The progress in constitutive models for unsaturated soils is briefly reviewed at first; and then the state of the art of elastoplastic constitutive models for unsaturated soils is summarized. This paper focuses on introducing an elastoplastic model coupling hydraulic and mechanical behaviour of unsaturated non-expansive soils. As an example, a coupled elastoplastic constitutive model proposed recently by the author et al. and its model predictions are shown herein for illustrating the structure of the coupled model and its performance. Hydraulic hysteresis in the soil-water characteristic is modeled as an elastoplastic process with the elastic region of the saturation degree. The effect of change in degree of saturation on the stress-strain-strength behaviour and the effect of change in void ratio on the soil-water characteristics are taken into consideration in the model; in addition to the effect of suction on the hydraulic and mechanical behaviour. By using the same values of the model parameters, hydraulic and mechanical behaviour of unsaturated soils can be consistently predicted under the control of suction or water content along various total stress paths. The elastoplastic constitutive model for unsaturated expansive soils and the application of the coupled model to the finite element computations are introduced in brief.

The principle of effective stress is the most important and fundamental principle in soil mechanics, by which soil mechanics has separated from continuum mechanics and become an independent discipline. Traditionally, however, the validity of the effective stress principle remains questionable for unsaturated soils. The historical evolution of the effective stress for unsaturated soils is reviewed firstly based on an expression of the work input into multiphase porous media; and then the formulation of the generalized effective stress for unsaturated soils is put forward. It is shown that neither the single effective stress nor the two-stress state variable approach is sufficient to describe the deformation and strength characteristics of unsaturated soils. By considering the deformation work input of unsaturated soils, the concept of generalized effective stresses that can be used to simulate the behavior of unsaturated soils is proposed. The proposed approach is fundamental and theoretically sound, paving a solid way to simulate the fundamental behavior and constitutive relation of unsaturated soils.

The effect of high temperature and temperature cycle is a new question in the progress of rock mechanics. Based on the evolution mechanism of microcracks in fractured rock mass which experienced temperature cycle and using scanning electron microscope(SEM), the fracture mesostructure investigation of heated marble was conducted. The data of microcrack parameters in different temperatures were processed based on statistical theory; and the regularities of distribution of microcrack parameters were obtained. The microcrack distribution in engineering rock was reappearance by means of the Monte Carlo stochastic simulation; the fractal dimension and the evolution characteristics of heated rock were studied by the fractal calculation to the two-dimension microcrack network models. It is a theory and reference for analysing the microscopic changes of inner medium by means of conventional mechanics method.

When the soil sample which has the feature of poorer permeability is used to do consolidated drained triaxial tests, its processes of saturation, consolidation and shearing will take a long time. A new drilling and sand replacement method of consolidated drained triaxial tests which is done by drilling and replacing sand in soil samples is put forward to improve the test efficiency; and the verification of this test has been done. As the experiment result of the scheme indicated, the sand drain, the replacement ratio of which are between 1 % and 3 %, has small effect on the stress and strain of consolidated drained triaxial tests, at the same time is beneficial to accelerate the soil sample‘s process of saturation, consolidation and drainage, pore pressure dissipation, shearing and drainage, and so on. The test efficiency is 5 times higher than that of before. The filter papers are pasted from top to bottom of the soil sample and the boreholes inside it are filled with many sands. Combining the above two practices, this method is a scientifically rational, effective and good method which has attained accurate and reliable parameters of the E-B model.

The compression tests are completed on saturated bentonite and sand-bentonite mixtures with different preparations. The test results show that the compression curves present a bilinear shape, which is different from that of ordinary normal consolidated clays. The coefficient of lateral earth pressure of saturated bentonite at-rest is obtained by K0-oedometer; and the K0 value is greater than that of ordinary clays. The change in the lateral stress is obtained during the water uptake test on compacted sand-bentonite mixtures which is transited from unsaturated to saturated states. The compression curves of compacted specimens saturated by the water uptake test and the vacuumized methods tend to be consistent in the relatively high stress range. Thus the vacuumized method for saturating the specimens can be adopted to save time for performing the water uptake test. The concept of skeleton void ratio is used to judge if the sand skeleton is formed in sand-bentonite mixtures, and to obtain main factors affecting the compression behaviour of the mixtures.

The mechanical behaviour of soil-structure interface was investigated by using ring shear apparatus. The different interfaces include three types. The test results show that the stress-strain behaviour of different interfaces is apparently different. Mud-cake can change the contacting properties of interface. For the case without mud-cake, failure plane may occur in soil or on soil-structure interface. For that with mud-cake, for example drilling pore pile, failure plane is always taking place in mud-cake. In all tests, the relationship between average shear stress and normal stress is linear; and the shear strength of interface may be described with Mohr-Coulomb criterion. Friction angle of interface with mud-cake is only 63.4 % of that without mud-cake.

Particle breakage of coarse granular aggregates modifies its structure directly, influencing its dilatancy, friction angle, strength and permeability. In order to accurately describe stress-strain relationship of coarse granular aggregates, especially in high pressure with significant particle breakage, it is indispensable to develop coarse granular aggregates constitutive model incorporating particle breakage. According to triaxial test results, the stress-strain relationship incorporating particle breakage is developed, on which a constitutive model is generated incorporating particle breakage with application of associated flow rules. The constitutive model incorporates the influences exerting on dilatancy and friction angle by particle breakage. The parameters of model are determined by mutation particle swarm optimization algorithm, on which the stress-strain curves of triaxial test are simulated. The simulation of model presentation and test results accurately describe dilation and contraction, strain hardening and post-peak strain softening features of the coarse aggregates at various confining pressures.

Under the condition of seawater seepage and by considering the behaviors of strength reduction for surrounding rock after yielding, that is plastic-softening, the analytical equations for calculating the radius of plastic-softening and plasto-residual zones as well as the displacements around openings are proposed according to the elastic-softening- residual plastic triple linear stress strain model. By comparing with other two situations, one is considered seepage only, the other one is considered non-seepage and non-softening, it demonstrates softening is more disadvantaged to the stability of surrounding rocks. The influences of different softening extents on the results are also analyzed. The results provide a theory base for stability analysis of surrounding rocks and engineering practice in subsea tunnels.

When solving Biot’s consolidation equations, different researchers used different continuum equations. The methods Biot M.A. used to deduce the consolidation equations are firstly reviewed. It can be seen that some mistakes exist in the strain energy density function. In order to derive the correct form of continuum equation, two methods are used here. Firstly, based on the analysis of the deformation of the representative element volume (REV) of the soil, a fluid continuum equation which can take the compressibility of grain and fluid into account is derived. Secondly, based on the method Biot M.A. used with modified strain energy density, another continuum equation is derived. The continuum equations deduced from the two methods listed above are found to be equivalent. In addition, the equations are compared to the continuum equation derived by other researchers based on mass conservation law, and they are found to be coincident. Then, the right form of fluid continuum equation is proved and the result can provide theoretical support to consolidation calculation.

Geomaterials are frictional materials, and their strength indexes play a key role in depicting strength characteristics. Illegible knowledge on dilatancy angle has existed for a long time, which caused large errors in theoretical analysis and numerical simulation. It was proved with the generalized geotechnical plastic mechanics principle that the angle of dilatancy should be ? /2 and the corresponding volumetric strain is zero for geomaterials under non-associated flow rule, based on traditional slip line theory. The classic foundation bearing capacity topic of Prandtl’s solution, which has accurate theoretical interpretation, was analyzed systemetically with step loading finite elements under the following three conditions: 1) associated flow rule, 2) non-associated flow rule with the dilatancy of ? /2 and 3) non-associated flow rule with the dilatancy of 0. Results showed that the errors of ultimate capacity obtained under the above three conditions were within 2 %, but the slip line fields were quite different. The slip line field obtained under conditon 2) was identical with that by Prandtl’s solution, but a large deviation existed between condition 3) and Prandtl’s solution. Thus a correct ultimate load and a slip line field with a great error can be acquired under condition 3), but both are precise under condition 2). Therefore, the angle of dilatancy should be ? /2, not 0 widely used at present when non-associated flow rule is applied.

A new meso-mechanical testing scheme based on SEM is developed to carry out the experiment of microfracturing process of rocks. The image of microfracturing process of the specimen can be observed and recorded digitally. The microfracturing process of Jinping marble specimen in Sichuan province under uniaxial compression is recorded by using the testing scheme. Quantitatively investigated the propagation and coalescent of cracks at meso-scale with digital technology, the basic geometric information of rock microcracks such as area, angle, length, width, perimeter, are obtained from binary images after segmentation. The failure mechanism of specimen under uniaxial compression with the quantitative information is studied from macro/micro scopic perspective. The result shows that during the damage of the specimen the distribution of microcracks in the whole specimen are still subjected to exponential distribution with some microcracks concentrated in certain regions. The conclusion indicates that the testing scheme is applicable.

Soil compacting effect of jacked-in pile in the saturated soft clay is a topic of concern in the geotechnical engineering. Monitoring laws of lateral displacement of soil, pore pressure and land upheaval during pile-sinking is a project that a lot of researchers hope to implement. In this research, three full scale jacked-in piles are penetrated into the saturated soft clay and mostly studied by monitoring the law of lateral displacement with depth and radial distance to pile-sinking, the law of land upheaval with depth of penetration and radial distance to pile-sinking, and the law of pore pressure with penetration depth and time. Characteristics of maximum excess pore water pressure with radial distance and depth are also analyzed. From this test results, it is obtained that the maximum lateral displacement occurs at a depth of about 0.75L; land upheaval build up rapidly and reach the maximum when the pile tip arrive at depth of about 6 m; and the increment of excess pore water pressure reaches the maximum when the pile tip arrive at the piezometer level; while the maximum excess pore pressure presents a hysteresis quality with radial distance.

Triaxial consolidation undrained shear tests were performed on both undisturbed and remolded samples of soft Lianyungang clay to investigate its undrained shear strength behavior. The test results indicated that the strength envelope of the undisturbed sample is composed by two straight lines separated by the triaxial consolidation yield stress. The strength envelopes of remolded samples, however, are straight lines through the origin. When the applied confining stress is less than the triaxial consolidation yield stress (i.e. pre-yield stress state), undrained shear strength of undisturbed samples are larger than remolded samples due to the resistance of soil structure. While at post-yield state (the applied confining stress is larger than the triaxial consolidation yield stress), strength envelope of the undisturbed sample lies among the remolded samples with different initial water contents. This difference is found to be caused by the difference in initial water content. The changing in water content and strength with confining stress for undisturbed sample at post-yield state behave like as a remolded sample at given initial water content. The compression behavior of undisturbed sample at post-yield state or remolded samples of different initial water contents can be well normalized by the void index proposed by Burland.

The matric suction has very important influence on the characteristics of unsaturated soil; and it is closely relevant to water content. In order to discuss the relationship among the matric suction, water content and dry density, the matric suction is measured with filter paper method in laboratory. The soil-water characteristics curves （SWCC）for unsaturated laterite with different dry densities are obtained. The equations fitting the SWCC are presented for different dry densities of laterite. The test results show that the matric suction decreases with increasing water content under the same dry density; and the law is more obvious when water content is less than 24 %. The analysis of the parameter of unsaturated laterite shows that the strength of laterite does not increase obviously with the increasing matric suction under the unsaturated condition. The matric suction is not sensitive to density changes for a high water content laterite , and that is contrary for low water content.

Based on tests, electrical resistivity indexes are taken to reflect the changes in soil structures and define the disturbed variable, which is convenient, continuous, economical and practicable. Meanwhile, disturbed function is built by the results of undrained triaxial shear tests and electrical resistivity tests. Additionally, rotational hardening parameter is taken to describe disturbed state of natural soft clays; accordingly, a disturbed state concept constitutive model taking into account stress-induced anisotropy for soft clays is presented. As a result, the traditional methods measuring disturbed variable and establishing disturbed function may be optimized, and the applicability and accuracy of model may be improved. Results from undrained triaxial shear tests show that the model can describe the stress-strain characteristics fairly well and could be applied to practice.

Saturated hydraulic conductivity of landfilled waste was measured by laboratory tests. Soil-water characteristic curve (SWCC) of landfilled waste was measured using a ceramic plate extractor. A method to predict unsaturated hydraulic conductivity of landfilled waste based on its SWCC was proposed and was verified by a laboratory test. Saturated hydraulic conductivities of landfilled wastes in shallow, middle and deep depth of a landfill are measured to be 4.81×10-2cm/s, 3.50×10-3cm/s and 3.56×10-4cm/s, respectively. The results of SWCC tests show that the saturated and residual water content of landfilled wastes are high and that the SWCC curve is steep when matric suction is relatively low. The unsaturated hydraulic conductivity predicted using the proposed method is verified by an infiltration test. The result illustrates the feasibility of the proposed method.

A great many researches show that the rockburst is related to the mechanical properties of rock. The microcracks in rock mass are formed, expanded and converged which have remarkable influences on the mechanical properties of rock. It may bring about material inferiority and failure. For rock samples under uniaxial compression test, its failure forms include friction slippage, self-similar propagation and crankle expansion of microcracks. Based on the fracture mechanism, these mechanisms of crack propagation situated close to the boundary are studied by theoretical methods with considering three different boundary shapes, i.e. straight, convex and concave. Based on “Interface” element of FLAC simulation technology, the direct numerical simulations of crack propagation are proposed and analyzed. When the crack is situated close to the straight and convex boundary, the beam asymptotic model can be employed to find the crack-free surface interaction. A crack-hole-ellipse interaction model is proposed when crack propagation is near a concave boundary using some simplified methods. The expressions for crack propagation near different boundaries are all derived. The results show good agreement between the numerical and theoretical results. The proposed model can analyze the propagating, interaction of crack with free boundary due to stress distributing of surrounding rock, which can provide new basis for rockburst and theoretical research.

Modern industry makes an increasing number of CO2 emissions. CO2 Capture and Storage (CCS) is an enabling technology that will mitigate the greenhouse effect caused by CO2. Salt caverns may be an option of permanent or temporary repositories for CO2. Salt cavern storage of CO2 is attractive for several reasons, e.g. high sequestration efficiency and high rate of filling etc. Storage of CO2 in salt caverns differs from natural gas storage in salt caverns for the continuous cavern pressure buildup of the former. Four main possible factors will influence the long-term pressurization of a CO2 sequestration cavern: salt creep, compressibility of CO2 as supercritical fluid, leakage from caverns and leakage along the wells. The basic concept of CO2 storage in salt rock caverns is described; the research advance of the influence of those factors and their coupling effect is summarized. This paper suggests that since the emission of CO2 in China continues to increase, the coupling effect of the creep-compressibility of CO2-seeapage will be an attractive topic if the geological condition and mechanical behavior of Chinese bedded salt rock are included.

The interior physicochemical and structural properties of rock change under middle-high temperature and triaxial stress; and all these Changes would make a series of the acoustic emission phenomena. The law of the acoustic emission of granite sample under triaxial stress (axial pressure 860 kN, confining pressure 1 150 kN) with temperature is primarily studied by experiment. It is shown in this research that: ① The acoustic emission phenomena of rock discontinuously occur under the effect of temperature. ② There is the threshold for the beginning of granite thermal cracking, which is around of 120 ℃. ③ There are 5 stages for the acoustic emission phenomena of granite cracking under the effect of temperature: movement stage of the rock’s original cracking; stage of the acoustic emission before the thermal cracking; the acoustic emission of thermal cracking stage; still stage of the acoustic emission after the large-scale thermal cracking; second thermal cracking stage.

Based on considering the influences of dry density and water content, the calculation of two parameters, water volume change and permeability coefficient kw, about moisture migration of unsaturated expansive soil is studied. It is shown that the and kw are not constants but functions of matric suction that is closely connected with water content. So the parameters change with the change of water content. In addition, they are influenced by dry density clearly and change with the change of it. Furthermore, it is shown that the relationship between kw, and matric suction is nonlinear by taking the soil density and water content into account. The results provide the fundamental data for further research on water sub-field change in unsaturated expansive soil ground.

Excessive settlement of road on soft subsoil induced by traffic load is the main reason leading to pavement failure. To predict this part of settlement correctly is very important for road design. A simple empirical model for predicting residual strain under repeated load suitable for soft clays is proposed based on test results. The validity of the model is verified by cyclic triaxial test results of Shanghai soft clays. For practical boundary value problems, the traffic-load-induced dynamic stress is calculated by multilayer elastic theory; the residual strain distribution of subsoil induced by traffic load is calculated by the proposed model; and then the settlement can be given by integrating the residual strain along depth. A practical problem, Saga Airport Road, is analyzed to illustrate the proposed prediction method.

Experiments are conducted in a wave flume to study liquefaction of silty soil and development of hard layer under wave actions at the Yellow River Estuary. Results indicate that under wave actions superficial silty soil is in liquefaction for most of the times, which leads to a W-shaped sliding interface between the oscillatory layer and the underlying layer; with the passage of time, thickness of the oscillatory layer decreases while that of plume-like sediments increases till the oscillation is stopped. Therefore, the liquefaction of silty soil is the prerequisite for the development of hard layer, while the oscillation of liquefied soil body due to wave actions makes possible the development of hard layer.

The effects of different initial stress states on the constitutive relations of clay are studied. With clay selected as test sample, two series of triaxial consolidation draining compression tests are performed under different consolidation conditions, isotropic consolidation and K0 consolidation. Based on the tests under the two different initial consolidation conditions, the elastoplastic constitutive models which contain two yield surfaces of two relatively independent hardening parameters and are derived by using numerical modeling method. The three-dimensional surfaces of the stress-strain relations in the whole stress field are drawn through visualization. Moreover, the comparisons of the stress-strain relation curves with the simulated results obtained by the numerical model, Cam-clay model, Duncan-Chang hyperbolic model and from test data are made. It is shown that the numerical modeling method is reasonable, which can reflect the effects of stress paths and stress history.

Many calculation methods for soil nailing walls have been developed. Having ignored applicable preconditions sometimes results in the incorrect conclusions. This paper presents in detail the typical methods widely-used in practice, and particularly the suppositions in deducing them. The preconditions are highlighted to evaluate the specific stability of soil nailing walls. Some noticeable issues to use these methods, such as reasonably selecting a computational model and specifying a slip surface in shape and further appreciating the definition of factor of safety, are presented aiming to provide some insight into the safety, economical and optimal design of soil nailing walls to propose.

Based on unsaturated soil mechanics theory, the instability process of ash storage dam in a power plant is analyzed and failure mechanism of that is revealed. With the increase of lasting time of retaining water by the1st sub dam, some phenomena will occur, such as water infiltrates into the dam body gradually, the phreatic surface rises constantly, the unsaturated region reduces corresponsively, the pore water pressure increases and the shear strength decreases continuously in the site which is influenced by water infiltration. When the process develops to a certain degree, the damage and slide of this ash storage will happen. The analysis in this paper explains clearly the reason why the stability of this ash storage dam suffers great threat if the dry beach disappears for a long period. This study may provide a reference for stability evaluation and forecast of those ash storage dams and tailings dams with the similar working condition.

Ground freezing enclosure is a new technique that makes water in soil be ice by the way of artificial refrigeration, thus change original soil to be frozen retaining wall and waterproof curtain in foundation pit engineering. Based on the freezing principle, frozen soil curtain formed from aquifer has some super performances such as excellent waterproof, higher rigidity and strength, etc. As a new structure system of deep foundation pit in the large anchorage engineering, its important features include that piles and internal strut are used to be exterior-protected construction while frozen soil curtain hold back ground water. Compared with the conventional supporting projects, previous research data of frost mechanical properties in envelope works are always poor. Therefore frost heave mechanical characteristics of frozen curtain are obtained from simulation of three-dimensional coupling numerical nonlinear analysis of the fields of temperature and stress; and the conclusions are verified by field test data in foundation pit engineering. Research achievements may provide theoretical basis of applications in the future, not only for its rationality in analysis and results but also its reliability in techniques and methods.

To reduce or eliminate the damage caused by geologic disaster, based on the data of geological mapping and monitoring, it is vital to build a visual monitoring and forecast system of geological hazards by using advanced computer and 3-D visual techniques. We first use TIN method to build 3-D geological model, which are integrated with the data achieved automatically and conveyed by North Satellites; and then, using time-series based techniques, we analyze these data and build a complete 3-D monitoring and forecast system of slope disaster, and provide numerous applicable GIS tools such as section analysis tool, etc. As a result, the quickness and visual of warning of landslide disaster are enhanced. Finally, to validate the system, we examine the project of Xiakou landslide of Ya’an, Sichuan province.

The neutral point theory is the important theory in underground engineering reinforcement theory. At present, the formula to determine neutral point position has been existed some unreasonable place. The neutral point theory had been further consummated and improved on the foundation of pre-researchers. Base on the developed analytical model and the theory of frictional resistance is zero at the neutral point, the factors have been detailed analyzed for affecting the neutral point position; and the correlations have been gained which affecting neutral point position. Through analyzing, it is revealed that the hydrostatic primary stress, bolt length, bolt spacing having no influence to neutral point position, and the radius of tunnel, Young’s moduli of rock and bolt, the bolt diameter having remarkable influence to it. Among them, it is linear relation among the radius of tunnel, the bolt diameter with the neutral point position, but it is exponential function relations among the Young’s modulus of rock and bolt with the neutral point position. The relationship of Young’s modulus of rock mass and neutral point position presents exponential decreasing; the relationship of Young’s modulus of bolt and neutral point position presents exponential increasing. Through the factors analyzed, it has obtained that the general functional between the neutral point position and the correlation parameter, for further to study the neutral point theory providing the certain reference significance.

The rock resistant coefficient K is an important parameter and it reflects the resistance of the rock around the tunnel in the geotechnical engineering. A formula of rock resistant coefficient is derived based on unified strength theory, which can be adopted to obtain rock resistant coefficient in other situations or strength thoeries simplified by assuming the parameter value in the formula. The strength differential effect, intermediate principal stress effect and the ground water permeation effect are considered in the formula. The results indicate that the coefficient b, cohesion ,friction angle ?, the pore water pressure ,the in-situ stress and the lining pressure all have significant influences on the rock resistant coefficient K.

As a explicit behaviors of the complicated nonlinear dynamic system，the displacement of landslide is characterized with many uncertain factors. In order to reduce the limitation of traditional method, the set pair analysis (SPA) theory combined with fuzzy-Markov theory is introduced to describe the landslide dynamic system, and then the SPA-fuzzy-Markov prediction model for landslide displacement is set up. In this new model, the fuzzy-Markov theory is applied to analyze and predict the state transition of the uncertain factor in SPA model. By this way, the precision can obtained a significant improvement. Based on the correlation coefficient and mean square deviation of eigenvalue, two verify methods for fuzzy-Markov fitting in multidimensional space are suggested. Furthermore, based on these two verification methods; the sensitivity analysis for fuzzy-Markov model in two factors, such as fuzzy interval overlap and state transfer steps, can be done. By this way, the optimal parameter combination can be recommended. As a test，the SPA-fuzzy-Markov composite model is used to analyze the displacement of Liujiatuo landslide. The results indicate that the state transfer step is more sensitive than fuzzy interval overlap in this case. It is proved this new model can conspicuously improve the short-term prediction precision than just single SPA model; and this new model is worth popularizing in geotechnical monitoring. Moreover, the introducing of fuzzy-Markov guides a new way to develop basic research of SPA theory. This new method has theoretical and practical values not only in geotechnical monitoring, but also in other related fields.

Through analyzing the Knothe time function model for the dynamic process of the ground surface subsidence due to underground mining, it is found that the model can’t accord with the observational data. By adding a constant parameter k to the Knothe time function, a new time function model has been set up. The velocity and acceleration worked out from this new time function model is in accordance with the dynamic process of the surface subsidence. In this new model the parameter c decides how long the subsidence would continue; and the parameter k decides the path of the subsidence on the axis of time. This new subsidence dynamic model fits well the curve of the observation data on the inclining section of the surface subsidence basin of a certain coal mine, the parameter c is obtained by practical consideration and the parameter k is obtained by least square method. Combining this new time function model with the section function of the surface subsidence basin or the basin model, a dynamic process model for the surface subsidence due to underground mining is set up; form this model the subsidence and velocity and acceleration of some point on the subsidence basin or the section could be worked out in anytime.

In order to take the effects of the profile on the trajectory of rockfall into account, the boulder is approximately supposed to be elliptic. According to the five common forms of rockfall, containing rolling, slide, collision, freely falling body movement and parabolic motion, the formulae to calculate the velocity of different kinds of motion are proposed respectively. When the boulder collide with earth, the elastoplastic deformations of earth are considered. Coefficient of restitution, which relates to the velocity before collision, the shape of boulder and geomaterial of earth, is presented. Moreover the impulse force due to collision are obtained on the basis of contact mechanics. Besides, the criterion of continuous rolling is put forward. Finally, an illustrative example is given to show the capability of the presented model to predict the rockfall trajectory of Shoulishan in Wanzhou of Chongqing.

A large scale landslide took place when constructing a port on soft clay foundation. A series of engineering measures were taken for reconstructing the port. Detailed investigation and finite element analysis of slope stability were performed to determine the possible causes of slope failure. In the analysis, the excess pore water pressure in the subsoil caused by piling and the traffic load has been considered especially. The analyzing results show that the failure of the slope was caused by the superposition of several unfavorable operation conditions. It is concluded that the primary cause for the slope failure is under-cutting combined with the low tide level. Furthermore, the pile driving and the traffic load on the slope topside also play a negative role in slope failure. The pile driving construction has a notable impact on slope stability and the safety factor considering the piling effect is much less than that without considering it. However, the influence of the traffic load is not so large relatively. The ground at failed slope was rehabilitated using vibro-sand-piles together with a crushed stone layer on the ground surface for consolidation. Finite element method is applied to simulate the ground improvement effect. The analysis results and successful practice show that the use of sand piles for reinforcement and consolidation is an effective technique for rehabilitating the failed slope.

In the process of designing rigid pile composite foundation, thickness of cushion is very important. It is one of the most important factors in the bearing capacity. But there is no theoretical method in designing the thickness of cushion. Based on the relation among pile-soil-cushion, a method for calculating rational thickness of cushion in rigid pile composite ground is derived. The optimization design of the rigid pile composite ground can be performed with this method. Analysis shows that adjusting the stress ratio by changing cushion thickness would exert the bearing capacity and reduce the engineering cost.

IN light of the present situation without mature formulations to calculate the loading of multi-arch tunnel for highway in China, the formulation of the earth pressure is derived based on the loading feature of multi-arch tunnel and PU’S equilibrium arch theories. Considering the division altitude of deep tunnel and shallow tunnel specified in the tunnel code, the division altitude and the loading formulation are proposed. Thus a fully calculation system is formed here. Lots of analyses and calculations validate that the formulation presented is reasonable by comparing with other formulations. Good effects are achieved when applying this formulation in the design of both multi-arch tunnel and bifurcation tunnel for the highway from Shanghai to Chengdu.

Field tests on groundwater level and yield of water was carried out for researching the varying process of groundwater level and yield of water under vacuum preloading. It is concluded that the groundwater level descends rapidly at the beginning of vacuum preloading and then becomes relatively stable; it ascends rapidly after the end of vacuum preloading; there is groundwater recharge from the outside to the inside of the reinforced area during and after vacuum preloading, which forms a depression-cone, until the outside and inside groundwater level become balanceable in motion; the plastic drain has a great effect on the movement of groundwater; the average yield of water is large at the beginning of vacuum preloading and then decreases rapidly until it becomes stable; the average yield of water of the center area is larger than that of the margin area.

An analysis method of piled raft foundation with rigid cap is presented with the research results about allocation rhythm of side resistance in pile group. Based on displacement compatibility relationship, pile body stress and strain equation and force equilibrium relationship, stiffness matrix which relate top force to displacement is deduced. Four types of intreraction is considered herein, that is pile-soil-pile interaction, pile-soil-plate interaction, plate-soil-pile interaction and plate-soil-plate interaction. It is mentioned that pile group can be comprised of piles with the property of various lengths, radii and stiffnesses. The method does not involve the discretization of the soil or piles and it follows the same analysis process and the content of stiffness matrix is just related to the number of pile and soil nodes under foundation cap. Comparison with the results of other analysis methods shows that the method is feasible and accurate.

It is very important to carry out the reliability analysis of soil nailed structures since there are lots of uncertainties in geotechnical engineering. Considering the function of Solver and VB programming of Excel, the spreadsheet computation model for the reliability analysis of soil nailed structures is set up. This spreadsheet model is suitable for layered soils and it can get the minimum reliability index and the location of the corresponding slip surface. The spreadsheet model is composed of five parts: module of input parameters; computation module of soil nailed structure; computation module of soil layers; computation module of reliability index and module of optimum calculation. Once the model is set up, it is very convenient to carry out the reliability analysis for different soil nailed structures. It is demonstrated that the method proposed is correct, simple and direct. It is easy to carry out the reliability analysis of soil nailed structures for different computation cases; and it can also be easily simplified to carry out the corresponding deterministic analysis.

In order to analyze the stability of surrounding rocks of Zhoushan subsea tunnel with drill-and-blast construction method, a typical cross section is chosen according to geological information. A model for numerical analysis is established according to geometrical parameters and geological information.of the typical cross section. An international calculating mode is used to simulate explosive load, and the explosive load is imposed on simulative blast holes in equivalent stress form due to characteristics of dynamic calculation of FLAC3D. By means of analysis of velocities and accelerations of survey points, it is easy to draw the conclusion that each velocity-time curve and each acceleration-time curve satisfy the explosive distortion rule; and the peak values of vibration velocities are less than failure criterion of rock. The influence scope under explosive load is within the recommendatory thickness of rock overburden. Then the rationality of recommendatory thickness of rock overburden and explosive scheme is validated. Eventually, in order to define the effects that are imposed on the surrounding rocks by the thickness of rock overburden and charge amount, the calculation results under different conditions are presented. Some conclusions are drawn so as to benefit the future construction and other analogical rock engineerings.

The slope failure is the common geological hazard and there are lots of methods to evaluate this geological hazard, which expose some disadvantages during the use process. In order to solve these problems, a model of generalized regression neural network is made to meet the slope stability evaluation, which uses the neural network tool kit in Matlab to analyze and calculate the input and output data. Then the reliability and feasibility of the model is trained and tested. It is concluded that the output data agrees well with the actual data by using the model that can overcome the disadvantage of BP neural network used before, if the smoothing factor is chosen appropriately. So the good engineering prospect will be expected when the slope stability evaluation is based on generalized regression neural network.

Surrounding rock stability evaluation of coal tunnel is the basis for judging the level of support difficulty and carrying on support design. Based on analysis and selection of the influence factors on surrounding rock stability and evaluation index, this article proposed an evaluation method of multi-factor single comprehensive index value. AHP Analytic Hierarchy Process is utilized to determine the weights of evaluation factor and weighted average method is to establish calculation models and calculation methods for single comprehensive index value. The results showed that the method of weighted average evaluation for surrounding rock stability of coal tunnel can reflect the stability characteristic of surrounding rock scientifically and provide a reliable basis for rock control and support design.

In order to get the artificial boundary that suits to analyze nonlinear structure-foundation interaction problems, the viscoelastic artificial boundary simulating radiation damping of the far field medium was obtained from the elastic wave theory and viscoelasticity theory. The ability of viscoelastic artificial boundary to simulate radiation damping and methods of seismic wave motion input were studied. The results show good precision when simulating radiation damping of far fields with the viscoelastic artificial boundary obtained from this paper in solving structure-foundation interaction problems. Precise results can be obtained through seismic wave motion input methods obtained in this paper whether the input wave is simple harmonic one or simple nonharmonic one. The displacement peak value at the free earth surface is times as high as that of input wave in viscoelastic medium.

For the influential factors of rock slopes are numerous and their relationship is very complicated; it can not be solved by traditional methods; so generally based on engineering analogy, the clustering methods are used widely. For the complicated environment influence of rock slopes, this clustering problem is a complicated fuzzy and random optimization problem; and it can not be solved by traditional methods very well. So, here a new bionics clustering optimization method, ant colony clustering algorithm, which is proposed recently, has been introduced into rock slope engineering field for the first time. Based on this new bionics clustering method, a new method for study stability of rock slope is proposed. Based on analyzing the data of rock slope samples, from the engineering analogy thinking by ant colony clustering algorithm, the stability of rock slopes can be estimated. The engineering application can prove that: this new algorithm can automatically sort the rock slope samples; and the validity is very high; the computing velocity is very rapid; so it is a very practical method for rock slope stability analysis; and it should be popularized.

During construction of the portal for a tunnel, collapse accident occurred. According to the field geological and construction conditions, the numerical model is set up; and the commercial software ANSYS is adopted to simulate the behaviors of the tunnel and surrounding rock. Based on the results of plastic zones in surrounding rocks, deformations in rock and lining, and the inner forces within rock bolts and reinforced concrete lining, the deformation of the tunnel and the causes of tunnel collapse are analyzed. The results show that: shallow tunnel bias, poor mechanical properties of rock and construction support landslides resulting from collapse. The comprehensive remedy measures consisting of reinforcement inside, surface grouting reinforcement and excavation control are proposed. Good results are achieved so as to offer reference for the future similar projects.

Searching critical slip surface is very necessary in slope stability analysis. Noncircular slip surface search is a multi-dimensional optimization problem to find out several control points, and more complex than searching circular slip surface, in which only center and radius of circular slip surface need to be determined. Common optimization methods can not search critical noncircular slip surface very well due to the complexity of the problem. To overcome the multiple redundancy and low efficient solving of genetic algorithms as a result of no feedback ability, as well as low speed of ant colony algorithms owing to absence of original pheromone, a modified ant colony algorithm has been improved, which is capable of searching in continuous space, to integrate with genetic algorithm to complement each other’s advantages. Finally, a suppositional example calculated by text-mentioned methods and GEO-SLOPE, is illustrated to explain effectivity of the algorithm.

The three dimensional vibration of pavement and double-layered subgrade coupled system subjected to a rectangular moving load are investigated analytically. The pavement-subgrade interaction is considered, and the subgrade is divided into an elastic single-phase layer and a saturated soil layer with the underground water level as their border. By employing Lame decomposition theorem of displacement field and potential functions, the governing equations of the system are solved in the transformed field domains of moving space. Considering the mixed boundary condition at the upper surface，the fixed boundary condition at the lowest surface and that the stress and displacement at the interface of the layers are continuous，analytical solutions of vertical displacement and pore pressure in the form of integral are derived using the Fourier transform and the inverse Fourier transform. Numerical results are obtained by using IFFT algorithm and adaptive quadrature algorithm. Reference is made for analyzing dynamic responses of subgrades.

Pile foundation underpinning method can be used to construct the underground space of the existing buildings .The construction processes are constituted three steps: before the pile foundation underpinning, after the pile foundation underpinning and soil excavation. The construction processes produce secondary settlement deformations, which will result in the additional internal forces affecting superstructure safety. Numerical models of three-dimensional finite element analysis based on Ansys code are established to study the settlement of socles on pile foundation underpinning construction for a three-floor frame structure, on which a flat basement is built. The settlement curve and the settlement difference are obtained by defining paths method. Some conclusions are drawn as follows:The total tendency of socles is basin-shaped settlement which is bigger in the middle position socles than the peripheral position socles before the pile foundation underpinning. Pile foundation underpinning augments the differential settlements. After soil excavation, middle position socles rebound obviously owing to unloading action, which lessens the differential settlements between middle and peripheral position socles.The most differential settlement is produced after pile foundation underpinning but before soil excavation. The additional moment of the superstructure can be gained from the finite element model based on Ansys.

Through considering nonlinear dynamic soil model, reasonable artificial-boundary and coupling damping model, a 3-D finite element dynamic model of rigid pile composite foundation-superstructure interaction system, is established. Through calculations the different seismic responses of the structure with rigid pile composite foundation and with common pile foundation are compared. At the same time, the influential factors and aseismic capability for rigid pile composite foundation is studied by considering soil modulus and soil layer, embedment depth, pile length and pile diameter, sand-gravel cushion thickness and modulus, structure characteristic, etc. All the results and conclusions will provide theoretical basis for engineering design and practice.

The failure of a high rock slope is a common phenomena in nature, however it is a very complex subject which is worth studding. This paper presents an analytical method, which is a combination of methods of engineering geology and back analysis, for simulating the deformation behaviors in earthquake and providing some useful insights into the deformation mechanisms. Based on a project of a high dip bedding rock slope of a hydropower station in Southwest China, at first the engineering geological characteristics of the high slope is analyzed. Secondly, a 3D numerical model of the slope before the earthquake is established by estimating the ancient topographic and morphologic characteristics and reinstating the glided mass. Then the software FLAC3D is used to analyze the seismic time-history response of this slope. The calculated results accord with the situation happened in the earthquake. Finally, this 3D dynamic response back analysis method can provides the dynamic coefficients of rock mass which can be used in the next numerical modeling for this slope.

Seepage field has a great influence on stress field of shield tunnel structure during construction under high water pressure. The FEM has been used to analyze the coupling seepage field and stress field under different water pressures based on the drainage tunnel project crossing the Yangtze River at the downtown of Chongqing city. The segment’s stress distribution, displacements and pore pressure distributions are calculated. Water pressure distributing rule has been studied emphatically; and the results are verified by the in-situ data. The calculation show that segments need to take more tensile force under coupling effect. The achieved results offer helpful reference and basis for design and construction of this project.

The existence of the joints is an important characteristic of rock mass distinctly different from rock, and it is also an important factor leading to the heterogeneity and anisotropy of rock mass. The failure characteristic of jointed rock mass under blast impact load is not only a hot subject in study of rock mass mechanics, but also an engineering problem in rock blasting, while such models as those created by finite element method and discrete element method cannot objectively reflect the actual distribution law of joints in rock mass. However, the new kind of numerical method——numerical manifold method can create the calculation model completely according to the actual distribution law of the joints in rock mass, and can perfectly simulate the occurrence of the new cracks and opening of the existed joints in the rock mass under the action of external load. By corresponding program of numerical manifold method, the failure process of the rock mass with such three kinds of joints as horizontal joints, vertical joints and no joints under the impact load perpendicular to the circumference is simulated. From the simulation result, it can be evidently seen that the existence of the joints plays a vital role on failure form of rock mass. The failure form of the intact rock mass has good symmetry, while to horizontal jointed and vertical jointed rock mass, their failure forms are controlled by the distribution of the joints to large extent. The study result is of certain meaning in rock blasting engineering design.

During the course of earth pressure balance shield tunnel construction, support pressure on the cutting face influences the stability and deformation of stratum ahead the face greatly. Stress condition of stratum ahead the face is analyzed theoretically and classified five kinds. Stability of the stratum ahead the face is judged by support pressure. Three-dimensional finite difference model is built to study the relevance of cutting face support pressure and deformation. The results show that the relation curve of cutting face support pressure and deformation is parabola in unloading conditions and is hyperbola in loading conditions respectively. Detailed configuration of the curve is relevant to the stratum conditions. The results of research can offer reference for the confirmation of support pressure during the course of earth pressure balance shield tunnel construction.

Pile may incline due to the excavation of tunnel or pit, incorrect driven sequence and other reasons. It is a common practice that pile inclines partially. For example, the upper part of a pile inclines due to flexural deformation while the lower part still remains vertical. Based on the results from load-tests on totally inclined piles and finite element analyses, finite element models are constructed to analyze the bearing capacity of partially inclined pile. Finite element analyses show that under the same vertical load, settlement of partially inclined pile with the degree of inclination within 5 % is smaller than that of vertical pile. When it is above 5 %, settlement of partially inclined pile is greater than that of vertical pile. Under the same vertical load, settlement of partially inclined pile with the degree of inclination within 7 % is smaller than that of totally inclined pile with the same degree of inclination, while when it is above 7 %, the trend reverses. For partially inclined pile, axial load transferred to the top of lower part of inclined pile will produce a lateral force on the lower part, which will lead to larger inflection deformation and moment in the lower part of the partially inclined pile especially when the joining point is below the point of inflection. The deeper the joining point, is the greater the lateral displacement is at partially inclined pile top, which will certainly make it easier for the inclined pile to fail due to excessive flexural deformation.

An analysis of 3-D steady seepage field by the stochastic finite element method (SFEM) is performed. The formulas of response variables (water level and hydraulic gradient) in stochastic seepage analysis are deduced based on first order Taylor series SFEM; and then the stochastic analysis of seepage field is performed; and a corresponding program is developed. The permeability tensor of infiltration domain is dealt with 3-D anisotropic random field; and vector separable local average method is adopted for discretization of random field. The number of random variables derived by discretization will be various if the parameters are selected with different values. Finally, an example is given and discussed; the results of random seepage field in cases with different numbers of variables are derived. Then the feasibility of the proposed approach is proved by comparing these results with the results which are derived when the permeability tensor is only dealt with random variable.

The apparatuses of measuring method of flow velocity based on distributed optical fiber sensing technology are introduced briefly. By studying the heat-transfer process between optical fiber and running water, the theoretical equation of the method about flow velocity, stable temperature rise of optical fiber, heating power and other parameters is deduced. Model test is designed. And temperature rise tests of different flow velocity and heating power are carried out. Based on test data, temperature rise rules of still water and running water are compared. The results indicate: all curves of temperature rise compose of two stages, and the temperature rise in still water is higher than that in running water, and the temperature difference becomes greater with flow velocity and heating power. The effect of heating power on temperature rise of still water and running water is studied; and it is found that the stable temperature rise in still water has linear relationship with heating power. Stable temperature rise of optical fiber has nonlinear inverse relationship with flow velocity. At last, this method is discussed; and further study advice is put forward.

The article tries to carry out the image reconstruction of pile body based on the principle of ray tracing with grid, and by using the method of ultrasonic tomography, which combines successive linearization iteration with least square QR decomposition with damping. According to test results of model piles with defects to be pre-set, ultrasonic tomography method is used to analyze the ultrasonic velocity and its characteristic impedance. The results show that the ultrasonic tomography method can be applied to the integrity testing of pile foundation, and to identify the position, shape and size of defects of pile body in the cast-in-place pile. Moreover, it can reach the higher precision. Especially, for analyzing the characteristic impedance, it can provide the exact data for the quantitative testing of integrity of pile foundation. Therefore, it will have higher application value in the integrity testing of pile foundation and geoengineering treatment of defects.