Extensive laboratory tests and field observations show that soft clay exhibits long-term deformation. For further understanding of the creep characteristics of soft clay, the mechanism of creep is first discussed from the microscopic physicochemical viewpoint. Then, the evolution of second compression coefficient and its determination under 1D condition, triaxial creep characteristics under drained and undrained conditions, long-term shear strength, and the creep characteristics under complex stress conditions are analyzed. The relevance of creep characteristics to strain-rate and strain relaxation characteristics under both 1D and 3D conditions is discussed. Finally, some new development of the creep characteristics of soft clay are presented in three aspects: the relevance of second compression coefficient to microstructure, accurate description of nonlinear creep, and the stress-dilatancy during drained and undrained creep.

It is found from laboratory tests and in-situ observation that earth fills in high dams are usually crushed under high pressure and soaked condition. Particle crushing will change the distribution of earth fills and density; accordingly change the stress-strain behavior. In order to model this behavior, a method is proposed to develop a hypo-plastic constitutive model. Rock particle crushing and density changing, as well as the stress induced anisotropy change in high dams are considered. The hypo-plastic model can also be used to describe cyclic behavior in combination of crushing and density changing effect. The developed model needs test data verification; and then it can be further used into dynamic elastoplastic FEM programming and analysis of high earth-rock dams.

The purpose of this study is to investigate the stability and failure mechanism of embankments on sloping ground with weak interlayer. Centrifugal model tests and numerical simulations are conducted; and some useful conclusions are drawn as follows. The failure mechanism of embankments on homogeneous sloping ground is still circular sliding. Due to the effect of weak interlayer, the tensile crack will emerge and develop easily; and the embankment will become more instable and slide along the weak interlayer.

Collapsibility is an important engineering characteristic of loess, which is indicated by the collapsibility coefficients, dead weight collapsibility coefficients and the initial collapse pressure under the condition of one-dimensional compression stress. There are many influencing factors of collapsible deformation characteristics such as grain size, density and moisture of soil. There is a certain correlation between the influencing factors which are not completely independent. Based on the physical indices statistical analysis and correlation analysis on the collapsible loess fields of loess high platform of Xi'an metro line No.4 and loess tableland of high-speed railway tunnel from Baoji to Lanzhou, the ratio of water content to the liquid limit, and the void ratio are determined to be the factors by the factor analysis method. The multiple linear regression analysis method is used to obtain the relationship between the dead weight collapsibility coefficients, the initial collapse pressure, the modulus of compressibility and the factors according to the test data of two collapsible loess fields. The deviation tests of calculated value and the measured value of the dead weight collapsibility coefficients, the initial collapse pressure and the modulus of compressibility are carried out. The rationality and the accuracy of determining the factors and establishing the relationship between the collapsible parameters and the independent influence factors are verified by the factor analysis method. The valuable significance of the rapid and accurate evaluation of collapsibility and the collapsible deformation of loess foundation is proved by setting up the correlativity of the collapsible parameters of loess in two types of topographic feature of two loess regions.

Based on the characteristic period of the seismic influence coefficient curve, a new method to calculate Rayleigh damping is put forward that taking 1/5Tg and 1/Tg as the two target frequencies respectively. Time domain results based on the method put forward by Annie and the new method in this paper, and together with the frequency domain results based on equivalent linear method are compared by three single homogeneous soils with different thicknesses and a multilayered soil under three different ground motions. The results show that: the errors of the ground peak acceleration of the two forms of Rayleigh damping are within 10%; and the ground acceleration response spectra are consistent, but the method in this paper is not sensitive to soil thickness and input ground motions, that is, the error dispersions are small with different soil thicknesses and input ground motions. What’s more, the method in this paper is simpler and more convenient in application. For the method in this paper, the Rayleigh damping values can be determined by the characteristic period obtained from local site category, without the need of solving natural frequencies of soil.

On the basis of the existing work and Mohr-Coulomb yield criterion, an elasto-plastic analysis solution for circular underground cavern is established considering the combined thermo-hydro-mechanical action. Under the conditions of single stress field, thermo-mechanical field, hydro-mechanical field and thermo-hydro-mechanical field and changing strength parmeters of a medium, the distribution and change of stresses and plastic zones in the surrounding rock mass are computed and compared respectively. The results show that the temperature field makes the radius of plastic zone some decrease, but the action of temperature is not obvious on the whole; compared with the action of the single stress field, the pore water pressure makes the plastic zones ,radial stresses and tangential stresses increase greatly.

To mitigate the effect of frost heave, a countermeasure of fiberglass reinforced plastics (FRP) covering was put forward and applied to the foundation engineering of Qinghai-Tibetan transmission line. There is limited information involved in the mechanical properties of the interface between soil and FRP. A series of laboratory direct shear tests of the interface between silt and FRP plate are performed. The results show that the yield shear displacement is very small; and the interface shows short or no significant strain hardening stage. For frozen samples, the strength of the interface is drastically lost when the load reaches its critical strength. For unfrozen samples, the shear stress-displacement behavior of the interface is ductile failure and there is no obvious peak. The shear strength of the interface slowly decreases with the increase in water content for unfrozen samples. The strength of frozen sample increases with the increasing of negative absolute temperature and water content. Moreover, the temperature effect on the shear strength of the interface is more significant if soil water content is higher. When the soil water content is greater than 19%, the shear strength stabilized. The impact of temperature on the shear strength is mainly reflected in the change of cohesion. With the increasing of water content, temperature effects enhanced. The internal friction angle of the interface decreases with the increase in the absolute value of negative temperature and decreases with the increase of water content.

Soil-water characteristic curve (SWCC) is a very important curve in the study of unsaturated soil mechanics; and the curve fitting parameters of SWCC are significant for analyzing the properties of unsaturated soils. To obtain the curve fitting parameters of SWCC accurately and efficiently, the experimental design and the curve fitting method of SWCC are studied. Based on the osmotic method and the filter paper method, a SWCC of an unsaturated expansive soil in a construction site in Hefei is measured. The van Genuchten model is used to represent the relationship between gravity water content and matric suction of the tested soil. The Lsqcurvefit function of the scientific language Matlab is adopted for carrying out the curve fitting of SWCC because the Lsqcurvefit function can set the lower limits and upper limits of fitting parameters. The problem of multi solutions of curve fitting parameters of SWCC and its influence factors are studied. It is demonstrated that when only the experimental data of the osmotic method is used, the range of suction is relatively small; and the multi solution phenomenon of SWCC’s fitting parameters is obvious. However, if the experimental data of both the osmotic method and the filter paper method are used, the range of suction is relatively large. Then, the multi solution phenomenon of SWCC’s fitting parameters can be diminished. And if the range of suction is large enough to represent the shape of the whole SWCC, the number of experimental data points need not be too much. Based on these conclusions, the experiment for measuring the soil-water characteristic curve can be designed more efficiently; and then the curve fitting parameters can be obtained more accurately.

The mechanical characteristics of shale with different beddings coring were investigated by MTS815 rock mechanical test system. The failure modes，deformation and strength characteristics are obtained. The results indicate that: (1) It shows significantly different properties, when the sample paralleled to bedding plane; it has maximum value of compressive strength and minimum value when the sample has a angle of 30° with bedding plane. The elastic modulus deceases with the increase of the coring angle. (2) Under the condition of uniaxial compression, the angle of 0°, the main failure mode is split failure along the beddings; the angle of 30°, it is shear failure along the weakness plane, the angle of 60°, it is wide-angle shear failure along the weakness plane; the angle of 90°, it is stretch-draw failure. (3) Under the condition of triaxial compression, angle of 0°, it shows several failure surfaces, combined split and shear failure actions; the angle of 30°,it shows shear failure along to the beddings; the angle of 60°, it shows shear failure and the angle of failure surface is 45° to 50°; the angle of 90°, it shows shear failure and it has several parallel failure surfaces. The results can provide an important way for fracture optimization design.

The global rotation angle of a homogeneous soil slope induced by seism is well harmonize with the arc-sliding behavior of slope failure and so is a more superior parameter of deformation and stability than the permanent sliding displacement. And the strain energy because of transient seismic deformations is reversible and equivalent to the random fluctuation to a slope system, and critical rotation angle is an inherent property of slopes and independent of the seismic oscillation. Substantially, the critical rotation angle is in essence corresponds to the catastrophe point of the system potential energy. A cusp catastrophe model is set up based on the characters of seismic instability of homogeneous soil slope; and a method for determining the critical rotation angle of arc-sliding is proposed; and it is found that the critical rotation angle is only related to the constitutive model parameter m and of the constitutive model of soil in slide belt and the radius R of the arc slide belt and in essence represents the effect of many factors and deserving wide application.

Shear dilatancy is one of the most common phenomena of geological materials. A series of experiments were conducted in a newly manufactured large-scale direct shear apparatus to study the dilatant behavior of intensely weathered coarse-grained soils, including that 3 groups of various moisture contents, 4 groups of various shearing rates and 5 groups of various gravel contents samples were tested, respectively. Dependence of vertical and horizontal displacements on the applied normal stress was analyzed. The results show that when other controlling conditions are fixed, the shear shrinkage increases with the applied normal stress. The maximum shrinkage increases with the increase of moisture content or the decrease of shearing rate; and the shrinkage of samples with gravel content less than 30% is significantly larger than that with higher gravel content. Our results suggested that for those samples with gravel content less than 50%, the effect of fine content became significant, so that the samples show a strain-softening behavior; and the dilation tends to a fixed value. It is shown that the two-dimensional dilation formulation proposed by Matsuoka is not applicable to the coarse-grained materials. Instead of the formulation, a quadratic polynomial can be adopted to represent the relationship between the stress ratio and the strain increment at the peak strength, the value range of experience parameters μ in this formula is given.

In order to find out an effective and practical approach to reduce the settlement and increase the strength of an approach embankment filled with loess so as to avoid the bump at bridgehead, the methods were suggested by mixing a proportion of sand into the loess or reinforcing the loess with geogrid, or by using these two skills together. For examining essentially the feasibility of these ideas, the deformation and strength properties of geogrid-reinforced loess, loess mixed with sand (LMS) and geogrid-reinforced LMS were investigated in laboratory. A series of resilient modulus tests and unconfined compression tests were conducted respectively using samples made up of LMS or pure loess either with or without geogrid-inclusions. Each sample varied either in the number of reinforcement layers from 0 to 5, or in the degrees of compaction of 88%, 92% or 96%. Based on a detail analysis of the test results, the following conclusions are drawn: (1) The resilient modulus of the loess increases significantly either by mixed with sand or by reinforced with geogrid. More improvement is demonstrated while the both methods are applied together in a loess sample. (2) The compressive strength of LMS is much greater than that of loess when the LMS and the loess both are either with or without geogrid inclusions, especially under small compressive strain. (3) The compressive stress-strain pattern of a geogrid-reinforced LMS changes gradually from strain-softening to strain-hardening either while the geogrid layers increase at a certain degree of compaction or when the degree of compaction decreases at a given geogrid layers. (4) There is an appropriate strength match between the geogrid and the LMS, according to which a geogrid-reinforced LMS with higher density is suggested to be reinforced with smaller reinforcement spacing so as to obtain a maximum strength derived from a compatible deforming between the geogrid and the soil.

In order to make clear the relationship among the piles, slab and soil, the pile-slab structure vertical stepped loading and horizontal loading tests under different conditions are carried out, based on the similarity theory, such as different spans, with or without soil supporting under the slab and so on. Systematical study is made on the pile-slab-soil interaction mechanical characteristics of pile-slab structure. Some conclusions are preliminarily drawn as follows. (1) Slab-soil interaction has obvious effects on the force of the pile-slab structure. When ignoring the soil supporting under the slab, the deflection of the slab, the stress, the force of the pile and the slab-soil contact pressure will have a significant increase; and the greater the span is, the more obvious the influence will be. From this we can know that, it is conservative for engineering design that without considering the soil supporting under the slab. Therefore, it is recommended that the design of pile-slab structure should consider the supporting of the subgrade soil. (2) The pile-soil interaction is obvious under horizontal loads, and the influence areas mainly within the range of 1/2 of the pile upper part. The test also shows that the slab span has a little influence on the pile-soil interaction, but has greater impact on the lateral deflection of the slab; and the greater the span of pile-slab structure is, the larger the bending tensile stress of slab under lateral force will be. It is recommended to check the tensile stress indicators of the slab under horizontal loading during span design of pile-slab structure.

Firstly, the importance of study on mechanical parameters of rock mass is presented, and some methods to determine mechanical parameters are introduced, whereas their accuracy are questionable and argument. As there is difficulty in determining the disturbance factor D relayed on the Hoek-Brown strength criterion, fuzzy comprehensive evaluation is employed. Considered the factors influencing on disturbance and relevant engineering experience, the value of D is calculated accordingly, which is more corresponded to the practicality. Afterward, the rationality, that the bounds characterized by slip surface for dividing disturbed and undisturbed zone, is discussed; and it overcome deficiency of other expressions. Additionally, to further verify the reasonability and significance of such dividing, and with a practical engineering, calculation of the factor D is given using the modified and other methods respectively. According to the comparative analysis, it is shown that the former is more suitable to the disturbance degree in-situ.

Most of the existing cyclic triaxial tests on saturated soft clay were conducted under undrained condition because of the very low permeability of soft clay. But as for traffic loading, the actual drainage condition is partially drained because soft clay is subjected to long-term cyclic loading for a series of years. Triaxial tests with large number of cycles (50 000) are conducted under on natural Wenzhou soft clay undrained and partially drained conditions. Influence of drainage condition on dynamic behavior of saturated soft clay is analyzed. Results show that the dynamic behavior of soft clay under partially drained condition is very different from that under undrained condition. With the increasing number of cycles, the pore water pressure firstly increases and then decreases with a peak value. After a large number of cycles, the resilient strain gradually decreases and the stress-strain hysteresis loops under a single cycle shortens with smaller area. It is indispensable to conducting tests under partially drained condition to predict the long-term settlement under traffic loading.

Quality subgrade filler is scare in the construction of highway in the desert area, aeolian sand is selected as subgrade filler which is massive in the desert area, of which the mineral composition, chemical composition, pH, salt content and gradation characteristic are analyzed according to the principle of proximity. The change laws of dry density of aeolian sand and compaction characteristics are explored by using different test methods, i.e. compaction test, shaking table test, surface vibration compactor method, and controlled conditions of test. Compaction curve and vibratory compaction curve of aeolian sand show the multimodal feature of vibration compaction, vibration loose and vibration compaction again; dry density by shaking table test is superior to the density by the compaction test under the same water content ratio. Maximum dry density of aeolian sand is attainted while the water content ratio is close to saturation by shaking table test which vibration effect is best. The effect of vibration compaction by three layers filler is better than one layer filler of surface vibration compactor method. The results can provide guidance for construction.

The surface vibration compaction test, indoor heavy compaction test, interior California bearing ratio(CBR) test and modulus of resilience test have been carried out on sericite schist coarse aggregates and four modified soils, because the sericite schist belong to the soft rock, strength low, which is easy to make road collapse and pavement cracking when it as subgrade filling material. Test results shows that it is a big difference in the maximum dry density of sericite schist coarse aggregates by using heavy compaction test in contrast to the surface vibration compaction test. The results of maximum dry density is 2.01 g/cm3 by using heavy compaction test; but another is 1.92 g/cm3. The main reason is that due to particle breakage in sericite schist. The effects of the change of the optimum moisture content is not obvious for sericite schist coarse aggregates, as well as for four modified soils, which is beneficial to compaction. The modulus of resilience of sericite schist coarse aggregates is low, less than 32 MPa. However the modulus of resilience of modified soil have been remarkable improved, up to 50 MPa above all. The CBR both only have 3.7 when blend it with 20% red sandstone or 20% clay. But the CBR ascends obviously when to mix it with 3% or 5% cement. Sericit schist after chemical modification by adding 3%, 5% of cement can be used in the embank kment of highway 94 zone and 96 zone.

Based on flow theory of unsaturated soil, a model for moisture migration is set up to study steady flow subjected to vacuum preloading. Meanwhile the governing equation and the corresponding analytical solution of pore water pressure distribution are given. The model is first verified by in-situ measured data. Then parameters are analyzed. Results show that the calculated results agree well with the in-situ measured data. Both diffusion flux (Q) and unsaturated coefficient (?) have a marked effect on the formation position, indicating that they affect strength and thickness of unsaturated region. The larger diffusion flux is, the larger matrix suction of soil surface is and the greater variation trend of pore water pressure is. Unsaturated soil is seldom influenced by unsaturated coefficient ? when it is in range of 0.3-1.0 kPa-1.

A series of collapsibility tests on Q2 loess of Pucheng power plant in Shaanxi province under 1D and 3D stress conditions were conducted using GDG high pressure oedometer and unsaturated collapsible triaxial apparatus. Under 1D stress condition, the collapsibility of Q2 loess is moderate or weak. The maximum coefficient of collapsibility decreases with the increase of depth. The Q2 loess is not collapsible under low pressure, but it is possibly collapsible under high pressure. The collapsibility of Q2 loess layer is stronger than that of ancient layer. The collapsibility sensibility of Q2 loess is weaker. Large-scale projects should use actual pressure to evaluate collapsibility of Q2 loess. Under 3D stress condition, curves of collapsible strain in terms of quantity of wetting are divided into three stages: the collapsible strain increasing slightly, the collapsible strain increasing rapidly and the collapsible strain being almost unchanged. The influences of net confining pressure, deviatoric stress and suction, especially the latter two, on the collapsible strain during the process of wetting are obvious. The collapsible volumetric strain increases with the increase in the collapsible deviatoric strain and the relationship is almost linear.

A total number of 21 consolidated undrained triaxial shear tests on Nanyang expansive clay have been performed by GDS stress path triaxial system. The specimens are prepared in kinds of 4 different overconsolidation ratios (OCR) for reduced triaxial compression (RTC) shear tests and 3 for reduced triaxial tension (RTT) shear tests, which all sheared at three different stress relief rates. The influences of OCR and stress rate on stress-strain relationship, pore water pressure, effective stress path and deformation modulus are investigated. The results show that the influences of OCR and stress rate on mechanical behavior of expansive clay in compression and tension are similar. As the increase of stress rate and OCR, the deviatoric stress in stress-strain curve increased monotonically to the maximum with the same axial strain. The pore water pressure is always negative with different OCRs and unloading stress rates in compression and tension. The decreasing range increased with the increasing of OCR, and the influence rule of stress rate on the change range of pore water pressure is shear stress path related. The deformation modulus E100 increased with the increasing of OCR and stress rate; but the anisotropy of deformation modulus is becoming weaker as the increase of OCR under different stress rates.

Collapse loess is a special structured soil because of its special sediment environments. When moisture and stress suffered from changing, macromechanical characteristics would change significantly. To analyze the stress-strain relationship changing laws and structural damage evaluations of loess under moisture and stress coupling effect, the sub-loading surface and super-loading surface ideas are introduced into soil constitutive model by Asaoka et al, in this paper, based on the original super-consolidation parameter and structural damage evaluation parameter, the effect of water content changing is considered in super-loading and sub-loading surface constitutive model; and new initial super-consolidation parameter and structural damage evaluation parameter are defined. Base on the sub-loading surface and super-loading surface ideas, the general stress-strain relationships are derived by introducing structural index and structure yield strength into constitutive model; at the same time, the effects of parameters are analyzed. Finally, the accuracy and rationality of the constitutive model proposed are verified by comparing with experimental results of collapse loess in oedometer tests and conventional triaxial tests conditions and calculating results of constitutive model proposed in this paper.

Microstructure unit of the offshore clay— clay domains contains a large amount of intragranular pores, of which the diameters are small to nanoscale. These pores have an important influence on the physical indices, water stability, expansion and shrinkage characteristics. However, general methods are difficult to accurately describe intragranular pore characteristics. The scanning electron microscopy (SEM), mercury porosimetry(MIP), nitrogen adsorption(NA) are used on the Zhanjiang clay to study its microscopic pore characteristics and control factors of pore distribution. The relationship and sensitivity analysis of the microstructure and physical parameters, mechanical behavior are established. Results show that the Zhanjiang clay has the unusual combination of poor physical properties and good mechanical properties; it is a kind of high sensitivity and strong cementation structural clay, the main mechanism was disorderly orientation and open flocculation structure with cementation bond; furthermore , pore structure is a space frame system which has higher strength and stability of the side-surface-angle connection. Therefore, the retention phenomenon of mercury-ejection curve and hysteretic loop in adsorption-desorption isotherm occurring because of special space frame system and ‘ink bottle’ type pore. In addition, the research shows that, the combination of SEM, MIP, NA methods can accurately , qualitatively and quantitatively evaluate overall pore system characteristics of offshore clay.

The vertical buried pipelines will be damaged by soil movements around pipe induced by tunnelling, but the relationship between soil movement and pipeline displacement has not been understood deeply. Three sets of model tests are established to simulate the effects of tunnel excavation on buried pipeline, in which different embodiments, caliber and bending rigidity are considered, the research is carried out about the displacement of soil and vertical pipelines during tunnelling. The results show that the modified Gaussian curves can describe accurately the Greenfield settlement trough due to tunnelling in sand, and the parameter ? varies between 0.2 and 1.0, which is proportional to the depth of soil in sand; The width coefficient of Greenfield soil has great influence on pipeline displacement, and the displacement of pipeline varies inversely to its bending rigidity for the same buried depth; The bigger the caliber is, the more obvious positive downdrag which dominates the behaviour of deep pipelines, however, negative downdrag greatly affect the displacement of pipelines for shallow case; Smax /i is one of the key influence factors for relative pipe-soil settlement, on this basis, a modified formula to calculate the relative pipe-soil rigidity is presented in this paper.

To explore the development law of the strength of lime-treated expansive soil and red clay, the unconfined compression, consolidated quick direct shear tests and consolidation test are carried out to compare the Nanyang expansive soil and Chenzhou red clay modified by quicklime and hydrated lime respectively. The study found that during the one-year curing period of lime-treated Nanyang expansive soil and Chenzhou red clay, the unconfined compression strength is linear with the logarithm of curing age. The strength of the samples with moisture content larger than optimum moisture content for 3% after 28 days curing is higher than that of the optimum moisture content samples. In addition, the modification effect of quicklime is better than the effect of hydrated lime. Due to the different mineral composition, the modification effect of lime-treated Nanyang expansive soil is better than that of Chenzhou red clay.

Three-dimensional analysis of slope stability is developing. Compared with two-dimensional method, this method can reflect the condition of slope more closely to the fact. Based on the upper bound limit analysis method, a new three-dimensional rotation-translation combined mechanism is proposed to study the stability of slope with weak interlayer. And this combined mechanism can be expended longitudinally through the plane insert; so the method could be used to analyze the slope stability with different lengths. The proposed failure mechanism is finally verified by comparisons with the elastoplastic finite element method. The comparisons show that the proposed mechanism improves the efficiency of the previously-developed rigid block mechanism to account for the presence of the weak interlayer in the slope and can be used as a simple evaluation method for the engineering design.

In order to reveal the mechanism of consolidation-creep of soft soil, the settlements of soft foundtions after the completion of projects are calculated. The triaxial consolidation and creep tests have been carried out which simulate of soft soils under consolidation by vacuum, surcharge, and combined vacuum-surcharge preloading. The microstructure tests of soft soils before and after triaxial tests have been carried out also. The elasto-viscoplastic (EVP) model which could consider the change of microstructure of soft soils is set up. The outcome is drawn as follows: The results of triaxial tests show that the course of consolidation and the course of creep of samples under the loading of three different preloading methods have the coupling effect. The results of microstructure tests show there are relationships of supplement each other between the change of microstructure and the change of engineering characters of soft soils. The specific stress path of change is weakened in EVP model, in which parameter reflected the elastic and parameter reflected the plasticity and viscosity of soft soils could be determined by the microstructure parameters. The improved EVP model not only can calculate the EVP deformation of soft soils but also considered the microstructure changes of soft soil, which can better reflect the essence of soil deformation.

Based on uniaxial compression test of sandstone under the different drying-wetting cycles, the laws of drying-wetting effect on mechanical behaviors of sandstone, such as deformation behavior, intensity behavior and failure characteristic, were analyzed. The results show that the elastic modulus and the peak strength of sandstone trend to decrease with the increase of drying-wetting cycles, and its reduction range is changed from large to small; moreover, the decrease of above data can not develop limitlessly but there is a constant value as critical value; in this test, the constant values of elastic modulus and the peak strength are experiment data of 20th drying-wetting cycles. The failure characteristic of sandstone is also affected by drying-wetting cycles, the less drying-wetting cycles are, the more obvious brittle damage is; that are, with the strengthen of drying-wetting effect, the damage law of sandstone present a transformation from brittleness to ductility. On the basis of these tests, taking the strain and drying-wetting cycles as input layer and the stress as output layer, the three layers neural network constitutive model, whose structure is 2-12-1, was proposed. Through the massive samples learned and inspected, the model can well describe the mechanical properties of sandstone under the cyclic drying-wetting effect, which also confirms that it is feasible and reliable for the neural network method to establish the rock constitutive model. At last, the intact function relations between the mechanical behavior and the cyclic drying-wetting effect were built.

Based on the theory of discontinuous and self-stress rock mass as block-hierarchy structure in deep, the effect of viscoelasticity in block-rock partings to the propagation of pendulum waves is studied. Acceleration response of intermediate block-rock in the initial and the end regional and amplitude of positive and negative pendulum of each block-rock acceleration on five different kinds of viscoelasticities in partings are analyzed. It is shown that: it has no effect on acceleration attenuation cycle when viscous variation in block-rock partings. However, amplitude of positive and negative pendulum decrease more when viscous partings increases more than periodic increases. Attenuation cycles of acceleration are changed when partings elasticity variation, but amplitude of positive and negative pendulum of each block acceleration translation to equilibrium position when elasticity decreases. In the first half of the block-rock structure, the amplitude of positive and negative pendulum has a fluctuation when elasticity periodic decreases and the negative pendulum fluctuates significantly. Acceleration of each block attenuates rapidly when block-rock partings elasticity step increases; meanwhile, amplitude of positive and negative pendulum have a fluctuation in the initial regional.

In order to study the mechanical properties of frozen soil-concrete contact interface, a kind of dynamic direct shear system for frozen soil was developed. Based on the framework of a static shear apparatus, it was installed with a dynamic loading system and a temperature control module. With this dynamic direct shear system, dynamic shear tests of frozen soil under specified temperatures are able to be operated. Then dynamic parameters of frozen soil are measured. By placing concrete blocks in half of the shear box and frozen soil in the other, we operated a series of dynamic shear tests on the frozen soil-concrete contact interface. The results show some behavioral characteristics of the contact interface under dynamic loads, multi-factor comparison revealed the influencing factors and the variation.

Loess in China is thick, and groundwater levels are always very deep in loess area where is characterized by low precipitation, which makes loess always at unsaturated state. Soil-water characteristic curve is the foundation of researches on stress state, strength and permeability of unsaturated loess. This paper experiments on typical Malan loess in Longdong plateau, the soil-water characteristic curve of undisturbed sample is determined by tensionmeter, and the experimental data are then fitted with three theoretical models, of which Gardner model is the simplest with the least parameters, while Fredlund & Xing model has the best fitting effect. The relationship between permeability coefficient and matric suction or water content of unsaturated loess is built based on the measured soil-water characteristic curve by Childs & Collis-Geroge model which is commonly used to predict unsaturated permeability coefficient. The results show that the permeability coefficient decreases dramatically as saturated loess becoming unsaturated, the relationships between permeability coefficient and matric suction or volume water content of unsaturated loess can all be expressed in exponential form. Study of the soil-water characteristic curve and permeability coefficient prediction of typical loess provides loess engineering problems, such as the slope stability evaluation with the effects of rain infiltration and the computation of collapsible deformation of unsaturated foundation, with theoretical basis.

To study the expansibility and mechanical property of expansive soil in natural state, a series of expansion and mechanical property experiments, were carried out on Nanyang weak expansive soil with different humidifying degrees under the same initial condition. Through the experiments, the following conclusions are drawn: with the increase of humidifying moisture content, both natural expansibility and loaded natural expansion rate gradually increased at first, then slightly reduced, and finally became stable step by step. Load-free expansion rate almost increased in linear manner in earlier stage, then gradually became stable. By shearing strength experiments of expansive soil with different humidifying degrees, linear relation curve and relational expression between cohesion, internal friction angle and humidifying moisture content were developed. For completed projects, actual expansion property and shearing strength of expansive soil can be obtained by moisture content monitoring, which can be used to assess safety conditions of projects.

In order to observe microstructure cementation bond, determine the element composition and its spatial distribution microstructure, a series of SEM-EDS tests for Zhanjiang clay using the method of ‘whole area to micro zone, consolidation point’ are carried out. Moreover, the relationship between microstructure, chemical composition and mechanical behavior is discussed. The results show that the soil properties depend largely on the particles connection performance. In fact, Zhanjiang clay structure unit is actually many clay mineral plates stacked clay domain; the open flocculation structure combined with the free iron oxide as the main component of Zhanjiang clay is as a result of the cementation bond characteristics of the basic reason of the high sensitivity, strong structure. When stress level exceeds the structural yield stress, mechanical performance degrades rapidly; the structural unit body gradually transfers into aggregation and lamina of weak connection strength and strong dispersion. Studies also show that connection strength of soil particles, the structure morphology and its contribution to the structural strength are the essences of undisturbed soil and remolded soil properties difference; Zhanjiang natural clay is controlled by microstructure features, however, the remolded soil is controlled by clay mineral particles features.

Red clay is one of the special soils which contains cementing material. Compared with common cohesive soils, the strength characteristics of red clay are more complicated. Some direct shear tests are performed on the unsaturated red clay samples with water and propanetriol solution; and the experimental results show that the strength and cohesion of samples exhibit double peaks of strength increasing with the increase of solution content; while the internal friction angle does not change. Besides, the strength of samples diminishes obviously with the propanetriol solution instead of water. Based on Bishop's effective stress for unsaturated soil and the characteristic of pore distribution acquired by NMR tests, the impact mechanism of pore distribution characteristic on strength is discucsed, and a conclusion is drawn that pore distribution characteristic has much effect on strength of red clay samples.

Getting erosion is the characteristic of dispersive clay which would cause series of damages to hydraulic projects like dams. AlCl3•6H2O, MgCl2•6H2O, CaCl2 and CaO were selected as chemical modification materials of dispersive clay based on the mechanism of dispersivity. The judgments and comparisons of soil samples were made using pinhole tests and crumb tests. Tests show that with the modification materials selected above, the ability against erosion of dispersive clay was improved; and the dispersive clay would turn into non-dispersive. The results indicate that cations with higher valence state mixed into dispersive clay could reduce the diffusion layer by replacing sodium ions in soil particles surface or by lessening soil alkaline; as a result, it plays a role in modification. According to mechanism of dispersivity and the results of modification test, the chemical modification principles of dispersivity are put forward; modification materials contain cations with higher valence state or pH is acidic. Materials should environmental friendly and have lower price, and also facilitates the construction,

In-situ stress is an important factor in stability analysis of slope. Based on the measured stress data in the high and steep slope of Xingshan iron open pit, the inversion of in-situ stress field in the slope is performed by using multivariate linear regression method considering the impact of the gravity of rock mass and tectonic stress, in which 11 kinds of boundary conditions are included in five categories. In terms of the limits of linear and the whole region inversion, this method cannot accurately inverse the stress field of the metal ore body, which has extremely complex internal structure and big differences in lithology and topography within the mining area. In order to overcome the above defects, nonlinear neural network inversion method is used. According to the differences in lithology and topography of the rock mass, the mine is divided into five zones. Sub-regional inversion of the in-situ stress field of the mine is achieved by introducing a lateral pressure coefficient k0. The study results show that under a complex geological condition, the inversion of initial in-situ stress by neural network method can give a rise to a more reasonable result.

Pre-soaking treatment is a kind of important means on loess mechanics and foundation treatment in loess area. The necessity of in-situ soaking test is briefly analyzed. The historic development and the present researches on in-situ soaking test in China are concluded; and some comments are accordingly given. The main achievements are emphatically recommended, including key technology of soaking test, law of collapse deformation and collapsibility evaluation, etc. The main problems existing in the current criterion and some relevant suggestions are pointed out on collapsibility evaluation, the thickness of foundation treatment, remnant collapse and the standard of cutting off the water, etc. Finally, the future research trends are presented.

The stress and deformation of a typical 100-meter-high hardfill dam is investigated. Both the process of the construction of the dam and the stress-strain relationship of the hardfill material which varied with the construction age and stress state have a great impact on the stresses and the deformation of the dam. The elastic modulus of the foundation has a great impact on the stresses of the dam. The stresses are quite different in a dam with a low elastic modulus compared with that with a rigid foundation. While the elastic modulus of the foundation decreases, the minor principal stress of the dam at the middle of the horizontal section adjacent to the foundation decreases; and the maximum principal stress at toe and heel of the dam increases at an empty reservoir. Both the tensile strength and compressive strength of the material may not meet the requirements of the dam on a foundation with a low elastic modulus. The compressive stress above the basement increases and the tensile stress decreases at a full reservoir compared with that in the empty reservoir. The anti-compressive safety factor of the dam decreases and the anti-tensile safety factor increases at full reservoir. The factor of shear strength safety is always high. Hence the analysis of a hardfill dam should be focused on the compressive and tensile strength safety.

The finite element method for strength reduction recently used in slope stability analysis has disadvantages in revelation of soil deformation behavior and instability criterion. Based on stress strain curves of soil, Duncan-Zhang nonlinear elastic model and direct reduction of strength parameters (cohesion c and friction angle φ) of soil, discount method for tangent modulus Et is presented. The connotation of reduction is entirely revealed. And the exchange of deformation energy in potential slip area is proposed as instability criterion. On the characteristics of relation curve of deformation energy in slip area and reduction coefficient, two straight lines are drawn, the value of reduction coefficient at intersection point of the two lines is choice of safety factor of slope stability. The calculation results by modified Duncan’s finite element method with new instability criterion and references are compared, the influence of calculation area on deformation energy is analyzed, the new method is used in slope stability analysis of south channel of East line in South-to-North Water Diversion Engineering. All results show that the soil behaviors of deformation and strength are more entirely considered in modified Duncan’s finite element method for shear strength reduction, new instability criterion of slope is reliable and calculation is steady; safety of slope construction can be ensured.

Loess collapse with toppling style is one of the common disasters in loess area. Based on its forming feature, the solutions of upper and lower bound for vertical fracture of the loess collapse are derived in light of the critical state of both static equilibrium and plastic flow. The underside attitude of the collapse is calculated by the Mohr-Coulomb criterion. Thereby the geometric characteristics of the collapse can be determined; then the stability criterion is established based on the balance of force and torque; and the stability evaluation of loess collapse with toppling style is realized. The kinematics equation for loess collapse with topping is built by its toppling deformation conditions. By solving the equation, the trajectory of the loess collapse with toppling style is reconstructed; and the range of the disaster can be detected. The research results reveal the forming mechanism of loess collapse with toppling style, so as to provide a theoretical basis for its governance approaches and its identification with the safe zone of construction project.

The shallow instability of granite residual soil slope could easily induced by rainfall. Based on the analyses of influence of rainfall on the water content of slope soil, the effective rainfall resulting in soil from unsaturated to saturated condition is derived from the relationship between saturation and water content. Results show that not all rainfall will cause the instability of soil slope, and only when the soil saturation caused by rainfall infiltration reaches a certain degree the slope fails. There exists a critical depth in the unsaturated and saturated zone of slope above which the rainfall infiltration leads to a transition in soil from unsaturated to saturated, different shear strength could be used to calculate the stability of soil which was divided into fluctuation two parts by the critical depth. The soil unsaturated zone and saturated zone can be taken to calculate the stability of the soil condition. The results are useful for determining rainfall threshold of slope instability, so as to further understand the mechanism of landslide instability and landslide prediction.

Based on the basic characteristics of Merchant, Bergers and Butterfield creep models, three kinds of empirical models for predicting creep settlements of concrete-faced rockfill dam are proposed. Taking Pushihe concrete-faced rockfill dam for example, the sequential placement processes of concrete-faced rockfill dam are simulated by using nonlinear finite element method. The empirical model parameters are determined by using regression analysis procedure according to observed data of creep settlements in-situ. The relationships between creep settlements and times are presented. The engineering practical applications show that the fitting settlements agree well with observed values. The creep settlements of concrete-faced rockfill dam are related to not only times, but also stress state, location and elastic modulus of observing points.

Non-heaving soil is widely used as cushion material for filling the canal foundation naturally made up by frost heave soil in North China. The design of the cushion is not as appropriate since non-heaving soil has not been technically defined; and thickness of the cushion relies heavily on empirical design. Frost heaving of coarse grained soil is mainly affected by the particle size, water content and groundwater level. Initial water content of frost heaving and the ability to stop capillary water from rising should be taken into consideration when choosing the right cushion material. This paper puts forward a method for choosing cushion material according to capillary water potential in layered soil based on the analysis of frost heaving resistant mechanism of cushion. The method includes two criteria, relationships between groundwater level and effective grain size and the coefficient of nonuniformity respectively. Working conditions of the design are given by assuming the most critical water content after investigation of canal working conditions in winter. After considering the allowable displacement of lining structure, the formula for thickness of canal cushion is deduced basing on thermal resistance equivalent principle. Both traditional and the proposed methods are used in the design of trapezoidal canal with curved-toe slope of Dayuzhang North main canal in Shandong province. The calculation results by the proposed approach are the same with those by the traditional calculation method which selects minimum displacement rate, but reduced 27cm of cushion compared with the traditional method which selects maximum displacement rate. Average surface temperature and frost heaving ratios of canal were measured during freezing period. Frozen soil can be considered as negative thermal expansion materials whose negative linear expansion coefficient is the ratio of frost heaving ratios and the average temperature. Elastic moduli and Poisson's ratios of frozen soil and frozen sand in different temperatures are selected which are widely used in other literatures. Meanwhile, the finite element software ANSYS was applied to simulate thermal-mechanical coupling process before and after laying cushion. The results show that the cushion can undermine frost heaving by improving temperature field and moisture field. Numerical analysis indicates that frost heaving and frost-heave force of the lining structure are apparently reduced, up to 90% at the shady slope.

When tunneling in high geostress region, the surrounding rock often produces obvious rheological deformation. The deformation would lead to stress concentration at the connection between side wall and inverted arch, which might result in floor heaving during tunnel operation period. So, a reasonable section shape of tunnel which could reduce stress concentration is very important for the long-term stability of tunnel. Considering rheological effect of surrounding rock, the parameterization design of tunnel section is programed into ABAQUS by Python. And a tunnel section optimization algorithm is established based on combination penalty function and Nelder-Mead function. An optimized objective function is established for Xiakou tunnel considering excavation area, floor heaving, creep damage area, axial force and bending moment of supporting system. The optimization results will provide scientific guidance for high geostress soft rock tunnel.

The rapid developments of geotechnical constructions have greatly expedited the applications of 3D numerical modeling. Large-scale 3D finite element computations may lead to a series of large linear systems of equations, and solving these linear equations may significantly influence the efficiency of entire finite element computation. Complex geotechnical problems usually involve multi-body and multiphase coupling interactions, and the remarkable contrast in material properties for different phases or materials may lead to slow convergence or even failure of a Krylov subspace iterative method. To improve the solution efficiency and reliability of a Krylov subspace iterative method, a robust preconditioner should be employed. Based on some typical geotechnical problems, a partitioned block preconditioner is developed. By using some numerical examples, performances of the preconditioners are examined and their applicability is evaluated.

Underpinning pile-soil nailing (UPSN), a composite structure of underpinning piles and soil nailing, is a new retaining technology. Base on the hypothesis that the underpinning pile top load is equal to the upper structural load with its settlement greater than that of the underpinning pile top, the retaining characteristics of UPSN are analyzed; and its deformation coordination mechanism and load transfer path are discussed. The computing methods of lateral deformation, vertical settlement and inner force are proposed. Parametric analysis shows that UPSN can obviously reduce the deformation and internal force of supporting structure compared to conventional composite soil nailing; the deformation and internal force increases as the upper structural load and horizontal spacing of the micro-pile increases; less affect as the embedded depth of micro pile increases.

The effect of train running on elevated bridge of high-seed railway on existing railway subgrade is analysis by means of the establishment of a pier-soil-subgrade model which is proved to be reliable by comparison with in-field test results. First, the stress state of the existing railway at different traffic conditions is simulated while the influence of rail irregularities and soil modulus is discussed; then, the cumulative settlement deformation under traffic loads of trains is predicted. The research results show that running trains on elevated high-speed railway bridge have little effect on the stress state and accumulated deformation of existing railway subgrade. As a result, the distance between piers and the line spacing in existing railway just need to adjust by the clearance diagram requirements. In case of bad rail irregularities and soil modulus decline, the stress increase induced by high-speed trains won’t exceed 0.5 kPa.

To improve the prediction precise of support vector machine model, an adaptive multiple kernels learning (AMKL) method is proposed. In this method, a tree structure is used to screen the kernels. Additionally, this processing can be implemented with growing and cutting branches manipulation for adding and multiplying the kernels in each layer. This would enhance the nonlinear and diversity characteristics of multi-kernels. Grid traversal and particle swarm optimization method are applied to solve the optimization problem of kernel parameters, weight coefficient and model parameters. It could offset the assignment deviation of parameters which occurs in the lack of a prior knowledge of the training samples. AMKL method is used to predict the settlement of metro tunnel. Comparisons between experimental results of AMKL and the ones of single kernel functions show that AMKL effectively improves the accuracy and generalization.

Effect of wetting-drying on soils derived from granite is significant; and it causes collapse of caved walls or damage of engineering facilities. Slaking test and consolidation test with 6 wetting-drying level treatments are performed to identify effects of wetting-drying paths and consolidation pressures on relative deformation ratio. The results show that crack is the main reason for the relative deformation ratio at dehumidifying stages, while relative deformation ratio depended on matric suction, slaking property, and soil texture at humidifying stages. Relative deformation ratio increased with consolidation pressures especially in excess of preconsolidation pressure of 103.06 kPa. The relationship between coefficient of compressibility and initial water content conformed to an exponential function, and coefficient of compressibility increased rapidly with the initial water contents beyond 25%. Laterite layer ① had the most range of compressibility coefficient （0.15-0.62 MPa-1） with the average value of 0.31 MPa-1. The mechanism of caved wall collapse also is revealed from non-uniform settlement due to wetting-drying effect. Some countermeasures of engineering facilities in disintegration erosion area against nonuniform settlement are discussed. The obtained results could offer references to engineering maintenance and slope disintegration erosion control.

With the Taohuayu loess tunnel of Wu-Xi expressway as the research object, it use field experiment and numerical simulation methods to research the influence laws of grating supporting and section steel supporting on shallow large-span neighborhood loess tunnel. The field experiment shows that the settlement caused by construction is uniform, and the control overall settlement ability by grating supporting and section steel supporting are similar. The stress of grating is smaller than section steel; and the stress distribution of grating is more uniform than section steel. The stress state of grating is similar to section steel; and they are reasonable. The numerical simulation shows that the displacement of section steel supporting is smaller than grating supporting. Compared with grating, the displacement on top arch of section steel supporting decreases 16%-18%, the convergence on side wall decrease 23%; the displacement on arch skew decrease 18%. Using twin-side heading method to excavate large-span tunnel in V grade loess tunnel, the surrounding rock has large plastic deformation. Plastic regional development range is very large, and it needs timely supporting. The plastic development scope by grating supporting and section steel supporting is similar.

In order to forecast and control the damage zone of surrounding rock under blasting load, sound wave tests have been conducted in the construction site of Meihuashan Tunnel in Jiangxi province dragon railway. Based on the change rate of sound wave speed, damage zone size of surrounding rock are obtained. On this basis, a statistics-based damage variable of rockmass has been proposed based on micromechanics. Damage zone size of surrounding rock under blasting load at different in-situ stresses is thus studied by using three-dimensional finite difference software. Calculations show that the numerical simulation results agree well with the site monitoring results. With the in-situ stress increasing, the size of damage zone decreases first, then increases, and increases by a large margin; when the in-situ stress is high, local parts such as tunnel roof, floor damage is more obvious; it is shown that the in-situ stress has significant impact on surrounding rock damage distribution. With the lateral pressure coefficient increasing, the size of damage zone decreases first, then increases, but the growth rate decreases. The results provide foundation for stability analysis of tunnels under high in-situ stress and supporting design of the cracked surrounding rock.

The experimental section is located in the class Ⅳ dead-weight collapsible loess site and is composed of three different kinds of loess foundation treatment measures. The transition sections without foundation treatment exist between them. All 22 m depth of collapsible loess is treated in zone of piles with down hole dynamic compaction. The upper 15 m depth of collapsible loess is treated in zone of cement soil compaction piles. The upper 6 m depth of collapsible loess is treated in zone of dynamic compaction. The results show that the collapsibility of loess within treatment depth has been completely eliminated. Their bearing capacity is higher than the standard value. The composite foundation settlements of piles with down hole dynamic compaction and cement soil compaction piles are less than 15 mm after construction for high-speed railway; but the dynamic compaction foundation can not meet the same requirement. In zone of pile with down hole dynamic compaction, the minimum and average coefficients of compaction are respectively more than the standard values of 0.88 and 0.93; but the average coefficient of compaction and compression modulus of piles are respectively less than the standard values of 0.97 and 100 MPa. In zone of piles with cement-soil compaction piles, the minimum and average coefficients of compaction, or the average coefficient of compaction and compression modulus of piles are also less than the same standard values. Average compression modulus of dynamic foundation is less than the standard value of 15 MPa. The reasonable values of test standard need further study.

Wudongde hydropower station is the upper cascade of the four cascaded hydropower stations on the Jinsha River lower reaches. The dam is 265 m high double curvature arch dam. Based on nonlinear finite element method, the dam and foundation were considered as a system together to analyze. The contraction joints, radiation damping of infinite foundation and nonlinear behavior of the slide surfaces in abutment wedges were all taken into account. The aseismic safety of strength of dam body and stability of abutment wedges were studied under the design earthquake and check earthquake. The ultimate aseismic capacity of the dam-foundation system was explored as well. The results show that, in the design earthquake, only the tensile stress of the arch end areas exceeds the tensile strength, while the compressive strength is all within the strength, and the abutment wedges are stable; the stress increases a little in the check earthquake and the dam-foundation system won’t break under the check earthquake; with the inflection points in the displacement or deformation curves of the typical points as evaluation criterion, the seismic overloading safety factor of the dam-foundation system can be taken as 2.7; while the corresponding horizontal peak acceleration is 0.729g; and the strength reserve safety coefficient can be taken as 2.0 conservatively, which proves that the Wudongde high arch dam owes strong ultimate aseismic capacity.

While the shear strength reduction (SSR) technique based on finite element method is employed to analyze slope stability, the safety factor of slope is dependent on the criteria used for evaluating critical instability condition. Due to the existing variety and uncertainty of the criterion, the rationality and uniqueness of the numerical solution of the safety factor are in doubt; thus, it is especially important to choose an instability criterion, which can not only meet with engineering need but also can facilitate its application. Firstly, a typical example slope is analyzed by using the elastoplastic FEM based on the SSR technique in order to examine the reasonability and applicability of various criteria, such as the abruptness of the displacement , deformation at a certain characteristic location, connectivity of plastic zone. Then, an improved criterion based on the criterion of displacement has been proposed by plotting the curve of displacement multiplying power to shear strength reduction ratio.

Due to the excess pore water pressure dissipation, the post-construction surface settlement will be continued caused by shield tunneling. Based on past research, a calculation method of initial excess pore water pressure around the tunnel is put forward. By using layerwise summation method, the surface consolidation settlement can be got within disturbed region of excess pore water pressure dissipation. Combining with the surface settlement in tunnel construction phase, total transverse post-construction surface settlement is obtained. The total surface settlement after soil consolidation is proposed; and surface settlement rate changes over time are also studied. As is shown in analytical calculation, the calculated results of the transverse surface settlement curves are in good agreement with the field data; and they are also in accordance with the normal distribution law. The development of total surface settlement rate is in good agreement with the field data.

In order to research the reasonable controlling critical technical problem of ground treatment and remnant collapse in the area of dead weight collapse loess with great thickness, a large area and deep level immersion load test was made for pile ground by using different treatment depths. The test results indicate that the foundation treated by the pile ground would have the occurrence of different degrees of foundation collapse settlement after deep immersion in the range of 6-12 m. The remnant collapse of foundation treatment in the depth of 15 m is more than 200 mm; and the foundation’s whole subsidence is relatively small. This phenomenon indicates that the current regulation, Code for Building Construction in Collapsible Loess Regions, is too strict about the minimum depth of treatment for class B and class C building foundations; and it dose not agree with the current standards of economy and technology. It is suggested that the 12-15 m could regard as the foundation treatment rational depth for class B and class C buildings in the area of dead weight collapse loess with great thickness. In light of unreasonable regulations about the remnant collapse of class B and class C buildings in current code, this article puts forward the concept of “remnant collapse reduction factor” and its recommended value, so as to give a reference for the same kind of construction projects and code revision.

High liquid limit soil has some characteristics such as high natural moisture content, high plasticity, high void ratio, and low compactness. Finding the settlement deformation law of high liquid limit soil embankment becomes the key to use it scientifically and reasonably. Based on the mechanical properties of high liquid limit soil, a 26.5 m high embankment was constructed using high liquid limit soil and a long-term settlement observation was carried out. Observation results show that the road settlement value is very high during the subgrade construction; the settlement is smaller in the natural sedimentation time; and the settlement is very small after the pavement construction, about 0.2% of the height. The settlement value is proportional to the subgrade height. Adopting simplified unsaturated soil consolidation theory, the settlement and deformation of high liquid limit soil have been calculated; the calculation results is basically identical with the measured settlement of high liquid limit soil embankment, consolidation theory of unsaturated soil provides a new technical mean for high liquid limit soil embankment settlement calculation. The results prove the post-construction settlement of high liquid limit soil will not be larger; so as to provide a technical basis for its popularization and application in highway engineering.

A large three-dimensional model of double hole four dimensional Danba hydropower station diversion tunnel excavation is established, and rock mechanics are calculated by using the Mohr-Coulomb model finite element analysis method and unloading rock mass theory and method, and the effect of stress on tunnel is considered to excavate in different depths of tunnel face, from the hole to a certain depth. The displacement changes of tunnel faces at different key points at each excavation are counted. In comparison, the depth of the best tunnel face propulsion should be selected. Under the propulsion depth, the amount of reserved displacements at different segments and locations of holes is counted to provide data support of necessity of advanced support so as to ensure the construction process successfully. It provides references for other similar engineering design.

Adopting Monte Carlo simulation technique, a method for describing the variability of site transfer function (STF) with respect to the variability of site characteristic parameters is proposed. Two Kik-Net seismic strong-motion stations, which were installed on hard ground (FKSH12) and soft site (FKSH14) in Japan, were selected and corresponding probability site models were established. 50 site soil profiles were randomly generated for hard ground and soft site via Monte Carlo simulation; and then the STFs were calculated as well their standard deviations, respectively. The standard deviations of STFs and the site characteristic frequencies were discussed in three cases, i.e. varying subsoil thicknesses (case I), varying subsoil shear wave velocities (case II), and varying subsoil thickness and shear wave velocities (case III). The results show that: the standard deviations of site characteristic frequencies of hard ground is overall larger than those of soft site; the standard deviation of site characteristic frequency of hard ground is the smallest in case I, followed by case II, while in case III the standard deviation of site characteristic frequency is the largest; the standard deviations of soft site characteristic frequencies in case I and case II are comparative but weakly smaller than that in case III; the standard deviations of STFs in case III for soft site and hard ground are slightly larger than those in case I and case II; but the standard deviations in the three cases are not considerably different; the standard deviations of STF are fairly large in the vicinity of site predominant frequencies with peak values corresponding to peak values of relevant mean STF.

Geotechnical engineers attach great importance to the uplift problem in design and construction of the deep foundation on the seaside. It is very important to know upheaval of foundation and deformation of support structure due to uplift pile before deep excavation, which can save the project cost and ensure the safety of construction. This case study how to deal with the excavation of open-cut section of Gongbei tunnel. The hard contact model of uplift pile and soil is established. And the simulated results are in good accordance with simulation of the uplift pile. Use the range analysis method to study the effect rule of deformation and stress of the whole support structure caused by the change of the length and diameter of pile. The results are obtained as follows: By increasing the pile length can be more effective to reduce the surface settlement; the larger the pile diameter is, the smaller the deformation of retaining wall is; Increasing the length and diameter of pile can control the upheaval of foundation effectively.

Software for nonlinear analysis of a single pile response based on load transfer method is presented in this paper. Different load transfer functions such as a hyperbolic model and a softening model can be adopted in the present software to capture the relationship between unit skin friction and pile-soil relative displacement and the relationship between unit tip resistance and pile tip displacement. In the present software, the single pile is divided into different segments to consider layers of soil, and the influence of the groundwater level on the single pile response can be taken into account. The single pile response derived from the present software is generally in good agreement with the field-observed behavior. The proposed software is efficient, and suitable for the analysis of nonlinear response of a single pile.

The traditional ultimate bearing capacity formula is verified through numerical analysis in this essay. It is shown that the contribution of base width to ultimate bearing capacity in traditional formula is correct. Through the numerical analysis, aiming at the contribution of base width limitation to foundation bearing capacity in code method, we studied a reasonable method for ascertain the bearing capacity, and we believe that determining the bearing capacity of soil with settlement and safety factor of the real foundation is more reasonable. The reflection of the bearing capacity of soil from base width has already effect the settlement and safety factor, therefore we can receive the bearing capacity of soil more reasonable with no necessary to limit the base width.

A three-dimensional finite element seepage-coupling numerical modeling is performed on a 6m thick soft foundation reinforced by geosynthetic-encasement stone column (GESC) with diameter of 0.8 m. The load transfer mechanism and deformation characteristics of GESC composite foundation subjected to vertical loading and excess pore pressure dissipation are analyzed using the numerical model. Compared to conventional stone column (CSC) composite foundation, the stress concentration ratio (SCR) in GESC composite foundation apparently increases while the excess pore pressure, settlement and column shaft bulging apparently decrease. The performance of GESC is further improved with an increase of geosynthetic stiffness. An apparent differential settlement between column and surrounding soil emerges to form a soil arching during consolidation of the surrounding soil, which leads to little change in SCR values after loading. Reinforcement length is found to have a significant influence on SCR and settlement in GESC composite foundation. Full length reinforcement is required for GESCs in composite foundation to assure their entire stiffness and less settlement.

As clean energy, nuclear power has shown broad prospects for development, so it is of great importance to investigate response of nuclear power plant under seismic loading. Firstly, finite element model of the AP1000 nuclear island is built to perform modal analysis for obtaining vibration modes of nuclear island. Then, by using infinite element to simulate the far field ground and finite element to characterize the near field ground, the seismic responses of nuclear island on different ground conditions are studied with the foundation embedment and soil-structure interaction effect considered. Results show that as foundation stiffness becomes larger, the response acceleration of nuclear island increases, while the period corresponding to peak spectral acceleration of nuclear island decreases. At the same time, the node stress of nuclear island increases but its relative displacement reduces. By considering soil-structure interaction, peak value of response acceleration of soft foundation diminishes while the period corresponding to peak spectral acceleration of foundation rises, which implies that soil-structure interaction has significant influence on seismic input of nuclear island on the soft ground. For hard rock foundation, the influence of soil-structure interaction on seismic input can be ignored.

Based on Terzaghi’s one-dimensional consolidation theory, a numerical simulation procedure of oedometer test is developed using the finite difference method. A numerical simulation program written in C++ is implemented and a Matlab fitting process of automatic solving coefficient of consolidation is also developed. The program can simulate the consolidation process of sample with different sizes (drainage heights). Several effect factors such as drainage height, hydraulic conductivity and initial stress, are discussed in detail. The numerical results indicate that the ratio of consolidation coefficient obtained from square root of time method and log time method decreases with the increasing of drainage height and hydraulic conductivity. This variation is more obvious in the condition of lower drainage height. The less of the initial stress, the more time needed for the primary consolidated process. Finally, the numerical simulation results are compared with a set of test data for different drainage heights. The numerical results indicate that the proposed numerical simulation procedure could simulate the oedometer test well, and make it possible to analyze the consolidation properties for largy size specimens under certain conditions, which have a certain theoretical and practical significance for revealing the deformation of soft soil consolidation.

As a new type structure form in soft soil foundation treatment, PCC pile-net composite foundation has been used in high speed railway construction in soft soil area. The dynamic characteristics of PPC pile composite foundation under the train vibration load is worth studying. A reasonable train dynamic loading form is determined in this paper. A three-dimensional dynamic coupling finite element model of tracks-embankment-pile-soil composite foundation is established using software ABAQUS. The dynamic characteristics of embankment, pile and foundation soil are studied based on the modulus changes of foundation bed, pile, cushion layer and foundation. The results show that the dynamic response of PCC pile composite foundation is different from the solid pile; the reflection overlap effect of dynamic stress occurs in the pile. The dynamic interaction of pile and cushion layer is greater than that of soil and cushion layer. The modulus changes of foundation bed don’t affect the dynamic stress of pile-soil seriously. The dynamic load sharing ratio of the pile body increases with the increasing of the cushion stiffness. Meanwhile, the increase in modulus of the cushion enhances the dynamic stress of the pile top, which is due to dynamic deformation coordination occurring between piles and cushion. The increase in modulus of the pile enhances the dynamic stress of the pile and increases the propagation speed of dynamic stress. The PCC pile can bear most of the dynamic load and reduce the dynamic load of the soil, thus reduce the influence of upper load on composite foundation effectively. As the distance increases with the center pile, the dynamic stress of the side pile decreases.

Fractal model for the pore distribution of capillary action of unsaturated soil is built; the maximum rising height of capillary water in unsaturated soil is obtained. Meanwhile, based on Richards equation of water movement, boundary and initial conditions are introduced; based on Laplace transformation, analytical solution of the moisture changes in unsaturated soil subgrade under the action of capillary is obtained. Meanwhile, a calculating example is introduced; the proposed analytical solution and the numerical calculation results without parameters simplification are compared. Finally, the moisture changes under the action of capillary considering different factors in unsaturated soil subgrade are analyzed. The results show that: The results got respectively by analytical method and numerical method without simplifying parameter are consistent. It is proved that the analytic solution is reasonable and feasible. The greater the initial moisture content of subgrade filling is, the smaller the initial suction of the filling is, the smaller the rise height of capillary water and the change amount of moisture are. The rising speed of capillary water with the better subgrade filling permeability is faster. But the rise height is smaller, capillary water can rise to the largest height in a short time. Different types of subgrade filling have different moisture change states of subgrade under the action of capillary. Corresponding waterproof and drainage measures are needed according to different types of subgrade filling.

Geogrid-reinforced and pile-supported expressway embankment has been widely applied to soft ground improvement; but its bearing and deformation mechanism has not been deeply understood. Combining with the Fourth Yangtze River Bridge’s north-line soft ground reinforced project in Nanjing, the numerical method is used to analyze the variations of settlement and stress of pile and soil, pile axial force and excess pore water stress. The results show that road embankment load is mainly borne by piles as a result of the soil arching effect. The soil pressures of pile and soil increase with the development of embankment load firstly; and then the pressure of pile continue to increase while the pressure of soil decreases in the consolidation process of soft soil. The pile axial force increases quickly during the process of filling. Negative skin friction develops along most part of X-section cast-in-place pile shaft; and the neutral point ascends firstly; with the consolidation of soil, the depth of the neutral point becomes deeper; then the neutral point position is unaltered at the end of soil consolidation.

Firstly, on the basis of wheel-track interaction theory, a function of exciting force of moving train on elevated line is established. Then, the exciting force is acted on the three-dimensional numerical models of rail structure, elevated line and soil foundation by utilizing the finite element software. The surrounding environment vibration response caused by train operation is simulated; and the numerical results are compared and verified by the field measurement data. Furthermore, the parameter effects of length of bridge span, train speed and soil properties on environment vibration are studied. On the basis of investigation of parameter influence characters and according to the statistical analysis, a prediction formula of vibration level on ground induced by urban rail transit with elevated line is presented and validated by the field experiments. The research results show that the numerical simulation and prediction can truly reflect the actual environment vibration caused by urban rail transit with elevated line.

Based on an engineering example, this paper explored a method to determine engineering parameters by utilizing mutable characteristics of monitored values during numerical simulation. The carrying capacity limit of engineering structure was inferred and engineering parameters were reasonably determined, based on comprehensively considering variation features of stability safety factor, displacement and tensile stress in characteristic position along with the change of engineering condition. Compared with common ways, this method was less effected by human factors, which meant more objective result. Analysis steps of this research method are listed in the paper, which provided analysis of similar engineering problems with some learning experiences.

Jointed rockmass contains numerous discontinuities. Many of them are not distinctly separated and have certain cohesive strength. The bonded interfaces enable the jointed rockmass to have a high strength. When subjected to the dynamic load, these discontinuities will debond, dissipating the strain energy accumulated in rockmass. The cohesive properties of the discontinuities govern the fracture energy of rockmass to great extent. The debonded interfaces significantly weaken the rockmass. The improved Xu-Needleman potential function can well describe the cohesive properties of cohesive discontinuities. Based on the improved Xu-Needleman potential function, the paper derives the cohesive discontinuities element. To simulate the cohesive discontinuities in a jointed rockmass, the cohesive discontinuity element is embedded into the element partition method, which allows an intact element to accommodate a discontinuity without introduction of external degrees of freedom. When the cohesive discontinuity element is identified to debond; it will be automatically replaced by a usual joint element to reflect the contact and the friction effect between the debonded discontinuities. The simulation example suggests the discontinuity element in conjunction with the element partition method is an efficient method to simulate the discontinuity debond and growth in the jointed rockmass. The perspective of the present method should be highly inspiring in simulating the failure behaviors of the jointed rockmass subjected to dynamic load.

Joint systems in rock masses are geometrically complex; and investigation of the hydraulic properties is important for understanding the hydraulic behavior of jointed rock masses and stability analysis of rock engineering. A discrete fracture network (DFN) model was designed using C++ language based on VC++6.0 platform to realize a fracture network for seepage analysis. The permeability coefficients, possibility of equivalent permeability tensors of the jointed rock masses were examined by simulating flow through DFN models of varying joint properties. A directionality coefficient was defined to quantitatively assess the principal flow direction in jointed rock masses. The results show that the permeability coefficients are anisotropic according to permeability tensor analysis for rock masses with only one set of joints. The degree of obliquities of joint plane affects obviously the principal direction of permeability. The permeability coefficients increase logarithmically with the increase of joints connectivity rates. In the scenarios where two sets of joints existed, the anisotropic properties vary with the joints geometrical distribution. The permeability anisotropy in a fracture network with two mutually perpendicular sets of joints still exists; and however, the directionality coefficients are examined smaller. For the dip angles whose probability distribution can be effectively by normal function, the permeability coefficients increase with increasing of the standard deviation. The principal direction of permeability runs similarly along the direction of angle bisector between two sets of joints.

A model of joints with five different roughnesses has been built successfully by using the particle flow code(PFC) in two-dimensions; and a series of numerical simulation direct shear tests which under 5 different constant loads have been done. We can observe the morphology damage and crack evolution mechanism of five different roughnesses joints under different constant loads from the viewpoint of mesomechanics. At the same time, the influence of JRC value and particle friction coefficient of joint on the joint shear strength is analyzed. And a joint plane shear strength parameters and relations with JRC values are back analyzed. Detailed results are as follows: normal constant load larger is, the greater the peak shear stress of joints is, the smaller the dilatancy phenomenon is, the greater the range of joints morphology injury is. With the development of shear, the surface contact area of the upper and lower joints reduced; microcracks produced along the joint surface. As the shear displacement continues to increase, the number of microcracks increase significantly, and not limited to the vicinity of the joint plane; but to enter inside the model. The peak shear stress of joints increases with the increase of joint roughness (JRC value) and the particle frictional coefficient of the joints. Joint shear strength parameters Cj and ?j increase with the increase of the JRC value. The results can provide reference and basis for the indoor tests and engineering applications.

Surrounding rock loose circle support theory has been widely recognized and accepted by engineers, how accurate and fast detection loose circle depth better for engineering services become all issues of concern, the new Lan-xin railway girder tunnel based on field test, the test section of surrounding rock loose circle depth by single-hole sonic test method, the ground penetration radar(GPR) for detection and combining with the ground stress and physical and mechanical parameters of rock mass according to the result of the benchmark for the numerical simulation analysis shows that with single span acoustic test results for reference, GPR test results and acoustic method test results are basically the same, in the surrounding rock water area test results in some deviation, geological radar emit electromagnetic fields to water area is relatively sensitive, transmit and receive interference is bigger, but the geological radar as a rapid and nondestructive detection method should be strongly applied: Due to the numerical calculation of surrounding rock loose blasting without considering the influence of the circle, the calculation results are slightly smaller that ones obtained by the acoustic detection, but the trend is basically consistent. Numerical calculation should be based on the physico-mechanical parameters of rock mass stress and according to the test results, so as to make the results of calculation more real and better for the decision of project service.

In order to investigate the effect of pressure variation on the deformation of surrounding rock, a rod-type fiber-optic displacement sensor based on the fiber Bragg grating(FBG) sensing technology was developed and successfully used for displacement monitoring in the geomechanical model test of salt rock gas storages. The test results show that: the gas injection and extraction rate is an important factor affecting the operation safety of salt rock gas storages. Convergence displacement is monitored during gas injection while expansion is monitored during gas extraction. Both of the displacements increase with time and pressure variation rate. In the space domain, the pressure variation has most obvious effect in the middle part of the caverns. In order to ensure the operation safety of the caverns, the maximum gas extraction rate for the studied caverns should be less than 0.65 MPa/d; the maximum gas injection rate should be less than 0.75 MPa/d.

Computer aided inspection (CAI) has been successfully applied to measure the surface displacement field in landslide model test. The deformation and the surface changes during the test were tracked and monitored by 3D laser scanner with high degree of precision and resolution. The surface displacement field can be obtained by 3D measurement between the reference and tested object. The technical route for CAI in landslide model test was put forward and the practical test stabilized with piles has been carried out; and satisfactory results were achieved in the test. The results show that this method is available to provide a rapid collection of field topographical data with extremely high density and a comprehensive information for the surface displacement field that are difficult to obtain in point based measurement. The boundary effect and the soil arching effect can be represented more intuitively and vividly by CAI. The test results indicate that the surface displacement field measured by this technique is of evident regularity and its measurement results fit well with the qualitative analysis, theory analysis and phenomenon occurring in the process of the model test. And the displacement field results are creditable and reliable.

The dynamic parameters of frozen soils is one of the important bases of engineering design, also the indispensable factor for the numerical calculation. The dynamic parameters directly affect the correctness of engineering design and numerical simulation. By analyzing the dynamic load triaxial test, and with reference to the structure of ordinary direct shear apparatus, Beijing Jiaotong University developed a new dynamic load direct shear apparatus. The apparatus used dynamic load actuator instead of the traditional direct shear apparatus's static load part, which can provide a 0.1-6 Hz, 0-20 kN dynamic load. Power systems, measurement and control systems of the dynamic load direct shear apparatus are analyzed; and the parameter selection of instrument frame, direct shear box, dynamic load actuators and so on are analyzed. Finally, by using the apparatus, a set of validation experiments have been carried out. The results show that the dynamic load direct shear apparatus can complete its purpose; stress-strain curve of frozen soils under dynamic loading can be measured, so as to open up a new way for determining kinetic parameters of frozen soils.