The requirement of reinforcement effect of subgrade is stricter for railway than for highway. Cast-in-place concrete large-diameter pipe piles (PCC piles) are firstly applied to railway subgrade of connect-line of Nanjing south railway station. In order to explore the characteristics of railway subgrade reinforced by PCC piles, the field tests of quality inspections and performance tests are carried out, including low strain test, static load test, excavation test, and the monitoring of the stress of pile and soil, surface settlement of embankment, layered settlement of foundation, tensor force of geogrid, pore water pressure test. The quality inspections results indicate that PCC piles have good quality, and meet the requirement of bearing capacity design of railway subgrade. The performance tests confirm that the settlement is steady in 3 months after finishing construction of embankment; and the maximum lateral displacement is only 13 mm. As the settlement is steady quickly and small lateral displacement is strictly controlled; it indicates that railway subgrade reinforced by PCC piles can meet the requirement of control settlement with fast construction speed. It is expected to provide guidance for design and application of PCC piles reinforcing railway subgrade.

Filling is one of the processing methods for sludge disposal. In landfill of sludge there will be some geoenvironmental problems for sludge has special engineering characteristics. Layered rolling is used in landfill and test samples are prepared under energy of standard compaction test. The test results of shear strength and permeability coefficient for sludge mixed with municipal solid waste (MSW) as well as stability analysis of slope are presented, considering the effects of leachate and pore air pressure from degradation. It is shown that the strength of sludge mixed with MSW is lower than MSW and higher than sludge; strength characteristic of sludge is improved. Permeability coefficient of sludge mixed with MSW is a light different from MSW; permeability is not obviously worse than MSW and is higher than sludge. With the increase of sludge content, slope stability will increase firstly and then decrease. The suitable mixing content of dewatered sludge will be determined by results of test and slope stability analysis. The safety factor of slope stability analysis will decrease about 15%-20% considering the effect of pore air pressure from degradation.

The basic characteristics and creep properties of undisturbed and remolded soft dredger fills treated by vacuum preloading from reclamation site in Binhai New Area of Tianjin, are studied. The results show that the soft dredger fill treated by vacuum preloading not only has structural characteristics but also has creep properties; the structural characteristics play a very important role in creep properties of the soil. Through updating the modified Cambridge model, it can consider the impact of structural characteristics; then making it as yield function of creep model, a semi-empirical and semi-theoretical creep model considering the impact of structural characteristics is established. The calculated results show that this model fits the fact of structural soft dredger fill, so it can be put into engineering practice.

It is very important for protective design of tunnel entrance that assessing anti-detonating performance of surrounding rock using pipe roof reinforcement. Based on principle of similarity simulation, nature or grouting rockmass and steel pipe were replaced using cement soil of different cement-mixing ratios and plastic pipe respectively. Using the model tests, anti-detonating performance of tunnel entrance reinforced with pipe roof under explosive load was simulated. Length, width and height of three models are 2 m, 2.2 m and 2 m respectively. The dynamic response and failure characteristic on tunnel entrance reinforced with none, one layer and three layers pipe roof were simulated using the three models respectively under direct explosion in the model top. Experiments show that the pipe roof supporting can reinforce surrounding rock effectively, enhance integrity and make the distributions of stress more reasonable; the entrance failure decreases significantly with the increase of pipe roof layer, such as failure range from 1.55 m to 0.45 m, the maximum main crack width from 25 mm to 3 mm, the maximum netty crack width from 24 mm to 0.3 mm, the crack number from 14 to 3 in the arch crown of tunnel, and the blasting pit volume from 0.12 m3 to 0.05 m3 in the model top. The pipe roof advance support can control effectively explosion damage outside the pipe roof reinforced layer.

The size distribution of marble fragmentation subjected to impact loading is analyzed statistically from the view of fractal geometry. The result indicates that the fragment-size distribution of fragments has fractal property. Fractal dimension can quantitatively describe the fragment distribution characteristics of fracture process of marble; and can reflect the fragmentation degree reasonably. There is obvious relativity between the average fragment-size of marble and impact loading speed; but the relativity declines with the increase of loading speed. Subsequently, the relationship between the specific energy absorption and fractal dimension is established. It is illustrated that energy absorbency of marble is crucial factors influencing the changes of fractal dimension. The fractal dimension is an appropriate parameter which generally indicates the whole process of rock fragmentation.

The design of transmission line foundation in aeolian sand area is one of the key research topics in current power grid construction. Aeolian sand is special soil foundation; design in aeolian sand area has little relevant design basis. In the view of the characteristics of transmission line foundation engineering in aeolian sand area, the prototype tests of transmission line foundation are carried out. The deformation and bearing capacity, strain characteristics of the foundation and the contact pressure between the foundation and aeolian sand under the combination of uplift and horizontal load as well as the combination of pushdown and horizontal load are studied through the tests. According to the results, the design parameters of transmission line foundation in aeolian sand area are proposed. The test results provide a basis for design of foundations in Taiyuan-Tazhong 220 kV transmission line, which improve the reliability and rationality of the design of the transmission line foundation in aeolian sand area.

The acoustic emission evolution process of Jiaozuo sandstone with 20 ℃-1 200 ℃ temperatures is studied using acoustic emission (AE) test under uniaxial compression. By analyzing AE parameters and the mechanical properties of sandstone after high temperature, the AE characteristics of sandstone under different temperatures and different loading stages are explored. The results show that temperature has little effect on the acoustic emission of sandstone when temperature is less than 400 ℃. The AE ring-down accumulation counts change rapidly both at about 100 ℃ and 600 ℃ temperatures. It is shown that 100 ℃ is the threshold of crack growth for sandstone; and the internal structure composition of sandstone changes after 600 ℃; and acoustic emission phenomenon is very obvious. From 600 ℃ to 1 200 ℃, obvious brittle-plastic transition appears in sandstone. At the same time, the emergence of acoustic emission signals is delayed and the growth rate of acoustic emission signals rises because of high temperature. Sandstone releases intensive acoustic emission signals and presents plastic failure characteristics after 1 200 ℃.

A general principle, a practical method and a modeling process of three-dimensional solid models for sedimentary stratigraphic systems are discussed. Based on the structural characteristics of the sedimentary stratigraphic system, a new approach for generating 3D solid models from borehole data, termed the “boreholes-surfaces-solids method”, is presented and described. At first, a topologic dimidiate data structure is used to discretize borehole data into a series of scattered points. And then, the initial elevations of the top and bottom surfaces for each stratum are interpolated to automatically deduce the genesis of the missing strata. According to different geological geneses, surfaces intersecting, elevations adjusting and consistency processing are performed automatically on the missing strata’s surfaces and their control surfaces. Finally, the solid model filled with 3D blocks or triangular prism meshes is built. A concrete example of using the “boreholes-surfaces-solids” method to Shanghai’s construction projects is presented; and it is shown that this method is effective.

A series of high-strength silicon powder mortar material model specimens with single joint which containing the specific size and the particular inclination are made in the laboratory, the failure modes and characteristics of the single jointed specimens are researched by means of the conventional triaxial compression test. Three typical cracks are observed during the test; they are stretching mode crack (Ⅰ), sliding mode crack (Ⅱ), tearing mode crack (Ⅲ). Ⅱ, Ⅲ cracks are ubiquitous and Ⅰcrack is only local existing. The main failure modes are X-shaped shear failure; and the pure shear failure mode is found under specific conditions. The results show that: the expanding regularity of fault cracks has close ties with the preexisting fissures; the confining pressure is the main influencing factors that the failure modes of the single jointed specimens under the conventional triaxial compression test; the preexisting length mainly affect the size of the fracture extension and joint inclination is the cause of the crack initiation.

Joints have a great influence on mechanical properties of rock under unloading condition. The stress-strain characteristics and the influences of rock mass strength, deformation characteristics, failure law, joint spacing and depth on the mechanical properties of rock mass are analyzed, based on the triaxial unloading destruction experiment of the rock mass with two prefabricated intermittent joints with different spaces. The results show as follows: Comparing to the completed rock mass, the axial strain of the jointed rock during the process of falling from the peak strength to residual strength in unloading failure is 3-4 times larger than the completed rock mass; and the ultimate strength is significantly lower than the completed rock mass; also the brittle feature is not obvious as the completed rock mass. During unloading failure, the deformation modulus of the jointed rock mass reduces significantly, which the reducing degree is 6-7 times larger than the completed rock mass; and the deformation modulus decreases faster with the increase of joint spacing. Comparing to the triaxial loading experiment results of the rock mass with prefabricated joints, the damage degree of the jointed rock mass under unloading condition is more intense; in addition to the shear fracture plane, the tensile cracks of different classes distributed along the direction of maximum principal stress are well developed; and the space of prefabricated joints has little effect on the rock mass failure mode.

An elastoplastic constitutive model of unsaturated soils with capillary hysteresis and skeletal deformation coupling, is developed based on the modified Cam clay model. The new model considers the effects of matric suction and saturation on the yield stress, and can be used to describe simultaneously the elastoplastic deformation and capillary hysteresis of unsaturated soils. Based on the fact that the entry air value increases with plastic volume deformation, a formulation is developed to describe the effect of deformation on the soil-water characteristic curve. The new model can account for the effect of saturation on the prophase yield stress, properly represent the difference of soil strength under different soil-water states, and effectively describe the effect of drying/wetting history on the skeletal deformation. The simulations are compared to the experimental data available in the literature. It is shown that the new model can simulate the main mechanical features of unsaturated soil behavior.

A computation model of circular openings based on nonlinear constitutive relationship along slip lines is introduced. Discontinuous expressions for stress state around the openings after excavation are deduced based on the model. Distributions and values of stresses in surrounding rock are controlled by a uncertain load parameter, which could be determined by introducing a boundary condition. Stress distribution curves of surrounding rock in different ranges of the load parameter are obtained, where the ranges of the load parameter are determined by stress state in surrounding rock. The discontinuous analytical solutions of surrounding rock stress state are consistent with the numerical solutions of two dimensional finite element code for local shear strain.

Several variables of different damage models are listed and compared. Based on a specific project, the accuracy of five blasting damage models which are widely used are tested and compared through the user subroutine interface of LS-DYNA. The results show that the calculated values of KUS and RFPA models are more close to the measured values than other blasting models. Based on the KUS model, considering the compression damage, a modified method to determine the macroscopic elastic parameters is put forward; and then a new tension-compression damage model is established. The accuracy of the new tension-compression damage model is verified. The results show that the new tension-compression damage model can describe the damage effect better.

In order to study and compare the seismic response of railway embankment slopes of different compaction degrees, shaking table model tests on railway embankment slopes with compaction degrees of 95%, 91%, 87% and 83% in embankment noumenon are designed and carried out. White noise excitations are interspersed among seismic waves to obtain dynamic characteristic parameters of embankment slopes with different compaction degrees. Different amplitudes and different types of seismic waves are performed to study the distribution behaviors of acceleration magnification along the height of embankment slopes and their influential factors. The results show that the natural vibration frequencies of embankment slopes decrease, and damping ratios increase with the increase of seismic excitations. The dynamic characteristics of embankment slopes are greatly affected by the compaction degree of embankment noumenon. Acceleration amplifications increase nonlinearly along the height of embankment slopes; and the acceleration amplifications decrease with the increase of input excitation intensity. The embankment slopes make the spectrum characteristics of input seismic waves change greatly; and the spectrum characteristics of acceleration responses differ among the embankment slopes of different compaction degrees. The distributions of acceleration magnification of different compaction degree embankment slopes differ under excitations of different seismic waves, which are influenced by both of the spectrum characteristics of seismic waves and dynamic characteristics of embankment slopes.

Using miniature spherical explosive of 0.125 g TNT equivalent as explosion source and based on the observed velocities of radial particles of ? 1 370 mm×1 200 mm loess sample at 180-1 280 m•kt-1/3, the elastic modulus E=(1.927±0.216) GPa, bulk modulus K=(1.284±0.144) GPa and shear modulus G=(0.771±0.086) GPa are inverted by combining the assumption of strong discontinuous wave and variable modulus model. Assuming the loess as linear viscoelastic ZWT material for numerical simulation, the error function is defined using the particle velocity vmax , the particle displacement umax, and the corresponding time of vmax and umax obtained from the numerical simulation and experimental results respectively. When the error function gets minimum value, the relaxation shear modulus GM and the relaxation factor ? M are 0.13 GPa and 21 µs respectively. Using GM and ? M as the linear viscoelastic ZWT parameters, the numerical simulation of spherical stress wave propagation in loess is made. The results reveal that: the velocity curves obtained from the numerical simulation are consistent with the experimental results; the maximum deviations of vmax and umax are 8% and 6% respectively; the maximum deviations of the corresponding time of vmax and umax are 1% and 5% respectively; the radial stress ? r , the tangential stress ? ? , the radial strain ? r , the tangential strain ?? obtained from the numerical simulation are in good agreement with the results obtained from the assumption of strong discontinuity and variable modulus model.

Multi-reversal direct shear test is conducted on the undisturbed and remolded infilled joint soils under in-situ stress where normal stress is as far as 10 MPa for test from a hydropower station. It is revealed that the peak shear strength is higher but decreases more rapidly for the undisturbed samples compared with the remolded ones; however, it seems the residual shear strengths tend to be the same. In addition, a large amount of particle crushing occurs, Br (relative particle crushing potential) is adopted to quantify the degree of particle crushing in the shear zone and the non-shear zone. The results show that the amount of particle crushing in the shear zone is larger than that in the non-shear zone; and the mechanisms of particle crushing are different for the two zones. Furthermore, particle crushing is considered as the main reason for the nonlinear relationship of the residual shear strength under high pressure; the decrease of shear strength (ratio of the residual shear strength to the peak shear strength) is linear with Br and S2 (the ratio of clay fraction before test to the one after test for the shear zone). It is indicated that the energy liberation and continuously generated clay fraction caused by particle crushing decrease the shear strength.

The variable amplitude of the reservoir water level is the stability sensitive area of the reservoir bank slopes. How will the rock mass strength degrade under the “saturation-air dry” circulation function and the geological hazards caused by the circulation function are very serious and inevitable problems. Thereafter, taking sand rock in the variable amplitude of typical reservoir bank in Three Gorges reservoir area, tests are performed to simulate the process of the “saturation-air dry” cycles. The experimental results show that the compressive strength, cohesion and internal friction angle of the sand rock samples all deteriorate gradually in the "saturation-air dry" cyclic process; and the change rules are basically consistent. Moreover, tests also show that the greater change of the water pressure in immersion, the longer of the soaking time and the more cycle numbers of the “saturation-air dry”, the more serious damage of the rock mass, which indicates that the rise or decline of water pressure and the "saturation-air dry" circulation function have cumulative damage on the samples. At last, water-rock interaction mechanism under the “saturation-air dry” circulation function are discussed in detail based on the experimental research. Research results have an important reference for the study of deterioration law of variable amplitude rock in reservoir bank, and provide favorable evidences for the long-term stability analysis of reservoir bank slopes.

Based on the condition of one selected weathered granite obtained from the subgrade of expressway, “single line” wetting deformation test is conducted by applying the GDS unsaturated triaxial apparatus, in which the stress path of weathered soil is close to the actual one. During the test, the wetting behaviors of the weathered soil under various confining pressures and stress levels are investigated. The data collection throughout the whole experiment includes the stress-strain curves and the axial strain-volume strain curves of the weathered soil before and after the wetting test. The results show that there are axial strain and volume strain in the process of wetting; moreover, the anisotropy occurs after the wetting deformation. When under the same initial effective confining pressure, the shear strength indices c and ? are similar at different wetting stress levels. Compared with the dry sample, the cohesion of wet sample reduces significantly; however, the internal frictional angle has little change. Under a lower initial effective confining pressure, the volume deformation of the sample changes from shear shrinkage to shear dilatation when the axial strain reaches about 10%. However, the similar phenomenon does not appear under a higher initial effective confining pressure.

Experiments are carried out to study the influences of temperature and confining pressure on natural gypsum rock strength and deformation properties under triaxial compression using servo-controlling testing machine. The results indicate that gypsum rock has obvious plastic flow property under different confining pressures. There is no obvious shear failure surface but lateral dilation is observed. Based on Coulomb-Mohr theory, the strength criterion and shear strength parameters of gypsum rock are obtained. With the increase of temperature, the strength of gypsum decreases. At high temperature, gypsum dehydration process takes place with result of transformation from gypsum to bassanite. Scanning electron microscope (SEM) and X-ray diffraction (XRD) methods are used to study the process. With the dehydration process, the pore pressure increases and the failure property becomes brittle. With load continuing, failure surface tends to heal. Obvious plastic flow characteristic and fast self-healing property of gypsum rock are fundamental to sealing stability of natural gas caprock.

Based on the foundation treatments of Xiamen-Shenzhen railway Chaoshan station and in-situ distribution of soft soil layers, two laboratory models of pile-net composite foundation with different pile spacings are designed to study the load transfer mechanism, pile load sharing ratio, pile-soil stress ratio and settlement laws. The results show that the axial force of pile shaft increases first down along pile shaft to a certain depth, then gradually reduces. With the increment of pile spacing, the bearing pattern tends to be ending-bearing form; and the neutral point and the position of maximum negative skin friction move down. The pile spacing has obvious effect on pile-soil stress ratio, but minor influence on pile load sharing ratio. The differential settlement of center soil between piles and pile top is smaller for double pile than that of four piles. Tensile strain of geogrid rises gradually as the embankment filling load increasing; tensile strain curve is initially smooth, then steepening gradually; the rising rate of curve is slow at first then becomes fast afterwards.

Using the resistivity logging principles, a method for measuring the flow field of large-scale outcrop model is established. On this basis, flow field distribution regularity is studied by the model making by ultra-low permeability sandstone outcrops. The research shows that: for the large-scale outcrop model with nonlinear seepage characteristic, the flow field characteristic of the well pattern element is that the injection fluid advances rapidly along the main stream line but impact area is small; and non-flowing area exists, where displacement efficiency is low. The changing laws of flow field at different multiples are analyzed. The influences of different factors on flow field and displacement efficiency are studied. The large-scale outcrop model can reflect the dynamic process of flow field and displacement efficiency, and can simulate the seepage law of the real reservoir better.

Taking typical soft rock-muddy siltstone as research objective, the unloading triaxial rheological tests by constant axial stress and unloading lateral stress by steps are performed under different stress levels. According to experimental results, the axial and lateral rheological deformations are very significant and have strong aeolotropy. The axial rheological deformation is larger at higher confining pressures; while the development of lateral deformation is more rapid than that of the axial direction with the decrease of confining pressure. At failure confining pressure, the lateral deformation of sample is much more larger than that of the axial direction. After detailed research and analysis of the unloading rheological test results, the linear rheological Burgers model can preferably present attenuation and steady rheological stages of rheology curves at different confining pressures; but it can not describe nonlinear accelerative rheological stage at failure confining pressure. Based on the above analyses, a nonlinear damage rheological model is proposed. By taking the least square embedded in Levenberg-Marquardt algorithm, the test data curves are fitted to obtain the nonlinear rheological parameters of soft rock. By comparing with the test data, the fitting curves are well fitted with test curves. It is shown that the rheological model can preferably present unloading rheological curve characteristics of soft rock at various stages.

The composite lining is the most frequently used form of lining in new tunnels and existing tunnels. The situation, which is the deterioration or even failure of primary support, will appear inevitably in the long-term operation; and it will reduce the bearing capacity and the durability of the tunnel system. Based on indoor model test, the members of primary support are made by deteriorated gypsum model. The deterioration process is simulated and the state change of secondary lining structure is recorded. The variation of bearing capacity of tunnel is determined by increasing load. The results show that the deterioration of steel frame and shotcrete layer has larger impact on secondary lining structure than the bolt deterioration. Failure of the primary support does not result in destruction of the lining structure; and the secondary lining has adequate safety redundancy. The deterioration of primary support members will reduce the bearing capacity of the tunnel structure system. The effect of anchors is obvious, but the effects of steel frame and shotcrete layer are little.

With the increasingly urgent demand of underground energy reserves, more and more underground salt rock gas storages are put into use. Underground salt rock gas storages are adopted around the world, because of their good features. Therefore, it is very significant to study the safety and stability of underground salt rock gas storage in operation period. During operation period, gas storage cavity is under time-varying pressure of the inner gas. At the same time, the storage has some risks because of objective uncertainties and it is difficult to study the storage risks with deterministic method. Jintan underground salt rock gas storage is taken as an example. The time-varying pressure curve is created and the transient mechanics method is used to study the long-term rheology of the underground salt rock gas storage. Based on stochastic mechanism method, the failure probability variation of the underground salt rock gas storage during operation period is obtained by ANSYS-PDS with taking the volumetric shrinkage as the control criterion. Calculations show that the displacement of the cavity increases in a wavelike form under the time-varying pressure of the inner gas and the amplification reduces gradually. The failure probability shows this variation: it grows slowly first and then grows fast gradually and it slows down and is stabilized finally. The influence of velocity of gas recovery and injection on the gas storage stability is discussed. Reducing the velocity of gas recovery and injection can suppress the volumetric shrinkage and improve the stability of gas storage. It is meaningful to the risk analysis and assessment of other similar underground salt rock gas storages.

The construction of Daxiang mountain tunnel in water-rich fault has great risks of causing water bursting and mud gushing easily. High-position drainage can reduce water pressure ahead of working face effectively. By using field test and numerical simulation, under different water-level conditions, the interrelation between method of high-position drainage and stability of tunnel is studied; and the optimal plan of arrangement of high-position drainage pipes is put forward. Studies show that: maximum water pressure of Daxiang mountain tunnel in fault is up to 1.98 MPa. The tunnel can be constructed securely after drainage and the maximum water head is only 10 meters. Therefore, prevention of water bursting is mainly concentrated in the period of tunnel face excavation. The drain volume of drain pipes at vault is maximum. The closer drain pipes and arch foot are, the more poor drainage capacity is; and the density of drain pipes at vault should be higher than that at arch foot. In actual construction, for faster to reach drain effect, drain pipes at vault should be first to arranged, then at arch foot. Interrelation between number of drain pipes, drain volume and extrusion deformation of tunnel face is studied. According to economy and effect of hydrophobic reinforcement, reasonable drainage scheme is put forward.

There are some different explanations for the inclination origin of the south and north pagodas of the Three Pagodas in the Chongsheng Temple, Dali. Based on detailed site engineering geological survey and laboratory tests, combining the regional geological background and historical literatures analysis, it is presented that the main reason for the inclination of the two towers is earthquake rather than the nonuniformity of ground soils according to foundation settlement calculation and seismic simulation. The whipping effect derived from seismic action of the pagodas is significant which has caused several times top destruction in history. The vertical compressive forces at bottom layer fluctuate greatly during earthquake but it is safe comparing with the ultimate strengthen of brick masonry. Tension forces take place obviously at the middle part which cause fractures in case of high seismic magnitude. It is considerably reduced by the silt clay under the pagodas foundation that the propagation of earthquake wave from ground and the effect of the seismic vibration.

The current research situations of anchor beam support system and composite members coupling support are summarized; and the necessity and significance of coupling support research of composite members in anchor beam support system are also researched. High strength pressure relief anchor box beam support system is developed, which is guided by the support idea: controlling at first, pressure yielding behind and then resistance. The coupling efficiency weights of composite members are obtained through the method of analytic hierarchy process; and utilization ratio of whole performance, coupling efficiency and control effect of surrounding rock of members in support system are put forward. The results of thirteen numerical test schemes show that coupling efficiency of Ⅱ12c+? 22 cable, Ⅱ12b+? 22 cable and Ⅱ12a+? 17.8 cable support system are good; the coupling efficiency of support system is markedly affected by cable type; increasing prestressing force is good for raising whole utilization ratio and coupling efficiency, and improving control effect of surrounding rock. The force measuring anchor box beams are designed and made; and the Ⅱ12b+? 22 anchor beam support system is applied to field test. Monitoring results show that the utilization ratio of whole performance is 54.51%; the coupling efficiency of members is 75.61%; members of system keep pace with each other in load supporting; roof settlement in coal roadway is 148 mm and walls displacement of roadway is 180 mm; and surrouding rock deformation is controlled well during roadway excavation.

SHAKE has been widely used by engineers to predict ground responses in seismic design. Although SHAKE analysis is simple and straightforward, to generate accurate and reliable output still requires significant experience and skills; especially with regard to the significant uncertainty of soil parameters in ground response analysis. These uncertainties come from a number of factors such as initial shear modulus (or maximum shear modulus), dynamic shear modulus degradation curves, damping curves, and the existence of soft layers. For large infrastructure analysis, the results of ground response analysis have an important influence on the economy and safety of the whole design. Therefore we propose to perform a systematic sensitivity analysis to account for the uncertainties. Based on the results from these analyses, a systematical and rational way for researchers and industrial designers to carry out reliable ground response analyses is suggested.

Outwash deposit is one of the typical mixed materials, which is made up of soft soil grains and hard rock mass; and it is very difficult to determine its mechanical parameters and analyze its mechanical characteristics. Digital image reconstruction method is used here to help construct the structure of outwash deposits and to reflect the distribution of stones as well as the feature of clump. So a modeling method with particle discrete element method based on image recognition is built up, by which the laws on mechanical parameters of media distribution, strength of soil particles are researched. Then deformation characteristic, peak strength and shear strength after peak are analyzed. It is shown that the deformation curve before peak strength presents a feature of nonlinear hardening process, while it is like perfect plasticity after peak strength; composite friction angle of mixed material will decrease with the increase of bonding strength; when the stone content is less than 25%, composite shear strength approximately is equal to soil strength; when the stone content is higher than 25%, the shear strength will increase with the increase of stone content. Due to the effect of rock structure, the correlation coefficient between stone content and friction angle is greater than that between stone content and cohesion strength; and it can be concluded that the actual friction angle of geology deposits of Gushui Hydropower station is 0-8 degrees higher which is agreement to engineering conclusion. This method can consider stones of large size, which is a great difficulty in laboratory test, and can be a beneficial method for mechanical test in determining shear strength.

Based on the Abaqus software 64 CPU parallel computing cluster platform, a three-dimensional finite element model of train-track-viaduct-foundation-soil coupling is established. Ground surface vibration characters caused by trains running under different conditions are obtained; and the law about that ground surface vibration level decreases with the increased distance between the ground surface and the viaduct pier is parametrically analyzed. Then the main conclusions are drawn as follows. With the increased train speed, ground surface vibration level increases obviously. The fully loaded train capacity only slightly increases ground surface vibration level of the site near pier, having little effect on the site away from pier. The number of carriages has no obvious effect on ground surface vibration level. Ground surface vibration level under train running in double line is much greater than it under train running in single line. The increase of fastener stiffness could slightly decrease ground surface vibration level. With the increase of pile length, ground surface vibration level decreases much. The increase of pier span could decrease ground surface vibration level, however, when pier span increases to a certain value, there isn’t apparent effect on vibration reduction. Pier height has no apparent effect on ground surface vibration level. The ground surface vibration level tends to gradually decrease with the increase of shear wave velocity of soil.

Distribution laws of blast loads on arch structure induced by underground explosions are studied by numerical method. The results show that the load distribution on arch is mainly effected by the explosion height, the arch span and the angle of monitoring point. The distribution form of load is shape of saddle as a symmetry axis around vault. Load distribution on the arch will be more uniform with the increase of the ratio of explosion distance and span. Conversely, it will be more concentrated. The load distribution on side-wall is mainly effected by the explosion height, the arch span and the side-wall height; and it reduces gradually from wall tip along the wall, finally tends to even distribution. On this basis, a method to calculating load on arch structure with large span is proposed. After calculating the load factor on arch structure, it is found that the load factor around the arch is not a constant value and increases with the increase of arch angle. The minimum value of the factor appears at the vault and it equals to 1.5.

Based on the formula deduced by Aleksandrowski for calculating pitch direction of fault slip data, an improved method for determination of tectonic stress tensor was put forward. A method for back analysis of tectonic stress field was deduced by least square method based on the relation between tectonic stress with pitch direction of fault slip data in different stress ratio values. At last, the calculating process was deduced by Matlab program. The fault slip data were obtained in the Wushan mining region, Jiangxi province. On this basis, by the improved method of inversion of fault slip data, the parameters of tectonic stress tensor in mine region were determined. The tectonic stress field in this area since Late Jurassic was obtained, by comparing the faults with the average stress field of the region obtained from focal mechanism solutions and studying distribution of the strike-slip faults and the tectonic setting of this area. It is indicated that the tectonic stress field in this area has better stability since Late Jurassic. The progress of solving tectonic stress tensor and the application of the improved method show that, comparing with the graphical instrument method put forward by Aleksandrowski and the method for back analysis by Etchecopar, the method is simple and more feasible, and the focal mechanism solution is reasonable.

The authenticity of dynamic finite element’s results has a close relationship not only with boundary condition and the inputted datum of seismic wave. This paper calculates seismic response of large slipmass under different boundary conditions and inputted datum with time history method. On the basis of the calculating results to analyze the impacts which arise from radiation damping and inputted elevation on seismic response of slipmass and the law of seismic response. The results demonstrate that the upper part of Shangtian-town large slipmass has large displacement response and small shearing strength; but the response of lower part is opposite to the upper. Viscoelastic boundary can reduce the seismic response of slipmass; and the change of inputted elevation of earthquake wave can produce considerable influence on seismic response. The simulative rationality of radiation damping of foundation and inputted elevation of earthquake wave can influence the objectivity of seismic analysis.

Introducing and modifying the continuously yielding joint model, and simultaneously considering the composite impact of mechanical dilation/compaction and pressure solution on fracture aperture, the FEM code for analysis of the thermo-hydro- mechanical coupling in dual-porosity medium established by the first author was improved. Through the numerical simulations in which there were two patterns of changing the fracture stiffness for a hypothetical nuclear waste repository, the variations and distributions of temperatures, fracture stiffnesses, normal stresses, pore (fracture) pressures, flow velocities of groundwater were investigated. The results show: compared with the case of unchangeable fracture stiffness, the temperatures in the computing domain are lower in the case whose fracture stiffness is an exponential function of normal stress; the magnitudes of stresses within the rock mass in two cases are also some different, but the characteristics of stress distribution are similar to those of fracture stiffnesses obviously; and the negative pore (fracture) pressures in the case with changeable fracture stiffness are smallish (about 98% of case of unchangeable fracture stiffness).

The construction of ten adjacent panels of a diaphragm wall of an ultra deep excavation in Wuhan city is simulated by a three-dimensional finite difference method. The construction procedure consists of the excavation supported by slurry, concrete pouring, and concrete hardening. The excavation is simulated by the constant distributed hydrostatic pressure while the concrete pouring process adopts variable distributed hydrostatic pressure. The concrete hardening process is finished by linear elastic solid elements with variable elasticity modulus and Poisson ratio. The results of the numerical computation show good agreement with the field test data. According to the process of single jumping excavation, the pressure monitoring reveals the influence of diaphragm wall construction on stress redistribution. The earth pressure fluctuates along the retaining wall after the construction completion of the ten panels. The peak value appears in the middle of the panel, while the trough value appears around the junction of two panels. The fluctuation range is related to the depth. The differences between slurry pressure, concrete pouring pressure and earth pressure are the main reason influencing the redistribution of earth pressure. Reasonable slurry unit weight and ideal concrete pouring method are suggested to avoid disturbance of soils.

The present work is the further development of the previous works of the writers on internal variable gradient model for zonal disintegration phenomenon near deep tunnels. Strain gradient model is used to study zonal disintegration phenomenon. As an additional variable, strain gradient, is introduced. The equilibrium equations, boundary conditions and flow rule are obtained by using virtual work principle. Constitutive equations are obtained by using Clausius-Duhem inequality. For deep circular tunnels the governing equations are obtained from the general equations of the proposed model for elastic deformation regime, elastoplastic deformation regime and plastic deformation regime without consideration of elastic deformations. The solutions of the governing equations are obtained; and the behaviour of the solutions is analyzed. The proposed model not only expands the classical elastoplastic model for surrounding rock near tunnels, but also serves as theoretical basis for numerical study of zonal disintegration phenomenon near deep tunnels.

A new method which couples the level set method with meshless method to simulate crack growth is presented. The coupling of level set and meshless method can achieve naturally because they all set up based on the discrete nodal data. Two level sets that are orthogonal to one another at the crack tip are used to represent the geometry of crack and the location of crack tip, and to construct the Heaviside skip function and the Westergaard enriched function near the crack tip in the element-free Galerkin method (EFGM) discontinuous approximation. New crack tips are defined by the update algorithm of level set easily when the crack is growing. The coupling method does not use the visibility method, the diffraction method or the transparency method. The singularity is reproduced very well; and the convergence for elastic problems is improved. The passage of crack has no influence on the nodal domain. Smaller domain is used to calculation, which keeps the band and sparsity of the over all stiffness matrix. In addition, the level set makes the selection of enriched nodes and the establishment of additional function simply; and its update process needs no evolution equations. The numerical results show that the presented method has higher computational accuracy; and the simulated expanding path of crack is coincided with the tested curve. So, the results verify the validity and accuracy of the presented method.

Three-dimensional deformable discrete element method is an appropriate numerical method for studying mechanical behavior of discontinues geo-material. The ability of automatic contact detection and discretization of particle and structure by finite difference grids, makes it had inherent advantages in simulation discrete-continuum coupling problem. The deformable discrete element method is employed to study the mechanical behavior of soil-structure interaction problem, in which the coarse-grained soil is modeled by random simulation technique. The mechanical behavior of interface between soil-structure is compared under direct shear and simple shear conditions. The numerical simulation results are investigated from macroscopic and mesoscopic levels, respectively. The results show that the numerical simulation can reflect the mechanical behavior of soil-structure interface; the curves of shear stress-relative shear displacement have a good agreement with the experimental results; the interface roughness has a great impact on the strength and deformation properties, due to the disturbance of particle induced by shear. The shear stress-relative shear displacement relationships of simple shear and direct shear are both hyperbolic. The initial stiffness of simple shear is smaller than that of direct shear; and the shear strength of two are similar.

There are many ruins of ancient earthen sites in Northwest China, many of which are destroyed by violent processes of the wind erosion. Reinforcements are needed to protect these cultural heritages. The mechanism of reinforcement and resistance of environmental factors are the fundamental of the reinforcement theory. Particle flow code is used to simulate the soil before and after potassium silicate (PS) reinforcement, which is achieved by changing the parallel bond strength between particles. Compressive and tensile strengths of soil are calibrated with considering the soil particle size and density. The calibrated models are used to simulate the processes of the wind erosion. Sand-driving wind flow is represented by random generating particles with original vertical velocity. Results show that under the erosion of 20 m/s sand-driving wind flow, the magnitude of erosion increases as wind flow duration increases. The increasing magnitude of erosion of soil before reinforcement is much larger than that of reinforcement soil. The resistance erosion capability of reinforcement soil is greater than soil before reinforcement. These conclusions are generally agreed with the indoor wind-tunnel test results. The calibrated particle flow model of this research can be used for further analysis of ancient earthen site soil, such as wind erosion, water erosion, freeze thawing etc.

The strength reduction method, which is popular at present in the slope stability analysis, is used to analyze the relative error of calculation results by using software MIDAS/GTS, FLAC, ANSYS with D-P and M-C yield criteria in three cases (soft clay, hard clay, weak expansive soil). In the case of soft clay the relative error of calculation results by using D-P criterion and M-C criterion is relatively small. For hard clay slope, the relative error of calculation results by using D-P criterion and M-C criterion increases significantly. The calculation results by using three kinds of software with two yield criteria all indicate that sliding surface in hard clay is shallower than the sliding surface in weak expansive soil and soft clay. Under the same circumstances, sliding surface determined by MIDAS is shallower than the result by ANSYS. When the slope is small the safety factor of the calculation by MIDAS is smaller than that by FLAC (M-C); when slope is large the result is opposite. When slope is small the calculation convergence is realized after the breakthrough of plastic zone, but for large slope calculation divergence occurs before the breakthrough of plastic zone. In the case of small slope the difference between reduction factors upon appearance of calculation divergence and upon breakthrough of plastic zone is significant. But the difference between reduction factors is relative small in the case of large slope, even breakthrough of plastic zone does not occur upon the calculation divergence, which is more remarkable when using MIDAS software.

During the design of multi-row and embedded anti-slide piles of large landslide, the most important thing which most designers are concerned about is the landslide thrust of each row of piles and the distribution mode along the pile when the row distance or embedded depth is different. It’s difficult to study all kinds of large landslides, so a typical landslide with polygonal line slip surface is studied. And in order to simplify the analysis, it’s assumed that it has specific landslide surface. Based on indoor model test, the general law about landslide thrust of each row of piles with different row distances is obtained. Also by the strength reduction finite elements, the distribution mode of landslide thrust along the pile with different embedded depths is analyzed. The result that the change of row distance or embedded depth is a proper method for optimizing the ratio of each row of piles is presented; and the landslide thrust distribution law of row of piles is a guidance for the civil engineering designers to accomplish more reasonable design of multi-row and embedded anti-slide piles in reinforcing large landslides.

Underground structure seismic damage process simulation is an effective means to study the underground structure aseismic performance. Through setting artificial boundary condition, taking dead weight stress of rock and soil mass as an initial state of dynamic response simulation, the static-dynamic coupling numerical simulation of earthquake response of the underground structures is realized. Based on finite element analysis software ABAQUS, taking ultimate shear strain as a failure criterion, the seismic damage process of underground structures is simulated by the birth-death element method. Considering structure depth, the influence of initial geostress on aseismic performance of underground structure is analyzed. The results show that the aseismic performance of underground structures has a most unfavorable depth, namely the most easily damaged depth in earthquake. When the depth exceeds the most easily damaged depth, the ultimate aseismic capacity of structures enhances. If the earthquake damage occurs, the damage degree of structures will be greater with the increasing of depth.

On the basis of Froude similarity law, model test studies of the anti-explosion ability of tunnels which are reinforced by common anchor bolts, slightly dense anchor bolts, long-dense anchor bolts, short-dense anchor bolts, and long-short alternation anchor bolts are carried out. This article, from five aspects, including stress in surrounding rock, acceleration of tunnel wall, relative displacement between vault and footwall, tangential strain of tunnel wall, and failure mode of tunnels, analyzes the different characteristics of tunnels reinforced by fully grouted anchor bolts which have different lengths and spacings. Furthermore, by using FLAC3D program and parameterized modeling methods, numerical calculations and corresponding model tests are also carried out; and the variation regularity of vault displacement with the change of anchor length and spacing is analyzed. The results show that, as comparing with increasing anchor length, the reinforcement effect of decreasing anchor spacing is better. It just prevents cracks from extending into the reinforced region only when anchor spacing decreases to a certain density. Under the same anchor length, acceleration peak at tunnel vault, peak and residual values of relative displacement between vault and footwall, and peak and residual values of compressive strain at arch springing in the tunnels reinforced by dense anchor bolts reduce greatly. But the reinforcement effect is not evident when the length of dense anchor bolts increases to a certain length; it contrarily arouses the sharp increment of the peak of acceleration at footwall and the peak of tensile strain at vault. The optimum anchor length is one-third of the tunnel span and the optimum anchor spacing is one-fifteenth of the tunnel span.

The spring element method (SEM) is a numerical method that uses a spring system to describe an element. Different elements can be described as different spring systems; and the definition of the spring stiffness expressions in the systems is the key point of the spring element method. The four-node rectangular element is described by 6 basic springs, each of which contains two derived springs: normal spring and tangential spring. Poisson spring and pure shear spring are used to describe Poisson and shear effects of the element. Thus a four-node rectangular spring element is presented. Compared with the element stiffness matrix of finite element method, the stiffness expression of each spring is obtained. Springs of the same kind have the same expressions. The stiffness expressions of the normal and tangential springs have corresponding coefficients to be decided. By varying the coefficients in the stiffness expressions of springs, expressions of constant strain, bilinear or Wilson incompatible finite element are achieved by this element. The accuracy of the SEM is verified by theoretical derivation; and this method is applied to the continuum-based discrete element method (CDEM) for case verification. The features of the four-node rectangular spring element are as follows. Different accuracies can be found in different elements. This element can significantly improve the accuracy of the bending problem of beam. Elements with different accuracies can be achieved by using different coefficients.

The stability of large underground caverns in high geostress area has always been the hot topics of many rock mechanics professors’ attention. Based on the happening mechanism of opening displacements and considering the theory of energy dissipation, this paper makes a preliminary study of the constitutive equation of brittle rockmass in high geostress zone and their engineering application. First, a variational-modulus model has been received during the unloading course from the point of energy dissipation and this aspect is considered in the constitutive equation. Dissipation of energy can be gained from the theory of crack growth. Second, taking advantage of FLAC3D, we compile the above constitutive equation model on the Microsoft Visual C++ environment, and realize the secondary further development of FLAC3D. Third, the stability of surrounding rock and the excavation step in the large underground caverns of Jinping hydropower station are simulated by the developed program. The results indicate that this variational-modulus model is closer to real excavation. It offers some instructions to similar projects.

The pile group foundation of Sutong bridge is the largest in the world. It is composed of 131 overlength cast-in place bored piles which are 117 m long. The sensors worked under this engineering environment must subject to large pressure, as well as construction factors, and they damage easily. In order to improve the installing survival rate of the sensors, some sensor protection techniques are put forward after several field tests, including concrete strain gauge, surface strain gauge, hydrostatic level and water pressure gauge. The installing survival rate of sensors can be ensured by implementation of sensor protection techniques. The average survival rate exceeds 96%. The rules of load mechanism and uneven settlement are analyzed by monitoring data. The results show that the load mechanism of overlength cast-in place bored piles is different with the piles in common. The uneven settlement of large-scale pile group foundation appears in the direction across bridge; and the uneven settlement in longitudinal direction can be ignored.

Spherical template indenter (ball mode device) has been widely used in the mechanical properties of permafrost soil testing in the former Union of Socialist Soviet Republics (USSR) and Russian Federation. In the past 60 years of engineering practice, the test method, test theory, etc. were improved. It is simple, easy to test. And the results reflected the mechanical properties of frozen soil better. So, it widely used in long-term strength’s evaluation and forecast of the cohesion for the frozen soil. This paper made a brief introduction to the equipment, the test theory, and test methods. Moraine clayey loam in the outskirts of Moscow city was used as the object of study. In constant temperature (from -7 ℃ to 20 ℃) conditions, in a closed state, the freeze-thaw cycle tests were conducted, 3, 6, 20, 40 times, respectively. Physical properties of soil were tested in different experimental stages; and strength was tested on the frozen soil with spherical template indenter after the freeze-thaw cycle. After freeze-thaw cycle test, soil’s physical properties indicators reduced in varying degrees. With the increase in the number of freeze-thaw cycle, soil strength decreases. The volumes of water in soil change in the freeze-thaw process, which caused soil density decreases and the porosity increases. This is the reason for the reduction of soil strength.