The rapid development of airport construction in western mountain area of China leads to increasing number of high-fill foundations, of which the main features are the large fill volume, high height and the existence of soft quondam foundation under fill. These features also increase the difficulty of post-construction settlement prediction. According to composition characters of high-fill foundations of mountain airport, the post-construction settlement can be divided into the creep deformation from upper coarse-grained filler and the consolidation deformation from lower soft quondam foundation. Firstly, a simplified calculation method to calculate consolidation deformation of soft quondam foundation is proposed on the base of analyzing and comparing existing calculation methods, which can consider construction process, and the calculation result by this method agrees relatively well with the field measurement data. Secondly, by analyzing laboratory test data, it is considered that hyperbolic model is also able to characterize the creep deformation of coarse-grained materials; base on this, another simplified calculation method to calculate creep deformation of upper coarse-grained filler is proposed.

Inner force of soil nail is a key parameter of soil nailing design. Virtual excavation stress is used to simulate the excavation status of soil nailing. On the basis of the hypothesis that there exists no load on the face of soil nail, a calculation model is presented that the distribution of shear forces between soil and nail is double-triangle. The calculation formulas of axial force and shear force of soil nail are derived. The lateral displacement of soil at potential break surface and the end of nail by the virtual excavation of soil shear stress is obtained based on Mindlin strain solution. The zero relative displacement and the equivalent axial force of soil nail at both sides of potential break surface can provide two equations for two unknown coefficients of the calculation model. The measured data from French research test on soil nailing are used to illustrate the validity of the proposed calculation model

The strength of geomaterials is strongly influenced by their fabric anisotropy, which can not be characterized by the isotropic failure criterion reasonably. A general anisotropic failure criterion is proposed. To characterize relative orientation between the loading direction and material fabric, an anisotropic variable expressed by the joint invariants of the stress tensor and fabric tensor is introduced. The failure criterion is developed based on the failure characteristics of geomaterials in both the meridian plane and deviatoric plane, which leads to a general three-dimensional description of strength anisotropy. Compared with the isotropic failure criterion, only two new parameters are introduced in the anisotropic one. All the model parameters can be readily calibrated based on the conventional laboratory tests. Comparison between the model predictions with the test results on sand, clay, natural clay as well as rock demonstrates that the new criterion can characterize the strength anisotropy of geomaterials in a reasonable manner.

Liquefaction real-time monitoring and warming techniques are novel ways to mitigate liquefaction hazard. The key point is to establish a reverse liquefaction detection method based on seismic records. In this paper, the reliability analysis of the existing liquefaction detection methods, i.e. Suzuki method, Miyajima method, KY method and SY methods, are presented using same sample data which include as many seismic records on soft sites as possible. Assessing results and improving aspects of the methods are proposed. The analysis indicates: the success detection rates on the collected samples by SY method, Suzuki method, KY method and Miyajima method are 98%, 85%, 77% and 52%, respectively; site category influence on success detecting rates are principally notable; with site softening the success rates by Suzuki method, KY method and Miyajima method decrease and are all under 55% for detecting D sites; a parameter correlated with absolute periods are selected as a detecting index in Suzuki method, Miyajima method and KY method, hence the values on soft sites and liquefied sites cross, resulted in misjudge; selecting a relative change of ground motion parameters as a detecting index in SY method, some details in the method need deep discussing and improving even though its success rates for detecting D sites reach 92%.

In-service hydrocarbons must be transported at high temperature and pressure to ease the flow and prevent solidification of the wax fraction. The buckling of submarine pipelines occurs due to the introduction of axial compressive forces caused by the constrained expansions set up by thermal and internal pressure actions. Vertical buckling is particularly of interest with respect to buried submarine pipelines. To lay pipeline in trench with a certain depth is an effective measure to avoid vertical thermal upheaval buckling. Therefore, it is very important that study of the maximum resistance which soil can provide as well as the soil resistance changing procedure with the pipeline buckling amplitude. Fine sand was chosen as the soil medium in view of Bohai Gulf conditions. A model test was carried out to establish the relationship between soil resistance and pipeline displacement in laboratory. The pipeline segments with different diameters and different covered depths were used in the test. The soil resistance and the pipe segments vertical displacement were both recorded in great details. Then the numerical analyzing methodology was applied to simulate the model test procedure. Test data and analyzing results show that when the pipeline doing vertical uplift movement, process of soil resistance exertion can be affected by the buried rate of pipeline, when the buried rate is small, soil resistance decreases until stable after reaching peak; while when buried rate is large, the soil resistance doesn’t significantly reduced after its peak. In the practice, the maximum soil resistance can be gained when the pipeline upward displacement reaches to approximate 0.1D.

Based on the in-site plate loading curve, the undisturbed soil tangent modulus of soil can be computed based on its stress level; then the foundation settlement can be computed by using undisturbed soil tangent modulus in the layerwise summation method. This method takes the nonlinearity and original state of soil into consideration, and can be used to different kinds of loading curves and in the large scale. it can also overcome the shortcomings of the original tangent modulus method which supposes the loading curve to be a hyperbola. The validity of the method is also proved by the in-site loading test and engineering practic

Silt soils have been encountered in most of the estuary of Qiantangjiang. Based on the study of dilatant characteristic of Qiantangjiang alluvial saturated silts, general triaxial drainage tests of five groups of silts of different saturation degrees have been conducted to study the dilatancy of the unsaturated silts. The test results of the slightly dense silt show that one of the most significant properties of Qiantangjiang unsaturated silts is the dilatant characteristic; and that the amount of potential dilatancy is mainly governed by the saturation degree, and confining pressure; and that the influence of the saturation degree on stress-strain curves of silts is slight; and that the shapes of stress-strain curves are slightly softened. The ratio of residual strength to peak strength (qr / qmax )is mostly between 0.9 and 1.0. The research also makes it clear that the amount of dilatancy rises with the ascent of the saturation degree, and falls with the rise of confining pressure. There is a clear correlation between the volumetic strain and the intermediate principal stress at the critical state. Under the confining pressured of 800 kPa, the volumetic strain of slightly dense silts is in the range confined by the two almost parallel lines = 12.020 2 – 4.939 2lnp and = 15.771 7 – 5.775 1lnp. The most amount of dilatancy is less than 5%

The relationship between reinforcement and soil in reinforced soil is similar to that of steel and concrete in reinforced concrete; and they share similar computation methodologies. Equivalent additional stress method can be the same with integral method or combined method depending on the equivalent method of additional nodal force calculated. Classical integral method and combined method for reinforced concrete constitute the theoretical basis of equivalent additional stress method. In turn, from the view of equivalent additional stress, the essences of the three methods, separate method, integral method and combined method are actually the same despite different stiffness matrices. The main differences lie in the distribution mode of equivalent additional nodal force on the boundaries. (In general, integral method and separate method can both be considered as combined method with special modes.) The idea of equivalent additional stress reveals the inherent principle of the three methods and can be used to interpret the reason of sameness and difference of numerical results based on the three methods in reinforced concrete. Referring to the studies of interface element, an appropriate strain ratio coefficient introduced in the integral method and combined method can make it possible to simulate the slippage between reinforcement and soil.

Soil-bentonite vertical cutoff walls are effective and economical as engineering barriers for geoenvironmental containment. The compressibility and permeability of zeolite-amended soil-bentonite vertical cutoff walls for the purpose of enhancing the chemical compatibility have not been well addressed. These two engineering properties of soil-bentonite backfills before and after amended with zeolite are assessed via a series of oedometer tests. The results are discussed using the generalized state parameter (i.e. e/eL) and the void index Iv, which are used to analyze the intrinsic properties of remolded clays.

he GDS single vibration triaxial test is carried out on the marine deposit soft clay in line 1 of Ningbo urban rail transit, and the dynamic strength and pore pressure property of the soft clay in condition of different dynamic stress amplitudes and frequencies are analyzed. It is shown that the shear strength in isotropic consolidation is greater than that of K0 consolidation in case of similar dynamic stress. The shear strength increases with increasing frequency in the same dynamic amplitude. Furthermore, the greater dynamic stress is used in the test, the higher shear strength of samples is obtained; and a hardening phenomenon occurs. With increasing of vibration times, pore pressure increases, except that there occurs a stable tendency in layer ③ when the stress amplitude is 5kPa. At last, the data of the dynamic triaxial test is fitted; and the parameters are used to model the accumulative pore pressure.

Optimization of group piles below a rigid raft is analyzed; and load carried by individual pile is adjusted by the length of pile, respectively. To analyze elastoplastic behaviour of piles, a “cut-off” method is adopted to limit pile capacity in the integral equation considering linear behaviour of piles; and then the optimization results are easily obtained. The analysis shows that the corner piles reached to their bearing capacity at first; and then the side piles come at their bearing capacity gradually with redistribution of extra loads of the corner piles. With the increase of acting loads, the inner piles come into ultimate state finally. In that case, the whole piled raft system reach to failure state at the same time. A “cut-off” method can be used to improve the foundation design based on the optimization of variable rigidity, which is more consistent with the actual situation.

A large-size reinforced soil pull-out test was carried out and was simulated by particle flow code(PFC) to investigate the microscopic properties of geogrid-soil interface. The results show that the behavior of trigonometric group particles developed based on “clump” inherent in PFC is close to that of practical sand particles. The upper and lower geogrid-soil interfaces are not symmetrical such that the disturbed area of lower interface is higher than that of upper interface. Under the condition of low compactness of sand as well as low normal stress, the thickness of geogrid-soil interface decreases with increase of normal stress, exhibiting negative linear relationship.

Free face geometry shape plays an important role in determining failure and evaluating slope stability. Kinematic analysis is a very effective method in solving these issues stated above. Most kinematic analyses for rock mass slope stability mainly focus on the research of failure mode and maximum safe slope angle for single free face slopes. However, there are many slopes with double free face along strike of cut slope in engineering applications. In this paper, research on rock slope stability is extended to slopes with double free face. The corresponding sliding modes are divided into four types: (a) plane sliding along a discontinuity; (b) wedge sliding along a single discontinuity plane; (c) wedge sliding along the intersection line of two discontinuities and (d) toppling failure. On the stereographic projection, sliding zone for plane and wedge sliding can be marked as the area formed by the true dip direction lines of the two faces that form the double free face and the friction circle where the dip vector or the line of intersection vector should lie. The toppling zone can be marked as the area formed by the true dip direction lines of the two faces that form the double free face, friction circle and the periphery of the stereographic plot where the normal vector to the discontinuity should lie. The procedure to obtain the maximum safe slope angle for a double free face rock mass slope and the design principle to estimate the cut slope angle are suggested. Based on the method presented above, Shengjipo double free face rock mass slope, which is located in Zigui county, Hubei Province, is used as a case study to illustrate determination of failure modes and maximum safe slope angles.

The cement-soil mixing anchor, which can provide a great bearing capacity, is introduced. The effect of the cement-soil mixing anchor is superior to that of the soil nail in the same condition. However, the performance of controlling deformation of the anchor is inferior to that of the supporting brace. Therefore, the fracture morphology and the existing problem in this anchor is analyzed and presented based on the previous experiment and engineering application. Furthermore, the improved experimental schemes of increasing blades and the second grouting are presented to improve uplift resistance of the cement-soil mixing anchor. The setting of the blades is designed and the test is executed firstly; and then the distribution of axial forces along the anchor is tested. The results show that the effect of an anchor with a length of 12 m can play a role of an general cement-soil mixing anchor with a length of 15 m when the blades are added. The blades can help to improve the uplift resistance and decrease the displacement. In addition, the performance of the second grouting is not remarkable when the grouting pressure is low.

The environmental and geotechnical problems induced by spilled oil from China-Russia crude oil pipeline (CRCOP) need to be urgently studied and resolved after it was operated. A leaking experiment was conducted in laboratory to simulate and study the migrating process of oil contaminants. The results show that a dynamic equilibrium exists among volumes of oil, water and air in soil when oil contaminants are migrating through soil samples. Three of them jointly occupy the whole pore volume in soil. Oil contaminants exhibit three processes when they are migrating. Firstly, some contaminants are absorbed on soil particle surface. Some continue to migrate downward under the leaching of water. Finally, some are accumulated above the frozen layer. The different components of oil have the different migrating rates when they are migrating. Both carbon number and structure of hydrocarbons have significant impact on their migrating rates. The frozen layer in the lower part of soil sample, which has a low permeability, stop the migration of oil contaminants. The experimental results can provide solid basis on research of water-heat-mass transfer model of the multiphase flow in soils and impacts of oil on geotechnical properties of soil.

At present, the surface settlements of deep foundation pit excavation in soft soil can be estimated by regarding the surface settlement curves as normal distribution and skew distribution respectively. The two methods mentioned above are suitable but complicated due to computing the envelope areas of the surface settlement curves. The uncertainties of the results increase at the same time. Thus, improvement has been made for the two methods based on empirical relations to simplify the computation process. The surface settlements of four engineering cases have been computed using the improved methods; and further comparison between the two methods has been performed on based computing results. The results show that the improved methods for computing surface settlements are more simple and practical; and it is better to compute the surface settlements by regarding the surface curve as skew distribution.

With the soft clay samples of the 4th soil layer in Shanghai prepared by isotropic compression and K0 compression respectively, some mercury intrusion porosimetry (MIP) tests were carried out to investigate the microstructural characteristics of the volumetric deformation of clay under different compression stresses. By analyzing and comparing the pore size distribution curves (PSDC) obtained from MIP tests, some conclusions are drawn as follows. The pores in tested clay can be divided into macropore, mesopore, fine pore and micropore; where the fine pores account most on the volumetric deformation of clay; under the isotropic compression state, the soil particles move and get closer to each other with the development of compression, which make the main peak according to fine pores moves towards left (become smaller) with the pore shape unchanged in PSDC. While under the K0 compression state, the soil particles rotate and the pores become flat, which presents that the peak value of fine pores in PSDC drops down evidently.

During the drying process of a soil under constant total stresses, the increase of soil suction will induce the drainage of pore-water and the shrinkage of soil pore-structure. For a soil at a particular state, the microstructure determines its void ratio; and the soil suction determines the water content. During the drying process, if the pores are assumed not to shrink until the pore-water drains, then soil suction provides a bridge between the soil microstructure and soil draining behavior represented by the soil-water characteristic curve and the soil shrinkage curve: (1) the envelope of the cumulative pore volume curves is the soil-water characteristic curve; (2) the shrinkage curve is found to locate in a narrow range which can be determined using the cumulative pore volume curve.

The equivalent material model experiment is one of the important methods to study the geotechnical engineering. Based on the similarity theory, the creep similar model of rock salt is derived by dimensional analysis method and the similarity criteria of the corresponding parameters are obtained. The aggregate of equivalent material includes the salt particles with different diameters and iron power, the adhesive of equivalent material includes epoxy and ethylene. The blending ratio settling for the creep similar model of Jintan rock salt is got by a great deal of material proportioning tests, which is the solid basis for studying the distortion and breach of the salt caverns for storing oil or gas by equivalent material model test

he pore water pressure of saturated soft clay under cyclic loading is researched by GDS cyclic triaxial system. The effects of cyclic stress ratio，initial shear stress and vibration frequency on pore water pressure are analyzed. It is observed that the pore water pressure increases with the increase of cyclic stress ratio. There is critical cyclic stress ratio of soft clay under cyclic loading. The value of critical cyclic stress ratio can also be obtained by pore water pressure curves. At the beginning of cyclic loading, the pore water pressure rate is larger and then it decreases with the progressive of time. With the increase of cyclic stress ratio, the pore water pressure rate increases. The vibration frequency influences the relationship between pore water pressure ratio and cyclic number significantly; and the pore water pressure ratio decreases with the increase of frequency. However, the effect of vibration frequency on pore water pressure ratio-time and pore water pressure rate-time curves is indistinct at the frequency larger than 1Hz. With the increase of initial shear stress, both the pore water pressure ratio and pore water pressure rate increases. It shows linear relationship between pore water pressure rate and time at log-scale. Based on the test results, the empirical equation between pore water pressure rate and time is obtained. The pore water pressure model of soft clay under unidirectional cyclic compressive loading is obtained by integration.

Principal stress rotation is a kind of typcial stress path supplied to the ground,when it is subjected to wave or vehicle loads.In order to study the strength characteristics of silt under different combinations of principal stress orientation, a series of hollow cylinder sample tests were performed with saturated silt of Dr = 70% from the sea entrance of the Yangtze river. The tests include cyclic principal stress rotation (CPSR), cyclic triaxial (CT) and cyclic torsional shear (CS) tests. It is found that isotropic consolidated samples under the above tests would collapse at minor strain and liquefaction, which is featured by the excess pore water pressure reached initial effective confining pressure. And the effective stress states at collapse points could be normalized by the parallel quasi-instable lines in the p’-q space. As to the liquefied and collapse cycles, CS had the maxium and CPSR had the minimum under the same peak values of shear stress. Furthermore the collapse energy is put forward to evaluate the dynamic strength under different paths. It is shown that the energy is related to the kinds of stress paths but not shear stress level. And the collapse energy decreased in CS, CT and CPSR in turns, which matched the characteristics of increased effective confining pressure at the collapse points under these three paths. The adoption of collapse energy overcame the interference of nonunified shear stress level on the failure criteria under complicated stress path, in which the shear stress might be constant or change cyclically.

Pull-out strength of a soil nail is an important parameter in the design of a soil nailing system. The pull-out strength is determined by the normal stress acting on the soil nail surface during pull-out. The variation of normal stress in soil surrounding a drill-and-grout soil nail during drilling, grouting and pull-out is studied through both laboratory pull-out tests and numerical simulation. It is found that for a drill-and-grout soil nail, most of the normal stress in the soil surrounding the hole is released after drilling. For a soil nail grouted under low pressure, the normal stress does not substantially recover after the nail is installed. During pull-out, the normal stress acting on the nail increases with the increase in pull-out distance because of the constrained dilatancy of the soil surrounding the nail, which eventually increases the pull-out resistance. It is indicated that the dilatancy of the soil is very important to a drill-and-grout soil nail. For soils with low dilatancy, further measures, such as high pressure grouting should be employed to compensate the released stress during drilling.

Beam-spring model method is a primary method for designing of retaining structures in actual excavation projects; it is based on foundation reaction coefficient method for calculating vertical elastic piles acted by horizontal loads. Unfortunately, the current method cannot consider the unloading effect on the soil lateral resistance coefficient and the soil deformation in the pit, so as to lead to underestimate the horizontal deformation of the retaining wall. The distribution of unloading stresses is deduced using the Mindlin solution. On the basis of previous experimental studies, the soil resistance coefficients considering the effect of excavation unloading under different ratios of unloading are derived. The development of deformation of retaining structures is divided into two stages: the first is the instantaneous unloading deformation of the soil in the pit; and the second is the deformation of retaining wall induced by the lateral earth pressure differences on the wall. Then a modified beam-spring model method is presented considering unloading stress paths and unloading deformations. Finally, the method is applied to two typical 3D numerical excavation cases. It is shown that the horizontal displacement of the wall calculated by the modified method is greater while the difference between the internal forces is quite small; the greater the excavation plane size is, the more obvious the differences between the deformation results are. The modified method can better reflect the effect of the size of the base plane on the deformation of the retaining structure.

Gridding concrete retaining wall(GCRW) is a new-type supporting structure usually used in excavation of foundation pit in soft soil region; and interaction between GCRW and soft soil is the key issue to be studied profoundly. Centrifugal model and test plan were made firstly by means of background engineering; then the interaction between GCRW model and soft soil was successfully simulated through centrifugal model test of step by step excavation; finally, we made a comparion between measured results of earth pressures and ones based on Rankine theory. The results show that nearly all of the earth pressures take on linear distribution characteristic increasing along depth; GCRW produces deformation and displacement because of earth pressue on the inside of front wall caused by excavation. GCRW and soft soil in the gridding as a whole keep balance under the action of earth pressues, of which the stressed characteristics are similar to those of gravity supporting structures. While this structure is in its most unfavorable conditions, the earth pressures in active region are between earth pressure at rest and active pressure; but those in passive region are bigger than passive earth pressures. One of the reasons that front wall doesn’t overturn is the pulling force from partition wall prevent the front wall from overturning

Using equivalent material simulating experimental method, with the help of digital speckle correlation technique, the rock burst tendency of deep tunnel surrounding rock is studied. The regularities of rock burst and surrounding rock failure considering the strength of materials, excavation speed and support pattern are analyzed. The internal relations between rock burst and surrounding rock deformation and failure in deep tunnel are sought. The experiment results contrasted with the actual rock types of the granite, diorite, etc. which has higher strength of rockburst, the surrounding rock failure characteristics are similar. The higher surrounding rock strength is, the greater probability of rock burst is; in the high stress state and intact rocks the excavation speed has a greater impact on the rock burst; bolt-mesh support has some control function to the tunnel wall rock deformation; but also to some extent avoided rockburst. Supporting test result is in conformity with the field situation; with the higher support strength, the tunnel resistance increased, the overall distortion reduced, the surrounding rock stability improved. The experiment results will provide technical guidance and theoretical basis for the rational design and safe excavation of deep tunnels and have great significance, for innovating deep tunnel excavation and support technology

Solutions for settlement and consolidation calculation of soft ground with vacuum preloading are studied by considering the loss of vacuum. Firstly, an axisymmetric deformation model is developed under equal strain condition according to the vacuum pressure condition of sand drain with vacuum preloading. Formulae of deformation and volumetric strain are derived from spatial axisymmetric displacement control functions by using the displacement method. Then combining the obtained volumetric strain functions and the existing Hansbo’s sand drain foundation consolidation theory, and modifying some boundary conditions with vacuum preloading, analytical solutions for consolidation of soft ground under vacuum preloading are conducted when vertical water flow in soil is neglected. Finally, a comparison between the present solution and some previous solutions is made, and compared those theoretical solutions to test data in situ too. The results show that the volumetric strain has great effects on pore pressure and consolidation calculations; it would lead to large errors in consolidation calculation of vacuum preloading while quoting the volume strain formula of surcharge preloading directly. And using Hansbo's approximate method to calculate degree of consolidation can meet the requirements of precision; the calculation results are in good agreement with experimental results

By means of the freezing-thawing tests of different times, four types of rocks (granulite, amphibole granulite, bedding granulite and biotite-amphibole-plagioclase gneiss) sampling from the slope of Mengku Iron Mine were studied from the aspects of physico-mechanical characteristics that contains appearance, mass loss rate, strength loss rate, freezing-thawing factor and freeze-thaw weathering factor. The research results show that the degradation of granulite and amphibole granulite are unapparent while bedding granulite and biotite-amphibole-plagioclase gneiss are obvious. Taking blasting vibration of mining into account, slopes of the latter two rocks were easier to be damaged under the freezing-thawing effect; they should be focused on during design and construction.

In order to put the resistivity method into damage study, firstly soaking cemented soil sample in pure water, sewage and industrial wastewater for ninety days, the variation of its electric current are measured in the unconfined compression tests. Combining pictures, the relationships between the current-strain curves and stress-strain curves are compared. Being a basic parameter of the damage degree, the concept of “effective current” has been put forward; and based on it, the damage model of cemented soil is obtained through the statistical method. Finally, the damage model of cemented soil has been normalized. The analysis shows that the variation of current is easy to measure; and the current are varied regularly with the increase of strain. The current-strain curves and stress-strain curves can be divided into four stages which well describe the whole damage process of cemented soil. This model can be unified into a quartic polynomial equation in the whole strain range; and the equation form is irrelevant with cement type and pollution type. The results fully illustrate that it is completely feasible through the current changes to reflect the structural damage process of cemented soil.

Mechanical behavior of municipal solid waste (MSW) is important to geoenvironmental engineering; and it is necessary to understand it properly. Laboratory direct shear tests are conducted on MSW with 3 short fill ages, namely 1 d, 4 d and 7 d. Three different densities are taken into accounted in each fill age. Experimental data show that MSW’s shear failure still satisfies the Mohr-Coulomb criterion. As to bigger density, shear strength of MSW increases within 1-7 d fill age. When density becomes smaller, its shear strength increases within 1-4 d fill age but decreases within 4-7 d fill age. With fill-age developing, friction angle of MSW increase monotonously, but cohesion force of it first increases and then decreases. On the other hand, shortcomings of traditional shear stress-displacement model are analyzed; and one composite tangent- exponential model is proposed. The proposed model has good mathematical behaviors and more applicability than traditional models. Experimental data show that it can well describe MSW’s stress-displacement curve with correlation coefficient bigger than 0.99. This research results are helpful for design and numerical simulation of corresponding MSW landfill

Ideal point method is a method commonly used in multiobjective decision analysis. That basic idea is to target the problem by constructing a multiobjective ideal solution and negative ideal solution, and take close to the ideal solution or away from the negative ideal solution as basis to evaluate the objects. Based on the ideal point method, a model of tunnel surrounding rock classification is established. It has great influence on the final evaluation results for the reasonable weight values of the evaluation indices. The rough set theory is adopted to determine the weights, and the problem of weights is converted into the attributes significance estimating in rough set. The method is fully derived by engineering samples, and no experience is necessary, with a strong operational. Finally, the model of tunnel surrounding rock classification is established based on rough set and ideal point method, and is applied to the practical engineering. The results show that this method is reliable and provides a new idea to surrounding rock classification

This paper uses state vector method to solve the three-dimensional consolidation problems of a poroelastic layered rock by taking into account the compressibility of pore fluid. Starting from the governing equations of a saturated poroelastic rock with compressible constituents in the Cartesian coordinate system, the state space equations of the three-dimensional Biot’s consolidation problems are obtained by introducing the Laplace-Fourier transform. The transfer matrix of displacements, stresses, excess pore water pressure and flux between the ground surface and an arbitrary depth z is obtained by using the Cayley-Hamilton theorem. Then the transfer matrix method is utilized to derive the solutions for three-dimensional consolidation of a layered rock in the transformed domain by combining the continuity conditions between the adjacent layers and the boundary conditions. The actual solutions in the physical domain are acquired by inverting the Laplace-Fourier transform. Numerical analysis is carried out for a layered rock, which illustrates the influences of the compressibility of pore fluid on the consolidation behavior of the rock.

Under the circumstance of single-dehydration process and dry-wet cycle process, the soil-water characteristic curves (SWCCs) of Chongqing compacted clay soil samples with different compaction degrees and different gradations were respectively obtained by means of temple apparatus and pressure plate apparatus. The testing results show that: (1) After compaction degree exceeding 90%, the linear sections of SWCCs of the soil samples with different compaction degrees close each other, which indicates that the SWCCs gradually tend to stability within the common matrix suction changing scope of this compacted clay soil. (2) With the increment of compaction degree, the hysteresis loops of dry-wet cycle process gradually move upward, and the SWCCs change from steep shape to mitigative shape; this indicates that the moisture in the soil samples is more difficult to be intaken or drained out, which is beneficial to the stability of subgrade. (3) Under the same water content, there is a boundary of compaction degree of 85% for the compacted clay soil, the matrix suctions of the soil samples with less than or more than this compaction degree basically do not change with compaction degree changing. (4) Under the same compaction degree and water content, the matrix suctions of the soil samples with more coarse grained soil are more smaller; and the hysteresis loops of SWCCs are also smaller, which indicates that the influence of dry-wet cycle process on coarse grained soil is smaller. Therefore, coarse grained soil is more suitable for use as fill material of subgrade.

Slopes containing interlayers are common phenomenon in practice and it makes sense to research stabilities of such slopes. So far as the recent research is concerned, it mainly focuses on the stability of rock slope and little recognition of clay slope is involved. In fact, it is more dangerous for clay slopes containing interlayers under excavation conditions and correct recognition of failure modes of clay slopes contribute to the reasonable assessment of stability. Some centrifuge model tests were conducted with clay slopes containing interlayers in the middle part under excavation conditions. Comparison of failure modes was made between clay slopes with and without a 5 cm thick horizontal sand interlayer. The results show that the existence of sand interlayer diminishes the stability of slope; and the bottom boundary of sand interlayer is the weak plane

As a special granular material, the mechanical properties and characteristics of sand are significantly affected by particle shape such as packing density, shearing characterization, compaction, and crushability. However, grain shape quantification techniques to distinguish one sandy material from another have not reached a stage of development for inclusion in the interpretation of the behavior of sand. In this paper, the light microscope was employed to capture the grain shape digital images, which were subsequently converted into binary picture to produce contour boundary for particle shape with the help of ImageJ. The Java program language was used to compile a new plugin to determine several grain shape parameters of all sand samples in our test. Finally, relative density and direct shear tests were conducted to determine the limit void ratios and shearing strength index. It is concluded that the overall outline coefficient, sphericity, angularity could be taken as the key shape parameters to distinguish grains; and these key parameters are related closely with the angle of dilation and critical state angle as well. The proposed method can be used as an effective means to accomplish the sand particle shape quantification; and the key shape parameters can also be applied to the mechanical properties analysis and the related numerical simulation work

Based on the Wheeler model, a hydro-mechanical coupling model of unsaturated porous media is presented. The formulation of capillary hysteresis with internal state variables is adopted as the soil-water characteristic curve in this model. The effect of capillary hysteresis in the hydraulic history on the deformation of unsaturated porous media and the effect of deformation of unsaturated porous media on the flow processes can be simulated by this new model. The strength of unsaturated soil is related to suction and the saturation degree. Although the soil experienced drying and wetting have the same suction value, the saturation degrees are different. So the strengths of unsaturated soils are different too. The irrecoverable change in volume fraction of water and the plastic volume deformation are used to be hardening parameters. The new model can be used to describe the effect of the saturation degree on strength and deformation, in addition to the hardening effect of matric suction on the unsaturated soils. The comparisons between the model predictions and test results confirm that the model can simulate the main features of unsaturated soil behavior. The theoretical framework is developed for the isotropic loading condition; so its generalization to a more general stress space is needed in the future

The differential pressure between mud pressure at bottom hole and pore pressure in formation influences the rate of penetration(ROP) when drilling oil and gas wells; but its mechanism is not clear. The pore pressure near the well bore bottom is not the original pore pressure; and it is related with location and time. This paper uses one dimension unstable seep model to describe and calculate the law of actual pore pressure under various times and locations. The shear stress and normal stress at any plan can be calculated based on crustal stress, bottom pressure, pore pressure and the stress caused by insert invasion. Using the Mohr-Coulomb model to judge the rock failure and get the invasion depth expression. Because the invasion depth of bit tooth is closed with ROP; with that expression the effect mechanism of differential pressure on ROP is studied and explained explicitly. The mechanism can be applied to some fields, such as getting higher ROP in under-balance drilling and providing an explicit parameter to calculate the suitable condition for dc index method

Least mean standard fitting deviation is used as an evaluation index; we analyze the applicability of five conventional triaxial strength criteria to describe the nonlinear strength characteristics of rocks based on test data of ten rocks cited from public literatures. It is obvious that linear Mohr-Coulomb criterion can’t describe the nonlinear strength characteristics of rocks. Parabolic Mohr-Coulomb criterion can describe the nonlinearity feature of rock strength; but for the reason that the fitting error is very great and the parameters from calculation is not consistent with the real data; so it is not suitable to apply parabolic Mohr-Coulomb criterion in geotechnical engineering. For the nonlinear strength characteristics of rocks at low-to-moderate confining pressure level（ ）, the Bieniawski criterion with a single parameter and Hoek-Brown Criterion is better than Bieniawski Criterion with two parameters; their fitting accuracy is close to exponential strength criterion with three parameters; but they can’t be used at high confining level. When nonlinear strength characteristics are very significant under high confining pressure, the fitting deviations of Bieniawski criterion with three parameters and exponential strength criterion with three parameters are smaller; so they can be used to evaluate the strength under high geostress

For the analysis of the rock engineering concerned with rock discontinuities which should be taken into consideration separately; it is of great importance to adopt the valid constitutive model for rock discontinuities which can account for the major observed mechanical properties of rock discontinuities. Due to the limitation of available constitutive models for rock discontinuities within the framework of classical continuum mechanics, a new constitutive model for rock discontinuities is presented by taking use of the direct methodology based on the strength and deformation behaviors of rock discontinuities. In the presented model, the tangential stress and deformation curve and dilatancy curve are divided into linear part before peak point, nonlinear part before peak point, and softening part after peak point; and the mathematical models which can accurately characterize the major mechanical behaviors of rock discontinuities are given. Then, based on the above-mentioned, the incremental constitutive model for rock discontinuities is developed. Finally, two classical direct shear tests of rock discontinuities are simulated by the developed model and the Plesha’s model which is used widely The results show that the major mechanical behaviors of rock discontinuities can be reasonably described by the presented model. The simulation ability of the presented model is better than the Plesha’s model.

The pre-strain process can be considered to be the effect of stress history. To investigate the stress relaxation characteristics of Lanzhou loess, a series of laboratory stress relaxation tests under confined conditions are conducted. The relaxation curves of loess under different pre-strains are analyzed. The experimental results indicate that the initial relaxation stress increases with the growth of the magnitude of pre-strain, which ultimately leads to bigger instantaneous relaxation. According to the characteristics of relaxation curves, a new conception of relaxation degree (RD) is proposed. With the pre-strain gets bigger, the time to reach the same relaxation degree becomes shorter; and with the development of relaxation, this kind of difference tends to be more obvious. Based on the analysis of experimental data, the stages of relaxation are analyzed and the whole process can be divided into three stages, including instantaneous relaxation stage, attenuation relaxation stage and stable relaxation stage. The constant strain rate loading is chosen; and its influence on the relaxation process under different strain rates is analyzed. Based on the experimental results, a new rheological relation is obtained and its reliability is verified by the validation test.

Classical coaxial plasticity constitutive models implicate an inevitable limitation that directions for principal stress and that for principal plastic strain rate are always coaxial; so they are not capable of simulating non-coaxial phenomena during the rotation of principal stress axis. And they are not suitable for the conditions which the density of the sand and the confining pressure are changed on a large scale. In this paper, the sand model put forward by Pietruszczak and Stolle(1987) is modified based on the existing state-dependent critical state conception of sand; and the non-coaxial plasticity theory is introduced to describe the non-coaxial behavior under principal axes rotation. With a series of numerical simulations of simple shear and hollow cylindrical torsional shear tests, it is shown that the non-coaxial model combined with critical state theory is able to simulate successfully the non-coaxial behavior of sands subjected to principal stress axis rotation

Based on the unified strength criterion with parabolic failure envelope, the nonlinear improved expression of the two-parameter twin shear unified criterion is obtained. Elastoplastic analysis of pressure tunnels is presented by considering the seepage and intermediate principal stress. The results show that the intermediate principalstress parameter b in unified strength theory has significant effect on the radius of plastic zone. The radius of plastic zone is decreased along with the increase of the intermediate principal stress parameter b. An example is analyzed and contrasted with and without considering seepage. The radius of plastic zone with considering influence of seepage is larger than that without considering the seepage influence. The results also indicate that the parameter b and seepage have significant influences on tangential stress and radial stress. The results obtained by the original linear expression and the nonlinear improved expression of the two-parameter twin shear unified strength theory are large difference. In tunnel design, the unified strength theory parameter should be reasonably adopted according to surrounding rock material properties. So as to provide theoretical supports for tunnel design.

The artificial control of pre-exhausting shallow gas is a necessary measure for preventing geological disasters before the construction of Hangzhou Metro. By analyzing the gas-water migration process during the formation of shallow gas reservoirs, it can be found that original pore water pressure and matric suction in aeration zone of reservoirs present linear distribution along the thickness; and the pore water pressure is equal to hydrostatic pressure of the same position. The original saturation distribution of reservoirs can be obtained through experimental research on soil-water characteristic curve of reservoir sample and in-situ survey data. Based on analysis of the gas-water migration inside of reservoirs during gas release, deformation studies of gassy sand in wetting process were carried out by GDS unsaturated stress path triaxial system; and a method to predict settlements of the aerated stratum induced by gas release was proposed. Results show that the shallow gassy sand going through natural dewetting during the formation of reservoirs is further compacted; the wetting deformation of sand caused by decrease of saturation degree or matric suction is very small during water immersion or re-wetting induced by the engineering measure of gas release; and the effect can be ignored; settlements of the shallow gassy soil caused by controlled gas release decrease gradually from top to bottom along the thickness of reservoirs; and the total settlement is about 1‰-5‰ of the total thickness of gas reservoirs.

Strain localization is a very important subject in rock and soil mechanics; the influence of strain localization on slope stability must be considered. Considering the combination of two kinds of regularization mechanisms, this paper applied the nonlocal model method to elasto-viscoplastic constitutive model, and carried out slope stability analysis based on finite element slip surface-stress method. The results of limit equilibrium method and slip surface-stress method based on linear elastic model were compared with the results from this paper’s method. The results show that the numerical result of this paper is rational and is instructive for engineering application.

Internal stability refers to the ability for the coarse fraction of a broadly-graded soil to prevent the loss of its fine fraction due to seepage flow. The internal stability of a soil is influenced by geometric conditions (i.e. grain sizes and their distribution and pore sizes and their distribution), hydraulic conditions (i.e. hydraulic gradient and flow direction), and mechanical conditions (i.e. compaction efforts). From the geometric standpoint, soils are classified into two groups: well-graded and gap-graded, based on the information of 167 soils in a laboratory test dataset and understanding on the control variables for internal stability. Each group is further divided into three categories according to the fines content (< 0.063 mm). Finally, new internal stability criteria for each category of well-graded and gap-graded soils are proposed. From the hydraulic point of view, the influence of complex stress states on the initiation and development of seepage erosion is investigated. It is found that both the initiation hydraulic gradient and the failure hydraulic gradient increase with confining pressure. This is mainly due to the increase of friction between particles.

The static and dynamic characteristics of cast-in-place concrete large-diameter pipe pile (PCC pile for short) are not the same as a common solid pile because of the difference of inside and outside frictions. Based on an analytical solution deduced by the authors, the dynamic responses of PCC pile, solid pile with the same cross-section area and solid pile with the same outer diameter are analyzed. The results indicate that the displacement amplitudes among different pile models have little difference when the tip resistance is relatively small, however, they have greater difference when the tip resistance is relatively large. The displacement amplitude of solid pile is larger than that of PCC pile with the same section area, while the displacement amplitude of solid pile with the same outer diameter is smaller. The phase-frequency curve of the displacement presents periodical oscillation; the peak value of solid pile is larger than that of PCC pile; and the frequency corresponding to the peak of solid pile is higher than that of PCC pile. The oscillation aptitudes of dynamic stiffness among three pile models are different. The real part of the dynamic stiffness of solid pile with the same outer diameter is the largest; that with the same section area takes the second place; and that of PCC pile is the smallest. The imaginary part of the dynamic stiffness of solid pile with the same outer diameter is the largest; that of PCC pile takes the second place; and that with the same section area is the smallest. The velocity admittance has similar characteristics. The velocity admittance with the same outer diameter is the largest; and that with the same section area is the smallest. The capacity of unit volume concrete is fully exerted for PCC pile; thus the dynamic response of PCC pile is smaller than solid pile with the same cross-section, and the concrete is more economic than the solid pile with the same outer diameter.

Unsaturated loess is a typical structural soil. The triaxial shearing tests for four kinds water content intact unsaturated loess and remolded unsaturated loess under three kinds of consolidtation pressures were carried out. Based on the tests and the concept of geo-binary medium model, the stress share ratio as a quantitative parameter has been proposed to study the structure of unsaturated loess. The effect of consolidation pressure and water content are analyzed and the stress share ratio is described by a mathematic formula. Results show that the structure of loess is mainly affected by consolidation pressure and water content. The stress share ratio increases linearly then decreases exponentially with the increment of strain. Further the stress share ratio was applied to the constitutive model of intact unsaturated loess

Taking axial stress and radial strain under fixed axial strain as study parameters, the evolution law of mechanical properties of coal containing gas under unloading confining pressure is experimentally studied; and the relationship between test conditions and study parameters is fit. The results show: the axial stress of coal containing gas decreased with two stages if confining pressure is gradually unloaded under fixed axial strain; the relationship between decrease rate of axial stress and the difference between confining pressure and gas pressure is positive. The total decrease of axial stress is larger when the confining pressure is unloaded by unit value as gas pressure increasing; and sensitivity of the influence is stronger, the relationship between axial stress and confining pressure unloaded amounts can be show by quadratic function. The radial strain of coal containing gas shows gradually increases tendency when confining pressure is gradually unloaded under fixed axial strain; the total increasing of radial strain is larger when the confining pressure is unloaded by unit value as gas pressure increasing; the variable quantity of radial strain is influenced by sum of the confining pressure unloaded and gas pressure; the relation between radial strain and confining pressure unloaded can be show by modified logarithm function.

The regularities of parameters are gotten from the pressuremeter test at the estuary of the Yangtze River. The result of pressuremeter test shows that: the initial pressure P0 increases linearly with depth; the Pf , limit pressure Pl and the pressuremeter modulus Em are significantly impacted by soil properties and they have the same trend in the soil layers. The trend is: muddy clay

Because of high water content, low strength and low permeability, dredged clays could not be directly used as engineering materials. Dump-disposing for dredged clays always occupies a large scale of ground and these resources were wasted. Based on traditional solidification method, a new flow-solidification method is put forward which considering the current dredging method in China. And this method can deal with dredged clays with high water content efficiently. In order to study the fluidity of the treated mixtures, a series of laboratory fluidity tests have been performed. The experimental results show that both the initial water content and the adding quantity of solidification agent have good linear relationship with the fluidity of the mixtures. And there exists a critical value of the initial water content for flow-solidification; and the critical value is 2.5 times of the liquid limit. A concept of generalized water-cement ratio is defined; and a prediction method of fluidity is established based on initial water content and adding quantity of solidification agent. Finally, the validity of the proposed formula is verified.

By the grouting test in sandbox, the influence of seepage on grouting in sandy gravels is studied. First, the groutability of sandy gravels is verified on condition that the slurry is chosen as grouting material; and the relevant parameters, including water cement ratio, grouting time, grouting pressure and grouting depth are determined. Second, in the absence of seepage, the relationship between grouting pressure, water cement ratio and grout diffusion distance is studied. Finally, under seepage, the relationship between grouting pressure, hydraulic gradient and grout diffusion distance is studied by adjusting water head difference between the upstream and downstream. It is shown that there is no significant influence of seepage on the linear relationship between grouting pressure and grout diffusion distance; and that the relationship between hydraulic gradient and grout diffusion distance shows nonlinear behavior under the different grouting pressures

Two typical study areas (Chezigou fishing village subjected to serious erosion process and Huanghe Haigang remaining in the balanced state between erosion and siltation) were selected to conduct a series of experiments including wave-loading simulations, flume erosion tests and geotechnical tests aiming at studying the erosional characteristic evolution of fine sediment in the process of wave loading actions and exploring the evolutional mechanism. It is demonstrated that the sediment erodibility at Chezigou fishing village study area is widely higher than that at Huanghe Haigang both in the absence of wave action and weak wave conditions; however, with a more evident downward trend under wave loading due to the more significant liquefaction characteristics of fine soils in Chezigou fishing village, which can contribute to the serious coastal erosion this study area subjects to. Additionally, basing on the analysis of the sedimentation data and particle composition of the fine sediments in the two study areas, the reworking of wave loading to transport fine particles of the bottom sediment upward accelerates the coarsening process of seabed sediment, which promotes the evolution of sediment erodibility of fine soils in coastal areas.

The large-amplitude variation of the reservoir water level will easily lead to the concentration of incremental interstitial pressure, which will decrease the effective stress on the fracture surface, and increase the stress intensity factor of the crack tip. When the stress intensity factor reaches the critical value, the crack and fracture in the rock strata will transfix, expand and then damage; the continuous complex failure surface will shape; and the slope stability will decrease which will causes the destabilization of the bank slopes. Based on the previous contents, the impact of fissure water pressure on the crack intensity factor is analyzed from the point of fracture mechanics, and the expand of Ⅰ-Ⅱmixed mode crack is analyzed considering the impact of fissure water pressure. The results show that the crack growth angle of Ⅰ-Ⅱmixed mode crack change not only with the crack closure degree, oblique crack inclination angle and the magnitude of the biaxial stress, but also with the magnitude of the fissure water pressure and the friction coefficient of the crack edges. Moreover, in the same circumstances the non-closed crack growth angle is larger than the closed crack growth angle. For closed crack, the smaller the friction coefficient of the crack edges is, the larger the crack growth angle is. Finally, the rock mass fracture toughness KIc, KIIc considering the role of the fissure water pressure and the Ⅰ-Ⅱcompound fracture criterion under the compression-shear are conducted based on Mohr-Coulomb criterion. The relevant conclusions of our research provide an important reference for studying fractured rock mass failure under the water-rock interaction.

By using the integrated experimental apparatus for syntheses of gas hydrate sediment and triaxial tests, a series of static and dynamic tests are conducted on the tetrahydrofuran (THF) hydrate with fine sand and Mongolia sand as the skeleton. The stress-strain curves, strength and liquefaction characteristics of the sediments before and after hydrate dissociation are obtained. The mechanical properties of the two kinds of hydrate sediments with fine sand and Mongolia sand as the skeleton, as well as the liquefaction characteristics of the sediment after dissociation of hydrate and the corresponding saturated sand are compared. It is shown that the hydrate-bearing sediments all behave as plastic failure, strength of which the increases with the formation of hydrate and the confining pressure. The dissociation of hydrate can lead to the great decrease of the strength of the sediments. The liquefaction of the sediment after dissociation of hydrate needs shorter time relative to the corresponding saturated sand

In order to calculate the temperature of the one-dimensional soil freezing process, the equivalent heat capacity model which considers the unfrozen water content has been applied; and the semi-analytical solution for the temperature field has been obtained. The solution procedure has been based on the Fourier method, and the solution has been confirmed by comparing with the numerical solution in some references. The comparison between the equivalent heat capacity model and the apparent heat capacity model has been made; and the results indicate that, during the transient stage, the advancing velocity of the freezing front calculated from the apparent heat capacity model is smaller than that of the equivalent heat capacity model; during the steady stage, the thickness of the frozen zone calculated from the apparent heat capacity model is larger than that of the equivalent heat capacity model. Considering the situation that the water flow induced by the freezing process is weak, then the better the soil freezing characteristic is, the larger the error gets when the apparent heat capacity model is used to calculate the temperature field; and the results are unsafe for the design of the artificial ground freezing engineering.

In order to investigate the stress-strain behavior and its variation with the micro-fabric for granular materials, a series of tests and corresponding micro-fabric analyses were conducted on dimensional ideal 2D granular materials with circular and elliptical shapes of cross-section, which were prepared at different maximum principal stress direction angles δ, using the biaxial testing system under three different stress paths including isotropic compression, constant lateral pressure shearing and constant mean principal stress shearing. The anisotropic property in shear strength and dilatation induced by shear were presented and analyzed. Based on the experimental results and micro-fabric analyses, the following new findings involving the failure mechanism of granular materials were confirmed, including that: (1) There exists a preferred shear direction towards which the long axis direction of particles tend to rotate as shear strain increases; and along this direction a shear band will be triggered and finally formed under large shear strain. (2) This preferred shear direction is irrelevant to the bedding plane, and the angle of the bedding plane with the preferred shear direction is about equal to 45°+ /2, where is residual internal friction angle. (3) The effect of particle rolling on the shear failure becomes more significant with the increasing angle of the bedding plane with the preferred shear direction, and such difference in the effect of particle rolling is the main reason why there is the anisotropy shear strength and different dilatation induced by shear.

The treatment of dredged sludge with high initial water content is very important in geotechnical engineering. Based on the traditional cement-treatment method, a new solidification additive by mixing cement, lime and polymer is proposed, in order to reduce the dredged sludge’s water content and increase unconfined compressive strength rapidly and broaden the water content of cement-treatment method so as to achieve efficient treatment of high water content dredged sludge. A series of laboratory tests have been performed to investigate the variation of unconfined compressive strength and the relationship between material mixing ratio and unconfined compressive strength. The experimental results show that the unconfined compressive strength of solidified sludge increased remarkably by adding cement and lime. The new composite additive could solidify the high liquid limit sludge with initial water content more than 2 times of the liquid limit just with low cement dosage, while its early strength is more than 0.5 MPa, 28 d strength is more than 1 MPa. Finally, a prediction expression of unconfined compressive strength is proposed and verified.

A set of test system for studying capillary rise has been developed by using MP406 moisture probe, WM-1 suction probe and DT80 logger, etc. The system has been used to carry out 3 poles of different initial water contents capillary rise tests on unsaturated clayey sand with controlled 1.7 g/cm3 dry density. The relationships between different cross-sections water contents and suctions and time are obtained. The results indicate that the initial water content has a great effect on capillary rise hight and rising velocity. This system could measure wetting front advancing velocity at different time and study changing water content and suction of different cross-sections. This system could fix quantity study capillary rising maximum hight and unsaturated hydraulic conductivity to resolve the difficulties that using general methods couldn’t measure. It can measure unsaturated hydraulic conductivity according to wetting front advancing velocity, water content changing & suction changing of samples. Coefficient of permeability will be get from soil water characteristic curve. At the same time, the laws of wetting front movement are given under different initial water contents.

It is necessary to understand the water holding capacity of laterite soil, which is the basis of preventing cracking and instability of the soil subgrade. Firstly, soil water characteristic curves (SWCCs) of compacted samples with four different dry densities were investigated by using 15 bar pressure plate apparatus. Test results show that there has appeared a plateau stage in the soil water characteristic curve with the decreasing of dry density. What’s more, the length of the plateau stage is intimately related to the dry density of samples , the lower the dry density is, the longer the length of the plateau stage is. Then, combined with pore distribution curves of the four samples, reasons for their different water holding capacities are investigated from the viewpoint of microstructure. Finally, SWCC equations for soil of different compactnesses are established through data fitting.

In order to investigate the rheological properties of hornblende plagioclase gneiss in Xiaowan Hydropower Project, triaxial compression rheological experiments for hornblende plagioclase gneiss spceimens are carried out on the rock servo-controlling rheology testing machine. The rheology testing results show that rheological properties of hornblende plagioclase gneiss is very obvious. Based on the triaxial rheological experimental results, the variance law of axial strains of hornblende plagioclase gneiss specimens with the time under different pressures is investigated; and the development trends and characteristics of rock deformation in stage of accelerated rheology are discussed. At the same time, the scanning electron microscopy experiments of rheological rupture fracture are carried out; the rupture forms and mechanisms are analyzed. Based on the relation between creep rate and stress level in the stage of steady-state creep, a new method is put forward to determine long-term strength. Combining statistical damage model and Burgers rheological model, the corresponding damage rheological model is proposed; and then rock statistical damage rheological model is verified by accelerated rheological test curves of rock spceimen. The results show that the rock statistical damage nonlinear rheological model agrees well with the rheology test results, and can exactly describe the rheological properties of hornblende plagioclase gneiss in Xiaowan Hydropower Project.

Cyclic torsional shear and cyclic triaxial tests are performed on undisturbed marine silty clay by the hollow cylinder apparatus; and the shear modulus and Young’s modulus are obtained respectively. Meanwhile, the effect of effective confining pressure and stress ratio on dynamic Poisson’s ratio is investigated on the basis. It is found that the dynamic Poisson’s ratio increases with generalized shear strain, but decreases with increasing effective confining pressure and stress ratio. The effects of effective confining pressure and stress ratio on dynamic Poisson’s ratio is weakened as the generalized shear strain increasing. The dynamic Poisson’s ratio is about 0.48 when the Poisson’s ratio increased to 1.8×10-2 or so, and the tests are terminated. There are no shear dilatation during all tests because the Poisson’s ratios are smaller than 0.5. It is indicated that the undisturbed marine silty clay tested in the paper has a good stability under cyclic loadings

In engineering design, the soil arching and the entire stability of the soil mass between the soldier piles are usually neglected. The research was carried out on the soil arching and the entire stability of soil mass between the soldier piles in excavation. Expressions of the loading ratio and the spacing of the piles were obtained. Through the verification in four types of clays, it is found that in the silt and clay with higher strength index, the loading ratio reaches 100% when b/S is up to 0.5; where b is width of pile cross-section; S is pile spacing; and in the mucky clay with lower strength index, the b/S should be 0.8 for the 100% loading ratio. The pile spacing can be relatively wider under the condition of the entire stability of soil mass. For the pile with regular diameter, the pile spacing should be designed meeting the stability of the soil arching, while in silt with higher friction angle but lower cohesion, especially for the piles with large diameter, the pile spacing should be designed according to the entire stability of the soil mass between piles.

The mechanical properties of unsaturated soil become complicated because of the pore air. The pore air affects the strength and the deformation of unsaturated soil. A series of triaxial compression tests was performed on samples of Yunnan red cohesive soil with different initial saturation degrees and different dry bulk densities. The pore air can influence the strength and deformation of unsaturated soil. The cohesion c does not decrease monotonously with increasing saturation. The friction angle decreases with increasing saturation degree. Both cohesion c and friction angle increase with increasing dry bulk density. The dilatation occurs frequently in the process of unventilated testing. As increasing saturation degree and decreasing dry bulk density, the dilatation disappears. The destructional forms of samples may be influenced by dilatation.

The shear strength of soil is an important mechanical parameter for slope stability analysis. The large scale direct shear test is an effective method to obtain the shear strength index of coarse grain soil; but it is difficult to excavate massive undisturbed soil. The undisturbed sample was excavated in-situ, the laboratory small scale direct shear tests were carried out on undisturbed sample and compacted sample for comparison. It is approved that the shear strength indices of undisturbed sample could be replaced by the test results of compacted sample when the density and water content of compacted soil could be controlled effectually. The results of small scale shear test of undisturbed soil and large scale shear test of compacted soil were comparatively analyzed. The shear strength of residual soil achieved from small scale direct shear test is more slightly high than that of test results from large scale direct shear test under the same pressure. The research results show that the shear strength indices of small scale direct shear test is slightly bigger than that of slope take place slide in-situ. It is suggested that the peak value strength and remaining strength achieved from large scale direct shear test should be selected for slope stability analysis when the density and water content of compacted soil could be controlled effectually; it is more reasonable to calculate slope stability by this method.

In order to investigate the bearing behavior and deformation rules of cohesive soil slopes during crest loading, centrifuge model tests of unreinforced slope and soil nail-reinforced slope were conducted. The loading and deformation process were observed and measured. Based on the comparison of bearing capacity and deformation rules between the unreinforced and soil nail-reinforced slope, the results show that soil nails improve the bearing capacity of slope obviously by confining the displacement toward slope surface. The deformation on the weakest location-footing edge is enhanced due to a nail-influence zone formed in reinforced slope; compression deformation of soil in middle and upper parts of slope is increased and shear deformation of which is decreased, resulting in the strengthening of slope stability. Soil nails in upper parts of reinforced slope has much more significant effects on reinforcing as load increased. Also in middle and lower parts of slope, the interaction between soil and nails becomes intensive near the slope surface.

The method of level-layer analysis is improved to calculate the earth pressure with arbitrary displacement modes. By the stress analysis of the differential element under different displacement modes, it is supposed that the displacement mode only influences the equivalent internal friction angle of interlayer. And the relationship between them is incorporated into the method of level-layer analysis with the existing concept that the internal friction angle acts gradually; and then a new calculation method of earth pressure that quantifies the displacement mode is proposed. Further study indicates that the resultant earth pressure is independent from displacement mode and consistent with the results of Coulomb’s theory; but the distribution of earth pressure and the point of application of the resultant earth pressure vary greatly with the displacement mode. The results are in agreement with the experimental ones. So the presented mothed can be a reference for the calculation of rigid retaining walls.

During the consolidation process of new deposited seabed which had been simulated both on tidal flat of the Yellow River Estuary and in a circular soil bin indoors, the critical shear stress and physico-mechanical properties, such as bulk density, water content, penetration resistance, shear strength, were measured to analyze the influencing factors and variation of the critical shear stress of silty sediment in the Yellow River delta. Research shows that there is a positive correlation between critical shear stress and bulk density, penetration resistance, shear strength; while negative correlation between critical shear stress and water content and good quantitative relationship between critical shear stress and dry density, shear strength. Comparing test results with ones calculated with formulae in references, the individualism of critical shear stress of silty sediment in the Yellow River delta is obtained.

Based on the unconfined compressive strength of cemented soil and lime-cement soil that are analyzed by tenacity method, the study of the curing mechanism of lime-cement soil is carried out. In the aspect of unconfined compressive strength, the experiment of cemented soil specimens and lime-cement soil specimens which are made according to the ratio of cemented soil and lime-cement soil, has been completed after 28 days’ standard curing. Ca(OH)2, CaCO3,and cement were chosen as addtives with different levels to be mixed in the cemented soil and lime- cement soil. Its compressive strength is tested and the experiment result is analyzed. The research results indicate that the strength of cemented soil and lime- cement soil originates mainly from the composite binding effect and the physical filling effect in the cemented soil. The physical filling effect, pozzolanic effect and particle of clay ionic exchange and quadrate reaction, action of cement hydrate and combined action exist in lime-cement soil. The research results also indicate that the action of cement hydrate is the mian reason for the increasing rule of the strength of cemented soil and lime-cement soil; and the hydrated lime can restrict cement hydration but doesn’t stop cement hydration.

The remolded bentonite samples with different water contents were prepared after drying with air dry method, drying method and freeze dry method. Their cumulative intrusion curves were obtained with mercury intrusion test. The division of pore scale for remolded bentonite samples were made according to the test result; then the quantitative analysis of pore criterion distribution characteristics was made according to the test result. The results show that the pore diameters and pore-scale distributions of soil prepared by air dry method, drying method and freeze dry method are great different. The higher of water content is, the more obvious difference is; the pore diameter of soil prepared by air dry method and drying method become small, causes the change of micropore characteristic; the pore diameter of soil prepared by freeze dry method does not become small, so does not cause the change of micropore characteristic. And the conclusion is drawn that the freeze dry method is the best method for drying remolded bentonite sample using mercury intrusion test.

Through unconfined compressive strength test of soil-sand-cement in laboratory, its development rules in different sand contents and different curing ages are studied. The experimental results indicate that the mixing with a certain amount of sand can significantly increase the strength of cement-soil under a certain cement content condition. When the cement content is 10%, the sand content is 50% reaching maximum strength. And according to the measured stress-strain curves, through detailed analysis of the soil-sand-cement failure modes, it is brittle shearing damage. Moreover, with the increasing amount of sand content, the shear angle of the soil-sand-cement admixture increases gradually. At the same time, the reasons for unconfined compressive strength of soil-sand-cement admixture growth are analyzed from different viewpoints, so as to provide test data and theoretical basis for the practical application of engineering

The relationships between compactness, initial water content, cover load and expansion rate have been studied through expansion experiments at the state of K0 stress for Handan strong expansive soil. Then a constitutive model of expansive soil which considered the effects of these three factors is set up. The relationship between ultimate water content, compactness, initial water content and cover load is also set up. Finally, a constitutive equation for linear expansion coefficient of Handan strong expansive soil is proposed. It takes compactness, initial water content, cover load and ultimate water content as variables. With this constitutive equation, constitutive relation of any water content can be obtained. The experiments and expression of this model are relatively simple and of certain practical use. This model can provide theoretical basis and reference for design and construction.

A nonlinear constitutive model with tension cut-off is developed by use of C++ based on Mohr-Coulomb constitutive model in FLAC. For stresses and displacements of monitored elements or nodes, comparison is conducted between the numerical solutions (including solutions based on Hoek-Brown constitutive model, Mohr-Coulomb constitutive model and defined nonlinear constitutive model) and the analytical solutions (based on Hoek-Brown constitutive model). Validation of the defined nonlinear constitutive model is verified. Strain localization of the surrounding rock of a circular tunnel is modeled using the defined elastic-brittle-plastic constitutive model. The tunnel is excavated after the model is loaded to an equilibrium state. On the condition of symmetric boundary conditions of computational model and homogeneous constitutive parameters, four symmetric V-shaped notches are found; as is consistent with observations in situ and experimental results of rockbursts in a hydrostatic pressure. However, if the very brittle strain softening Hoek-Brown constitutive model is adopted, then symmetrical numerical results cannot be observed.

Municipal construction causes damage to nearby pipelines. Based on the Winkler foundation model, which simplified the pipeline as Euler-Bernoulli beams of variable stiffness, the transfer matrix method is proposed to analyze the performance of the pipeline according to the beam’s element differential equation. This method is verified by comparing with analytic solutions for beam with constant stiffness section. Then it shows the influence of joint stiffness on the deflection and internal force of the pipelines. It’s hoped that the work above can supply technical support and guidance to the design and construction of pipelines

In order to find out the failure mode characteristics of sandstone under the reservoir water pressure, some sandstones are chosen from a certain landslide area of Zigui district in the Three Gorges reservoir area as the experimental material. The self made rock dissolution tester YRK-1 is used. Three different soaking pressures 0, 0.4 MPa and 0.8 MPa are set to do the comparative analysis. The soaked sandstones which are affected under different water pressures are uniaxially compressed and triaxially compressed for different soaking periods. The quantitative results concerning different conditions are obtained. The results show that with the growth of soaking time the failure laws of sandstones are as follows: (1) The crack angles of sandstones under three differrent confining pressures decrease gradually and then approrch stable values; moreover, the soaking pressure greater is the tendency of decrease more obvious is. (2) The shear fissures on the surface of sandstones gradually become shorter but the stretch-draw fissures gradually become longer under uniaxial compression test; furthermore, the soaking pressure greater is the tendency of variation more obvious is.

The influence of loading frequency on dynamic modulus and damping ratio has been inconclusive in dynamic triaxial test. Therefore PFC2D is adopted to simulate dynamic triaxial test of the inverted filler of earth-rockfill dam in different vibration frequencies. The simulated results have tallied in general with those of the test, which shows the influence of frequency on dynamic modulus and damping ratio can be ignored when the frequency is not higher than 0.1 Hz; and that the modulus will decrease in small strain but it will begin to converge as the strain become larger when the frequency is lower than 0.1 Hz. Though the damping ratio has a little fluctuated at 0.05 Hz, it is still in a narrow range when compared with that in other frequencies; so it can be believed that the influence can be ignored.

The Burgers model could only describe the behavior of rock material before the third creep-phase. The viscous components of Burgers model are replaced by non-stationary viscous components. The modified Burgers model is also called as non-stationary Burgers model; and its creep compliance is obtained. Comparison between the results obtained from non-stationary Burgers model and the experiment shows that this model can well describe the initial attenuation creep phase, the stabilization creep phase and the speedup creep phase of the creep curve

In order to study the effects of strain rate on strength and stress-strain behavior of gravelly soil and its mechanism, consolidated-undrained triaxial compression tests under different confining pressures were carried out for saturated gravelly soil mixed by clay and gravel. Effects of strain rate on undrained strength were analyzed quantitatively within the strain rate range from 0.028 %/min to 0.690 %/min. According to those test results, it is shown that the stress-strain curves under different strain rates are similar. For this kind of gravelly soil, undrained strength would increase 7.4% - 29.9% with the increase of 10 times of strain rate. The effects of strain rate of gravely soil are caused by both pore water pressure induced by shearing and cohesion of the soil material. However, for these two aspects the degrees of influence on strain rate effects are different under different confining pressures.

According to geological material, analysis of geological features of great thick coal seam massive fully-mechanized top-coal caving mining under the Jing River in Xiagou coal mine, in order to achieve mining safety under the water, it is determined the mining plan that remained the isolated pillar with a definite width between the work faces. By similar material tests, analysis of the isolated pillar with a definite width to have an effect on overlying strata failure under geological conditions in the area; the achieved results prove that the isolated pillar can effectively control overlying strata failure. The test results provide the largest ratio of fissure zone height and mining thickness of single work face, and by the least vertical height calculating of the safe coal post preventing water, hold that geological conditions meet the requirements of the safe stoping. Research results successfully guided the safety stoping of the five work face; it will provide references to those mines with similar conditions in Xiagou mine area.

According to the characteristics of the decision factors of supporting schemes for deep foundation pit, such as information incompleteness and their gray correlation, using gray system theory, vector projection synthetically and fuzzy mathematic theory, a fuzzy gray relation projection method for the optimization of supporting schemes is established based on the gray relation projection method. Combined weights are used to interpret the impact of various factors more reasonable. A method for sensitivity analysis which bases on the distinguishing degree of the optimal plan is presented. Then the model is proved scientifically and effective by an example and easy to realize programmed. The algorithm which has the high sensitivity level offers more reliable basis for decision-making. So it has some generalization and application value

Based on Xi'an Metro #2 interval tunnel through the south gate of the ancient city wall, three possible construction programs by the establishment of FLAC3D numerical model are accomplished. The program is suggested that is formed by segment support and grouting behind the segment, chemical grouting in the soil within the city gate and piling bored piles closed to the ancient city wall south foundation as the best joint construction program. The deformation law of the ancient city wall caused by the joint program is studied; and the monitoring program is given. It is shown that the method suggested of deformation control technique for the ancient city wall is reasonable; and the deformation of the ancient city wall and the surface caused by metro shield tunneling is in the safe range. Deformation law is obtained from the ancient city wall caused by the metro shield tunneling and its control technology. The experience are beneficial to the Xi'an Metro #1 which will be through the east and west ancient city wall.

A theoretical approach to predict landslide displacements, in which the support vector machine (SVM) method is coupled with the empirical mode decomposition (EMD) in signal processing, is suggested through the multimode SVM function regression modeling. On the basis of the historically recorded data of displacements for a slope, several intrinsic time modes for the evolutionary of displacements are obtained in the process of landslide forming by using EMD method; and they are components of statistical learning samplings with multimode information, determining the multiscale adaptive information of slope displacements varying with time. Corresponding to the information of displacement evolutionary in each empirical mode, the multimode SVM modeling method is introduced; and then the estimations of landslide displacements are obtained by the composition summing the results of slope displacements from different empirical modes. The theoretical results calculated by the proposed approach based on the monitoring data of Wolongsi new landslide and Xintan landslide show that the applications of the SVM method coupled with the EMD method, comparing with those of the genetic algorithm neural network method, have a more powerful ability for landslide displacement prediction; and the theoretical estimations are identical with the monitoring data very well.

In accordance with the occurrence behavior of roof strata and the breaking convergence characteristics of main roof in shallow seam longwall mining, this paper studied the catastrophe mechanism and the catastrophe control of main roof during the first weighting by using the initial post-buckling theory and the catastrophe theory, added the sufficient conditions of instability due to sliding for controlling rock blocks after the main roof breaking, perfected the criteria of step convergence of rock blocks for contacting and not contacting with the waste rock from fallen roof, determined the step convergence values, derived the formulae of support force for controlling the step convergence and ensuring the roof stability, and presented an application with the example of Daliuta 1203 face. It is pointed that the rock blocks are in a state of non-equilibrium after main roof breaking, the mechanism of the step convergence is instability due to sliding of structure; the step convergences before and after contacting with the waste rock from fallen roof have some determinate relations with the breaking convergence and the mining height respectively; the intense roof weighting is mainly caused by key roof block sliding; and controlling step convergence is essentially controlling sliding for rock blocks. The results also indicate that the synthetical application of initial post-buckling theory and catastrophe theory can determinate whether step convergence will take place before contacting with the waste rock from fallen roof in accordance with the occurrence state and structure characteristics of roof rock layer, can determinate the motion form after contacting with the waste rock from fallen roof according to mining height of working face and effective filled thickness, and can determinate the support force for controlling step convergences before and after contacting with the waste rock from fallen roof in accordance with the breaking span, the breaking convergence value and the friction coefficient.

Unsaturated hydraulic conductivity functions of deposits body are obtained based on Fredlund and Xing methods as well as field tests. According to the generalized geological model, the finite element model of unsaturated seepage analysis is built. Distribution characteristics of pore-water pressure in the slope at different times in the process of reservoir impounding are obtained by numerical simulation. Distribution of transient pore-water pressure and the strength theory of unsaturated soil are applied to the analysis of general limit equilibrium to study the transient stability of the slope while the water level is rising. The results show that the whole stability of the slope is descending with the water level rising. And its local stability coefficient is descended firstly and then ascended with the reservoir water level rising. Owing to the existence of a risk water-level, the lower part of slope body tends to be unstable under certain condition

Loading experiment process, safety monitoring method and results of rock-anchored beam in Jinping I hydropower station underground powerhouse, are introduced. The results show that anchor stress,crack openings, rock deformation and anchoring load losses are caused by secondary stress; their increments caused by test loads is far less than monitoring physical quantities; most of the anchor bolts stresses are tensiles. C anchor stress increment reflects more sensitive than A, B anchor stress increments; anchor stress increment diminishes quickly with the buried depth increases; during the whole process, all levels of load variation monitoring physical quantities are less than their design control standard values. It is suggested that the rock anchor beam design and construction should consider surrounding rock and rock anchor beam jointed effects in surrounding rock deformation.

Aimed at regulated scheme of Three Gorges Reservoir and extreme rainfall events, 10 working conditions were set for stability analysis of bazimen landslide of Zigui county. Transit seepage due to associative action of reservoir water lever fluctuations from 175 to 145 and rainfall infiltration was simulated adopted by SEEP/W software. And by using SLOPE/W software, the computed transit pore water pressures were used for limit equilibrium analysis of this landslide, then the landslide stability factors of different work conditions (different rainfall intensity) were decided and the rainfall could be used to predict landslide at last. The stability study showed it would have a great influence on landslide stability when the rainfall is greater than 150 mm/d, and rainfall infiltration had time delay. In the same condition of rainfall, the influence of one day’s rainfall intensity on landslide stability had greater than five day’s rainfall intensity. During the process of water lever descending from 175 m to 145 m, the landslide would be instability when the critical rainfall was 100 mm/d. That is to say, the landslide failure probability was high during the rapid drawdown. During the process of water lever ascending from 145 m to 175 m and the stable water lever of 175 mm, the landslide would be instability while the critical rainfall was reach to 200 mm/d, that means the landslide failure probability was low under the above two conditions. The results of moisture analysis on landslide showed that it mainly influenced upper soil by rainfall, and lower soil’s moisture was controlled by underground water, which indicated rainfall was accessible to cause shallow slope and local slope

Checking the dam's stability under seismic conditions has always been an important job for dam’s security; and using the reasonable calculation method is the basic guarantee for right result. The probability mean of reliability analysis for dam slope's stability is discussed based on the probabilistic limit analysis and the formulation what considered earthquake as a probability event for slope's reliability is deduced. To demonstrate the rationality of bringing exceeding probability into dam slope stability analysis, two typical examples and Xiaolangdi dam slope are taken to investigate the variation of single safety factor and reliability index under seismic condition. The research results show that the bringing exceeding probability into dam slope stability calculation can increase the value of reliability index to match the engineering practice compared to consider earthquake as deterministic events and can match the allowable factors of safety in specifications

It is common to have a foundation pit accident, when failing to deal with the effect of confined water. In order to avoid such accidents, the Jiangnan foundation pit of Qingchun Road River-Crossing Tunnel in Hangzhou was investigated. By analyzing the monitoring data of wall deflection, settlement, confined water level and strut load, we proposed how to deal with high confined water. According to the analysis of on-site monitoring data, it could be obtained that: ①The wall deflection is closely related to the plane size of the foundation pit, and through strengthening the stiffness of the central support, the large pit can "be separated" into several smaller pit to control the wall deflection. ②The maximum settlement point is 0.5 times depth of the excavation away from retaining wall. ③It is useful to treat the confined water with dewatering and cut-off walls, and during excavating the bottom of the foundation pit, we must ensure that the pumping wells keeping working; otherwise the safety of the construction can be affected. ④ The load of the first strut becomes smaller and even can be tensile force during excavation.

The geological structures at left bank slope of Jinping First Stage Hydropower Station are very complicated. Many deep cracks and faults, such as f2, f5 and lamprophyres X, are the most significant factors that influence the stability of the rock slope. Based on the strength reduction method (SRM), realistic failure process analysis(RFPA) is used in the full failure processes evaluation of rock slope after excavation and its corresponding weak-layers replacement. From comparison results of numerical simulation, it can be observed that the safety factor increases by 0.430 after weak-layers replacement in deep rock mass, which illustrates the structural safety can be greatly improved if weak-layers replacement is conducted before excavation and support of rock slope. Furthermore, by using RFPA-SRM, not only the failure mechanisms and fracturing patterns, but also the safety factors can be obtained. The results can in turn be used for stability assessment and construction process determination of rock slope before construction.

Pile foundation failures in lateral spreading ground have attracted the attentions of engineers and researchers since the Niigata and Alaska earthquakes. Study of typical cases of pile failures in lateral spreading ground and analysis of some previously proposed causes of the failures indicate that a mechanism which could completely explain the failures is yet to be found. By analyzing the failure of Showa Bridge during the Niigata earthquake through p-y method, this paper looks into influence factors for the failure of piles due to lateral spreading. Results show that appropriate p-y models for liquefied soil are vital in the analysis of piles in lateral spreading ground; further understanding and better aseismic design of piles in lateral spreading ground depends on the development of effective p-y curve models for liquefied soi

采用等效线性方法考虑土的动力非线性特性，利用一维波动模型分析了深软场地的地震反应特性，结果表明，与输入苏州人工地震波时的计算结果相比，大地震远场地震动作用时，深软场地的地表水平向峰值加速度明显增大，规准反应谱的特征周期值显著增大，地表设计地震动的水平地震影响系数值明显增大，且两者的差异随输入地震动峰值加速度的增大而增大；当土层剪切波速的变异性由+10%变化到-10%时，地表水平地震影响系数曲线平台值有降低的趋势，规准反应谱的特征周期略有增大，且-10%的变异性对水平地震影响系数的影响要比+10%的变异性的影响显著；土体动剪切模量比和阻尼比均有变异时对地表设计地震动参数的影响较大，且土的阻尼比由-2δ到+2δ变异时，地表水平向峰值加速度和地震影响系数平台值有减小趋势

To constitute the highway tunnel support system to direct the safe tunnel construction for all surrounding rock sub-classifications, based on the sub-classification method standard, the physico-mechanical parameters and characteristics of the double lane highway tunnel, the excavation methods, assistant measures, structure forms, support types and primary lining parameters for all sub-classifications have been ascertained by theoretical analysis, example statistics, numerical calculation. The results show that the full face excavation method and light load bearing support are fit for the rock class Ⅲ1, the bench cut method and medium load bearing support are fit for the rock class Ⅲ2; the bench cut method and heavy load bearing support are fit for the rocks class Ⅳ1, class Ⅳ2, class Ⅳ3; and the assistant measures which can raise the surrounding rock strength in reinforced area to the level of rock class Ⅳ1 are needed for the rocks class Ⅳ2 and class Ⅳ3; the bench cut method and the assistant measures which can raise the surrounding rock strength in reinforced area to the level of rock class Ⅳ1 are fit for the rock class Ⅴ1; the center cross diagram method and the assistant measures which can raise the surrounding rock strength in reinforced area to the level of rock class Ⅳ3 are fit for the rock class Ⅴ2; the center diagram method and the assistant measures which can raise the surrounding rock strength in reinforced area to the level of rock class Ⅳ1 are fit for the rocks class Ⅴ1 and class Ⅴ2; and the special load bearing support is needed for them; the inverted arch should be built for the surrounding rock sub-classifications from class Ⅳ1 to class Ⅴ2 .

Earthquake-induced sliding displacement is an important parameter for seismic design of earth structures. Using a novel ground motion selection method, we select and modify ground motions from a strong motion database to capture the median, standard deviation and correlations of response spectra of an earthquake scenario, making it an effective method to incorporate ground motion variability into dynamic time-history analysis of earth structures. Using the selected ground motions and a simple analytical model, the statistical properties of permanent sliding-displacement of earth structures were studied under various earthquake scenarios. The study revealed the influence of structural periods and yielding coefficients of the sliding interface on the statistical distributions of the earthquake-induced sliding displacements. Finally, a model is proposed for the sliding probability and sliding displacements of earth structures conditioned on various earthquake magnitude and rupture scenarios and different fundamental periods. It is demonstrated that the ground motion selection method can effectively represent ground motion variability of different earthquake scenarios. The results have important implications in performance-based earthquake design of earth structures.

The deformation is the dominant factor of the quality of the road constructed on the soft soil foundation. Tianjin Dongjiang port is located on the hydraulic filled soil foundation which is improved by using vacuum preloading method. Roads in this area often suffer wave type asymmetry settlement, which seriously affects the usage of the road and causes damage to both vehicles and human being. It is found that the initial wave asymmetry deformation of the road on very soft soil foundation is usually existing and will be developing continuously under the traffic load. The mechanism of the wavy failure of the road is discussed by establishing a mechanical model. The method of using geogrids to reduce the asymmetry deformation is proposed; the reinforcing effect is analyzed using finite element method.

Temperature field under highway embankment were studied respectively for concrete pavements and asphalt pavements by finite element method against the presences of large amounts of occurrent pavement diseases in permafrost region. The results of numerical analysis indicate that the maximum thawed depth under embankment of asphalt pavements is greater than the one of concrete pavements; and especially the maximum thawed depth differences between asphalt pavement and concrete pavement become greater under pavements for the embankment of 8.5m width. Both the maximum thawed depth and development rate of the maximum thawed depth are closely relevant to embankment heights and embankment widths. The effective measurements will be proposed to keep the thermal stabilities of highway embankment by the results and cut down the occurrences of pavement diseases and services costs. The results may also provide references for the future similar projects.

Based on Xi'an Subway Line 2, the settlement trough shape parameters are obtained by using three prediction formula to fit the measured surface settlement values. The fitting parameters and the " stiffness modification method " principle were carried out to forecast on the city wall foundation settlement induced by building subway under the city wall, meanwhile the three-dimensional finite element model of the city wall was established to do quantitative analysis of the ultimate deformation and bearing capacity. The results show that the Peck expressions can describe the character of the ground settlement well .And the ultimate settlement capacity induced of the city wall foundation shall not exceed 20 mm when considering creep and consolidation effect of the loess .This study is expected to provide a scientific reference to the ground settlement caused by underground construction and the response of buildings.

Excavation unloading, blasting vibration, rock rheology and rainfall are four main factors which affect the deformation of slope during the construction period. With deep analysis of different factors on the mechanism of slope deformation, a forecasting model of slope deformation based on the deformation mechanism is obtained according to slope displacement monitoring data. The formula of rebound slope deformation is derived under the simplification of the theory of elasticity which is used to calculate excavation unloading component; creeping constitutive equations based on Burgers model is used to calculate rheological component; and blasting component and rainfall component are calculated by using the existing empirical formula; the four deformation components are integrated to form forecasting model of slope deformation based on the deformation mechanism, from which a more scientific and reasonable explanation for the mechanical mechanism of slope deformation is got. The model has been used to conduct statistical regression analysis of monitoring data of the slope at the left bank of JinpingⅠHydropower Station. The results indicate that the proposed model gives a significant regression equation with small forecast errors; compared with traditional statistic models, the statistical multiple correlation coefficients and variance ratio are larger; thus the model has great application value

It is theoretically proved that the influence of model boundary the ground penetrating radar(GPR) data acquisition; and based on the theory, designing the physical model within the empty of tunnel lining, probing the model with 3D detection, then the visualization of 3D GPR detection data is realized. We analyze the features of the square hole in the different sections, based on the analysis of CL4 multi-wavelet theory, discuss the necessity of the multi-wavelet preprocessing, and process the CL4 multi-wavelet with balance, using Matlab to realize the CL4 balanced multi-wavelet threshold filtering algorithm; and comparing with the filtering effect based on the conventional Fourier transform. The results show that the 3D detection can determine the size and shape, also including location of the hole, understand the accurate information of hole comprehensive and meticulous, improve the reliability and accuracy of the analyses on radar map, evaluating the harm of hole in lining according to the size and location of defect. The conventional and CL4 multi-wavelet filter can distinguish the unusual target exactly; the target feature has been enhanced with the multi- wavelet transfer, therefore, it results to the cleaner phase axis, more thoroughly eliminate-noise, the same to signal reservation becomes more completely; and the picture also becomes more clearly. The implementation of 3D detection test for the tunnel lining automatic identification technology not only provides a reliable theoretical basis and method, but also has great significance to tunnel detection and quality judicatory appraisal

On-site tests in a nuclear power plant are performed to investigate the space distribution and correlation of dynamic parameters and static parameters. It is indicated that there exists a certain rule between dynamic parameters and depths, but not between static parameters and depths. And developed degree of cracks has an obvious influence on both the dynamic and static parameters. In addition, regression analysis indicates that there exists good correlation between dynamic and static elastic modulus. And the ratio of Ed and Es lies in the range of 0.9–2.19, but it does not change along with the depths. The research has important implications on geotechnical engineering designing and construction

In the light of the not unified present situation of the tunnel health criterion, using lab similar model test and combining with engineering practice, the failure law and ultimate bearing capacity of surrounding rock with supporting structure in the state of deficiency in lining thickness are studied; and the health criterion under corresponding force state is concluded. The results show that the displacement character of lining is spandrel inpressing and vault extruding; contact stress decreases gradually between lining and surrounding rock; structure bearing capacity gradually decreases with the deficiency in thickness increasing; with the displacement increasing and the structural flexibility increases gradually; the inside vault was crushed and the outside crazed as tension action; subsequently, the hance and side wall appear cracks and propagation and coalescence at last. The results show that the bearing capacity curve expresses S-shaped characteristics; it can be divided into slow, fast and complete degradation basis on the variety of velocity; and it is uniform to the health grades and levels of tunnel structures so as to provide reference for engineering application

Since 1990s, land subsidence accelerated again although net withdrawal volume of groundwater did not increase in urban center of Shanghai. Net withdrawal volume of groundwater in urban center, however, is not the crucial factor controlling the land subsidence. At the same time, more and more infrastructures, such as high and super-high rise buildings, deep building foundations, underground structures, subway tunnels, underground path structures, were constructed in the multi-aquifer-aquitard system (MAAS) in Shanghai. Land subsidence in Shanghai is correlated with activities of urban construction according to correlation anaylsis of land subsidence and urban construction. Investigation on urban construction induced land subsidence is now receiving a great concern. However, mechanism of how urban construction affects the acceleration of land subsidence in Shanghai has not been well addressed. This study was undertaken to evaluate the influential factors on the development of land subsidence with the process of urbanization in Shanghai. The influential factors include additional load consisting of static load and dynamic load during and after structures construction, underground structures construction involving foundation engineering and construction of tunnel, drawdown of groundwater level due to leakage of underground structures, decrease of recharged volume of groundwater from surroundings, and cut-off or partially cut-off effect of underground structures in aquifers.

The in-situ stress field evolution process, formation cause, formation time and evolution trend of deep fracture is analysed. Combined with deep fractures characteristic，tectonic evolution, valley evolution and near surface action theory, the formation and evolution process are summarized by stress field change and strain energy release with numerical simulation. The results show that: deep fractures in-situ stress field is fundamentally changed after vertical unloading; but deep fractures are not formed in this in-situ stress environment; the primary reason of deep fractures formation is lateral unloading and residual tensile stress caused by difference resilience; the formation time of deep fractures is about after Ⅲ terraces appearance

Based on the global positioning system(GPS) monitoring data from 2003 to 2008, tendencies of general deformation of the open-pit, No.1 Mine of Jinchuan Nickel Mine, are analyzed and compared according to spatial and temporal distribution; ground subsidence and horizontal displacement features of the mine area as well as the subsidence and horizontal displacement characteristics of the prospecting line varying with time are obtained. Deformation laws of rock mass due to transform from open-pit to underground mining in high stress area, where horizontal tectonic stress is dominant, are studied in comparison with deformation rules of the open-pit of transition period; theoretical analysis and numerical simulation are introduced to explain the reason of the difference. The results are conducive to understand the characteristics of rock mass movement and failure caused by transition from open-pit to underground mining and to guide safe production in mine area.

There has been success stories that granitic residual soil has been used to fill the embankment for expressways; however, the most stringent standard will be applied to high-speed railways subgrade cumulative deformation under the loads of moving trains of the track structure which locate on the substructure; that granitic residual soil can be used for high-speed railway subgrade has not been verified so far. Based on the granite residual soil and its improved soil mechanical properties and deformation characteristics, using PMS-500 cyclic load equipment experimental research on dynamic performance of granitic residual soil subgrade of Wuhan-Guangzhou high-speed railway in Qingyuan region of Guangdong Province were made to study the applicabifity of granitic residual soil for filling embankment and subgrade bed. The dynamic performance and deformation performance of improved granitic residual soil subgrade bed were analyzed under 5×106 cyclic loads with and without influence of the subgrade surface flooding, quality variation of the subgrade with and without influences of rainfall. It is indicated that all the dynamic indices and residual settlement of improved granitic residual soil subgrade meet the design requirements of high-speed railways; even though 6.7 m high improved granitic residual soil subgrade has been prolonged soaking saturated infiltration; its settlement is less than 7.0 mm so that the improved granitic residual soil could be used to fill the embankment and subgrade bed of high-speed railways.

The excavation of large underground caverns easily induces brittle cracking failure of high sidewall under high ground stress and other complex condition. Based on Mohr-Coulomb criterion and tensile strain criterion, a new composite tensile-shear yield criterion of high sidewall for large underground powerhouse was proposed. At first, according to the elastoplastic theory, associated and non-associated plastic flow rule were adopted independently for tension and shear yield. The calculation formula of this rule is deduced in detail in the finite difference method; and the dividing boundary of tensile and shear yield surface in stress space is determined. Then dynamic link library of the software is programmed adopting the C language; and the criterion can be used in the general software. Finally, taking the Lashiwa hydropower station located in the high geostress region for example, compared to FLAC3D own tensile-shear yield criterion, the results show that the tensile failure of high sidewall is obvious; and plastic zone and stress relaxation area is smaller by considering the tensile strain yield criterion; the proposed criterion can describe brittle cracking failure features of hard rock for high sidewall. Calculation of large hard rock underground caverns proves that the proposed criterion is reasonable.

When the construction of underground projects in alpine and gorge region is being conducted, different mountain slopes will have important effects on initial geostress distribution. In this paper, the initial geostress distribution of mountain at vertical and horizontal typical profiles were studied in the gravity field by numerical analysis, with conditions of slopes being 30°, 45° and 60°, respectively. After the comparison, it can be known that the calculated values of the vertical geostress which were obtained from direct depth of the mountains varied from the actual values greatly. The steeper the slope is, the greater the differences are. Then two caverns at different positions were set to excavation in the mountain, with slope of 45°in the computation models and the damage - fracture model of joint rock was adopted to analyze the rock stability for the two conditions. The results show that the damage degree of surrounding rock is very asymmetric; and the more close to the slope surface (or slope toe), then the more serious the damage degree is. Finally, the corresponding conclusions and recommendations are proposed.

The function and development of geological prediction are summarized. The misunderstanding of geological prediction and problems of various instruments are analyzed. The concept of geological prediction system is proposed. The contents of geological analysis technology of the tunnel area，prediction technology of bad geological bodies, and warning technology for close major geological disasters are illuminated. The steps of geological prediction system are as follows: the geological factors are classified by intricacy according to the conclusions of geological analysis technology and standards for intricacy classification of geological factors; different programs of geological prediction system are formulated for different geological intricacy degrees; and dynamic control on the site is considered. The geological prediction system is applied to an example of F3 weathered slots of Xiamen subsea tunnel. Finally, the development trend of geological prediction system is put forward. The purpose of this research is to improve the geological prediction work，make the geological prediction results really play a guiding role in the construction process on the site, so as to decrease the investment and casualties of the project to the best extent.

Upon rock-soil combinational geological condition in Qingdao, a summary is made to know the main supporting type for deep foundation pit in the area; and draw the conclusion that“ piled anchor in soil and anchor bolt shotcrete in rock” are in common use in such deep foundation pit. Taking two typical deep foundation pits of Licun station in Qingdao metro for examples, finite element method is used to do simulation calculation of the station foundation pits; and it is surely proved that pile-anchor and braced structures are well used in the area, especially in controlling horizontal deformation, the pile internal force and surrounding settlement. The work will greatly help the latter metro design in Qingdao metro construction and provide many ideas for the construction in similar geological conditions.

Evaluation of seismic stability of rock slopes is the important foundation for prevention of seismic unstability of rock and soil slopes. In view of the multi-source and fuzzy characteristics in evaluation process, by using engineering variable fuzzy set theory for reference, fuzzy variable evaluation model is applied to evaluate the seismic stability of rock slopes. First, by comprehensive consideration of the rock slopes internal structure and external natural conditions, six parameters including the characteristics of the geotechnical body, the characteristics of the neotectonics, slope height, slope angle, the annual average precipitation, site seismic intensity are selected as the indices for evaluation index system and established rating standard, then the weights of evaluation factors in the model are obtained from the index practical data discreteness by using improved entropy weight method; finally, by changing the fuzzy variable evaluation model parameters to evaluated seismic stability of rock slopes by linear and nonlinear, and obtained stability level by mean value. The method has been applied to natural slope and cutting slope instances. The results show that the fuzzy variable evaluation model results are reasonable and objective; and they have better reliability and stability so as to provide a new research method and idea for seismic stability of rock slopes.

As a new type of newly arisen nondestructive testing technology, the conduction of infrared imaging technique is based on changes of the objects’ temperature field, which is widely used in the detection of objects’ structure state, properties, internal defects, etc. at present. In order to explore nondestructive testing method for potassium silicate(PS) reinforced earthen ruins soil, adopting the disturbed soil collected from site of Jiaohe Ruins to make soil models, halves of which are reinforced by 10% PS; and the others are untreated. And to keep the PS reinforced soil models standing for 30 d under the condition of room temperature until being naturally air-dried. And then, a laboratory model test detecting the reinforcement effect of PS through infrared imaging is conducted. It is shown that the PS hinders the heat transfer process of soil; besides, there is difference in the infrared thermal images for the PS reinforced soil and the PS untreated soil, which provides a possible method to carry out the non-destructive inspection of the reinforcement effect for earthen ruins soil. Finally, field test that micro-penetrometer detected the PS reinforcement effect and the determination test of the thermal conductivity are conducted; and the test results show that the reason for the difference in the heat conduction performance of the reinforced soil and the untreated soil is that PS reinforcement decreases the thermal conductivity and enhances the mechanical strength of earthen ruins soil

Two kinds of ground treatment methods, gravel piles and dynamic replacement methods, are introduced, which are the most popular treatments at high fill foundation of airport in mountainous area. Comparative studies are carried out by the strength reduction FEM to analyze slope stability of 79-79? engineering geological profile in Kunming new airport under different ground treatments. Comparison between the outcome of stability analysis calculated by FEM and that calculated by simplified Bishop method is also implemented. Moreover, without reducing soil strength parameters, comparative studies of displacements and shear strains of the slope under different ground treatments are performed. The results show that the disposal of the relative soft foundation within slope toe with gravel piles or dynamic replacement method can not only enhance slope safety factor effectively, but also reduce maximum displacements and shear strains by leaps and bounds. Furthermore, safety factors and the most dangerous sliding surfaces calculated by the strength reduction FEM are close to that calculated by simplified Bishop method, when the most dangerous sliding surfaces are close to arc shape. And safety factors, calculated by the strength reduction FEM, are conservative as they are slightly smaller than those calculated by simplified Bishop method. Finally, gravel pile method is better than dynamic replacement method when the coating over moderately weathered bedrock is deeper than the treatment depth of dynamic replacement.

Wind erosion damage rules of desert highway are simulated using the Fluent software. The process of disturbance, acceleration, speed-down, and recovery of the sand flow that is obstructed by different highway cross-sections are analyzed. The influences of main cross-section design parameters such as subgrade (cutting) height, slope, and pavement width on the sand flow are determined; and the wind erosion rules of desert highway subgrade (cutting) are proposed. The results indicate that the influence of the pavement width on wind speed variety is slight, the changes of wind speeds at feature points are less than 5%; but the subgrade (cutting) height and slope have great influence on wind speed variety. The disturbance of sand flow field is reinforced with the subgrade (cutting) height increases, the wind erosion damage of subgrade (cutting) is more evidently. While the side slope is 1:1, the wind speed on the shoulder of windward when the subgrade model height is 250 mm is 1.15 times more than the speed when the subgrade model height is 60 mm, but the wind speed on the bottom of leeward slope decreases 45%; the wind speed on the shoulder of windward when the cutting model height is 250 mm is 1.05 times more than the speed when the cutting model height is 60 mm; but the wind speed on the bottom of leeward slope decreases about 80%. So it is suggested that the desert highway should use middle or low height subgrade (cutting) and shouldn’t be filled highly or digged deeply. While the height of subgrade (cutting) is certain, and the side slope is 1:1.75 or 1:2, the change of wind speed along the subgrade (cutting) is gentle; and the accelerate effect of windward shoulder and the speed-down effect of leeward bottom are inconspicuous. At this time, the subgrade isn’t destroyed by wind erosion and the leeward bottom of cutting isn’t changed by accumulation easily. The conclusions drawn from numerical simulating are consistent with the experiment results perfectly.

The impact of soft soil creep is not considered in surcharge precompression when determining height and time of surcharge preloading. This paper calculates the settlement of soft clay by using ABAQUS considering the effect of soft soil creep on Wuhan-Yingshan Expressway soft soil subgrade project. The relationship with different heights of surcharge preloading settlement and preloading time are analyzed, then compared with the measured results, it shows that the validation of considering the creep of soft soil in settlements prediction. The settlement of soft clay will increase with the height of surcharge preloading. Within a certain range, the height of surcharge preloading increases, the time of preloading will be shorter. But nonlinear relationship exists between each other; the existence of a best height of surcharge preloading makes the time of surcharge preloading shorter in the stability of the road foundation.

The soft soil foundation of the section K132+177～+258 of Langfang-Cangzhou Expressway in Hebei province is mainly composed of low liquid limit, middle-high compressibility clay layer, belonging to the type of coastal sedimentary deposit, which is treated mainly adopting static grouting. The test and laboratory studies respectively for grouting construction method of whole pore disposable and top-down segmentation tabulator in field are taken. On the basis of physical and mechanical properties of soft soil foundation and observation data of grouting test surface deformation amount, the diffusion processes of slurry in different grouting construction methods (whole pore disposable and top-down segmentation tabulator grouting) and different grouting pressures (0.5, 1.0 MPa and 2.0 MPa) are studied by using FLAC3D. The results show that the grouting effect of top-down segmentation tabulator grouting is better than whole pore disposable grouting in the same grouting pressure; and the increasing pressure is beneficial to grouting diffusion. But it would result flow-up of grout with the higher pressure. Therefore, we should choose reasonable grouting pressure according to the practical site situation

In order to study the acceleration distribution of high rock-fill dam, the dynamic response of homogeneous earth-rock dams over 100m were analyzed with three dimensional (3D) finite element method considering the height and slope of the dam，aspect ratios of river valley, dynamic shear modulus, peak acceleration and seismic waves. The results show that the 3D effect of dynamic response is apparent. The acceleration is significantly enlarged in the middle of river bed of the dam over 4/5 height and recommended distribution of the acceleration by the current code is inconsistent with response characteristics of the high dam. The reinforcement zone is suggested based on the calculation results of high dam.

The side-grouting uplift pile is a newly developed pile foundations. This paper aims to demonstrate the features of deformation and bearing capacity of this class of piles using experimental and numerical approaches. A series of large–scale direct shear tests were performed to show the effects of grouting on the behavior of pile-soil interface. Based on the experimental observations of the large-scale shear tests, the revised coulomb friction model is built and used in the finite element method. The bearing capacity and load-displacement curve for non-grouting and side-grouting piles are obtained respectively. The study results show that the side-grouting uplift pile possesses a larger skin-resistance because its deep critical skin-resistance can be fully developed. As a consequence, the side-grouting uplift pile displays a much higher bearing capacity than traditional uplift pile.

The sap engineerings have important function in war; at the same time,it is ease to be struck by cannonballs. In order to increase the protection capability of the sap engineerings, the basic theories and energy dissipation of wave are used for analytical research on rock deformation, energy dissipation during the process of rock friction and the propagation characteristics of explosive stress wave which passes through the interface between rock and air. Based on six conditions of normal working environment ,the numerical simulation results for the inspection nodes are simulated by finite element analysis software ANSYS—LS-DYNA . Comparisons with the theoretical analysis show that the unloading hole plays its role of reducing explosive loading. So that a new way for the protection design of sap engineerings is offered.

The drainage hole is an important seepage control measure, so it is one of the key problems to simulate the effect of the drainage hole in the seepage analysis. Although the substructure method is an effective and popularized method, its mesh generation, which is dependent on the global mesh, is still a difficult task in engineering practice. A novel method named superposed element method (SEM) is proposed to simulate the drainage holes. Firstly, the structure containing drainage holes is divided into two independent meshes. One is the global mesh without drainage holes, and the other is the local mesh of the drainage hole together with its adjacent zone. Then, the two independent meshes are coupled together through the virtual seepage on the outer interface of the local mesh. Finally, two numerical examples are studied, in which the effect of the drainage holes can be simulated accurately. According to the results of the sensitive analysis, the proper range of the local mesh is 1–3 times of the element length in the global mesh; and the permeability coefficient of the outer interface is suggested to be 102–103 times of the material permeability coefficient. Since the mesh generation of the superposed element method is quite simple, the new method is expected to be widely used to solve complicated seepage problems in engineering practice

Finite element methods are largely used in solving nonlinear geometrical and material problems. But standard finite element methods are ineffectively in handling extreme material deformation, such as cases of large deformation and severe mesh distortion problems in computation. Arbitrary Lagrangian-Eulerian (ALE) methods incorporate the advantages of Lagrangian and Eulerian methods and overcome their disadvantages. The methods can solve many problems which can be solved difficultly by Lagrangian and Eulerian methods. Based on ALE finite element methods and fundamental theory of elastoplastic large deformation, the soil slope stability problems of a simple soil slope and a complex soil slope with weak layer under self-gravity in geotechnical engineering are analyzed as the illustrative cases. The computational results show that the deformation behaviors of slope sliding and the critical slip plane can be defined clearly from the deformed shape obtained by ALE finite element method. The results show that the arbitrary Lagrangian-Eulerian (ALE) methods can effectively analyze the stability of soil slopes and be applied to the elastoplasticity analysis of geotechnical engineering.

Combined with swipe loading method and fixed displacement ratio method, the bearing capacity of suction caisson foundations subjected to horizontal and moment combined loading is explored through three dimensional finite element numerical studies. The effect of embedment to diameter ratio and soil strength nonhomogeneity on the H-M failure envelope of caisson foundations is investigated; and the soil deformation mechanism under various combinations of load components is shown. Through comparison with results under plane strain assumption, it is shown that the shape of failure envelopes of caisson foundations considering three dimensional effect varies from that under plane strain assumption; therefore to evaluate the stability of caisson foundation should account for the three dimensional effect. For nonhomogeneous soil, the failure envelope of caisson foundations with shallower embedment is negatively oblique. The equation of failure envelope available overestimates significantly the bearing capacity of caisson under this condition subjected to positive lateral and moment combined loading, and leads design of caisson foundation to unsafe side.

Grouted soil nails are widely used in the slope stabilization projects. It is of great interests to engineers and researchers to study the mechanism of the soil nail pullout resistance under different conditions. In this paper, a three-dimensional (3D) finite element (FE) model is developed to simulate the behavior of soil nail considering the effects of overburden pressure and dilation. The Mohr-Coulomb model is adopted to simulate the soil behavior. The interaction between the soil nail surface and the surrounding soil is modeled by Coulomb model. Contact pairs are used at the soil-nail interface so that the sliding failure can be considered during the pullout analysis. The model parameters are calibrated by the triaxial soil test data. It is found that the selected model can represent the soil stress-strain behaviour under different confining pressures. Large scale laboratory pullout test data are used to compare with the modelling results and verify the model. The soil stress variations surrounding the soil nail before and during pullout are demonstrated in FE modelling. Parametric analysis is carried out to investigate the effects of soil dilation and overburden pressure on the soil nail pullout resistance. It is found that the effect of interface soil dilation under small overburden pressures is not so significant as that under OP = 200 kPa and 300 kPa.

Humidity diffusion plays an important role on the deformation of water-sensitive rock in underground engineering. It is not only changed the stress state of rock mass, but also greatly weakened the physico-mechanical properties, which enhanced its time-dependent deformation. By introducing the humidity diffusion in numerical model and establishing the relationship between mechanical response of rock and the humidity diffusion, the numerical model is able to simulate the time-dependent deformation of water-sensitive rock. Numerical simulation of humidity diffusion in tunnel with support system shows that: humidity changes only occur on the surface of tunnel at the beginning of excavation, where the deformation induced by humidity is small but the deformation rate is great. With the humidity further diffusion, the deformation of tunnel increases but the deformation rate decreases, and eventually converges. Numerical simulation represents the stress evolution process of anchors, and the increase of tensile stress in anchors shows its effect on deformation of rock mass. The humidity diffusion reduces the strength of rock and induces rock failure. Failures not only cause the local stress concentration, but also enhance the humidity diffusion in rock mass. It is shown that the humidity diffusion and failures (damage) is an interactive process, namely the humidity-stress-damage coupling.

Process of shield driven in Tianjin Metro Line No.1 project is simulated by means of finite element method. Pressures and shearing forces are enforced on the soils to simulate the real reactions between shield driven machine and the surrounding soil during tunneling. Results from the model adopted here by the finite element method are fine agreement with those acquired in the Tianjin Metro Line No.1 project. Researches on the effects of shield driven tunneling on the pile foundation nearby are carried out with this model. The settlement at pile top and displacement along pile caused by shield driven tunneling nearly reach their maximum values during the process when the shield driven machine is approaching the pile; when it is leaving away from the pile, the increments of settlement and displacement are small. Under the same conditions, settlement at the top of long pile is small because the side resistances at the lower part of long pile can be exploited to a great extend. During the process of tunneling, pile with the length of 12 m inclines while piles with the length of 16m and 19 m bend and the maximum moments are at the position 12-13 m below the ground. During tunneling, there are back and forth displacements at pile top along the direction in which the tunnel is pushed forward. The greater the load applied at pile top, the larger the settlement caused by tunneling at pile top

The discrete element method (DEM) simulation of discs leads to typically low internal friction angles compared with real sand. The paper introduces a developed discrete element program NS2D, of which the subject is two-dimensional assemblages of elliptical particles. The basic contact models of the developed NS2D program are described; and the force-displacement formulations of the contacts of ellipse-ellipse and ellipse-wall have been deduced. Assemblages of elliptical particles with aspect ratio1.1:1 and 1.4:1 were generated with undercompaction method (UCM); then consolidated isotropically, and then sheared with biaxial compression at constant confining pressure, respectively. Their mechanical responses are both qualitatively and quantitatively in good agreement with the reported literature; and the simulated internal friction angles fall within the typical range of real sand. Therefore, the developed DEM program NS2D can be used to study the mechanical properties of real sand.

According to rock character of a certain soft rock tunnel of Chongqing, the model material is made from epoxy resin, polyamide, silicom rubber, firming agent of silicon rubber, quartz grit, powdery barite and gasoline. The physical model test of the unreinforced tunnel and bolt-reinforced tunnel are made in the true triaxial model test machine. By using strain measure technology, the strains of key parts of the surrounding rock and the bolt are measured; according to these data, the variability of the stress of surrounding rock and the variability of the axial force of the bolt are analyzed. The numerical simulation are made with the same boundary condition as the model test; according to these data, the plastic zone, stress field and the deformation of the surrounding rock are studied; the variation of the axial force of the bolt is studied. We compare the variation of stress of the surrounding rock and the variation of the axial force of the bolt of the model test with the numerical simulation and draw the conclusion that the two processes coincide with each other.

Numerical simulation (FLAC3D) and field experiments are used to study the shape effect of tunnel section. Stress of primary support and tunnel deformation under horseshoe-shaped section and large curvature wall, quasi circle-shaped section are analysed and compared. Numerical simulation and field measurement indicat that deformation and deformation rate of surrounding rock under quasi circle-shaped section could be effectively lessened, especially convergence of side wall, compared with that under horseshoe-shaped section. Ratio between lost displacement while measuring in-site and total displacement of surrounding rock is large, and the lost ratio of lower bench is largest. Field experiments of different support stiffnesses are conducted. It is measured and analysed that pressure of surrounding rock mass, axial force of anchor, stress of steel frame and stress of shotcrete under different primary support parameters. Also the contact pressure shared by secondary lining and the stress of mode concrete under different primary support stiffnesses are measured and analysed. Deformation of tunnel under different support stiffnesses are also measured. It is concluded that the contact pressure of secondary lining and pressure ratio shared by secondary lining increae with support stiffness increase. And suitable support form is synthetically determined. That would offer valuable practical experience to tunnelling in soft rock mass with high tectonic stress-field.

When the direction of soil principal stress rotates during the shearing process, there is a non-coaxial phenomenon between the direction of principal strain rate and principal stress; but the conventional elastoplastic constitutive model could not take this phenomenon into consideration. In order to reflect the non-coaxial phenomenon, a non-coaxial plastic strain rate term is added to the tangential direction of conventional constitutive model’s yield surface. The non-coaxial model is numerically implemented into the finite element analysis of suction bucket foundation bearing capacity with automatic substepping scheme and explicit integral algorithm; and then the relation between non-coaxial model and some factors, such as flow rule, friction angle and dilation angle, is researched. The results show that this model could obtain reasonable convergence accuracy with FEM software’s default allowable error; and it is available to the associated and non-associated flow rule. The influence of different flow rules on the numerical result could be neglected when the conventional coaxial model is used into the numerical analysis. But there is difference between the results of different flow rules when the non-coaxial model is used. The non-coaxial phenomenon has a softening effect on the bearing capacity-vertical displacement curve; and this softening effect would be more apparent when the non-associated flow rule is used.

The geocell flexible retaining wall is a new type of retaining structures for the slope protection; and it is widely used in highway engineering. The earth pressure against flexible retaining walls is closely related to the mode and amount of wall displacement. By employing the FEM software Plaxis, the deformation laws of geocell flexible retaining wall under different conditions are investigated. The effects of height-width ratio, slope ratio and surcharges on the deformation behavior of the flexible retaining wall is computed and analyzed. The study results show that when the height-width ratio is relatively large, the amount of horizontal displacement and flexural deformation of the wall is also large. And the shape of the wall back is an outer convex parabola. With the decrease of the height-width ratio, the amount of horizontal displacement and flexural deformation of the wall reduces and the shape of the wall back changes in turn. The amount of horizontal displacement of the top of the wall is large when the slope is steep but rapidly decreases when the slope becomes gentle. With the increase of the surcharge on the surface of the slope top, the amount of horizontal displacement of the wall top gradually decreases; while that of total wall displacements and flexural deformation gradually increases. The study results in can provide theoretical basis for the evaluation of the earth pressures against the geocell flexible retaining wall and thus have reference value for the design of such retaining walls

This paper presents an application of three-dimensional finite difference software FLAC3D to evaluate the efficiency of several treatment measures for shaft rupture induced by dewatering settlement. The treatment measures include steel set and shotcrete, grouting injection through fractured wall, surface grouting, and stress release slot in the inner shaft wall. The results indicates that the steel set and shotecrete method is suitable for emergency handling and preventing concrete collapse, but not suitable for long-term stability support. On the other hand, the injection through the shaft wall can control the displacement difference between the wall and soil to some extents. Therefore, this method, especially grouting before shaft rupture occurs is efficient for preventing shaft fracture. The surface grouting method has a good performance for solving the problem of shaft rupture. However, the locations of grout holes have significant influence on the efficiency of grouting under the same number of the holes. The stress release slot method can absorb the vertical strain and restraint the development of shaft rupture effectively. It works better when it is cut above the ruptured position. These results are helpful for the design and construction of shaft rupture treatment

Usually in the area with dense and intensive buildings, the construction of shield tunnel will influence the subsiding of adjacent building. In view of the structure’s different foundations, FEM is adopted in this paper to study and simulate on shield tunnel construction of adjacent structure. It is indicated as follows: With different forms of building foundation, their influence on tunnel lining’s force status are different. Tunnel lining undertakes greater internal force during the construction of nearby shield tunnel. In the condition of shallow foundation, tunnel excavation takes more affect on the building. But adjacent base side of tunnel excavation internal force changes relatively samll in building with pile foundation

A micro-bond contact model[1–2] proposed and verified by Jiang[3–5] et al. is incorporated into PFC2D developed by Itasca. Then biaxial test is carried out to simulate the mechanical properties of deep-sea energy soil; and comparison analysis with the triaxial test done by Masui [6] et al. is done. The results show that the macromechanical properties of deep-sea energy soil and the influence of gas hydrate can be reflected through the micro-bond contact proposed by Jiang [1, 2] et al.; and the existence of gas hydrate has some contribution to the strength of deep-sea energy soil.

Adjacent overlap multi tunnels are a complex spatial distribution form with the unceasing development of the metro construction. Relying on the project of Wuhan metro line 2 and line 4, for four adjacent and overlapped shield tunnels, 3D FEM is applied to analyzed the ground deformation law caused by dynamic construction of tunnel and the influence of latter tunnel excavation on former tunnel. The results show that the buried depth has a remarkable effect on the ground deformation; the final deformation caused by the construction is 32 mm, which beyonds the standard limits; the larger the buried depth is, the smaller the ground deformation is, but the larger the influence range is; for the ground deformation, the influence range to the ahead is 30 metres, to the back is 25 metres, and the influence range to the transverse for each side is 30 metres; for the tunnel deformation, the top and the bottom are compressed, the left and the right are outward-spread, so the tunnel changes into a inverted duck egg; the tunnel deformation occurs mainly near the cutter of the shield machine, whose range is around 1D, and it becomes steady quickly; the tunnel settlement mainly depends on the construction of the tunnel itself and the vertical tunnel, the construction of adjacent tunnel has major effect on the lateral displacement; the latter tunnel excavation has a great influence on the force of the former tunnel. The research results can provide some references and guidance for Wuhan metro and similar projects in the future.

Lunar soil can be classified as silty sand according to its particle size distribution. The Lunar environment is quite different from on the earth (such as with no water, low gravitational fields, very low atmospheric pressure, etc.). The Van der Waals forces between soil particles proposed by Perko et al. (2001) is taken into consideration in the simplified lunar siol contact model, which is then implanted into PFC2D. With this model several biaxial compression tests are simulated by the discrete element method (DEM). The effects of Van der Waals forces on the mechanical behavior of samples and the average coordination number of samples are then studied. The results show that the Van der Waals force is a very important factor in controlling the peak strength; and it will lead to extensive dilatancy of the samples.

The extended finite element method (XFEM) is proposed for discontinuous problems. It is widely used to solve discontinuous problems due to the independence of computational meshes and discontinuous interfaces. Therefore, the preprocessing that transforms discontinuous interfaces and computational meshes geometry information to topological information becomes precondition of this method. According to the application of two-dimensional XFEM to discontinuous rock masses problems, generation of mesh and topological information of elements are studied. Two-dimensional preprocessing program is developed according to the algorithm of automatic generation of topological information. The geometry information of interfaces and meshes is converted to topological information which is needed in the computation. The results demonstrate the applicability and correctness of the program. In addition, the promising potential of the XFEM application to discontinuous rock masses problems is proved

The shear strength parameters of rock masses are generally most important and difficult to determine when performing stability analysis of rock works. Due to a large number of limitations existed in laboratory and in-situ experiments and uncertainties of empirical methods display, there has been a strong need to develop a new in-situ testing apparatus that can measure the shear strength parameters of rock masses in a quick and reliable way. Since a Rock Bore Shear Tester (RBST) made by Handy Geo. Instruments, Inc. was introduced by IWHR, a large number of laboratory and in-situ RBST experiments have been performed. The shearing mechanism, numerical simulation of RBST shearing process and its applications to Xiangjiaba dam site are presented. It can be found from the numerical analysis and in-situ testing results that RBST is applicable to soft and intermediate hard rock masses. The cohesion and friction angle determined by RBST are generally less than those determined by tri-axial and direct shear tests. In addition, the interal friction angle determined by RBST is a little less than that determined by triaxial and direct shear tests when <40?; and the cohesion c is considerably less than that determined by triaxial and direct shear tests by 25%-50%.

The cone penetration test(CPT) can’t be used in harder soil such as loess or in deeper soil because of the higher cone resistance and the limited capacity of the equipment of CPT. Cone’s being smoothly pushed into the ground is prerequisite for applying probing technologies in harder or deeper soil. By theoretically analyzing the forces on the cone, the theoretical equations of total cone resistance and torque, excluding wall sided frictional resistance, is established, in which all the influence factors are given. Meantime the mathematic equation to determine the friction coefficient between the soil and the cone is deduced from the theoretical equations of total cone resistance and torque. In addition, the laboratory rotary cone penetration test (RCPT) is carried out. The validity of theoretical analysis is proved. According to the results of RCPT for the samples with different water contents and different dry densities, linear relationship exists between the toque and the total cone resistance on the cone. Although the calculated value of friction coefficient between the soil and the cone based on the results of RCPT is much greater than that of internal friction coefficient of soil, its relevance to the internal friction coefficient of soil appears in some extend. The reason why the lower total resistance acts on the cone when the cone is simultaneously pushed and rotated than that when being only pushed is given by taking account of property along the vertical different from that in the horizon plane of soil and existence of frictional resistance between the cone and soil.