Based on in-situ monitoring of the duct-ventilated embankment, the crushed rocks embankment, the embankment of crushed rock slope protection, the thermal-insulation treatment embankment and the common embankment along Qinghai-Tibet Railway in permafrost regions, the embankment deformation and the change of ground temperature under these embankment are analyzed. It is found that the embankment deformation are of behavior of settlement and closely related with the change of ground temperature under these embankment. After 2-3 freezing-thawing circles, the deformation are tending towards stability in the duct-ventilated embankment, the crushed rocks embankment, the embankment of crushed rock slope protection and the thermal-insulation treatment embankment; but the settlement of common embankment is not stable yet. Meanwhile, the deformation difference of the right-and-left shoulder of embankment is still existent and changed with different embankment types. Based on above-mentioned analysis, we also can obtain a revelation that the compressive deformation of warm frozen soil due to rise of ground temperature under embankment may cause bigger settlement of embankment, maybe it will be one of main reason to result in embankment failure in permafrost regions with warm and high ice content; we should pay much attention to it.

It is well known that due to the strain softening behavior, the strain localization along with shear band formation will occur in the dense sand subjected to shearing under drained condition. In numerical simulation there are quite a lot of issues should be solved, such as how to simulate the strain softening behavior of dense sand and how to avoid the divergence problem in finite element analysis, and more over how to deal with the discontinuous of stress. The above mentioned issues are discussed in detail.

A quasi-plane strain experimental device is designed. This device is implemented to analyze deformation localization phenomenon of Chongqing red mud-sand stone in quasi-plane state. Some specimens are tested in various loading speeds; and some are researched with different water contents. During the experiment, the onset of deformation localization has been monitored by elastic wave. The results show that, in quasi-plane strain state, there is a logarithm-like relation between the angle of localization band and loading speed. It is also shown that the water content could impact on the onset of deformation localization.

The soil static and dynamic universal triaxial and torsional shear apparatus recently facilized in Dalian University of Technology is employed to perform experimental tests on flyash with relative density of Dr = 60 % under three-directional anisotropic consolidation subjected to cyclic torsional shear loading. Through a series of soil tests, the effects of initial intermediate principal stress coefficient on dynamic shear modulus and damping ratio of medium-dense fly ash are investigated systematically. Based on the specialty of the apparatus, not only the precision of experiment can be improved by using the small angle displacement sensors and large angle displacement sensor installed in the triaxial cell, but also the whole changes of dynamic modulus and damping ratio with amplitude of dynamic shear strain can be obtained continuously.

The unified strength theory is a new theory system which can almost describe the strength characters of most geomaterials and has been applied widely. And FLAC3D is an excellent geotechnical program. If the former can be integrated in the later, many complex problems in engineering will be settled well. So according to this problem, the numerical scheme of elastoplastic unified constitutive model in FLAC3D was studied. And the numerical format of the elastoplastic constitutive model based on the unified strength theory was derived. The corresponding UDM interface codes were programmed. Finally, a circle tunnel case is analyzed using this program. The corresponding simulated results are presented and compared with the analytic solution. The comparison expresses a good agreement with the analytic solution and verifies the validity of the numerical scheme and the codes. The merits of the unified strength theory and the FLAC3D program will be utilized well in geo-engineering after their combination.

A pair of dynamic tests was performed on pile-group foundation models under both uniaxial and biaxial shakings, by use of the biaxial shaking table at the HKUST centrifuge. By comparing the bending moments developed on the piles, it is found that the symmetric property of pile-group foundation response observed under the uniaxial shaking does not exist any more when under the biaxial shaking. The results of numerical tests using PFC2D provide some explanation to the phenomenon of orthogonal loading effect. At the same time, the limitation of currently used analysis methods for soil-pile interaction is pointed out based on some derivation. The paper presents the preliminary study on soil-pile interaction under multidirectional horizontal loading, so as to provide basis and reference for further study along this line.

Considering the elastoplasticity of surrounding rock, and introducing into the birth and death elements in the finite element program, a 3-D simulation model of surrounding rock which can simulate the boring process is established; and the distortion model of surrounding rock of deep tunnel is obtained. Based on the distortion model of surrounding rock, and adopting the contact model and Coulomb friction model to simulate the nonlinear connecting effect of segment joint, a 3-D simulation model of TBM tunnel segment structure is given to analyze its stress and strain characters during different working stages (construction stage, application stage, overhaul stage), different rock types and different lining times. The results can provide the basis for water diversion tunnel’s timely lining and safe running.

Bit climbing method is introduced into genetic algorithm (GA) to improve generalization ability, calculating speed and precision of GA. Then this improved GA is used to identify the rheological parameters for materials of high rockfill dam with core wall of Nuozhandu Hydropower Station. Rheological parameters of various dam materials in different holes are identified, and the calculating results using the identified parameters perfectly agree with the tested data. Results also show that rheological parameters of different dam materials greatly differ from each other; so systematic experiments for all the dam materials are necessary. Also, there are some differences among rheological parameters of different dam materials, which may mean that various confining stresses influence the structure of dam material differently.

During shield construction there are many segmental partial ruptures caused by construction factors which is already confirmed by engineering practices. The segmental mechanical characteristics during construction stage are presented firstly; and then common local ruptures of segment concrete are summarized; and leading causes are analyzed. And based on which mechanical model for construction stage is developed. The model can be described as a fixed-simple component which one end is anchored by clotted grout and the other end is supported by shield sealing brushes. In order to study the segment mechanical properties, a shield tunnel as an example is analyzed; and several cases are simulated by FEM; then comparison between FEM results and field measurement values is made. Study has manifested that most segmental ruptures are located at the fifth ring to the seventh ring which is approximately same to in-situ rupture position of segment. In addition, thrust force and its obliquity and partial difference are the main causes leading to segmental rupture. Finally, some items are suggested to lighten local ruptures of segment during shield construction stage.

Limit equilibrium analysis method is used to estimate slope stability in common. And abundant experience has been accumulated in long time practice. However, a weakness of limit equilibrium method is that uncertainties of parameters and models can not be considered. And its application would be influenced in practice. Uncertain and correlative problems in slope system can be solved effectively by reliability theory. But the partial derivative of performance function is hard to be calculated. The reliability analysis method is inconvenient to be applied in practice. So as to solve the deficiency, a numerical computational method based on dual function approximation is developed. In a rectangle area, an incomplete dual quadratic polynomial which is constructed by Lagrange method is used to approximate the performance function. Then its partial derivative can be calculated approximately; and the mean and deviation can also be obtained. So the reliability index and failure probability can be calculated by the first-order second-moment method. Mabaoying landslide in Enshi region of Hubei province is used to be a case study. It shows that the results with first-order second-moment method based on dual function approximation is consistent with the results by the push method and Monte-Carlo method; and it can be satisfied the engineering requirements in practice.

Soil mass is treated as rigid blocks with slip contact models, active earth pressure distribution on rigid retaining wall is simulated by particle flow code (PFC2D) program under certain displacement of different wall movement models: translation(T), rotation about bottom(RB), and rotation about top(RT). The simulating results of model test show that the active earth pressure distribution on rigid retaining wall is nonlinear; and the out friction angle between soil and retaining wall, as well as the soil shear angle are significant effect on active earth pressure. The resting earth pressure is larger than the active earth pressure in 0.3 times height of retaining wall from the top, as result the soil arching is formed. At last the calculation values are in consistence with model test ones very well; so the method presented has theoretical value.

A bias factor is commonly used to account for the effect of differences in failure criteria on reliability of pile foundations. There are however, hidden statistical dependencies between the bias factor and the underlying random variables. It is not reasonable that the statistical parameters of bias factor are directly adopted for reliability analysis of pile foundations. This paper aims to propose a new generalized bias factor based on the linear regression theory. The Spearman rank correlation method is used to perform the check of statistical dependencies. Finally, a numerical example is investigated to illustrate the effect of such statistical dependencies on reliability of pile foundations. The results indicate that the statistical dependencies between the bias factor defined by previous studies; and the underlying random variables can be removed using the proposed definition of bias factor. Such dependencies have a significant influence on the mean of bias factor, but they have hardly influence on the coefficient of variation of bias factor. Reliability indexes are also influenced by such dependencies. Therefore it is recommended that such dependencies be removed so that reliability of pile foundations can be evaluated in a more rational way.

It is a kind of complicated geo-engineering surveying the weakness area of anti-seepage within surrounding rock masses of water-diversion system of a pumped storage power plant. In order to avoid the uncertainty involved only by one method, four methods, i.e. ?-ray radioactive determination, resistivity exploration, natural tracer and water quality analyzing method, were used in this case study. Essentially, the former two methods are based on geophysics, while the latter two ones are on geochemistry. According to the results, it is believed that some weakness areas of anti-seepage indeed exist within the domain. They were remarked with negative abnormal ?-ray density, lower resistivity, water chemistry mostly in coincidence with one as its recharge source, and others. As to the formation, it is resultant from the coupled action of multi-fields, in which hydro-dynamic and geochemical action are mostly active.

In consideration of coupled influence among soil- structure-fluid interaction, static and dynamic analysis of buried pipeline system conveying fluid is investigated by employing the traveling wave method. The dynamic analytical model of the shallowly buried pipeline is established based on soil-structure interaction (SSI) and fluid-structure interaction (FSI) theories; and the static and dynamic formulations are deduced by applying the equilibrium condition of forces. The analytical results are obtained by employing the traveling wave method. Based on the above work, the stress characteristics of the buried pipeline under fluid impulsive excitation are studied. Analysis results of numerical examples indicate that FSI can cause bigger stress level in the shallow buried pipeline. The stress amplitude of pipe under FSI has a remarkable change with the less amplitude variation of the fluid pulsation. In addition, the influences of embedded depth H, soil property and pipe radius R on pipe stress are discussed. Under the same impulse excitation action, the pipe stress reduces with the increasing of H, the soil spring stiffness and pipe radius R.

Strength and stress-water content-strain relationship of unsaturated soil is studied experimentally. Firstly, strength and deformation tests are done, which simulate the project characteristic that pore air pressure dissipates very quickly and water pressure does not. Secondly, a total stress strength formula is suggested by researching the relationship between the strength and water content. Finally, a nonlinear model is presented on the basis of the relationship between the parameters under different values of constant water content. A case study shows that the model is reasonable. The use of the theories of unsaturated soil has been limited because of the difficulties in measuring and calculating suction. The presented approach, choosing water content which can be gained easily in project, can solves this problem effectually.

The four hydropower tunnels of Jinping II Hydropower Station are mostly over burden of 2000 m, surrounded by more than 44.2MPa high initial stress and 10MPa pore water pressure. It is a great challenge for designers to determine the acceptable minimum interval under extremely complex geological conditions. So a integrated criterion for determining acceptable minimum interval is proposed according to (1) the plastic zone connecting or not; (2) the inflexion of displacement curve of key points in tunnel. (3) convergence displacement not exceeding the state specification. With above guidelines, the theoretical minimum interval of tunnel of 50 m is obtained, by hydro-mechanics coupling numerical simulation. At last, the modified result of 52 m is recommended for the acceptable minimum interval according to engineering analogy analysis of several typical deep tunnels. The conclusion shows that the design interval of 60 m at present is reasonable.

According to the characteristics of loess subsidence, the external factors such as water content and load and internal factors such as microstructure and mechanics features are analyzed. Deformation mechanism of loess subsidence is deeply researched according to the theory of microstructure un-stability. It is found that the primary causes of loess subsidence are changes of forces on the microstructure and water content after soaking, Through the analysis, it is discovered that steadily of microstructure model has enormous relatedness with the stiffness and force state of the model .When the connection rigidity reduces, the structure loses its steadily.

Natural soil deposits always exhibit strength anisotropy in some degree, however, few slope stability analyses by finite element method have considered the effect of anisotropy until now. Here the variation of soil cohesion with direction of main principal stress was linked into the material library of commercial finite element package ABAQUS, and the shear strength on every integration point was updated dynamically in increment-iteration calculations. Furthermore, the finite element method for anisotropic slope was developed with searching automatically for the factor of stability. Based on numerical simulations performed, it is observed the finite element results are close to that from upper bound limit analyses for homogenous slopes. If soil anisotropy is omitted and the strength from triaxial compression tests is used to evaluate slope stability, it tends to overestimate the safety factors of gentle slopes, especially when the value of cohesion in vertical direction is great. Finite element model with updating strength owns advantage over limit analyses in studying layered slopes.

According to the basic equation of dynamics, using FEM and NEWMARK implicit algorithm, an elastoplastic numerical analysis is made to analyze the effect of hidden holes in loess on the dynamic deformation response of pavement structure. In order to reduce the effect of wave reflecting on artificial boundary, transmitting boundary and semi-infinite element are respectively used to treat the lateral and underside boundaries. The cycle of dynamic load and the diameter and depth of hidden holes in loess are the mainly considered three factors. Finally, based on the numerical calculation results, their effect laws on deformation response of pavement structure are analyzed.

Dynamic responses of a multilayered site with saturated soils are computed by using the exact dynamic-stiffness matrix of layer and halfspace. The calculations of free field response (incident P and SV waves), Green’s functions and dynamic stiffness of strip rigid foundation are presented. The site model is more close to the real site. The degenerated results of this study are coincided with that of dry site. The influences of permeability of saturated soil on the dynamic stiffness of foundation are studied; and the results are compared to that of the corresponding dry site. The numerical studies indicate that the permeability conditions have an significant influence on vertical spring coefficients. It is shown that the porous fluid plays an important role in dynamic response of multilayered site with saturated soils.

Based on the general solutions of Biot’s wave motions of transversely isotropic saturated poroelastic media established by the author，the vibration attenuation at ground surface under the point harmonic excitation is researched. And the combined effects of the soil permeability and the loading frequency on the results are analyzed. The calculation results indicate that the characteristics of vibration attenuation of vertical displacement under the low and the high exciting frequencies are different obviously. Of all the parameters of transversely isotropic saturated media, the rates both in osmotic coefficient and in elastic constants between vertical and horizontal direction influence the vertical vibration attenuation mostly. The results also indicate that adopting dynamic model of isotropic saturated medium could not describe exactly the dynamic characters of the saturated poroelastic medium that has obviously anisotropic properties.

Based on a series of laboratory consolidation tests, the consolidation behavior and structural character of aeolian soil are discussed. The tests show that the aeolian soil represent different compressibilities in different variant conditions; it reflects mainly in e-p compression curve. The e-lgt curve is different obviously from saturated clay; it mainly because they have different microstructure and structural character. At the same time, there is a significant correlativity between the coefficient of consolidation and the consolidation pressure. Furthermore, it shows that the aeolian soil has special structural character by comparing the soil in Fuxin with the soil in other areas.

The practical investigation and theoretical analysis indicate that the soft rock-soil has rheological characteristics; the dynamic loading can accelerate rheological action of soft rock-soil, and become the important factor and primary power which induce geotechnical engineering disaster and geological disaster. The dynamic rheological characteristic of sludge soft soil are tested; the dynamic viscoelasto-plastic rheological model and rheological equation are established; and the expression of dynamic rheologic parameters are deduced. The dynamic rheological parameters of sludge soft soil are tested under dynamic shear action; the influential characteristic is analyzed that the factors such as dynamic shear frequency, shear strain, water content of sludge soft soil, etc. effect dynamic rheological parameters of sludge soft soil. The research results have actual significance for us to open out the influence disciplinarian of rheological mechanism characteristics and rheological parameters of sludge soft soil under dynamic loading. It has also important academic significance for us to find out rheological dynamics of soft rock-soil bursting out geotechnical engineering disaster and geologic disaster.

Overlength pile foundation is successfully used in more and more civil engineering, but the study on its behaviour is still very little. Based on an example of a large-scale overlength pile group foundation engineering, the behaviours of overlength single pile and pile group foundation are investigated using nonlinear three-dimensional finite element method (3D FEM). A hexahedron isoparametric element with 8 nodes is employed in the finite element model of pile, foundation slab and soil. A special thin element with a very little thickness is used to simulate possible nonlinear deformations between soil and pile. Linear elastic-model and nonlinear Duncan-Chang elastic model are used to simulate the constitutive relation of concrete of pile and foundation slab, and soil mass respectively. The course of building foundation slab is simulated by adding elements in calculating, and that of hardening concrete of foundation slab is simulated using the method of increasing its modulus. Calculating results indicate that the behaviour of overlength single pile is frictional, and its failure is the result from the failure of soil around pile firstly. In group pile foundation, many clear differences in behaviours of piles can be found among the piles located in different positions under the foundation slab, especially between the piles near the edge of foundation and ones in the centre of the foundation. The behaviour of side pile near the edge of foundation slab is almost same with that of single pile, but apparent difference from that of centre pile. Reduction factor of pile group can be obtained from both current technical code for building pile foundation and calculating results of 3D FEM. The large difference in the reduction factors of pile group from the two methods indicates that it is necessary to investigate further the behaviour of overlength pile group foundation, because the current technical code isn’t enough for the designation and construction of overlength pile group foundation, especially for larger-scale overlength pile group foundation.

Method of determining parameters in Wu-Bauer hypoplastic model and its defect are discussed. According to simplex designs in optimization, amelioration of parameter determination is made. The method is proved by virtue of triaxial consolidated drained test, oedometric test and load -unload test. It is shown that this method can ascertain the parameters. The merit and demerit of Wu-Bauer hypoplastic model are analyzed.

The reasonable utilization of polycrystalline diamond compact(PDC) bit cutters has an impact relation with exerting its technical advantage. At first, a brief review of drillability mensuration and grade criterion of PDC bit cutters in China is introduced. Secondly, a brief introduction to laboratory test, analysis and processing of experimental data, some qualitative and quantitative conclusions are recited in detail. Finally, from the practice, some reasonable essential techniques and fundamental for choosing and using PDC bit cutters are brought forward based on the collective function of cutting rock, inosculation between rock and cutters , and the parameter of drilling technology.

The discontinuous deformation analysis (DDA) method embedded with viscous boundary condition is used to simulate blasting wave propagation in jointed rock mass. The effect of the joints on wave propagation is studied; and the results show that the joints existing in rock mass are beneficial to wave attenuation. The more joints rock mass contains, the stronger wave reflection is, and the weaker wave transmission is. A field test of underground blast is numerically investigated; the simulated results are compared with the test data; and the law of blasting wave propagation and attenuation is obtained. The results indicate that DDA is applicable to simulate the propagation and attenuation of blasting waves in jointed rock mass.

The concepts, testing measures and changing rules about the structural strength of loess are described respectively. According to the relationship of power function between structural strength of loess and water content, as well as the collapsibility coefficient and water content, a linearly fitting formula between structural strength and collapsibility coefficient is found out. Furthermore, the impacts of structural strength on the collapsibility coefficient of loess are analyzed. The results show that the value of structural strength and collapsibility coefficient will be smaller when the value of initial water content is bigger. But when the initial water content is same or near, the collapsibility of loess will diminish with the structural strength increasing.

A high efficient direct integration method is proposed for evaluating the variation effect of nonlinear numerical simulation results of geomechanics subject to multi-random parameters. In this method, taking the interested results as stochastic implicit response variables, firstly the integration points are determined by the multidimensional integration theory and direct integration reliability analysis method. Then the sample points are calculated by using the numerical simulation software; and then high order probability moments of response functions are evaluated by integration subroutine; at last the numerical probability density function of response variable then the confidence interval is obtained from several proposed method including curve fitting method, the weighted residual method and the maximum entropy distribution solver software developed by the authors. The numerical examples show that this method has higher accuracy and the computational efforts are reduced.

The zero thickness interface element, which based on the framework of elastoplastic constitutive model, is convenient to implement in finite element code in the similar way as used for small-displacement material nonlinear problem, and is used widely to analysis the interaction between soil and structure. The integration algorithm of constitutive equation is a key issue for finite element computation. The integration method for three kinds of contact behaviors is discussed based on the non-associative or associative linear elastic perfectly plastic model, yielding with Mohr-Coulomb failure criterion. A pair of pseudo yielding function and potential function is introduced, in order to renew the stress that violate the yielding criterion and locate in the apex area of yielding surface. According to this method, a self-adaptive sub-stepping integration algorithm using back-Euler method is implemented in ABAQUS user defined element subroutine. Two examples are analyzed, using this code, to examine the ability of this algorithm to model three type interaction behavior. The results, which agree well with theory’s and limit analysis’s ones, show that the algorithm is effective.

The internal friction coefficient ( )of sandy soil exactly exerts influence on the stability of sandy soil surrounding rock. From the perspective of influencing factors of the stability of sandy soil surrounding rock and the stability classification of surrounding rock, this paper explores the influencing factors of internal friction coefficient which are related to the stability of sandy soil surrounding rock. It is discovered that the content of fine granules ( 0.075 mm) of sandy soil has distinct influence on the internal friction coefficient of sandy soil. The relationship between the compactedness and internal friction coefficient is not always a direct ratio which is relevant to the content of fine granules of sandy soil and water content of fine granules. It is held that it is more rational to adopt the water content of fine granules rather than water content of sand soil to access the internal friction coefficient of moist sandy soil. This article also makes a conclusion for the influencing rules of the water content of fine granules on the internal friction coefficient of sandy soil.

Based on the experimental and theoretic studies on the frictional materials in literatures , a generalized nonlinear strength theory is presented. The generalized strength theory has a form of Drucker-Prager strength criterion, in which a unified mathematical expression is used to describe the strength characteristic of various materials. The theory covers or approximates the classical nonlinear strength theories in existence. The generalized strength criterion is smooth curve between the Drucker-Prager criterion and the external contour line of Mohr-Coulomb criterion in deviator-plane, and which is linear function in meridian-plane. The hydrostatic pressure and the deviator stress are separated in stress space; so it can be easily integrated with the concrete constitutive model.

There are many important problems to be calculated in designing a spanning bridge in mountainous area, one of which is how to calculate the stability of bridge foundation slope. It used to be degenerated into plane problem. In fact, steric effect of bridge foundation slope is obvious. Adopting three-dimensional numerical method, combining traditional theories and empirical formulas, this paper synthetically analyzed the stability of bridge foundation before and after loading; reasonable position of bridge foundation, and the limit stress of piles. Hereby, it indicated reinforced position, and offered corresponding measures. At the same time, this paper jumped a circle that evaluated the stability of slope by a single stability coefficient, offered a new approach, which thought about the reasonable position of bridge foundation and foundation stress, to appraise slope stability of bridge foundation. Aiming at different slopes, different geologic conditions, different types of piles, different lengths of pile, different loads, and different stages of construction, it can analyze stress, strain, and whole stability. The results of analysis can help to confirm the positions and measures of reinforcement.

A silty sand made from a seriously decayed red sandstone was reinforced by biaxial geogrid. A number of samples of this reinforced soil with 0, 1, 2, 3, or 5 reinforcement layers at 90 %, 95 % or 100 % of compaction degrees were used to measure their modulus of resilience in laboratory. The relationships were concluded between the resilient modulus of the reinforced soil and the location and the number of the reinforcement layers and compaction degree of the soil. It is proved by the test results that a greater modulus of resilience may be obtained when a proper location and a rational number of the reinforcement layers are applied to reinforce the soil with a high degree of compaction; and it is shown a smooth connection may be achieved between the rigid abutment and the soft subgrade soil by using biaxial geogrid to reinforce the embankment of bridge approach. Therefore, the bump at bridge-head may be controlled.

In order to study the mechanics characters of the warm and ice-rich permafrost beneath the embankment of Qinghai-Tibet Railway, a series of pressiometer tests were conducted in the Beiluhe test site of Qinghai-Tibet Railway. The tests results indicate that: the temperature of the permafrost beneath the embankment gets higher; unfrozen water of the permafrost increases; the critical plastic load Pf descends 31 %; the ultimate load Pl descends 44 % and the shear modulus Gm descends 80 % because of the embankment. For warm permafrost, the sensitivities of shear modulus Gm to the temperature of both ice-saturated and ice-rich permafrost are higher than that of ice with soil inclusions; the sensitivities of the critical plastic load Pf and the ultimate load Pl to the temperature of ice-saturated permafrost are higher than that of ice-rich permafrost and ice layer with soil inclusions.

Numerical analysis of fatigue fracture process of rock materials, two phases, fatigue crack initiation and extension, are rightly associated by damage mechanics method. Based on fatigue curve in the crack initiation process, a numerical method to compute the fatigue crack extension, is proposed. The relation between crack length and fatigue life in the crack extension can be obtained by the damage mechanics-finite element method. The above two phases being separately dealt in existing researches are brought into a unified theoretical frame. This method is used to analyze rock-concrete materials, the fatigue lives calculated agree well with the experimental ones.

The space axisymmetric consolidation model is established for transverse isotropy soil among Jacked-in Group-Piles. Then, series solution can be found by using methods of mathematical physics, considering the initial distribution and boundary condition of excess pore water pressure caused by setting piles. The comparison between the calculation values and the consolidation degree values which are deduced from the practical bearing capacity shows that the series solution obtained is reasonable. On the other hand, the consolidation degree results from the series solution can also be used for predicting the capacity of group piles.

Some problems of tunneling system reliability are solved by using probability theory and system reliability analysis of engineering structures in light of characteristics of tunnel structure. The reliability of tunnel structural system contains reliability of lining sections, reliability of lining sections in various surrounding rock pressure. reliability of lining in the same surrounding rock sections and reliability of the whole tunnel. The whole tunnel can be regarded as a series system of the portals at two ends and lining sections rock condition in the tunnel. Damage to any section of lining or any one portal is regarded as damage to the whole system. Thereby, using the PNET method, the failure probability and reliability index can be obtained for the whole tunnel. Case calculation shows that the general reliability index of whole tunnel is lower than all single sections of structure.

Based on the test data of prestressed high strength concrete(PHC) pile at north bank of the Yangtze River in Nanjing and the limit state equation of dimensionless random variables, the standard of the integral reliability level in the current Specifications of Foundations is calculated with the method of calibration, and the reliability index is calculated. Further more, the influence of general assurance coefficient, loading effect ratio and different load compositions on the reliability index is investigated. Finally, the partial coefficient of the resistance is calculated. It is shown that the reliability index is related to general assurance coefficient, loading effect ratio and different load compositions. In addition, it is also indicated that the influence of general assurance coefficient on the reliability index is remarkable, whereas the influence of different load compositions on the partial coefficient is weak.

Rockburst is one of the disasters can occurr in deep mining and rock excavation. It is a kind of dynamic fracture excited by the released elastic energy previously stored in the rock mass. The elastic energy releasing is correlated to the post peak behavior of the excavated rock mass. On the other hand, the rockburst phenomenon is also correlated with the excavation rate. A numerical modeling for rockburst is presented. The modeling is based on the complete stress-strain behavior of rocks obtained in laboratory. The post peak stress-strain behavior is specially considered in the analysis. Furthermore, the influences of loading rates are also included. The excavation process of a tunnel in rock mass is simulated in the study. The fracture development and the elastic energy releasing rates under different loading rates are computed in the simulation. The computed results indicate that the fracture is likely to initially occur near the rock surface and then propagate towards the internal zone of the rock mass. It is also demonstrated that rockburst is more likely to be occurred under a higher excavation rate than that under a lower excavation rate.

Geogrids are used in the embankment of expressway to solve the construction problem of special soil in a certain extent for it can improve the indexes of soil, e.g. c and ?. Based on creep experiments for geogrids, it is shown that the bigger intensity geogrids have smaller strain under the same load action; and load and temperature have remarkable impact on the rheology of geogrids. Finite element method is effective to study the effect of geogrids on reinforcing soil; and the advantages and disadvantages of multifarious schemes can be compared conveniently. FEM(PLAXIS) is used to simulate the settlements under several different working states. The results indicate that the geogrids to control horizontal displacements is better than to control vertical displacement. The field load tests show that geogrids can boost bearing capacity of the road embankment severalfold , improve stress condition of soil, reduce differential settlements and total settlements effectively. Geogrids are good for reinforcing the road embankment observably and will be used in the practical engineering widely.

Finite element method based on Biot consolidation equation taking into account the interaction between soil skeleton and pore fluid is always used to analyze the consolidation of saturated soft foundation with undrained-incompressible limit. Because of restriction of Babuska-Brezzi inf-sup condition, conventional FEM based on equal interpolation orders u-p formulation will give a spurious oscillation result for pore pressure. Based on displacement-pressure linear equal interpolation, a new method in which the number of the independent degree of freedom of displacement is higher than that of pore pressure, is proposed. With suggested double-mesh interpolation method, the Babuska-Brezzi stability condition will be satisfied; and it is possible to use equal interpolation orders u-p formulation. Several examples are presented to verify the suggested method.

The cement-soil mixing pile composite foundations are getting more and more application to construction engineering. However, the research on their response under dynamic loading, especially under earthquake loading, is quite limited. Now, the seismic response analysis in the time domain is performed with ADINA program, considering the interactions among soil, foundation and the superstructure. Based on these analyses, some conclusions which may be useful for aseismic design of this type composite foundations are drawn.

The main contents of consistency theory is discussed systematically; the coherent viscoplastic tangent modulus is deduced; also the generalization condition and method for analogy Hoffman material is researched base on some result of Winnicki and Xiao-shiyun; and linear Drucker-Prager model is generalized to consistency model; backward Euler algorithm of FEM for generalized model is presented; the results of numerical example is compared with experiment data to show the validity of consistency Drucker-Prager model finally.

The concept of designing anti-slide pile is using discontinuous structure and the soil arching effect to support the sliding force. By the centrifuge model tests, studying the phenomenon of soil arching effect when anti-slide pile is used to reinforce the landslide, reproducing the soil arching in space of piles and its failure mode. Two typical failure modes are put forward; i.e. soil arching crown failure and soil arching springer failure; and the engineering measure preventing soil arching springer from failure is put forward. Based on the centrifuge model tests, using 2D particle flow method to analyse the distribution of stress and failure process of horizontal soil arching in space of piles, and then that the failure criterion of soil arching is the sharp change of load of the anti-slide piles, is proposed; i.e. the function of soil arching transfering load is lapsing partially; and this may lead to that the load of one or another pile sharply raises. The relationship of load and pile space of soil arching is also studied. The load of soil arching changes with the increasing of pile space nonlinearly. When pile space increases to a certain extent, the load of soil arching will decrease sharply; so the area of reasonable pile space can be confirmed.

To simulate the strain localization in the failure process of geomaterials, a model with embedded localized softening bands incorporating into the idea of strong discontinuities is presented. Based on the virtual work principle, the equilibrium equations of FEM considering the effect of localization deformation are established; and the bifurcation theory is adopted as the criterion of onset of strain localization. The model can describe the mechanism of pre-localization and post-localization continuously by regarding localization as a viscoplastic flow procedure. The main advantages of this algorithm are that the model needs little amount of computation, and it has exact physical meaning compared with other methods. Furthermore, it can be incorporated into the conventional finite element analysis procedure. Numerical results have been carried out to show the validity of the model.

The middle wall of an expressway multi-arch tunnel is calculated by using finite element numerical method aiming at its strength deficiency. The result indicates that the safety factors of the middle wall cannot satisfy Code’s requirements. The treatment projects of chiseling away the middle wall partly and wholly are researched; the result indicates that when the middle wall is repaired by the chiseling away partly method, the treatment of middle wall will have a small impact on the preliminary lining; the inner force of the original middle wall will increase slightly which exerts a small effect on the whole tunnel structure. However, when the middle wall is repaired by the chiseling away wholly method, the treatment of middle wall will have a marked impact on the preliminary lining. The study on the length of construction indicates that when the once length equals respectively to 12 m and 9 m on the three and four grade rock mass is reasonable. The safety of the repaired multi-arch tunnel middle wall can satisfy the Code’s requirements.

The embankment on the back of bridge abutment and the conical slope produce additional vertical stress in the bridge abutment subsoil; the stress is the key parameter to calculate the differential settlement, lateral movement of the bridge abutment, the lateral pressure and flexibility of the abutment’s pile foundation. Based on the elastic theory formula and the superposition principle, the calculation formulas of the stress are deduced so as to solve the problem of the existing code only applicable to single-track roadbed and error due to looking up table together with interpolation. In addition, the formula is apt to make a computing program.

At present, although some academicians import the concept of fuzzy reliability into reliability analysis of geomechanical engineering, there still are some questions to be solved; in which the how to calculate the membership function is very important; since it is a precondition to calculate the fuzzy reliability. The different choosing of membership function will conduce to different results, even the difference is greatly obvious. Aiming at this actuality, the authors studied the influence of choosing different membership function on the fuzzy probability calculative results. We choose three representative membership functions: descending semi-trapezia distribution, quadratic parabola distribution and ridge distribution. The difference of fuzzy probability calculating caused by these three different distributions is analyzed theoretically; and then some general criterion about how to choose the membership function for calculating the fuzzy probability of underground continuous wall is concluded. Finally, an engineering example is given to verify the analysis and calculative results are consistent with the theoretical analysis.

Static loading tests and in-situ measurement were carried out to analyze the load-bearing behavior and working mechanism of various types of rigid pile composite foundations in Guangdong Province. It is shown that the stress ratio between pile and soil can be much influenced by geological condition and the relative rigidities of pile and soil. The measurement results presented could be used for reference in rigid pile composite foundation design.

The interaction between pile and soil of discrete material piles composite foundation is studied. Experimental investigation indicates that the pile is damaged under some depth to the top. So the composite foundation is divided into 3 different sections: expanding, un-expanding and substratum. According to deformation compatibility condition, a new method to calculate the settlement of the composite foundation is deduced by elastic mechanics. An example is given; and the calculation result is consistent well with the on-the-spot monitoring result.

The situations of geotechnical engineering monitoring system are complicate; and there are a larger number of monitored data to need be analyzed. For the traditional database system，it is hard work to analyze the monitored data and forecast the situations of geotechnical engineering. Based on the object-oriented Visual Basic soft and the object-oriented database management development system SQL, this work develops the visual system of analysis and predication for the situations of geotechnical engineering by methods of engineering visualization and GIS, which successfully achieve good combination of the database management, analysis and predication of situations; and the information visualization. It can quickly analyze the monitored data and precisely forecast the situations of the geotechnical engineering.

Frequency spectrum is one of the most important dynamical parameter for microtremor. Frequency spectrum characteristics of microtremor signal is closely related to the thickness of ground covering layer and the stiffness variation of overburden layer, which can reflect not only the type characteristic of rock and soil layer, but also the dynamic characteristic of project site. The current method that analyzing commonly the dynamic characteristic of site by microtremor signal has been discussed ,researched and compared in detail. Meanwhile, the diversification rule has been analyzed through example; and the estimation of power spectrum and the frequency response characteristic of micro-tremor signal to the site rock and soil mechanism are introduced deeply.