Under high stresses, rock bursts, borehole breakouts and spalling are all common phenomena which occur around the underground openings. In substance, these three phenomena all belong to brittle failures of intact rock mass; but they reflect different failure extents of intact rock mass under the action of high stresses. After analyzing and comparing the stress-strength criteria for rock bursts, borehole breakouts and spalling put forward by other specialists, we find that these brittle failure phenomena share the same stress requirement. The stress requirements for brittle failures can be defined with the ratio of the maximum tangential stress around an underground opening to the uniaxial compressive strength ( / ) or the ratio of the maximum principal stress to the uniaxial compressive strength ( / ); actually, both indices reflect the same stress requirements. For / , the ratio of 0.4±0.1 should be the critical stress requirement, but for / , the ratio of 0.15±0.05 should be the critical stress requirement. Large amounts of engineering cases and the mechanical analysis based on the Hoek-Brown criterion also prove the validity of these two stress requirements. Here, the two stress requirements reflect a ratio range because the complicated rock mass ratings, lithology and geotechnical conditions shall have profound impacts on the stress requirement for brittle failures.

Base on the moment of inertia equation and sectional parameters, the X-section cast-in-place concrete pile (referred as to XCC pile) stress distribution and stress concentration equations under different directions lateral load were built; and influenced factor, such as, sectional parameters were analyzed. In order to comparatively analyze, the characteristics of circular piles and square pile with the same concrete amount or the same perimeters were carried out. Finally, one of optimized X-section type was proposed, which can be used for XCC pile design reference. The results show that, the maximum stress distribution increased with the decreasing of outsourcing diameter, the decreasing of open arc angle, and the increasing of open space with the same area. The maximum stress distribution increased with the decreasing of outsourcing diameter, the increasing of open arc angle, and the increasing of open space with the same perimeter. In this paper, 0.5-0.7 m outsourcing diameter, 0.1-0.2 m open space, and 110o-130o open arc angle can be chosen for recommended section parameters.

The direct shear tests of heterogeneous structural surface in rock mass taken from the engineering site for Ling’ao nuclear power project are investigated under different normal stresses and water condition. The curves of shear stress- displacement change of heterogeneous structural surface are obtained; and the shear strength property and deformability of heterogeneous structural surface are analyzed. Comparison with the computing results using JRC-JCS model and the testing results is presented. The research results show that the shear stress-shear deformation curves of heterogeneous structural surface present an elastoplastic residual deformation and the saturated specimens have a smaller elastic region and enter into peak region or plastic region earlier. The shear stiffness of saturated specimens is lower than one of natural specimens under the same normal stress, especially for a low normal force. Water makes obvious effects on the strength parameters of rockmass heterogeneous structural surface; especially on inner friction angle . The JRC-JCS model can provide reliable values for the shear strength parameters of joints in a real geotechnical project.

Derivation of the yield approach index (YAI) formula under JRC-JCS nonlinear model is deducted, the calculation method for the yield approach index under JRC-JCS nonlinear model is programmed; and its results are compared with the results of FLAC3D, the effects of various parameters on the yielding approach index are analyzed to obtain that the result from yield approach index =1 is the same with that of plastic zone distribution of FLAC3D calculation results; so that it is verified the program and results from the yield approach index can reflect the damage degree of non-plastic area of rock mass, and is better than the estimation method of plastic zone distribution. With the increase of joint roughness coefficient and rock mass compressive strength , the yield approach index of rock mass decreases gradually; the relation between and is linear feature; and the relation between and is exponential nonlinear feature.

In the rigid pile composite foundation that pile is long enough and is not more than 6 times the pile diameter, the internal shear force between pile and soil and under friction of the pile-soil interaction, the soil pressure in the top section of the pile only increased at a certain depth range, it decays rapidly with depth and axial force of top pile increases with depth in soil shear stress and friction. Based on this characteristic of the rigid piles composite foundation, when there is rigid pile composite foundation surrounding excavation and the excavation bottom is higher than rigid pile bottom, soil pressure on the retaining structure which is caused by the additional vertical stress of rigid pile composite foundation can be simplified as an inverted triangle; and the maximum earth pressure effect on intersection of the rigid pile top plane and supporting structure, as the depth increasing, the active earth pressure attenuates to zero. It is shown that the calculation method is consistent with the engineering reality.

The failure mode of soil-cement material, the bearing and deformation characteristics such as the pile-soil load share ratio, the pile-soil stress ratio, and the deformation in the deep soil between the piles of rammed soil cement pile composite foundation are measured by the indoor model tests. The effective pile length or the effective composite soil thickness of rammed soil-cement pile composite foundation with the given pile strength is provided in the test conditions in this paper. The effect of the pile strength on its bearing capacity should be considered for the design of the rammed soil-cement pile composite foundation. The pile design should be based on the control of the pile body strength and the bearing capacity of single pile determined by the pile strength should be greater than that provided by the soil surrounding the pile and pile end soil.

Studying the foundation treatment techniques of soils soil has become more important to improve the investment environment, speeding up the Bohai sea region development, using land resources scientificlly and rationally. The key of the foundation treatment techniques, scientific or not, is revealling the nature of factors which affect the deformation and strength of the soft soil from the structure characteristics of the soft soil.The quantitative parameters of the soft soil micro-structure is established by integrating the marine deposits soft soil physico-mechanical properties and microstructural characteristics with the deposited soft soil of the Tang-Cao(Tanshan-Caofeidian) highway as the research object. It conducts a systematic analysis between the microstructure and macro-mechanical properties of the marine deposited soft soil by indoor experiment and theoretical analysis. It also carries out the analysis and proof about the structural strength and engineering effects of the marine deposited soft soil. A pore structure factor has provided as integrated parameter, which integrated parameters to measure the structure strength and failure trend based on the fractals evaluation theory. And solving the pre-consolidation pressure at the same time, the structural strength of the soil can be determined quantitatively. It is a successful example and is helpful to engineers.

In simple shear test, under the constant stress increment ratio (CSIR) stress path, some soil-structure interfaces have the mechanical properties of strain softening and shear dilatation. Based on generalized potential theory, an elastoplastic model for soil-structure interface under the CSIR stress path is proposed. In the model, soil-structure interface problem is regard as a two-dimensional mathematical question in stress field; normal stress and tangential stress are taken as two potential functions respectively, and plastic state equations are used to replace the traditional yield surface. Relation curves of normal stress and normal strain in axial compression tests is described by an exponential function; and relation curves of stress ratio and tangential strain in simple shear test is simulated by a complex exponential function. Then, another complex exponential function is presented to express normal dilatancy and tangential strain relation curves. Furthermore, the model undetermined coefficient expressions are got by the differential of above fitting functions. Finally, the model prediction results have been compared with experimental data; and the results show that the model is reasonable and practical

The blasting-based squeezing and replacing method has been used to treat the soft clay in constructing the rockfill embankments in the reclamation projection in Xuanmen area, Zhejiang province. To obtain reliable soil parameters for the settlement prediction and stability analysis of embankments, in situ soils were sampled just before and after blasting operation in the range of foundations. Then oedometer consolidation and equipressure consolidation tests were performed. The compression and structural characteristics are preliminarily studied on the marine soft clays in the area. The results show that marine soft clays possess intrinsic structure, and behave differently from its disturbed counterpart. With introducing the concept of void index, the effect of soil structure is investigated, showing that the structure of soft clays is the intrinsic reason that the compression characteristics is very different between marine soft clay and its remolding counterpart; and the compression curves of undistributed soils and distributed soils merge into a single curve in the high pressure range. Blasting-based squeezing method can make marine soft clayey soils disturbed largely. And it influences significantly the physical and compression properties of clayey soils. Furthermore, the structural yielding stress and the structural strength are both reduced undergoing the disturbance effect. The defined structural destructive ratio can be used to quantify the degree of damage from blasting-based squeezing effect on the structure of the marine clayey soils. These results may be significant for developing the theoretical basis of blasting-based squeezing for treating the soft foundation of embankments.

The K-G model is much better than E-μ model for its each parameter directly contacts with soil modulus and convenient for the nonlinear theory and calculation analysis of geotechnical engineering. Taking the Yongdeng unsaturated loess in Western Gansu as the object of study, a large number of unsaturated loess conventional triaxial tests under different humidities is carried out; and then different initial saturations under the K-G model parameters are obtained, the change rule of these parameters with different initial saturations is studied. The relevant expressions of model parameters and initial saturation are established. So that in actual project, using the measured unsaturated loess humidity indicator, we can get the unsaturated loess parameters of K-G model for moistening numerical simulation analysis and avoid suction measurement and calculation. The result has a certain practical value.

Ultrasonic characteristics and splitting-tensile strength of granite after exposure at temperature ranging from 25 ℃ to 1 000 ℃ are studied using hydraulic servo system and ultrasonic detector SRM-5N. The results show that (1) the longitudinal wave velocity, waveform and splitting-tensile strength of the granite are closely related to temperature; (2) the longitudinal wave velocity and splitting-tensile strength of granite gradually decrease with the temperature increasing, when the granite is exposed at 1 000 ℃, the longitudinal wave velocity and splitting-tensile strength decrease by 90% and 65%, and the splitting-tensile strength is bound up with the longitudinal wave velocity; (3) with the temperature increasing, the waveform of granite turns from regular to disordered, from concentrated to scattered, especially at 800 ℃; (4) the thermal damage enlarges and the specimens become fragile after exposure at 1 000 ℃.

Geological materials are inhomogeneous natural materials having micro cracks and micro voids. Under the theoretical framework of breakage mechanics for geological material, the geomaterials are conceptualized as binary medium consisting of bonded blocks and bonded bands, evolvement equation of breakage ratio are reflectrd the fracture process degree of the transformation of fracturing or breaking of bonded blocks into bonded bands in the process of loading，which are analysed deformation and breakage development speciality, showed the change course of bonded blocks into bonded bands under loading. Finally, aimed at the loess in Yanglin region, through triaxial shear test, the influences of confining pressure and water content on the breakage rate evolution are studied. The results show that the breakage ratio of simple parameter binary-medium mode has no relation of the confining pressure and water content, it is the function of maximum principal strain from the test.

The stress states of suspended cut-off wall and strong permeable foundation plays an important role in the evolution of piping. A series of seepage-stress coupling experiments on the suspended cut-off wall and piping-typed sand gravel foundation under different stress states are carried out using a newly designed soil-structure contact shear permeameter. The results show that the stress state has a great influence on the critical piping hydraulic gradient of the suspended cut-off wall and sand gravel foundation; the larger the confining pressure is, the larger the critical piping hydraulic gradient is. A linear empirical formula on the critical piping hydraulic gradient denoted by the confining pressure is established based on the experiment results. The results show the intensive influence of the seepage-stress coupling effect on the seepage stability of the cut-off wall and sand gravel foundation, so as to provide an important theoretical basis for determining the reasonable penetration depth of the suspended cut-off wall in deep overburden foundation.

In order to study the seismic performance of prestressed concrete pipe pile, the tests on pile-soil-structure model under different seismic waves on the shaking table are carried out to study the distribution of stress, strain, bending moment and displacements along the pipe pile. The position of maximum bending moment and the force and failure characteristics of the pile and the pile cap are also studied, so that the reaction rules and characteristics of the pipe pile under earthquake are obtained. Finally, some conclusions are drawn as follows. The maximum bending moment of the pipe pile is located at the distance of 5-6 times the pile diameter to the top of the pile under El-centro wave of LWD wave and sine wave conditions. The acceleration response of the pile -superstructure system is rendered in height "K"-type distribution, etc.

Based on the block dynamics theory, consider simple harmonic vibration of seismic waves. a simplified model of slope bolting support under dynamic loading was established, according to the analysis principles of Pseudo-static. Then, the solutions of slope failure along the slip plane under resonance effect and the expression of internal forces were obtained by using of analytical methods. Based on these, the mechanical solution of bolt is proposed for seismic design. The parameters analysis of the slope bolting support showed that the frequency of seismic waves has a greater impact on sliding displacement amplitudes of damage body. Thus, the resonance phenomenon should be avoided in slope design. Moreover, the bolt spacing has also a greater impact on vibration amplitude of the displacement. As the spacing increases, the displacement amplitude also increases. When bolt spacing is constant, the slope slip displacement increased amplitude is significantly less than other influence parameters with the slope height increasing. With the rock slope angle increases, the displacement amplitude also increased and the bottom slope angle increases from 60° to 90°, the displacement amplitude increases from 7 cm to 25 cm. While the upper slope angle exceeds 25°, the displacement amplitude increases so rapidly that it should be paid enough attention in the design and construction.

The saturated-unsaturated seepage test system is established in order to study seepage under water level sudden raise and rapid drawdown. The matric suction in unsaturated zone within the dam model is tested. During the test, the atmospheric temperature and humidity of the laboratory are also recorded at the same time. The matric suction evolution under the changing water lever and its influencing factors are discussed. The results show that the matric suction in the model is not only related to the water level changes and the position of measuring points, but also affected by the impact of the atmospheric temperature, humidity, evaporation and other external environmental factors. The dominant factor between the changes of water level and evaporation, determines the matric suction evolution in the unsaturated zone.

Geotechnical inclinometer system is widely used in field monitoring of the deformations of soils and structures. Its working principle is that the deformations of an inclinometer casing are measured to reflect the deformations of monitored objects, with which engineering stability and safety can be analyzed. While the engineering stability and safety is under threat, accompanying oversize localized deformations are of common occurrence. This may result in that inclinometer probe cannot be lowered into inclinometer casing, leading to failure of the casing and losing of key data. In order to predict the possibility of the failure of the casing, 5 methods are proposed to determine the curvature or the deflection angle of localized deformation curves of the casing. By comparing the calculated curvatures or the deflection angles with their limiting values at failure, the possibility of casing failure is analyzed. A case of the failure of an inclinometer casing in a foundation excavation project is analyzed. The adaptability of the proposed methods is compared. Of the 5 methods, the method of biarc fitting of 5 data points with an end point constraint is recommended for detecting the failure of an inclinometer casing.

Digital image measuring principle and the way to eliminate or reduce error in the triaxial test are introduced; and digital image processing technique is used in triaxial shear creep test. The test results show that thickness of the water film between soil particles has big effect in creep. In undrained condition, Sample soil particles of water film unchanged and viscosity coefficient is constant too, so soil creep deformation has a greatly change. While in drained condition, water is discharged from the soils, soil is concretion and induration and soil particles of water film is thinning and soil density increases and viscosity enhances; creep deformation is smaller. And transient pore water pressure will continue to rise for Manadei-Cryer effect; the whole process is taken about 10 min. With the deviatoric stress level increasing, soil sample is bulging, then shear plane appears and it is usually located in the lower part of the sample. Comparison the results of digital image measure method and displacement conversion method gotten shear strain showed that: samples of the non-uniform deformation can lead to larger error in displacement conversion method for calculating the shear strain. Singh - Mitchell model describes the soil shear creep properties exactly. And parameter gotten by the two methods is not a big difference. When deviatoric stress level is low, the parameters can be gotten from displacement conversion method.

Great many results about the creep properties of rock have been achieved, while few reports on the cemented backfill’ s creep characters were obtained. In this paper, creep property of cemented backfill is characterized by Hoek-Kelvin model. Cemented backfill creep experiments are firstly conducted in the laboratory, then the parameters of Hoek-Kelvin creep model are identified using particle swarm optimization algorithm. Meanwhile, the sensitivity of creep parameters to the stress level is studied. Results show that the numerical value of EH and η vary little at different loading stress levels, and EK is very sensitive to the change of loading stress level. The proposed creep model for backfill is developed with the software FLAC3D; and it has been used to numerically simulate multi-stage loading on cemented backfill. The numerical results agree well with the experimental ones.

Time effect is defined as an increase in pile capacity over time after installation. The statistical analysis reveals that the average increase rate of bearing capacity for single pile is in the range of 15%-29% per log cycle. The set-up on the pile capacity is mainly due to the consolidations, the gains on shear strength，the aging, the creep and shell effect of surrounding soils. Based on the mechanism of pile set-up, a three-phase conceptual model is establisbed. In addition, a computation model is proposed based on consolidation theory for evaluating the soil set-up on pile capacity. The research indicates that the relative setup rate for friction-type open-ended pile under full coring condition is 10% larger than that for corresponding closed-ended pile.

In order to research the load transfer mechanism of composite ground with underlying layer, a series of model tests were performed. The tests were of various pile diameters, cushion thicknesses and underlying layer thicknesses. Increasing the diameter of pile can not improve the exerting degree of pile bearing capacity, and the cushion and underlying layer should be considered fully in the composite ground design. Test results show the distribution of axial forces, skin friction and pile-soil load shareing ratio, and provide useful information for the study on the composite foundation theory, and give a guide to its engineering design.

In engineering practice design parameters of drainage mats for consolidation method, such as drainage mat thickness, permeability coefficient, etc, are highly related to engineering experience. Silty sand is not recommended for drainage mat by engineering design specifications. Based on the prototype measurement of a certain reclamation project in Shanghai, characteristics of silty sand drainage mats of sea dike on muck foundation are studied via nonlinear FEM; and the impact of key factors on consolidation, such as mat permeability coefficient, mat thickness, mat length and relative permeability of body, etc, is further studied. On that basis, it is put forward that using transmissibillity coefficient of drainage mat as control parameter for design. Thus, the relating design formula for drainage mat, covering those factors, is presented accordingly; and it provides technical support for the design of drainage mat by using silty sand instead of medium sand or coarse sand. It is found that using silty sand to construct drainage mat is feasible in some project.

Based on direct shear tests on intact and remolded Angola Quelo/Muceque sand, the effects of structural characteristics, water content and dry density on the shear strength have been explored. The test results indicate that the structural characteristics have a relatively complex impact on the shear strength of the Quelo sand; and there are some significant differences in the shear strength parameters between intact and remolded samples. The water-weakening characteristics of the Quelo sand are remarkable; and the cohesion and the internal friction angle of intact and remolded samples tend to be approximately logarithmic attenuation with increasing the water content. The Quelo sand is well-graded and will achieve high shear strength after compaction, which is suitable to be used as backfill material. With increasing the dry density, the cohesion increases linearly and the internal friction angle can be divided into stabilizing section and increasing section, showing the characteristics of sub-functions.

To compare the bearing capacity of a screw pile and a conventional straight pile, two indoor static load model tests were carried out in sand. And the effect of the pitch of a screw pile on its bearing capacity is also evaluated. After the indoor static load tests a series of soil tests are carried out to study the physico-mechanical properties of sand. The test results show that under the same conditions the bearing capacity of screw pile is 1-4 times that of conventional straight pile; and the average ultimate friction is 3-4 times that of conventional straight pile; when the pitch of screw pile decreases within a certain range, the ultimate bearing capacity, ultimate friction and the ability to control the settlement gradually increase.

Progressive failure feature of slope is difficult for numerical simulation of slope. Also practical slope failure process is rarely a whole and sudden slipping one, is often step by step one from local deformation to final and overall instability, which is a chain domino style failures triggered by small disturbance under critical condition. Here by particle flow code(PFC), a numerical slope with cohesion between particles being 36 kPa, friction coefficient between particles being 0.36, 0.1m particle size and 10m height is designed, initial models damage will not occur under gravity condition. Slope failure is done by cohesion strength between particles reduced to half of initial one. Slope shapes of each 20 000 steps, total steps being 200 000, are obtained by monitoring change of vertical particle groups at horizontal intervals of 1m, which directly reveals progressive failure of slope. Found that failure is always beginning from local part, movement of slope body material results in secondary damage in slope, which forms final arc sliding surface. These account for sliding isn’t a whole declining of slope body, the body isn’t a rigid one. Stress conditions along slip surface don’t reach limit state at the same time. Change of stress in slope body isn’t a monotonous one, but a process with rises and falls. All these conclusions contradict assumptions in current limit equilibrium methods such as rigidity of finite slice, simultaneously reaching limit sate on slip surface, making statically indeterminate problem solved by force transfer mode between slices given, overall analytical method not presenting localization and progressive feature of failure, which hints future of slope computing method lies in discrete element methods can present dynamic practical problem and material real failure characteristics.

There are different calculation methods for checking shearing or punching shear resistance of reinforced concrete expand foundation according to the codes of many countries, which have many differences about the demarcation of foundation shearing or punching shear model, computational formula and so on. So they also have effects on the calculation results. Aiming at the design requirements of the three codes, i. e. GB50007[1], ACI318[2], EN1992[3], the influencing factors of shear failure of reinforced concrete spread foundations are comparatively analyzed and the thickness of foundations is compared combined with four examples with different loadcases. The results show that the factors such as the shear strength values, checking conditions, the shapes of punching shear cones , the influence of ratio of longitudinal reinforcement and the position of control sections have certain differences according to three codes above; it is reflected that the three codes have different thoughts about the influencing factors of shear and the different understanding of shearing failure mechanism of foundation; also these differences make computational method of shear and the thickness of foundation plate different. Through analysis, the further research of the position of control sections, the ratio of longitudinal reinforcement of foundation mat and the effect of the distribution of contact pressure on shear bearing capacity is suggested, so as to further improve the calculating methods of punching shear.

There are a few doubtful points in active Technical code for building slope engineering. This code claims itself could apply to the rock foundation pit, but many terms aim at building slope but not foundation pit; so we suggest that don't extend applicable range into the foundation pit; service lives of temporary slope are 2 years in this code, it is suggested to improve to 5 years for better meeting the engineering construction requirements now; some terminologies are not accurate and should be redefined; We suggest that adjust applicable slope height of this code and slope safety level because the old term couldn't meet the engineering construction requirements now; canceling estimate formula for slump area since it is little meaning and defective; extending applicable range of slope ratio method since the old term is too strict; canceling the design method that verify table of slope ratio since it is outdated; don’t reduce anchor fixed length in anchor base test because this way will get higher limit bond strength and lead to dangerous engineering design; rewritting anchor acceptance test standard since the old term is not clear and difficult to apply, etc. These opinions refer to code revision.

Study of distribution of rock mechanics parameter of carbonate rock has an important sense to prevention and decrease drilling accidents. Twenty group outcrops samples of carbonate rock were collected in the Northeast Sichuan, which buried depth of top surface is 3 568-5 983 m. With the help of MTS815.03, RMT150C rock mechanics test system and RSM-SYS5 ultrasonic tester, SEM examination, uniaxial compression test, triaxial compression test, acoustic wave test under confining pressure were carried out. Test results show that (1) carbonate rock is predominantly composed of biological-clastic dolostone and muddy-limestone, the diameters range from 0.01 mm to 0.2 mm; the main pore types are dissolution pore, intraparticle pore and inter-crystalline dissolution pore, porosity ratio range from 2% to12%; (2) spatial distribution characteristics of uniaxial compressive strength is some regularity but triaxial compressive strength has no regularity, be characteristic of chaotic; (3) velocity of longitudinal wave increases with the increasing of confining pressure; the velocity of longitudinal wave changes remarkably under the low confining pressure; and change little under the high confining pressure; the growth rate for dolostone is larger than that of limestone, The relationship between confining pressure and velocity of longitudinal wave is obtained. The results can provide technical parameters for drilling well in deep carbonate formation.

The cliff body has been severely damaged by diverse wind erosion and secondary relaxed fissures of cliff bodies in the Jiaohe Ruins. It is important to study the influence of diverse wind erosion and secondary relaxed fissures on cliff bodies and damaged pattern under both of them. The finite element software ANSYS is used to simulate cliff body damage under diverse wind erosion and secondary relaxed fissures. In order to verify the result of finite element software simulation, the basal contact friction test is carried out to simulate the cliff body damage process. The result of finite element software simulation illuminates that the maximum displacement of the cliff body is 487.326 mm, the maximum plastic strain is at the root of the relaxed fissure, and the cliff body is fracturing and toppling. The result of the basal contact friction test shows that the open width of the fissure is 20 mm after 2.7 h, and then the soil body is falling. The fracturing-toppling progress is that the bottom of silty clay layer incised by secondary relaxed fissure is empty; the root of relaxed fissure is pulled apart; the incised soil body is inclined deformation; and then the root would appear tensile failure and the soil body would topple and fall. For the impacts of diverse wind erosion and secondary relaxed fissures on damage of cliff bodies, the reinforcement program of cliff bodies is brought forward.

The occurrence time of landslides has a significant characteristic with periods distribution, according to landslide statistics and research results nowadays, in addition to rainfall reason, moon gravitational tide was recognized as another apparent reason. The formulas of tidal stress at the surface of earth were derivated by modifying a simplified elastic earth model proceeding from the theory of Earth tide. The formulation of simplified Fellenius method was modified taking the effect of tidal stress into account; then the mechanism of landslide triggered by tidal stress was discussed. The Xintan landslide in Zigui county, Hubei province occurred in 1985 was taken as an example, based on the modified broken lines method, to discuss the correlation between tidal stress and time, and how the safety factor of stability change at the time. The results show that, the tidal stress and the safety factor of slope stability changes with time at daily period; and range of safety factor of this slope could up to 3.4%, according to the calculation. Another conclusion is that the landslide occurs when the value of tidal stress rise to the maximum. It is also shown that the earth tidal stress is another probable triggering factor on landslide which has been in the critical failure condition, besides the rainstorm and other factor.

Jet grouting soil-cement-pile strengthened pile (JPP pile) is a new kind of composite pile composed of high pressure jet grouting pile and prestressed core pile. JPP pile has different combination forms depending on soil conditions as well as the bearing capacity requirements. Based on the simplified calculation method presented, the main factors of JPP pile bearing mechanism, different combinations, different soil-cement thicknesses, different elastic moduli of soil-cement, and different stiffness coefficient ratios, are analyzed comparably. The axial force of core pile, soil-cement axial force, first interface resistance and second interface resistance, are discussed respectively. The research results show that: (1) The sub-combination JPP pile has better carrying effect and should be adopted in actual construction. (2) Increasing soil-cement thickness can effectively improve the bearing capacity of JPP pile, but should not be too thick, and should not be greater than the radius of the core pile. (3) Soil-cement elastic modulus has small effect on axial bearing properties of JPP, but should meet structural requirements. (4) The stiffness coefficients should not be too small and not less than 100, so as to achieve deformation coordination for soil-cement and core pile, and improve bearing capacity and reduce settlement of JPP pile.

The evidence weights model based on the weights of evidence method was applied to study the zonation of the landslide geohazards in Hangzhou. The main data sources consisted of geological maps, digital elevation model(DEM), land use data and 1905 specical cases of geohazards collected from 1930 to 2009 in Hangzhou city. The evidence factors involve heavy rain, types and structure of rock, slope, slope direction and high slope, river network and Path buffer, which were derived from maps using Arcgis spatial analysis and information extraction. The weights for each evidence map were calculated using the frequency of known landslides in the classes of causative parameters; then the probability of landslide for arbitrary grid was produced by summation of assigned weight values using Arc-WofE extended module, achieving the goal of spatial prediction for potential landslide points. The accuracy verified by the spilt-sample validation method was 88.3%. The obtained results were well coincident with the occurrence of the known landslides in the study area. It is shown that the weights of evidence method could be evaluated objectively and quantitatively for multivariate analysis, as a basis of the choice of factors for landslide geohazards zonation. So the methodology is very useful and accurate, and it is worth popularizing and applying to the risk zonation and evaluation of landslide geohazards.

Calculation of negative skin friction on piles in areas of soft soil and collapsible loess is one of the issues must be considered in pile foundation design and construction; while studies on the calculation of negative skin friction on pile groups are relatively little at present. Effective stress formula, negative skin friction on single pile is calculated. Based on limit equilibrium theory, the calculation method of the pile group effect coefficient under negative skin friction is obtained. With field test results, negative skin friction and drag-load on X-section cast-in-place pile groups are analyzed. The influence of location of piles in pile foundation on drag-load along pile shaft is discussed; and the change rule of the group effect coefficient varies with different influencing factors. The results of calculation and field measured results are in good agreement; the greater the surface load is, the greater the drag-load on pile groups is, and the pile group effect coefficient increases with pile spacing increase and it decreases with the increase of negative skin friction coefficient and the depth ratio of neutral point.

A simplified analytical approach is proposed to study the behavior of the piled raft foundation with rigid raft subjected coupled loads in layered soils. Based on solutions of Mindlin, the interactions between pile and pile, pile and soil, soil and soil were taken into account to determine the flexibility matrix of the pile group-soil system; then the load-settlement relationship of piled raft foundation subjected coupled loads was obtained. Comparison between the results from the finite elements and the calculated results was carried out, and the feasibility of the present method for analyzing piled raft foundation is proved. Then the method is used to study the stresses and distortion characteristics of the pile raft subjected coupled loads. The numerical results indicate that the piles’ axial force and the settlement of piled raft foundation subjected coupled loads are nonuniform.

The research on expressway embankment with sand-gravel-cobble mixture is in discussing. In order to research on the compaction effect of expressway embankment with sand-gravel-cobble mixture, the screening test, heavy compaction test and California bearing ratio (CBR) test in laboratory have been carried out; and through these tests the grain composition of sand-gravel-cobble mixture, the relation between maximum dry density and coarse particle content, the relation between best water content with coarse particle content and the relation between CBR value with coarse particle content or compaction times are obtained. The results show that the maximum dry density first increases and then decreases when the coarse particle content increases; and CBR value increases when the coarse particle content increases. Then compaction mechanism of sand-gravel-cobble mixture used in embankment filling is analyzed. Based on compaction test in field, the construction technology of embankment with sand-gravel- cobble mixture is obtained. The compaction effect is detected by using compaction degree, CBR, deflection, modulus of resilience and settlement discrepancy. In the end, the suitable detection methods of embankment with sand-gravel-cobble mixture are suggested by analyzing the reliability of every detection method; and the standard value of settlement discrepancy is obtained based on statistics theories, and determined using both settlement discrepancy and compaction times to guarantee compaction. Some useful conclusions are obtained.

Micro-piles have been widely used in excavations due to their convenience and simplicity in construction. Taking a certain rock foundation pit supported by combination of micro-steel-pipe piles and rock bolt support for example, supporting mechanism of the micro-steel-pipe piles is analyzed by numerical simulation. Analytical results have indicated that when thick strong weathering rock or weak rock layer exists, the micro-steel-pipe piles embedded in it can effectively decrease the horizontal displacements of the foundation pit and adjust the tension in the prestressed anchor cables; while the micro-piles can bear notable bending moment and axial compressive force. Micro-steel-pipe piles constructed in strong weathering rock layer should be considered for supporting structure design of the rock foundation pit, and capacity of the micro-piles under bending moment and compressive force should be verified. When the micro-steel-pipe piles were constructed in integrated and hard rock layers, such as intermediate or weak weathering rock layers, the micro-piles had hardly any effect on excavation of the foundation pit; so for this situation the micro-piles can be cancelled.

The analysis have been done for the load-transfer mechanism of T-shaped rigid pile by assuming pile-soil load-transfer function which is hyperbolic model; the differential equations of pile and soil under the pile and pile cap have been established to express the relations, between vertical displacement, lateral resistance of vertical stress, pile-side friction force and depth control. The corresponding analytical formulas have also been derived by using approximate solution method of differential equation. Using directly the settlement of pile top as the known condition, the calculation results can image basically the work mechanism character rules of single pile with cap according to the method of the paper. As the depth increased, the pile axial force becomes diminution, Lateral resistance of piles with depth increasing showing the first increase after decreasing . The pile-stress ratio is bound up with load. The calculation results by using of the method are close to the test results, and can provide the theoretical basis for engineering design.

A series of on-site point load tests for the Middle Proterozoic Wudangshan Group (Pt2wd) schist are carried out based on the probability theory and statistics, to determine the grouping interval of the point load strength (vertical rock) of the completely, strongly and moderately weathered (Pt2wd) schist. The point load tests at different levels along the schist direction are carried out; the correlation of point load strength between parallel to the rock and vertical rock is analyzed; and the anisotropy index Ia of the schist is determined; combined with the results of uniaxial compressive strength test indoor, an empirical correlation relationship of the point load strength IS and uniaxial compressive strength Rc of Wudang Group schist is given.

Aiming at special method of installation of rammed soil-cement piles, laying special strain sensor and then the pile shaft can be measured. Based on test data of pile shaft compressions, the computation method of shaft compression is studied; and the distribution of pile shaft compression, and its influence on shaft resistance are analyzed. The shaft compression and its influence on bearing properties in different lengths and different cement contents of rammed soil-cement pile are discussed. Research results show that (1) the pile shaft compression is mainly distributed in upper range of pile length about 8 pile diameters; and the varying gradient is larger; and pile shaft compression the displacement of pile tip; (2) the axial load transfer, distribution of shaft resistance occurred mainly within this range; (3) the shaft friction distribution is uneven; and it plays more fully in upper part of pile and less in lower part of pile; (4) under cement mixing ratio within the common project and the length-diameter ratio＞12, the change of length-diameter ratio and cement mixing ratio is not significant effect on load-bearing characteristics of pile.

Variably saturated flow theory is the fundamental theory of geotechnical engineering; and it has wide applications to seepage of earth rockfill dam, contaminant transport, seepage and phase transformation of frozen soil, and slope stability analysis. In numerical solution of Richards equation for variably saturated flow, inappropriate computation of some parameters, particularly for the hydraulic conductivity, may lead to convergence oscillation of nonlinear iterative methods such as Picard method or Newton method, and consequently result in slow convergence and inaccurate solution. To eliminate or reduce the influence of iterative convergence oscillation, the under-relaxation method is often employed. By using 1D problem and 2D heterogeneous earth dam, the limitations of available under-relaxation methods are demonstrated. Furthermore, a novel short-term mixed under-relaxation method is proposed with verified practicability and reliability.

In order to investigate the mechanism and the beneficial effect of geogrid-reinforced pile-supported foundation, four comparative model tests were carried out, including unreinforced and no-pile foundation, geogrid-reinforced foundation, pile-supported foundation without geogrid, geogrid-reinforced and pile-supported foundation. The mechanism of geogrid-reinforced pile-supported foundation was described by comparing the results of the tests. The measured and computed results were compared and discussed, and then three-dimensional coupled mechanical and hydraulic numerical simulations were conducted to investigate the beneficial effect of geogrid-reinforced pile-supported foundation. The results show that the vertical displacement of geogrid- reinforced and pile-supported foundation are smaller than that of other cases, while the bearing capacity is larger than that of others. The pile-soil stress ratio of geogrid-reinforced pile-supported foundation is less than that of pile-supported foundation without geogrid under the same loading. With the increase of the spacing between piles, the vertical displacement of geogrid-reinforced and pile-supported foundation increases, while the pile-soil stress ratio decrease. With the increase of geogrid stiffness, the vertical displacement of geogrid-reinforced and pile-supported foundation decrease, while the pile-soil stress ratio increase.

Considering the existing calculation methods’ shortcomings of water gushing in foundation pit. The strain dependent modi?ed Cam-clay (SDMCC) model adopted to model the soil behavior and confined water was taken into account in the finite difference model by FLAC3D. With the increase of the confined water head (Hw), the foundation pit heave was divided into three stages: slow uniform deformation, accelerating deformation and sharp uniform deformation. A new method for determining critical water head (Hwcr) of water gushing in foundation pit was presented based on numerical analysis; and the calculation result of the new method was compared with other methods.

The main mechanism of rockfill rheology can be attributed to the rockfill deterioration due to variation of water level, rainfall infiltration, weathering and other environmental factors. At the same time, the particles have high contact stress-broken and rearrange-stress release, adjustment and transfer, this process incessancy owning to the continuous particle degradation. In the framework of deformable discrete element method, the stochastic granular discontinuous deformation method(SGDD) considering particle breakage is employed with the introduction of the strength degradation model to reflect the particle degradation. The method is employed to rockfill triaxial creep numerical experiments; the simulation results are consistent with indoor test ones. It is shown that the SGDD method considering rockfill creep caught the main mechanism, is suitable for simulation of rockfill creep deformation. Numerical experimental results show that with the external environment the degradation degree, degradation rate, parent rocks intensity has great influence on the macroscopic rheological deformation.

In order to research seismic performance of prestressed pipe pile under earthquake, and increase the level of ductility design of the prestressed pipe pile, the vibration characteristics of the pile foundation are grasped through the prestressed pipe pile shaking table test. This paper establishes the prestressed pipe pile numerical model of vibration analysis and simulates the whole process of the vibration test. On this basis, by changing the pile number and entering different seismic wave acceleration peaks, the reactions under the earthquake and seismic performance of the various pile foundation forms are explored. The results show that for four piles foundation, in the pile location of the three times diameter appears pile body reverse displacement; in the 2.5 times diameter of the pile appears pile body negative bending moment; within the region of four times to nine times appears cracking bending moment; in the position of the five times pile diameter appears the maximum bending moment; and under the location of fifteen times the pile diameter the pile body bending momeat decreases rapidly. The results provide a reliable basis for seismic design, manufacturing, construction of the prestressed pipe piles.

The rockburst mechanism is very complicate, which is influenced by many factors. By the attribute reduction and the condition properties importance evaluating of rough set theory, it could determine the main factors of rockburst under specific geological conditions, and remove redundant data. Using genetic algorithm (GA) to optimize parameters of radial basis function (RBF) neural network, low-dimensional model inputs were transformed to high-dimensional space through hidden layer; the nonlinear relationship between impact factors and rockburst was fitted. Finally, a rockburst prediction model of GA-RBF neural network based on genetics of rough set theory was established; it had not yet seen the application to rockburst prediction. Based on several theoretical criteria according to the project, the established model was applied to rockburst prediction of practical engineering. It is approved that the evaluation results are consistent with the actual situation well; and it could play a very good guide for latter construction.

According to rock character of a certain soft rock tunnel of Chongqing to Changsha highway, similar model materials and supporting test equipments are developed to reproduce the whole process of progressive failure of surrounding rock under different supporting conditions. Through solving a series of technological matters in execution and installation and testing, by using the strain measuring technology, the strain of key parts of the surrounding rock under different supporting conditions are measured; according to this, the variability of the stress of surrounding rock are studied. By model materials laboratory determining the related parameters of rock mass, the numerical simulation are worked with the same boundary condition as the model test, according to this, the stress field and the deformation of the surrounding rock are studied; the variation of the axial force of the anchor bolt is studied. We compare the variation of stress of the surrounding rock and the variation of the axial force of the anchor bolt under different supporting conditions of the model test with the numerical simulation and draw the conclusion that the two processes coincide with each other.

Evapotranspiration covers offer a number of potential advantages over conventional covers. But they are mainly used in arid and semiarid areas. Analyses of water movement and performance of evapotranspiration covers of landfills in humid regions become interesting. Influences of design parameters such as cover thicknesses, soil types, LAI and climate factors on performance of evapotranspiration covers were investigated by using a two-dimensional saturated-unsaturated flow model. Water movement, performance and applicability of evapotranspiration covers were evaluated. The results show that final percolation decreases with an increasing cover thickness and an increasing LAI. But their influence becomes inapparent when they are relatively large. Cover soils with a large storage capability and a moderate hydraulic conductivity are most effective to minimize percolation. Seasonal distribution of precipitation has a great influence on performance of evapotranspiration covers. The performance of evapotranspiration covers can meet design requirements when most of rainfalls companying with high temperature in a humid region. Capillary covers are more efficient than monolithic covers to minimize percolation under unsaturated condition because of a capillary break caused by the differences in the unsaturated hydraulic conductivity between finer-grained layer and coarser-grained layer. However, the performance of capillary covers will dramatically reduce under bad climatic combination when capillary break fails.

The wind power generation, as one of the fastest-growing new energy, gets more and more attentions. The optimizational design of wind turbine foundations under coupled loads becomes an important issue. In this paper, the accuracy and the ability of a finite element method to simulate the load coupled effect are verified through comparisons with published results. Then a piled beam-raft foundation of Guohua Tongliao wind farms is analyzed using finite element method. The research mainly focuses on the stress and deformation characteristics of the pipe piles, rib beams and the ring beam of the foundation under coupled loads. The internal forces of them are compared with those from design. At the same time, this paper analyzes the pile-soil-sharing ratio of the wind turbine foundation and investigates the bearing role of soil under coupled load. The results provide a reference for the actual engineering design.

The analysis of energy conversion during the set-out process of seismic landslide is very important for the late landslide kinetic theoretical studies. Because the analysis impacted by many complex influencing factors is fuzzy, there is no accurate quantitative calculation formula for energy conversion rate. Fortunately, the fuzzy synthetic evaluation method has obvious advantage in the analysis of fuzzy problems, which can take various complex factors into account to make an overall assessment. Therefore, the method can be adopted to determine the grade of energy conversion rate. After analyzing the effect of every factor on the energy conversion rate in detail, seven factors, such as seismic acceleration, structure of rock mass, characteristics of controlling structural planes, integrity of rock mass, stratum lithology, groundwater, and angle between the unfavourable interfaces and free surface, are selected as the major factors. Using fuzzy analytic hierarchy process, the important degree of the above factors characterized by the influencing weight is obtained. And the logic classification method is adopted to determine the membership function. On this basis, the fuzzy synthetic evaluation is then used to draw the grade of energy conversion rate with its value determined semi-quantitatively. The proposed method is applied to study the Donghekou earthquake-induced landslide; and the obtained results meet the objective reality, so as to indicate that the method is scientific and feasible. Consequently, it can be used for reference in other similar theoretical researches.

The lateral bearing capacity of the pile foundation of offshore wind turbine degrades due to the long-period cyclic lateral load. For the lateral loaded pile in undrained soft caly, a degradation model based on accumulated plastic strain is adopted to model the cyclic degradation of the undrained soil strength. Then a series of two-dimensional finite element simulations are carried out; and a simplified p-y curve method is presented to analyze the degradation of the lateral bearing capacity of a cyclically laterally loaded single pile. For the case of small cycle numbers, the results of the finite element simulations are consistant well with that of the simplified method. Based on this cognition, an attenuation law of the lateral bearing capacity of a pile subjected to long-period a large amount cyclic lateral load is obtained using the two-dimensional simplified method. It is found that, for the ratio of the cyclic lateral load to the initial lateral pile bearing capacity smaller than the reverse of soil sensitivity, although the lateral bearing capacity of cyclic lateral loaded pile degrades, the pile still remains in stable state without failure.

通过理论计算和有限元模拟分析，对采用植筋锚固技术进行基桩静载试验进行可行性研究。结果表明，按照理论计算进行植筋布置，可控制原有底板变形并满足荷载反力要求。试验过程中，试桩边缘的底板抬升值最大，距离试桩边缘越远，抬升量越小；试验对底板的变形影响范围为距中心点7 m的区域。通过预先调整钢筋的松紧程度，可使植筋受力均匀，避免植筋断裂。应用植筋锚固技术进行静载试验是可行的，该方法具有试验方法简便、安全和经济的优点，作为一种新的反力装置，可作为特殊条件下基桩静载试验的方法。

The influence of sectional shape of steel sheet piles on the active earth pressure against a steel sheet pile wall was investigated by finite element simulation. First the numerical model was validated through a numerical simulation of a small scale model test compared with the measured data. The verified model was then used to simulate the response of a steel sheet pile wall subjected to different displacement modes at the active state. A comparative analysis was conducted between the case of steel sheet pile wall and a planar wall to find out the sectional shape effect on the distribution and magnitude of earth pressure against the wall, and the possible mechanism and influencing factors. The results indicate that the sectional shape of the steel sheet pile wall affects the distribution of the transversal earth pressure against the wall. The active earth pressure acting on the extruding portion of the sheet pile wall is larger than that on the denting portion when the wall translates beyond the wall or rotates around the top, while such distinction is trivial when the wall rotates around the base. The shape-induced difference of the transversal earth pressure against the sheet pile wall roots in the soil arching; and it heavily replies on the sectional aspect ratio, and less on the wall-soil frictional properties.