A series of oedometer tests under different values of constant vertical net stress have been undertaken by by Alonso et al. To verify the test results presented by Farulla et al., two kinds of tests for overconsolidated unsaturated clays w Farulla et al. to investigate the behavior of overconsolidated unsaturated clays during wetting. It is shown in the experimental data that the volume change induced by wetting varies with the vertical net stress, which is not exactly the same as the assumption proposed ere carried out using the double-cell triaxial system. One is a series of tests to investigate the effect of overconsolidation degree on wetting behavior under the same preconsolidation pressure. The other is the triaxial drained tests under a certain suction to study the behavior of deformation and strength of overconsolidated unsaturated clays. The results of the experiments confirm the verification of the interpretation by Farulla et al. Moreover, the behavior of overconsolidated unsaturated clays under wetting paths observed in the experiments is modeled by the UH model.

An analytical method for estimating cracked rock mass equivalent deformation modulus is presented, by considering deformation of rock block and cracks separately. Verification of the method for determining the equivalent rock mass deformation modulus is conducted against closed-form solutions for regular cracked rock mass, leading to very good agreements. Furthermore, equivalent deformation modulus of the randomly cracked rock mass in Jinping hydropower station are studied. Results gained by the analytical method show that representative eleementory volume(REV) of the studied rock masses is 8 m, which is the same as the results achieved by finite element method. Study results show that the developed analytical method can be used in estimating the REV properties of fractured rock mass, which is of great important in parameters determination for fractured rock mass.

Focusing on outburst coal and nonoutburst coal, the permeability experiments on the outburst coal and nonoutburst coal briquettes during the complete stress-strain process were designed using “Coal Containing Gas THM Coupling System”; to study their permeable properties in the complete stress-strain process. The results show that: during the complete stress-strain process, the deformation of outburst/nonoutburst coal showed similar trends with gas volume flow velocity, which means, in the complete stress-strain processes of both kinds of coals, gas volume flow velocity is tightly related with the damage deformation process of coal. The gas volume flow velocity decreased with the compressing of coal volume, decreased to the lowest value when the coal volume was compressed to the minimum; and then when coal volume began to expand, gas flow velocity turns to increase. The gas volume flow velocity decreased with the increasing of confining pressure; and the higher the confining pressure was, the smaller the changing rate of gas volume flow velocity to strain was. The properties of coal show an evident effect on gas permeation; so the permeability could be treated as a significant criterion for the judgement of coal-gas outburst criticality.

Yieldable steel supports are common support forms in deep and weak roadways of a mine, to accommodate the large deformation of their surrounding rocks. The internal forces of a close type yieldable steel support are calculated, in which the support nodes are yielded in the cases of the great loads or large deformation of the surrounding rocks of a roadway. Actually, the underground structure is a hyperstatical structure. The yielding of the support is an irreversible process. And the shape of the support would be changed and the deformation of support would be limited by the ataples of the support nodes after yielding. So, they would produce the internal force in the yieldable steel support. The true internal force of the support after yielding could be got by calculating the residual internal forces due to the yielding of support and the staple’s limited and by adding the internal force due to loads. The results provide a theoretical basis for the design and calculation of yieldable steel supports

In order to solve the key technology of ultra-deep well drilling-improving cutting efficiency and rate of penetration in marine facies complex exploration area of south China, it is required to collect outcrops of Northeast Sichuan area formation, test and analyze their rock mechanical characteristics at normal temperature and simulated downhole conditions with available apparatuses. The goal and meaning of the test and collected samples were briefly introduced. The experimental scheme, testing apparatus, samples, the results and data statistical method were stated. According to statistical results, the method for analyzing rock mechanical characteristics of deep formation and related qualitative and quantitative results acquired were presented in detail. And the rock breaking mechanism of ultra-deep well drilling was qualitatively analyzed. Research shows that by testing and analysis: the mechanical properties of the rock directly related rock breaking. Under the action of temperature and pressure factors, the deep changes in mechanical properties of rock result in rock broken of cut way to scrape more difficult in the deep strata of rock. This is the key factor of the ultra-deep drilling speed can not be greatly improved. Through this pilot study and analysis, access to a set of rocks mechanical properties under different environmental conditions. Changes in mechanical properties of the qualitative and quantitative conclusions will provide technical support for rock breaking mechanism, high-performance bit research and selection in deep and ultra deep drilling

Water swelling and drying shrinkage due to moisture change is the expansive soil’s characteristic which is similar to the thermal effect of material. Stress is generated by the swell-shrinking deformation constraints and the concept of moisture change stress is put forward. The moisture change stress is adopted to calculate swell-shrinking deformation based on the thermal stress and elasticity theory. A theoretical model which could calculate the moisture change stress resulted from moisture change is established. The mechanism of cracking is the different rates of water loss in different depths which caused the uneven shrinkage deformation. The critical value of moisture change for initial cracking is presented, which is consistent with measured result. The initial depth of expansive soil cracks is put forward by proposed model. The relationship between the depth of initial cracking and soil parameters such as deformation modulus, swell-shrinking characteristics, etc. are discussed in detail.

Nanjing mica sand is anisotropic because of its contents of flake grains. A series of drained tests for principal stress axes was fixed at 10°, 30°, 60°, 80° were conducted with an automated hollow cylinder apparatus in Hong Kong University of Science and Technology, in order to study the inherent anisotropic characters of mica sand. During the tests, the coefficient of intermediate principal stress was fixed at 0.1, 0.5 and 1.0, and the beginning density of sand was same. When the orientation angle of major principal stress changes from 0° to 90°, the shear strength of mica sands at first tends to reduce, reaches its minimum value at the orientation angle of 60°, and then increases gradually. The coefficient of intermediate principal stress has a great impact on the shear strength and deformation of anisotropic sands

Based on the C.K.C cyclic triaxial testing system, a cyclic triaxial visible testing system was designed for studying the liquefaction behavior of saturated sands at the meso-mechanical level. The cyclic triaxial visualization testing was performed on saturated sands. The meso-fabric characteristics of saturated sands were studied such as motion and macro-axis orientation for sand granules, average coordination number and porosity. The results show that, sand granules continuously rearrange and redirect for the new stress state under cyclic loading; then liquefaction occurs. And the study shows that the meso-mechanism of sand liquefaction can be analyzed by the cyclic triaxial visualization testing system for real-time visible liquefaction

The engineering technology that expansive soil embankment, cutting and canal slope were reinforced with geogrids has been successfully applied to highway, railway and hydraulic projects in the recent years. But the strength and deformation characteristics of reinforced expansive soil are not yet researched thoroughly. This paper presents the results of CD triaxial tests of a middle-class rxpansive soil under different confining pressures and different reinforcing patterns (horizontal reinforcing with one layer/three layers, vertical reinforcing and un-reinforcing) for evaluating the reinforcing effects. The test results indicate that: (1) Reinforced-geogrids in expansive soil provide the drainage passageways, which accelerate the consolidation of expansive soil and are conducive to the stability of expansive soil slope. (2) Reinforced-geogrids reduce the strain softening of expansive soil, so the stress-strain curves of expansive soil possess strain hardening characteristics. (3) Reinforced-geogrid restrains the development of shear zone, which results in the changing of failure models of soil sample. (4) The internal friction angle of the reinforced expansive soil only changes a little under different reinforcing patterns, but the cohesion obviously increases. (5) Evaluating according to coefficient of reinforcing effect(R), reinforcing effects are all enhanced except horizontal reinforcing with one layer, among them, the effect of vertical reinforcing pattern is the best.

According to Barton-Bandis joint peak shear strength criterion, relationship between peak shear displacement and normal stress is analyzed; and the limitations of Barton’s formula of peak shear displacement are summarized. It is verified through direct shear tests in which joint roughness and normal stress are the two major factors influencing joint shear displacement. The results show that there is a negative relationship between peak shear displacement and joint roughness but a positive relationship between peak shear displacement and normal stress. A new formula is suggested which can consider not only joint roughness but also normal stress and can overcome the limitation of Barton’s empirical formula which just considers joint roughness. The validity of proposed formula is verified through fitting experimental data.

A mathematical model for grouting into a fracture with flowing water is derived and validated by a model test and calculation. The results show that grout propagation shape is round in prophase of grouting; and it is elliptic in anaphase of grouting. Penetration radius is in inverse proportion to viscosity and is in direct proportion to the opening of fracture and grouting pressure. Water flowing is propitious to propagation downstream the current and restrained the propagation against the current. The influence of velocity will gradually reduce when it increase or decrease to a certain value. And the influence of velocity on the penetration length against the current is greater than on that of downstream the current. Velocity of flow has the most important effect on penetration radius; and the opening of fracture takes the second place. Grouting pressure and viscosity have less influence on penetration radius.

Aiming at the poor results of Knothe time function in predicting surface dynamic subsidence, Richards model is proposed. Based on analyzing the characteristics of the surface subsidence induced by coal mining, the elementary features of the perfect time function which could describe the full subsidence process are presented; and then, Richards growth model is introduced and established before the qualitative and quantitative relationships between parameters of model and geologic and mining conditions are given. Finally, model applicability is discussed; precise results could be attained while Richards model is applied to continuous and gradual subsidence area. A case study is given. The results show that: Richards model which satisfies the requirements of perfect time function could effectively simulate the whole process of surface subsidence and quickly calculate the parameters, including movement duration and subsidence, velocity and acceleration of a certain point in the surface movement basin at anytime; additionally; the flexibility of Richards model indicates it could be used in practice widely.

Gaussian process regression (GPR) takes advantages of programming easily; self-adaptive acquisition of hyperparameters and prediction with probability interpretation. At present the hyperparameters are got by maximizing likelihood function of training samples based on conjugate gradient algorithm. However, the algorithm embodies the disadvantages of too strong dependence of optimization effect on initial value, difficultly determination of iteration steps, easily falling into local optimum. On the basis of mentioned above, particle swarm optimization (PSO) was used to optimize the hyperparameters of the GPR then formed the PSO-GPR coupling, and the corresponding source code was programmed. So the PSO-GPR with the neural network covariance function (NN), squared exponential covariance function (SE) and rational quadratic covariance function (RQ) is respectively applied to analyze slope displacement time series in order to test generalization ability of the algorithm. The analysis results of slope displacement time series show that the proposed PSO-GPR based on different single kernel function are all suitable for all kinds of slope deformation analysis and difference of prediction accuracy is little based on different single functions. Furthermore, the problem that there is differential the regression and generalization ability of kernel machine with different functions is solved; and the kernel function compatibility with different data is boosted

In order to study the features of shear strength of soils stabilized by cement mortar, to provide a theoretical reference to rationally determine the engineering application ratio of soils stabilized by cement mortar, some CU triaxial tests are performed on the soils stabilized by cement mortar, based on the four aspects: sand content, cement mixing ratio, water content of raw soil and sand diameter. It is shown that the mixed sand can improve the strength of stabilized soils, in general, the effective cohesion increased and then decreased with the amount of mixed sand increased, the turning point of the doped amount of sand is the best amount of mixed sand (about 10%), while effective friction angle increasing continuously. The cement mixing ratio increasing can effectively improve the strength of stabilized soils under a certain amount of mixed sand; as the water content increasing, cohesion of stabilized soil appears as linear decrease relationship approximately; while the internal friction angle remains almost unchanged; and when using cement mortar in the treatment of high water content of soft ground, the appropriately increasing the volume of mixed sand can more sharply improve the mechanical properties of stabilized soil. When the admixture ratio fixed, sand diameter can influence the shear strength of stabilized soil to some extent. In general, the shear strength of stabilized soil is higher when it using the sole sand diameter; and uniformity coefficient Cu tends to the largest, coefficient of curvature Cc tends to the minimum with the sole particle size and good gradation of stabilized soils

According to design principles of point anchor and frame anchor technology, a new earth pressure calculation method based on three-dimensional soil arching effect is proposed in order to solve computation model of earth pressure problem of the prestressed anchor pile design. Based on this, earth pressure exerted on pile and plate is derived by the limit equilibrium theory of soil slice. Secondly, a first-order linear differential equation and earth pressure distribution curve along the axis of the pile is established. Finally, distribution of earth pressure was compared with the calculation results of the Specifications of design for geological hazard stabilization[1] and the Technical code for building slope engineering[3] for different parameters “ ”and “ ”. The results show that the earth pressure distribution curve exerted on pile and plate along the axis of the pile plate is serrated and its value much less than code. Variation in parameter has a significant effect on the earth pressure and should not be overlooked in engineering design. Considering soil arching effects is more consistent with engineering mechanical charateristics

To reveal the corresponding relationship between the void beneath the tunnel bottom and the longitudinal deformation of the metro tunnel, a model test of circler tunnel is carried out under the research background of Xi'an Subway passing through ground fissure active zones. The law of the longitudinal strain and the vertical displacement of the tunnel are studied caused by the different profile activity patterns of ground fissure belts. With the increase of the dislocation between the hanging wall and the foot wall of ground fissure, the test results show that the expansion process of the separation between the bottom of tunnel and the soil layer under the tunnel can be divided into three stages, i.e. co-deformation stage, the initial stage of void and the development of void. In view of different profile activity situations of ground fissures, the stress in the structure presents variance considerably. Different designs are suggested to different profile patterns of ground fissure belts. Under the law of stress and strain of the tunnel in the model test, the trend of the void beneath the tunnel can determined by monitoring the stress of structure. The results can provide reference for the structure design and the safe operation of metro tunnel.

Because of the containing iron, glass and ceramics in solid waste, the geomembrane may be easily damaged and results in infiltrating into the surrounding ground and water; so it is very important how to evaluate the puncture performance of liner system. Taking into account the tensile strength, the thickness of geomembrane and the diameter of puncture probe, an evaluation formula of puncture resistance is presented based on the thin-walled structural mechanics theory; and the calculated values are compared with the experimental values. The results show that the calculation results of geomembrane are consistent with the puncture test results; but the calculation results of liner system composed of geomembrane and geotextiles are only about 70 percent of the test results. Geotextile used together with geomembrane could significantly improve puncture performance of liner system; so the geotextile should be spread on geomembrane for protection geomembrane. With an increase of tensile strength of geomembrane, puncture resistance becomes larger. Puncture resistance of geomembrans placed on compacted soil increases with ground strength and the trend is almost similar for different types of geomembranes. The results have certain referential value for the design of liner system

According to the function that GDS dynamic hollow cylinder torsional apparatus can apply three-dimengional dynamic loads, namely axial load, torque and one of inner and outer pressure, three possible stress paths those coincided with practical engineering backgroud are presented by exactly mathematical derivation. When the three-dimengional dynamic loads meet some corresponding requirements, the following paths can be realized, ①the stress path which the mean principal stress p and shear stress q are kept constant; ②the stress path that the shear stress q is kept constant when the effect of intermediate principal stress b equals to 0.5; ③the stress path that the mean principal stress p is kept constant when the mutation of which is the rotation of maximan principal stress relative to the vertical direction is 90º. In addition, the first two paths provided theoretical foundation for experiment of simulating the stress paths under wave loading while the third path can be used to simulate the dynamic characteristics of soils subjected to earthquake load, and the three above stress paths can’t be realized in the HCA which with two dynamic loads

The interface of soil and structure is often found in projects. Shear test is one of the main methods to study interface behavior. The simple shear test considering the stress and strain of soil can be used to discover the characteristics of interface. The relation between strain of soil and displacement of interface is not concerned. By comparison of static and dynamic simple shear tests of mucky silty clay under different normal stresses and different amplitudes of shear stress, relation curves of displacement of interface and cycle number of shear load versus strain of soil are presented. It is obtained by analysis of test curve that the shear stress is increased rapidly at beginning of static shear test; the rate of stress increase is slower in test; softening not occurred. When shear stress is smaller the shear displacement is mainly in soil sample; after some displacement is reached the interface slide of soil sample and steel plate is obvious. There is similarly linear of displacement of interface and strain of soil in some extent of strain in static tests; there is good linearity of interface and strain of soil in dynamic tests; the gradient of the relation line of displacement of interface and strain of soil in static test is steeper than in dynamic test; and there is narrow range of gradient of linear relation of displacement of interface and strain of soil.

Municipal sludge was modified by water glass, quick lime and flocculent fiber. The consolidated undrained triaxial tests were carried out for studying mechanical strength and failure characteristics of modified sludge composites. Three ratios of modifier were set as 5%, 10% and 15%. After 5 days maintenance, compared with pure sludge, the failure strength of three modified sludge composites were increased by 1.25-1.426, 1.12-1.33 and 1.20-1.50. After 10 days maintenance, the hardening speed of 5% and 10% modifier superior to that of 15%, the failure strength of three modified sludge composites were increased by 1.33-1.45, 1.154-1.35 and 1.56-1.67 respectively. When principal stress difference reached 20 kPa after 10 days maintenance, initial tangent modulus have great mutations. Moreover, strain of modified sludge composites with 10% and 15% modifier have obvious 3%-5% delay period. The internal friction angle of 5% and 10% modifier are larger than that of 15%, whereas their cohesion much less than that of 15%. Based on stress-strain hyperbola proposed by Konde, the ultimate value of principal stress difference was adopted as the normalized factor. Meanwhile, the normalized stress-strain relationship of modified sludge was established under consolidated undrained triaxial tests

The early strength of ecological slope-protected base material has an important influence on stability of base material onto slope and seed germination. Taking the unconfined compressive strength at 2 days of vegetation-growing concrete base material (VCBM) as research object, the characteristics of early strength of ecological slope-protected base material are studied. Through single factor affecting tests and orthogonal tests, which take cement dosage, organic matter dosage and water-cement ratio as influence factor, the analysis of tests data indicate: the three factors all affect the early strength of VCBM; and the degree follows by: cement dosage ＞ organic matter dosage ＞ water-cement ratio. When water-cement ratio is between 0.50 and 0.55, the early strength of VCBM reaches a maximum value. Regarding Cement dosage and organic matter dosage as independent variables on condition that water-cement ratio and other factors are constant, a multiple nonlinear regression model on the early strength of VCBM is established. And the confirmatory tests testify that the model could predict the early strength of VCBM approximately. According the model to estimating the minimum cement dosage and maximum organic matter dosage in course of the application of VCBM ecological slope-protected technology, it can ensure the stability of base material during early stage of implementation as well as propitious to vegetation recovery and sustained growth on slope in late stage

Taking limestone for research objects, the thermal expansion property is studied under high temperature; the porosity, ultrasonic wave velocity and elemental composition are studied in order to find out the reason caused thermal expansion. The results show that: the limestone produces thermal expansion under high temperature; the curves between thermal expansion and test time includes four steps, size of thermal expansion is determined by temperature; and the relation is nonlinear; the porosity increases as temperature increases after high temperature; it can be divided into two stages based on division temperature of 500 ℃, including slow increase step and rapid increase step; the test of ultrasonics shows that the law of wave velocity is complex wavy type after high temperature; the test of elemental composition shows the contents of key elements in limestone samples has a larger change; the change of both porosity and elemental composition is the key reason causing thermal expansion of limestone under high temperature

Initial shear stress has effect on soils in side slope,sloping ground and retaining wall, etc. Serious residual strain will occur in soft clay under initial shear stress. But, original Iwan’s model ignored this effect. In this paper, an empirical degradation model of soft clay has been incorporated into Iwan’s series-parallel model to account for cyclic degradation. Simultaneously, an ideal plastic element is paralleled to simulate the development of residual strain. Subsequently, the dynamic stress-strain relationship of each soft clay stratum is described with modified Masing’s rules. In this paper, a modified Iwan’s model is utilized in one-dimensional seismic response analysis. It’s observed that the constitutive model should consider this effect when initial shear stress existed and the earthquake is strong. Otherwise,velocities, accelerations and shear strains may be underestimated.

Steel tubular pile underpinning technology is an effective method to develop underground space in retrofitting of existing buildings. The bottom of steel tubular pile inserted into concrete pile while top connected with underpinning cap. The stability of the pile under compression load decreased after the soil around the pile dug, but the stability coefficient and length factor of steel tubular pile can not be obtained by currently code. According to the 1:2 model test and nonlinear buckling analysis respectively, the stress distribution and the ultimate bearing capacity of the pile is derived. The effective length factor for stability calculation is 0.616 gotten by test study; and the numerical result is 0.683. So the pile is restricted with base edge fixed and top edge articulated. More safety stability of the pile can be obtained by buckling numerical analysis which can provide reference for pile design.

Sheet pile wall is a potential structure for water-intake project of offshore power station. According to the preliminary design scheme, this paper presents the centrifugal model test on the water-intake project under wave loading. The safety of the structure is analyzed for the different buried depths of sheet pile wall. The centrifugal model test results show that a large horizontal displacement and a large bending moment occur at the cantilever sheet pile under designed wave loading. The main load inducing the displacement and the bending moment is the wave load above the ocean bed surface; and the main bearing capacity is obtained from the lateral earth pressure on passive side of the wall. The increase of the buried length of sheet pile wall cannot reduce the displacement as well as the bending moment of the sheet pile; therefore it cannot increase the bearing capacity of the sheet pile structure effectively.

Based on the revetment reinforcement project at Huzhou section of Chang-Hu-Shen Waterway using sheet piles, soil pressure cells were buried on both sides of sheet pile during the precast period and at the bottom floor of revetment during constructing revetment. The pressure variation of earth pressure cell in the course of concrete setting and hardening, the rule of earth pressure distribution at both sides of sheet piles and the bottom floor of revetment were tested and analyzed. The results show that the course of setting and hardening of sheet pile will produce biggish tensile and compressive stresses and gradually become stable. Owing to construction load earth pressure on both sides of sheet pile and at the bottom floor of revetment produces a comparatively large adjustment in the period of initial construction and gradually become stable. The earth pressure distribution is obviously different at the bank side and near the water side; the active earth pressure distribution at the bank side is nonlinear that is firstly increased, then decreased and finally increased; the passive earth pressure distribution near the water side shows linear distribution. The differences are firstly little but gradually significant with the depth increasing between the calculated standard values using the method of Sheet Pile Wharf Design and Construction Specifications [1]and the measured. The calculated values are always less than the measured. Earth pressure distribution at the bottom floor of revetment shows large at two poles and little in the middle under revetment load, just like a parabolic distribution.

In order to control the construction risk of karst tunnels, through statistical and theoretical analyses of relevant engineering projects, controlling factors and factors’ weight of water or mud inrush risks of karst tunnels are studied based on analytic hierarchy process; and a three-stage risk assessment and management method is proposed for the evaluation and controlling of construction risk of karst tunnels. Factors’ weight analysis results show that unfavorable geology, geological prediction, formation lithology and groundwater level are the main control ingredients of water or mud inrush risk. Macroscopic geological precursory information, monitoring measurement, contact zones of dissolvable and insoluble rock, geographic and geomorphic conditions, tunnel excavation and supporting are the minor significant factors; microcosmic precursory information, attitude of rock formation, layer and interlayer fissures, surrounding rock mass classification are the least important elements. The three-stage risk assessment method includes preliminary, secondary and dynamic assessment of water or mud inrush risk. Preliminary assessment is the evaluation of risk surroundings (karst hydrogeological and engineering geological conditions), and it is carried out for the estimation of risk before the enactment of the construction program. Secondary assessment is the evaluation of risk surroundings and risk factors (construction factors), and it is actualized for the appraisal of construction organization plan pre construction. Dynamic assessment is the evaluation of risk surroundings, risk factors and feedback information of risk management; and it is brought into operation for dynamic risk assessment and management. The three-stage risk evaluation and controlling process can be instantly, effectively, and accurately used for the management of construction risk of karst tunnels, and to realize dynamically amending and governing of risk. The research results are successfully applied to Jigongling Tunnel on the line of Fanba Expressway; and it is of consultant significance for similar engineerings.

Agricultural irrigation on Heifangtai loess plateau has triggered dozens of loess earth flows. In this paper, IKONOS image was first used to interpret the topographic features of those earth flows, complimented with a detailed field-walk survey. The results indicated that loess earth flows had a travel distance of over 300m, constituting the most destructive threat. The failed material was deposited in a flow-like lobe form. The elevation of the underlying impermeable clay was measured from the outcrops and boreholes, indicating that the eastern part of the plateau was lower than the west. It was observed from groundwater flow modeling that groundwater flow was controlled by the topography of underlying impermeable clay, and converged and partially discharged in the east margin of Heifangtai. This is in coincident with the phenomena that most loess earth flows occurred in the east margin. Laboratory stress path tests were then performed on undisturbed specimens to explain the failure mechanism of loess. The test results show that the initiation of loess earth flow is probably triggered by static liquefaction resulting from rise of groundwater table

Research on deformation and stability of reservoir bank slopes is one of the focus in the world. Taking a deposit slope in the hydropower reservoir area for example, the deformation and failure characteristics of the slope are predicted by FLAC3D while the reservoir level is rising and rapid drawdown. It is indicated that deformation mainly occurred in the deposit body while the reservoir level fluctuating; the deposit body is divided into three regions according to the deformation characteristics: the front traction deformation area with the largest deformation, the middle transition area with the smallest deformation and the posterior passive traction deformation area. Displacement monitoring points are set at different places of the slope body; so the displacement-time graphs during reservoir filling and rapid drawdown of reservoir level are obtained. The monitoring results show that the local instability occurred at the front of the slope during the rapid drawdown of the reservoir level. Owing to the influence of water two potential sliding failure surfaces in slope can be judged based on the shear strain increment.

Exploiting groundwater is a main reason to the ground settlement and uneven settlement can do great harm to the high- speed railway bridge. Centrifuge model tests are conducted to investigate the influence of exploiting groudwater on the high-speed railway bridge. The deformation of soils and the bridge are measured during the centrifuge model tests of exploiting water based on a drainage system developed to simulate exploiting water during centrifuge tests. The influences of uneven ground settlements on the rigid bridge, simply supporfed single bridge and simply supported multispan bridge are discussed. The results show that the bridge deforms intensively during the period of unsteady fluid flow after water was exploited initially. The axial strain of the deck can be decreased by reducing the length of the balk or replacing the bridge pier by hinged bearing. The horizontal displacement of ground can cause some deformation on the central part of the rigid bridg

Based on the statistics of salt cavern oil/gas storage accidents abroad, a study of salt cavern oil/gas storage risk assessment is conducted using risk matrix analysis in order to provide statistical proof for the risk management during construction and operation. This thesis analyzes the salt cavern oil/gas storage’s probability of tremendous accident, risk grade, accident types and the main accident causes. Research shows that the accident probability of a single salt cavern during construction and operation is 1.51%, and the general risk grade is between acceptable and unacceptable, so the related departments should pay more attention on its risk prevention mechanism; three main types of the tremendous accidents are oil and gas leakage, cavern failure and earth surface subsidence respectively; different from other two types whose risk grades are permissible, the risk grade of oil and gas leakage is acceptable, which calls for special attention; the most important causes of these accidents are casing failure, excessive creep and human error, and also overground setting failure and caprock breakage.

As a typical binary medium, talus deposit is made up of weak parent soil, stiff macadam or rock blocks. Cellular automata model is used in evolution of random and discrete elements to simulate the distribution structure and accumulation characteristics; then equivalent wave speed is calculated according to transmission theory of elastic stress wave; then the influence on dynamic parameters of medium distribution and rigidity are studied. The results show that the wave speed in talus is controlled by parent medium and fill medium; the more faint the parent medium is ,the more slow SV speed is; it exhibit as logarithm relation. The more content of rock filling can make more high wave speed; the speed and content of rock filling takes as logarithm relation, while there’s little correlation between amplitude ratio and rock filling; it primary depends on distribution construction. Due to the inhomogeneous density of talus, wave speed is closely related with incident wave frequency; high frequency makes high wave speed and low frequency makes low wave speed. With this method, the wave mechanics can be better considered; dynamic parameters of complex medium can be effectively achieved; and shortage of indoor and field tests can be greatly improved

The mechanical characteristic of shield tunnel segments lining and its influence during construction are analyzed. Firstly, the construction loads are divided into jack thrust force, grouting force, buoyancy, shield shell press, installation load, and other loads, etc. Then, the mechanical characteristic of shield tunnel segments lining is summarized as the typical three-dimensional character, indetermination, and the innegligible character. Afterwards, the influence of the construction loads on segments lining is discussed, including the cracks, partial breakage, sealing strip falling, segments leakage, and segments dislocation. Finally, some advices to protect the shield segments during construction are presented, such as jack controlling, grouting pressure controlling, and the repeated tightening the bolts. The result shows that the analysis of the mechanical characteristic of shield tunnel segments lining and Its influence during construction is imperative, and the construction loads should be emphasized in segments designing and the correlative criferia.

Based on the displacement sequence of slope, the stability of slope could be judged effectively by forecasting the displacement of slope in the future. After analyzing the advantages and disadvantages of grey forecasting methods and projection pursuit regression (PPR) method respectively; a new nonlinear forecasting model of grey projection pursuit regression (GPPR) is proposed. The new model not only developing the advantages of accumulation generation of the grey forecasting method, weakening the effect of stochastic-disturbing factors in original sequence and strengthening the regularity of data, but also using the quickly solving speed and the excellent characteristics of projection pursuit regression method for nonlinear relationship and avoiding the theoretical defects existing in the grey forecasting model. At the same time, the model is verified. At last, two engineering examples are given to testify the effectiveness of the grey projection pursuit regression forecasting method to predict displacements of two slopes. The results show that the new model has higher calculation precision, so as to provide a new way to predict displacements of slopes

For the duct-ventilated embankment with a perforated ventilation pipe in permafrost regions, the laboratory experiment on the moisture evaporative cooling effectiveness was performed. The mechanism of moisture evaporation affecting on the cooling effect of duct-ventilated embankment was analyzed. It is shown that during the ventilating period water content in the embankment soil is directly evaporated from the soil surface bared in the small holes of the perforated pipe wall, thus to cool down the embankment soil. During warm time, convective heat transfer between the ambient air and the pipe wall may raise the embankment soil temperature, whereas evaporation heat removal from the small holes of the pipe wall can cool down the embankment. During warm time, the water evaporative cooling capability from the small holes of the pipe wall is stronger due to big unfrozen water content in the unfrozen soil, thus, as a whole, revealing the cooling effect in the perforated ventilation pipe embankment

According to a practical case of composite foundation in collapsible loess foundation, the squeezing effects on compaction pile by tamping are studied. In field test, the undisturbed samples before treatment and the samples after treatment are first obtained; and then the physical parameters (e.g. void ratio, coefficient of collapsibility, coefficient of compactness, etc) are studied. Using the test results, the squeezing effects of the soil between piles with loading variation are discussed. Besides, the affecting scopes in horizontal and vertical directions are also analyzed. Finally, the reasonable spacing between piles which should be used in practical applications is discussed.

There is divergence of opinions on the effect of geosynthetic reinforcement and the selection of suitable geosynthetic materials; it is a constraint for its appropriate application. This paper investigates the mechanical behavior and the contribution of reinforced materials with an reclamation engineering example in Pinghu, Zhejiang province. Besides, in-situ test is made using improved displacement gauge. Based on the numerical analysis and in-situ test, further discussion is made on the type and the corresponding design parameters of reinforced materials. And some valuable conclusions are drawn as follows; the uniaxial-tensile geogrid should be put into the first place for the treatment of sea dike; the upper and lower bounds of the limit elongation should be prescribed, and so on

Based on systematic analysis of the landslide displacements and its evolvement characteristics, a detailed research is performed on the features of the complexity, catastrophe and nonlinearity in terms of the basic principle of multifractal. The single fractals are deficiencies in prediction of evolvement trend of landslide displacement. The evolvement of landslide displacement is determined by the multifractal dimensions. Firstly, taking the typical landslides——The Xintan landslide, Danba landslide and Huanglashi landslide as the practical examples, the evolvement of multifractal dimensions of the displacement-time are calculated. Secondly, the correlation between the displacement evolvement and multifractal dimensions is studied. It is found that the landslides are stable when the multifractal dimensions are D1 > D2 > … > D∞ and the landslides are unstable when the multifractal dimensions are D1 < D2 < … < D∞. Moreover, if there were inflexions in the multifractal dimensions of landslide displacements-time the landslide stability would change. For example, they are from D1 > D2 > … > D∞, through D1 > … > Dn < Dn+1 < … < D∞ to D1 < D2 < … < D∞, the landslides are unstable gradually. On the contrary, when they were from D1 < D2 < … < D∞, through D1 > … > Dn < Dn+1 < … < D∞ to D1 > D2 > … > D∞, the landslides are stable gradually. The study results show that the multifractal dimensions of displacement are an effective method to evaluate and predict landslide displacement evolvement

Double-row piles are often used to the large-scale landslide. The anchor double-row piles and the frame double-row piles are the two common types. Based on the finite element program ANSYS, finite element models of the two types double-row piles are established separately. Compared the internal force distribution of anchor double-row piles with frame double-row piles, it is found that the frame double-row piles could be better able to play anti-slide effect. For the anchor double-row piles, the difference of internal force distribution between the front and back row piles is very obvious. For the frame double-row piles, the difference is very small. Taking two engineering cases, an anchor double-row piles and a frame double-row piles for examples, through monitoring and analyzing the stresses and displacements of the piles, it is shown that the results are consistent with the finite element analysis. So we suggest using the frame double-row piles in the design

A support structure of systematic anchor bolts is a key part in the system of shotcrete-bolt suppcrts, and it is widely used in preliminary bracing of hiqhway tunnel at present. However, there is no effective quantitative way to calculate the role of the systematic anchor bolts for the stability of tunnel structure. Taking a certain expressway tunnel for example, the influence of anchor bolts on safety factors of tunnels under different geological conditions is calculated with FEM strength reduction method. Together with FEM numerical simulating and analysis to various kinds of effects from anchor bolts, conclusions can be drawn as follows. The anchor bolts have little influence on stability of expressway tunnel under much more geological conditions; therefore, it is suggested that experimental verification of canceling the systematic anchor bolts should be carried out gradually if possible, so as to provide more engineering basis for canceling anchor bolts in highway tunnels.

This paper presents a numerical investigation of cemented sand behaviours using the distinct element method (DEM). First, the test results of the contact behaviours between the idealized bonded granules were introduced in two-dimensional DEM code (NS2D) to simulate the bonding effect between particles in cemented sand. Second, a series of biaxial compression tests on cemented sand of different bonding strengths and confining pressures were carried out by the DEM simulations. Then, the DEM results were compared with the test results on artificially cemented sand obtained by Wang and Leung[1]. Finally, the analysis of micromechanical responses (i.e. contact force chain, bond breakage ratio, and displacement field) in DEM specimens was presented in this paper. The simulation results show that the DEM model is able to capture the main mechanical behaviours of cemented sand, such as the strength enhancement, strain softening and volumetric dilation. The different features between cemented sand and uncemented sand become more pronounced with the increasing of bonding strength and deceasing of confining pressure. The macromechanical responses (i.e. stress-strain and volumetric-axial strain relationships) of cemented sand are associated with the micromechanical responses (i.e. contact force chain, bond breakage ratio, and displacement field)

Because of interaction between solid granulae and pore water as well as different permeabilities of pile and saturated soil, the mechanical behavior of a pile in a saturated soil is greatly distinct from that of the pile in single phase soil. Based on the theory of saturated porous media, taking effect of the transversal deformation and inertia of the pile into account and modeling pile as a Rayleigh-Love rod, the dynamical behavior of vertical vibration of the pile in a saturated viscoelastic soil layer is investigated in frequency domain; and the analytical solutions for vertical vibrations of the pile and saturated viscoelastic soil layer are obtained; and an analytical expression of the dynamical complex stiffness of the pile top is presented. The responses of dynamic stiffness factor and damping of pile top against the frequency are shown in figures with the numerical method; and the influences of the soil parameters, modulus ratio of the pile to soil, ratio of the length to radius of the pile and Poisson ratio on the stiffness factor and damping are analyzed. It is shown that the influence of transversal effects on the stiffness factor and damping is much great for the pile with large diameter when the exciting frequency is large

In order to generate 3-dimensional stratum, a stratum data model of tri-prism based on borehole data is first presented, which is applicable to geological engineering and geotechnical engineering. Due to the local variance and spatial structure among attributes of boreholes, the geological properties at unknown location have to be estimated or interpolated by some special methods. However, classic statistical methods could not resolve such problem which includes selection of sample points, spatial estimation and comparison of bilateral data. A distance-weighted interpolation method for scattered borehole data points is proposed, which exploits the Kriging method in global geostatistics. On the premise that the distributed statistics characters of the spatial borehole data were obtained at first; accorded to the distributed statistics characters, the spatial interpolation was presenting successively. Moreover, Multi Fractal is presented to depict the local singularity which should be ignored by sliding weighted average algorithm of Kriging method. Case study shows that the generation of 3-dimensional stratum by proposed interpolation methods could give a good result in global and local occasions.

At present, the commonly used ambient vibration evaluation criteria caused by train vibrating loads is based on the test data and calculation results of a single train, which can not reflect the real vibration situations with multi-tunnels because of the rapid development of rail transit in China. There are four tunnels crossing each other between Hongshan Square Station and Zhongnan Road Station, which are the second line and the fourth line of Wuhan rail transit. The complicated multi-tunnels were simplified as four adjacent perpendicular tunnels with different distances according to its practical characters. Three-dimensional calculation models are established; and ambient vibration and spectrum characteristics are analyzed with different train numbers, different tunnel depths and different tunnel net distances. Approximate empirical formulas are suggested based on the calculation results and the vibration influence areas are determined accordingly. The research results can provide references to forecast and evaluate the ambient vibration for similar projects in future in China

Based on the difficult problem of surrounding rock control in deep coal roadway with large section and thick top-coal, surrounding rock deformation and failure mechanism and its supporting technology are studied. The results show that, for deep coal roadway with large section and thick top-coal, plastic zone of top-coal presents “arched” or “inverted trapezoid” with wide upper and narrow lower, however plastic zone of immediate roof presents “rectangular”; the shoulder stable region exists in the immediate roof. Bedding surface shear failure effect mechanism for “inverted trapezoid” plastic zone is proposed: under the effect of high stress (especially high horizontal stress) and horizontal stress caused by larger roof subsidence; bedding surface between top-coal and immediate roof goes to shear failure, which causes coal body near bedding surface failure; and it promotes the formation of “inverted trapezoid” plastic zone. Based on above, high prestressed bolt with strip and steel mesh combining with diagonal cable and beam structure support is put forward. It is thought that diagonal cable can be anchored to the stability region in the shoulder; and it can limit the shear deformation of bedding surface between top-coal and immediate roof, and also can prevent the development of top-coal plastic zone from “arch” to “inverted trapezoid”. The research results have been successfully applied to roadway supporting.

Eco-protection slope is the sustainable development of highway construction. Forest roots can reinforce and anchor surface soil of slopes. The finite elements software ADINA is used to analyze mechanism of eco-protection slope through robinia pseudoacacia roots in different slope gradients. Tests are carried out to gain basic parameters through roots at field sites. During simulation, soil model is Mohr-Coulomb, and roots model is elastic bar. The results show that robinia pseudoacacia roots group in slope can make the upper layer of slope soil more stable by changing its stress and strain fields. As the slope gradient increases, the stress in the bottom of slope would increase and concentration area of strain would expand, while tensile stress would produce at the slope shoulder and its value would increase also; in this case, the effect of roots reinforcing slope would decrease.

The failure process of rock in uniaxial compression tests is simulated by using the particle flow code(PFC). Fish language embedded within PFC2D is used to generate random imperfections and to develop the rock numerical specimens with different homogeneous degrees. The results show that inhomogeneous degree has great influence on characteristics of acoustic emission in rock. With the increase of inhomogeneous degree, peak strength of rock specimens decreases and the total number of AE increases greatly. The spatial distribution of AE becomes more extensively. Meanwhile, AE of rock samples appear earlier and sustain for longer duration. The intensity of AE after the peak failure retains higher level. The maximum intensity of AE under uniaxial stress state lags behind the peak damage to different extents. With the increase of inhomogeneous rock, the hysteresis effect of AE becomes obvious which suggests that rock failure appears earlier than the maximum intensity of AE.

The cutterhead and rock mass characteristics affect the excavation efficiency of full face rock tunnel boring machine (TBM) strongly. The numerical models are made by the particle flow code method (PFC2D) to simulate the rock fragmentation under TBM disc cutters. Numerical simulation tests show that some factors influence the rock fragmentation process strongly. In the relative weak rocks, the regular tension cracks and the big mucks form more easily, when the disc cutters penetrate rocks alternately; in hard rocks, the formation of small disc shape mucks depends on the lateral extrusion of cutter rings. Under the double disc cutters, the rocks crush more easily because of the tension stress which comes form strong compression of cutters, and the disc shape mucks only form in very hard rocks. There is optimal cutter spacing for different strength rocks, which increase with rock strength decreases. In the process of rock fragmentation, discontinuities control the propagation process of cracks and obstruct the cracks spread to the underside of discontinuities. The discontinuities will guide the cracks spread deep in rocks, when the angle of cut-in direction and discontinuity decreases. And the discontinuities will guide the cracks spread transversely when the angle increases

The radial point interpolation method (RPIM) is a new-style meshfree method. As its shape functions have the Kronecker delta functions property, essential boundary conditions can be enforced as easily as in the finite element method. The basic principle of RPIM is introduced; and the basic formulas of RPIM are derived. Based on the variational principle and Biot’s consolidation theory, the basic equations and numerical integration method of RPIM are proposed; and the corresponding calculation program is developed. Numerical examples of 3D cantilever beam and 1D consolidation problem are given to verify the validity and availability of the RPIM to the 3D elastic problem and consolidation problem

By using the explicit solution of three-dimensional landslide stability based on modification of normal stress distribution over the slip surface, the influence of the three-dimensional end effects on the factor of safety is investigated. The three-dimensional geometry of the slip surface is assumed to consist of a cylinder and elliptical ends. The values of three-dimensional factor of safety are computed with a series of combination of geometrical parameters. The computation results show that the ratio of the 3D factor of safety to the 2D factor of safety (F3/F2) will decrease with the increase of the ratio of the width to height of sliding mass (L/H). When L/H =2, 5 and 10, the maximum value of F3/F2 is 1.3, 1.1 and 1.05 respectively. In addition, with the increase of the internal friction angle of the soil, F3/F2 will become smaller, that is, the three-dimensional end effect would reduce slightly.

Through the research of structural mechanical model of the coal deep mining subsidence, the theoretical prediction model for the basin horizontal coal mining subsidence was put forward with two approximate calculation methods of whole and step. Using numerical simulation by changing the depth of coal mining and the length of working face, the related data were compared by fitting calculation with field subsidence monitoring measurement. The new proposed method can calculate the parameters of predicting mining subsidence based on the structural mechanical model, give a reasonable mechanical description against the predicted data with the overlying rock strata mechanical parameters, and overcome the shortcomings of the classical model of probability integration method relied only on the statistical method to predict mining subsidence; so as to provides a reliable scientific basis to predict and control the deep safe mining and the surface subsidence

For the structure of asphalt overlays on rubblized portland cement concrete (PCC) slab, properties of materials in each layer vary greatly. It is therefore not proper to be simulated by one mechanical model. For this reason, a numerical method which combines the finite difference and discrete element method (DEM) is proposed; in which the rubblized PCC slab is described using DEM while the asphalt overlays is simulated by the finite difference method. For purpose of smooth transition between continuous and discontinuous domains, conditions of compatibility and equilibrium along the corresponding boundaries need to be satisfied in the computation process. To illustrate the effects of rubblization more clearly, the rubblized PCC slab is further divided into three sublayers as the small particles layer, the surface layer and bottom layer. The mechanical response of the interaction between the rubblized PCC slab and overlays is discussed through varied the particles sizes. The results have shown that the tensile stress and strain at the bottom of the asphalt overlays are proportional to the particle size of the small particles layer. It is also found that the smaller the particles size of the surface layer is, the larger the tensile stress, strain are. In other words, strength loss of the old PCC is proportional to degree rubblization of the slab. This shows that the degree of rubblization should be properly controlled.