of the two factors, concentration and temperature, account for 95%.

Equivalent nonlinear model is usually applied in seismic response analysis. The shear modulus and damping ratio are two important properties in this model. Highly weathered granite is common in large engineering. It is essential to study dynamic properties of highly weathered granite. The shear modulus and damping ratio of highly weathered granite are studied with GDS resonant-column; as its the capability is excellent, it is popular in the world. The confining pressure and pore water pressure to consolidate can be controlled well by GDS RCA. After the end of sample’ consolidation, shear modulus and damping ratio can be given by experiment in the state of this effective stress. Changing confining pressure and pore water pressure, resonant frequency, shear modulus and damping ratio can be given with another effective stress. In different effective stresses, variation of shear modulus and damping ratio can be observed. And fitting curves of shear modulus and damping ratio that are put forward by Hadin-Drnevich[1] are turned out on the basis of experimental data. The authors discuss the damping mechanism of highly weathered granite sample by amfusing frictional theory. It can be seen that resonance frequency of the sample’s system has a positive correlation with shear strain, but sample’s damping ratio has a negative with shear strain. The effective stress can have impact on both sample’s shear modulus and damping ratio. However, pore water pressure can only act on damping ratio.

The performance of small-scale model piles embedded into red clay and tested under cyclic axial loadings is presented in this paper. The influences of cyclic loading levels and rates on long-term dynamic behaviors of pile are observed, and the mechanics of accumulated settlement is analyzed from the views of shear stiffness softening and skin friction degradation. Furthermore, the modified Hardin-Drnevich (H-D) model, being capable of reflecting the fatigue degradation of shear stiffness, is achieved in the FLAC3D, and the behavior of shear resistance degradation during quasi-static cyclic shearing under constant normal stiffness (CNS) condition is numerically investigated. Results indicate that the growth pattern of the permanent deformation is significantly affected by the cyclic loading amplitude; and the pile dynamic stiffness experiences a significant decrease in a short transition period, after which it remains invariable with cycles. The excess pore pressure caused by the shaft vibration is rather small; and the induced effective stress reduction can not sufficiently result in large friction degradation. The dynamic stiffness and acceleration of pile top increase simultaneously with the loading rates. With the modified H-D model re-developed in FLAC3D, the hysteresis curve of an easy case is well consistent with the theoretical result, which verifies the credibility of the program.

There are lots of factors that affect the dynamic load induced by high-speed train; the train speed is one of the most critical factors. It is rather difficult to determine the effect of train speed on dynamic load using theoretical method due to the complexity of vehicle-track-subgrade interaction. Large-scale physical model test has gradually become one of the most popular approaches for studying the dynamic characteristics of ballastless track structure of high-speed railway. A full-scale model of ballastless track subgrade was constructed based on the design and construction standard for high-speed railway line from Shanghai to Nanjing. The dynamic strain of type I slab and dynamic soil pressure of subgrade were obtained by conducting single wheel axel exciting test. The relationship between dynamic load and train speed was presented. The dynamic load magnification factors of slab and subgrade structure under different train speeds are obtained respectively. The magnification factors are of great significance for designing the dynamic load in type I track-subgrade system.

The triaxial compression experiments under different confining pressures for sandy slate samples have been conducted by MTS815 Flex Test GT rock mechanics test system. The anhydrous post-peak strength of the cracked rock mass is tested during the experiment. Then the residual strength of the cracked rock mass under different pore pressures is obtained by applying 4-levels dynamic and static pore pressures on the crack surface of the samples. The experiment results show that the mechanism of the influence on the strength of cracked rock mass caused by water mainly includes following aspects: saturated softening and pore pressure weakening. The saturated softening affection does not change with the changes of pore pressure; and the pore pressure weakening affection increases with the increasing of pore pressure linearly; which mainly influences the cohesive force while almost no effect on the internal friction coefficient. The weakening affection of static pore pressure is stronger than dynamic pore pressure’s. Through testing and analysis, the quantitative expression of the comprehensive effect of saturated softening affection and pore pressure weaken affection on cracked rock mass is obtained; and the engineering application of such results is discussed.

Slip behavior between soft landing mechanisms and simulant lunar soil is one of the most important factors, which influence the stability of lunar explorer landing. Duralumin was the material of cushioning mechanism foot pad. A series of simulant lunar soil - aluminum plate shear tests are performed by direct shear apparatus. The shear deformation and strength of interface between simulant lunar soil-smooth aluminum plate under different relative densities, different shear velocities and different normal stresses are studied. Interface under slightly dense soil presents ideal elastoplastic deformation, accompanied with strain-softening. The interface strength increases with the normal stress increase accompanied with shear velocity; interface friction angle is 26.8°- 31.4°.

There are so many merits of waste tire shred-sand mixture. Presently, it has been used as light filling. Series of shear tests of tire shred-sand mixture have been done; and the influence of different factors on shear performance is discussed, such as shred content, aspect ratio and compactness. The results show that it is nonlinear of the mixture Mohr-Coulomb envelope. The shear strength and friction angle increase with the tire shred content increase and the nonlinear behavior becomes more evident as the addition of the tire shreds. The friction angle of the mixture can increase by 8%-89% by means of optimizing shred aspect ratio, shred content and compaction. There is very little effect of shred width on shear performance. But the aspect ratio of the shred has obvious influence on shear behavior at other things being equal. There is one and only length for a fixed width of the tire shred, which can make the maximum friction angle of 65°.

A stability study is conducted for the top-arch collapse composite treatments of the Dagangshan Hydropower Station, based on a sophisticated analysis approach of the composite linings. The performance of the treatments during excavation is analyzed. The internal forces of the I-beams and the shorcrete are presented respectively for the distinct phases of treatment. In this manner, the stability of the treatments are discussed. The results indicate that the maximum incremental displacement after treatment is about 9 cm. Fail zones of the top-arch remain broadly unchanged afterwards. The changes of the cables’ internal force are relatively small, suggesting a good supporting efficiency and safety level. Although the initial treatments may suffer potential cracking, as the main components of the treatments, the phaseⅠand phaseⅡ treatments are in a good state. Therefore the stability of the entire treatment system may be insured. Monitored data are generally agree well with the calculated ones; the analysis reliably reflect the real rock mass deformation and the internal forces state of the supporting structures.

The flow motion law of the underground seepage of plane sliding landslide saturated under heavy-rain is studied; and then a new improved method for slope stability analysis of such landslide is presented, considering the coupling effect of hydrostatic pressure and hydrodynamic pressure. Using the principle of groundwater dynamics, on the basis of some assumptions to simplify the analysis process, the underground seepage flow equation under heavy-rain is derived. Based on the slice method theory, taking the non-uniformity of the flow activity at each point into account, the traditional calculation formula for slope stability coefficient is improved; and the critical condition of failure is also given. The proposed formulas are applied to Ermanshan landslide occurred in Hanyuan county of Sichuan province; and the obtained results prove the rationality of the method. The research indicates that the stability of plane sliding landslide under the heavy rain mainly depends on the internal friction angle of saturated rock and soil, the permeability coefficient, the scale of sliding mass (thickness and length) and the relative water-head between the slope crest and the toe. Such research results have a certain practical significance that can be used to guide the emergency rescues and disaster relief work.

The pile bearing capacity, base resistance and shaft resistance development of open PHC pipe pile can be confirmed through the interval re-pressed test of jacked pile with FBG sensors. It is indicated that the ultimate-bearing capacity shows logarithmic growth with elapsed time in the certain time after installation; and the magnitude is 140% after 284 hours with timeliness coefficient of 0.52. The increase magnitude of base resistance and shaft resistance is respectively 6.28% and 475.37% with time, which indicates that ultimate bearing capacity growth derives from shaft resistance in the test condition. The results show that the development of pile ultimate bearing capacity and shaft resistance accord with three-phase increase model and the time points are respectively 21.5 hours and 279 hours. respectively. The research results can provide evidence for timeliness coefficient and relevant design.

PHC pipe pile is widely used in recent years. The application of PHC pipe pile belongs to soil compaction pile-sinking mode. The compaction effect caused during piles driving would produce adversely effects on the surrounding environment and affects its possibility and bearing characteristics. The study of compaction effect was conducted based on the measurements and statistics of excess pore water pressure and horizontal displacement in the Guang-Qing Expressway Expansion Project. Horizontal displacements were monitored by fixed inclinometer measurements, pore water pressure was measured using vibrating wire, and using the automatic data acquisition system of data acquisition. The studies show that excess pore water pressure which caused by pile-driving in the project presented approximately linearly with the depth increasing and reduced with the distance increasing in the horizontal direction. Soil horizontal displacement of soil compaction effects decreasing as the distance increasing; it also has the significantly of hysteresis which can lead to pile body tilt. Piling on the widened foundation influences the original foundation slightly, while the site conditions have remarkable impaction on pile driving effect. The old embankment restraints horizontal displacement perpendicular to the roadbed direction.

In MU US desert, full-scale in-site tests on the bearing capacity of eccentric grillage foundations subjected to the uplift and uplift combined with horizontal loading were carried out respectively. The load-displacement both of foundation top plane and ground surface, and the soil pressure acted on the footing slab were measured. The uplift mechanism of foundation was analyzed. The results show that under the uplift, uplift combined with horizontal loadings, the load-displacement of the eccentric grillage foundation presented two-staged behavior. Under uplift load only, the ultimate uplift resistance is assumed to be the sum of the dead weight of foundation and the soil mass contained above the bottom of the assembled slab base. The movement resulted by the eccentricity reduced the uplift bearing capacity of foundation. However, under uplift combined with horizontal loading, the ultimate uplift load increased 8.7 percent by comparison to the uplift load case. It indicate that the eccentric foundation structure is more suitable to the load case of uplift combined with horizontal loading in engineering. The angle δ , the consultant to the line from centroid of slab to top plane , is suggested to reflect the eccentricity and applied loads. According to the test results, the pullout capacity decrease rapidly with the increasing of angle δ.

The small disturbing scheme that rotating and pressing the protective jacket tube to the depth which under the shield tunnel bottom about 3 meter and then boring the hole through the slurry circulating system has been used in the construction of cast-in-situ bored pile, which near to the shield tunnel of Shanghai Metro Line 9. The actual measurement shows that there is no ground loss in the scope of the protective jacket tube when boring the hole. The soil blocked the tube more and more serious with the increase of the depth of the protective jacket tube, and there is some soil squeezed out when the bottom of the tube under the axis of the tunnel, so the tunnel came-up and the vertical ellipse deformation occurred. In order to decrease the influence from the construction of the protective jacket tube, it is suggested that some of the soil should take out from the protective jacket tube when pressing it in the ground.

Based on the project in the tidal gate of Sanyang port in silt foundation, a field experimental study was conducted on lateral load capacity, in order to study the effect of filling pile enhanced by the soil-cement pile. For measuring the pile stress distribution of the body in the horizontal load and getting the distribution of bending moment, reinforcement meter were welded to the steel cage at different elevations when the filling piles were being driven; Soil pressure cells were buried on both sides of pile; in order to get the distribution of the soil pressure while the lateral load test was under way. The results show that, filling pile enhanced by soil-cement piles can control the development of horizontal displacement and increase the level of pile bearing capacity. Distribution of the bending moment value and the soil pressure of the soil around the pile are presented the developing trend of increasing initially and decreasing afterwards, and are mainly concentrated in the upper part of the pile and soil, and go to the maximum value of about 3m below the soil surface. Soil-cement pile can effectively reduce the value of bending moment of the pile, and can also weaken the emergence of anti-bottom. The soil around pile can provide greater soil pressure when the filling pile is surrounded by the soil-cement pile. The lateral load capacity of filling pile is impacted greatly by the upper level of soil, that is, raising the upper soil physico-mechanical properties can increase the level of lateral bearing capacity.

When lime-soil composite foundation bearing load, the expansion deformation of lime-soil piles would compact soil around and exert pressure on soil and piles. To enhance the reinforcement effect of the lime-soil composite foundation, it is critical to identify the radius of compacted zone. Based on the unified strength theory and taking the conditions of compatible deformation of soil and piles into consideration, the formula describing the relationship between settlement of composite foundation and radius of compacted zone has been derived. Furthermore, the various elements influencing compacted zone radius and the trend of the zone radius changing under different values of b, different pile diameters, and different foundation depths are discussed as well. The research results indicate that the radius of compacted zone decreases with the increase of foundation depth when the b value and pile diameter are invariable. The results also show the optimal range of compacted zone along the composite foundation depth is from the pile top to the 1/3 length of pile. The radius of compacted zone varies from 1.51d to1.68d under different conditions of b value, where d is the diameter of pile. And radius of compacted zone expands along with increase of the pile diameter d, when the b value and foundation depth are invariable. To exert the strength of material such as soil, the solution considered the intermediate principal stress has positive effect on the ultimate strength of material.

Focusing on large voids and bonds of natural loess, structural loess samples with different water contents are prepared by discrete element method (DEM) and their collapsible characteristics under one-dimensional compression condition are investigated. First, based on laboratory test results on natural loess and DEM numerical results on bonded granular materials, the relation between bond strength and initial saturation is proposed. Then structural loess samples with different water contents are prepared by using the authors’ multilayer under-compaction method and bonded contact model. Then double-oedometer tests on these samples with different water contents, single-oedometer tests on samples with same specific water content are simulated by DEM. The DEM results show that the structural yield stresses and the vertical pressures at maximum coefficient of collapsibility increase with decreasing of water content. The coefficient of collapsibility increases firstly and then decrease with pressure. The initial collapse pressure is equal to structural yield stress of saturated samples. The ratio of maximum coefficient of collapsibility to void ratio is near to that of natural collapsible loess. There is a nearly unique post-collapse compression line for DEM samples wetted at different vertical pressures. The yielding is related to bonds breakage and the collapse is accompanied with significant bonds breakage. Structural damage variable based on the bond number is proposed to reflect the damage degree of structure and its evolution during loading or wetting is studied. This study provides a foundation for learning the complex mechanical characteristics of loess and building constitutive law of loess.

The inverse T type breakwater with jackets and pile foundations is a new type of structure applied to port and coastal engineering, of which the stability is sustained by pile foundations and gravity. In terms of the hydrogeological conditions of Tianjin Port, a 3D elastoplastic finite element model is estabilished for stability analysis of the inverse T type breakwater with jackets and pile foundations. The safety factor of stability is determined by P-S curve. The soil resistance is calculated by analyzing the vertical and circumferential distributions of earth pressure on pile foundations in the limit state. Besides, the earth resistance calculated by the finite element method is compared with API. There are two main reasons which cause structural instability: Firstly, the structure itself is unable to meet strength requirement; Secondly, the soil is in the limit of state. For the first reason, calculate the safety factor of stability by p-y curve method. When the soil is in the limit state, simplified methods for anti-overturning stability based on the rotation point which is on the pile axis or deviates from the pile are set up. In comparison to finite element method, simplified calculation method is reliable.

The failure of slope is a progressive process which from quantitative changes to qualitative changes. The whole sliding surface will be taken place by gradual damage of the potential sliding surface in the slope body gradually. Based on the strength reduction method, dynamic strength reduction method that can simulate the progressive failure of slope was proposed. At first, yielding approach index(YAI) is used to appraise the damaged region of slope in the numerical simulation, the region that YAI is less than 0.2 is recognized as the damaged region. Then through the continuous local damage reduction of the strength parameters of the local slope body, the potential sliding surface is damaged gradually and evolved to breakthrough finally. The practical results show that the proposed method can settle the reduction region in the strength reduction method effectively; and overcome the defect of large plastic damage area by the whole strength reduction method. The trend of displacement and damage area change also has better consistency in the reduction process. Dynamic strength reduction method can simulate the progressive failure of the slope truly; and it provides quantitative basis of slope stability appraising for strength reduction method.

In order to find out the relationship between liner structure deformation and the support parameters of long tunnel with large cross-section built in phillite stratum of meizo seismic area, the paper takes a dynamic deformation and inner forces field test of 5 different support types on the basis of new concept, combining with the actual three-stepped method adopted in Dujiashan tunnel of experimental section under construction, the variation of tunnel crown settlement, peripheral convergence displacement, ground surface settlement and structure inner forces under different excavation and support schemes are discussed. After analysis, some preliminary conclusions are drawn as follows. The strong strength and rigidity of scheme F5 is more suitable for thousand pieces rock tunnel construction. Then 3D elasticplastic finite element simulation of the construction process under 5 kinds of construction schemes is carried out; and the tunnel structure safety and surroundings rock stability during construction are evaluated by the comparative analyses of simulated tunnel deformation and support inner forces and those of field tested after excavation. The comprehensive analyses of field test and numerical simulation results show that there are only 2 (F4 and F5) support schemes are suitable for the tunnel excavations; and the tunnel deformation and structure inner forces are more reasonable of F5 scheme comparing to any other schemes. F5’s reasonableness and effectiveness are also certified by the successful application in practice. The above-mentioned support parameter determination technology and methods of tunnels built in soft rock can provide reference for similar projects.

A new method for determining of parameters simultaneously in the coupled seepage-stress analysis in anisotropic rock is essential for large-scale cavern shape selection, stability analysis, and rock support system design. Based on the Levenberg-Marquit optimization method, a modified method has been put forward by employing a new step factor matrix , in order to calculate both of the parameters of rock mass modulus (E), the in situ stress (P) and the permeability coefficient (K) in the back analysis. Compared with traditional step factor in optimization algorithm, the new step factor matrix can change the step factors respectively according to the different sensitivities of parameters, with which a new algorithm is established on MATLAB platform. Two case studies show the method’s feasibility and validity in the coupled seepage-stress analysis in a anisotropic rock tunnel engineering; and the results demonstrate that the modified method with new step factor can improve convergence of iterative algorithm obviously which cannot be solved with traditional step factor.

A 3D elastoplastic finite element model is established for stability and stress analysis of the cellular steel sheet pile structure under wave load by employing ABAQUS finite element software. Shell element is used to simulate steel sheet piles and connector of hinge is set to imitate the influence of relative rotation of steel sheet piles next to each other; Mohr-Coulomb constitutive model is adopted for soil; and contact elements are set to simulate sliding, splitting and closing between sheet pile and soil outside and inside cellular. Based on a case engineering, mode of failure, stability failure property and stress distribution are studied, considering the influence of parameters variation on stability and hoop stress analysis of the structure; and anylisis of shear deformation in the sheet pile walls is carried out; suggestion is made for sheet pile interlock tension in some surface sections for examination. Results show that connector of hinge has little influence on stability but has a certain influence on hoop stress. Shear deformation surface mainly occurs in the medial axis of the cellular cell, which is consistent with the conclusion of Terzaghi.

By extending Darcy’s law to dry domain above the free surface and specifying a Signorini’s type of boundary condition on the potential seepage boundaries, a new initial-boundary value problem of entire domain is deduced from non-steady seepage flow problems with free surface of in fractured rock masses. A parabolic variational inequality(PVI) formulation equivalent to the partial differential equation(PDE) is proposed for reducing the difficulty in selecting trial functions, while the finite element discretization and iterative algorithm of the PVI formulation are detailed. The validity of the numerical approach is then verified by existing laboratory tests. Finally, as an application to the non-steady seepage flow analysis in rock slope including complex fracture networks, the calculation results well illustrate the variations of free surfaces during drawdown of reservoir water level; characteristics of seepage flow movement in fracture networks and inhomogeneity of flow distribution at seepage surfaces.

In order to study the mechanical characteristics of the cutter in rock cutting process and the prediction of mean peak force reaction on the cutter, a numerical model of rock cutting is established based on the fracture mechanics and finite element theory. The process of the rock reaction on the cutter is simulated and investigated; and the reaction forces on the cutter are obtained with different rock mechanical characteristics and impacting conditions of the cutter. The results show that the impacting velocity within a certain range has less effect on the peck cutting force, the variation of reaction force is unanimous to rock volume changes with stepwise decreasing. The relationship of mean peak force reaction on the cutter obtained from simulations, experiments and theoretical models is investigated with the linear regression analysis. The results show good correlations that the linear correlation coefficients between numerical results and the results of experiments and Goktan’s theory are 0.812, 0.930 respectively; and it is indicated that this numerical model is proper and feasible to simulate the rock cutting process.

Under the condition of plane strain, finite element limit equilibrium method is applied to evaluate the stability of tailings dam. This method can be better combined with characteristics of the limit equilibrium analysis methods and finite element stress analysis. And it is based on the elastoplastic stress-strain analysis. Considering the overall stress field of the structure reasonably and accurately; the most dangerous location of slip surface and the corresponding minimum safety factor are determined by Hooke-Jeeves optimized searching method. An example of stability analysis of tailings dam engineering practice is proposed. The differences of safety factor quantity, shape and location of slip surface among stability methods: finite element limit equilibrium method, limited equilibrium slice method and finite element shear strength reduction method, are compared and studied in the normal, flood and special conditions. The safety assessment of tailings dam is made by using finite element limit equilibrium method. The results can provide a reliable basis and technical support for the safety of the design and construction of tailings dams.

A new method to search three-dimensional(3D) critical slip surface for slopes is proposed based on the finite element method (FEM). The FEM is used to analyze the stress field for slopes and calculate the safety factor of 3D potential slip surfaces from the stress results. The genetic algorithm is adopted to search for the most dangerous slip surface and identify its safety factor as the safety margin of slopes. The advantage is that this method can work dependent on one time finite element calculation and without given slip surface. Moreover, it is suitable for 3D complex topography and geological structures. The method feasibility and the code reliability are verified by an example; its practical application is illustrated by a slope example in the reservoir area of Dagangshan hydropower station.

Reservoir landslide surge can cause great damages. It’s important to forecast the possible harm brought by reservoir landslides surge correctly and it’s one of the most important content of feasibility demonstration for engineering. The shallow water control equation is applied to finite element numerical simulation for waves generated by landslides. The governing equation is discretized by the two-step Taylor-Galerkin method, which is of high-order accuracy and easy to be carried out. To examine the performance of the numerical model, an example is simulated. The results indicate that the water wave pushes towards the surroundings with the water access point as a source point, companying with continuous attenuation. The decreasing amplitude of the wave height diminishes gradually with the increasing spread distance. And the calculated result agreed well with the measured data, including the primary wave heights and the laws of water level movement; furthermore, the wave propagation process toward upstream and downstream is visualized. The validity and reliability of the method are proved by the result of the study. The research result can be used to forecast and prevent landslide disaster.

Based on the research needs of the relation between mining stress fields and gas outburst during the process of rock cross-cut coal uncovering, a set of outburst simulation experiment system of rock cross-cut coal uncovering is developed which takes ground stress, gas pressure and coal structure into account comprehensively, while outburst model of rock cross-cut coal uncovering is still on the stage of laboratory research and most don’t comprehensively consider the effect of gas, ground stress and physico-mechanical properties on outburst. To get accurate, objective the experimental effect, the design of key technologies such as main composition structure, function of this experiment system, outburst roadway, quick opening device and nitrogen balance system are introduced. The experiment results reflected the change of stress and gas pressure during outburst in uncovering coal seam using this experiment system. This experiment system provides new technical means for studying on and revealling the change law of mechanism of coal and gas outbursts and ground stress, gas pressure during the process of outburst.

The key of structural plane model mechanical test is to make similar surface morphology model sample to the natural rock structural plane. Based on the making particularity of rock structural plane in different scales，sample modes in series scales with perfect match to upper wall and bottom wall were developed; and the making process of model sample was designed. Through this, the natural rock structural plane can be used repeatedly, which will increase the using efficiency, reduce the sample cost and trial cycle. What’s more, the different scales of structural plane model making on the same natural rock structural plane are achieved. In the second part of the work, the similar evaluation results of surface morphology show: the model sample made by inverse controlling technology is capable of duplicating the same surface morphology of rock structural plane and highly match between upper wall and bottom wall model samples, which is suitable for the demand of making model samples in different scales. The inverse controlling technology is able to overcome the problems of low match to upper wall and bottom wall model samples and unable to get samples in multiscale of natural rock structural plane, which provides conditions for experimental research on shear strength scale effect of real surface morphology rock structural plane.