A limiting equilibrium method for calculating cyclic bearing capacities of suction anchors in soft clays using undrained cyclic shear strength of soft clays was developed based on the failure mode of suction anchors with inclined loads at the optimal loading point. Effects of average shear stresses due to average mooring loads on cyclic shear strengths of soft clays and cyclic bearing capacities of suction anchors were considered for the method. In order to verify its feasibility, a large number of model tests of suction anchors with combined average and cyclic mooring loads were conducted associated with different test parameters. The displacement criterion to failure at the loading point associated with the vertical pullout failure mode was determined based on test results. Cyclic bearing capacities of model tests with different parameters were determined based on the criterion. Cyclic bearing capacities associated with different model tests were further calculated by limiting equilibrium analyses using the relationship determined by undrained cyclic triaxial tests between normalized cyclic strengths and normalized average stresses and measuring shear strengths of model test strata. Comparison between calculating and testing results show that calculating results larger than testing results for the vertical pullout failure mode of suction anchors with taut mooring system. The average difference between them is 1.9%. Most of differences are not more than 10%. Therefore, it is appropriate that the calculating result is decreased 10% if the cyclic bearing capacity associated with the vertical pullout failure mode is calculated using the method for suction caissons with taut mooring system in soft clays.

A series of laboratory creep tests have been performed on sandstone, shale and dolerite to investigate the creep behavior of rocks subjected to different stresses and at different initial strains. Error analysis has been performed to study how to select time increment for the calculation of creep rate. The applicability of time-dependent creep model in describing the creep behavior under complex conditions is examined. An internal state variable creep model is proposed, in which the irreversible strain is considered as the internal state variable. The fitting of test data into the model shows that the internal state variable creep model is capable of describing the creep behavior of the three rocks in laboratory tests. A primary study of the applicability of the internal state variable model in describing rate dependent behavior of rocks is performed; and test data in literatures are used to verify the applicability.

Traditional pile-based structure design methods imply that by neglecting the effect of soil-structure interaction in dynamic analysis; the obtained results tend to be conservative; but seismic response spectra analysis and pile structure failures during recent catastrophic earthquakes have indicated that liquefaction and soil-pile-structure interaction could in fact lead to an increase in the inertial response of structures on pile foundation. Through analysis of the influence of ground liquefaction on structure-pile inertial interaction using dynamic centrifuge model experiments, a simplified analysis method for the computation of pile based structure inertial response in ground with a liquefied top layer was proposed and used to analyze model experiments described in this paper and by Wilson et al.; computation results show good agreement with experiment results, which demonstrates the effectiveness of the proposed method.

The traditional block theory is just used to analyze the static stability of the block, while not concerned with the dynamic stability analysis. Based on block theory, the located block’s dynamic stability under the action of earthquake is studied by utilizing the concept of accumulated slippage of Newmark method. Several important results are obtained. ① By using accumulated sliding displacement and dynamic safety factor commonly to evaluate dynamic stability of the block. ② A contact area identification and area computation algorithm, considering the adverse influence on the block stability caused by the variation of contact area and can do large displacement analysis during block’s sliding. ③ The shear strength evolution of structural plane is considered during the earthquake. ④ It can be used to do static-dynamic analysis to the complicated convex and concave blocks. At last it is applied to analyze the stability of the left slope of shiplift boat box in Three Gorges Project. The results show that the block slides for a distance in the process of the severe earthquake, but it still keeps stable after the earthquake.

Aiming at the formation mechanism of rockburst, the unloading rockburst mode were analyzed by rockburst examples and true triaxial loading and unloading test. The damage evolution equation of splitting failure and shearing failure of surrounding rock unloading rockburst were established. The results show that the fracture evolution of rockburst represent the composite destroying forms of splitting failure and shearing failure, just the difference depends on the size of the respective components；along with the increase of shearing components, blasting pit present the changes from flat bottom to arc so much as triangle or v shape; along with the increase of stress, surrounding rock has a quiet periods (no damage) and damage acceleration is obvious, once damage begin and rock with rockburst tendency has strong critical sensitivity; splitting failure always occurs preferentially; and the containing shearing composition becomes greater as the surrounding rock stress level after unloading becomes higher; and the rockburst intensity also becomes stronger.

Fractal dimension of AE (acoustic emission) serials of different types of rocks was investigated by uniaxial compression test. The complete stress-strain curves, the AE characteristics and the fracture patterns were obtained. The rupture instability specimens of destruction were observed; and the load change relationships of failure process were analyzed. Different mechanical properties, the AE sequence of time domain features and fractal feature of different rocks were researched emphatically. The results show that the AE rates ad AE energy rates can be very good to describe the collapse of the rock masses. The correlation dimension of the AE rates and AE energy rates during the progressive failure process has a strong characteristic of fractal feathers. The fractal dimension of AE sequences reflected the statistical evolution of the initiation and propagation of the microcracks in the rocks. The fractal dimension for all the specimens decreased when the loading stress increased. The evolutions of the fractal dimension of AE during failure can be divided into a mode for rocks. The fractal dimension for a mode of “fluctuation→gradual descending”. The descent of the fractal dimension can be regarded as the precursor information to predict the collapse of the rock masses.

Cracks propagation and the friction coefficient belong to different research objectives and were seldom connected. The friction coefficient often come from experiments and lacked describing theoretically. Based on ‘Griffith ellipse cracks’, a ‘Griffith face cracks’ model which links the compression shear rupturing and microcrack friction is discussed. The macroscopic slit expectation, force ,stress concentration that under uniaxial stress and three-axial stress situations is calculated. Because of locking, only cracks near the crack angle can extend. Larger stress ratio ( ) means smaller direction concentration ratio. The lock angle were increased with the increase of or confining pressure. Those tension cracks can not develop and transform into compression-shear cracks mode. Those convex-concave are from direction discrete of microcracks become the inclination angle of the asperities in a surface and affect the friction coefficient. The friction coefficient, direction concentration ratio and the stress ratio is a coupling relationship; on the one hand, large friction coefficient helps the direction concentrati, on the other hand, the direction concentration leads to the decrease of the average angle of asperities which in a macroscopic crack and decrease the friction coefficient furthermore. The coupling model reveals that the ambient pressure and stress is an important controlling factor of the friction coefficient. The stress ratio is often the conditions that allow the cracks developing. The friction coefficient were inversely proportional to the critical stress ratio. The average inclination angle of surface asperities and fractal dimensions of macrocracks have some memory function with respect to the stress condition and may thus be useful in characterizing the paleo-stress field.

Stress-dependent permeability of volcanic gas reservoir rock has been studied using the larger size rock samples because the volcanic gas reservoir has some special features including complex pore structure, mineral composition and different diagenetic mechanism compared with the conventional sandstone reservoir. The experimental results indicate that the low permeability volcanic rock has strong permeability stress-dependent. The permeability of rock decreases with the increase of effective stress but most of the permeability reduction happens when the effective stress is less than 20 MPa. The rock permeability continuously decreases when the effective stress is larger than 30 MPa. It has been also found that difference in rock pore structure is the main factor affecting the feature of stress-dependent permeability. Rock samples containing fractures demonstrate the strongest stress-dependent permeability. Repeated loading and unloading experiments suggest that stress release caused by drilling is the key factor leading the hysteresis phenomenon. The rock samples occurs mainly elastic deformation when loading and unloading in the second cycle. Rock permeability under high effective stress is only fifty percent of that under low effectiveness.

Rock damage and fracture is closely related to each other, and there is a specific relationship between strength criterion parameters and fracture toughness of fracture theory. Based on these, a compact test scheme was designed for three-point bending fracture toughness test, compressive strength test and tensile strength test of sandstone under the states of dry and saturated. The test results show that after saturated in water, the softening effect of modeⅠfracture toughness of sandstone was obviously, and the fracture toughness ratio of water-saturated sample and dry sample is close to the sandstone softening coefficient of the compressive strength, showing a similar softening effect. Meanwhile, the relationship of the modeⅠfracture toughness and the tensile strength was discussed through theoretical analysis; and a large number of experimental data was used to verify the analysis results. As a result the analysis results can provide a theoretical basis for the previous statistical fitting formulas between modeⅠfracture toughness and the tensile strength. Finally, statistics and analysis of the relationship between modeⅠfracture toughness and compressive strength, cohesion, friction angle and some other strength parameters was made. Research results have an important reference value for the study of the correlation between modeⅠfracture toughness and strength parameters of sandstone, and the related test methods, test results and conclusions can provide favorable evidences for the experimental research of other types of rocks.

The geotechnical material’s actual mesostructure is significant in that its characteristics will largely affect its macroscopic mechanical behavior. With the digital image processing technology being more and more mature, the partial differential equations (PDE) method based on variation level set attracts increasing attention meanwhile finds increasingly more application in the field of image processing. C-V model, as a frequently used method, is a typical one among those using the PDE method. This paper deals with how to use C-V model combined with background filling technology to realize the three-phase split (feldspar, quartz and mica) of the granite pictures after the digital image of the rock has been got; thus to provide the conditions for further mechanical analysis. The purpose of quantifying the mesostructure of rock can be achieved by the method described in this paper, which ultimately can be used to get pictures that accurately reflect the internal characteristics of the rock, thus to provide real geometry model for finite element analysis in the future. The numerical value results indicate that the PDE method is very effective indeed. By selecting the appropriate number of iterations, it can get a higher quality of the rock mesostructure quantitative geometric images consistent with the real mesostructure images.

In the engineering of Passenger Dedicated Line from Beijing to Shijiazhuang, a 5 km long tunnel parallel to the existing Jing-Guang railway line with a distance ranging from 5 m to 20 m was built with open cut method. A testing length supported with pressure dispersed anchor cables was designed and constructed to compared with the commonly used tension concentrated anchor cables on both dynamic response and anchorage effect. Based on data measured for half a year on site, the research on performance and character of these two kinds of anchor cables was made. It is proved that the anti-vibration ability of the pressure dispersed anchor cable is 5 times stronger than the tension concentrated anchor cable. Furthermore, the former has advantages of shorter stress transfer time, stable anti-vitration of long period, less loss of prestress.

With the rapid development of subway network, the situation where shield tunnel going across the adjacent tunnels are becoming more and more common. But the research on the interaction between shield tunneling and nearby tunnels is still under perfection. On the background of Shanghai’s typical soft layers, method of centrifuge modelling is adopted to study the effects of above-crossing construction of shield tunnel on existing tunnels and nearby strata at different grouting ratios. The in-flight tunneling simulation techniques are used in centrifuge model tests to simulate the construction of shield tunnel, where discharge or injection of heavy fluid is adopted to simulate the excavation unloading, ground loss and grouting successfully. The existing tunnels’ behaviour and the ground response in terms of settlement, pore pressure and internal forces during and after the construction period at different grouting ratios are analyzed. Results show that the existing tunnel structure would undergo heave during the above-cross of a new tunneling; while grouting can alleviate the heave. However, excessive grouting ratio during construction would disturb the surrounding ground and cause more settlement in the long run after the construction.

Drilling core samples, standard penetration test, and load test are common methods for checking the quality of soil-cement columns in China. They have disadvantage of high requirements and ineffective in time and test cost. Because of these reasons, a new method for checking the strength of soil-cement columns is proposed. The method includes measurement of the pH value and the electrical conductivity at the initial stage to determine the unconfined compressive strength and the characteristics of cement treated soil. In this study, the fourth layer of Shanghai clayey soil is used. The cement content of variables, cement treated soil’s chemical properties and strength characteristics researching tests were done. The relationship among pH value, electrical conductivity, and cement content, curing time, unconfined compressive strength are investigated. Test results show that when pH value and the electrical conductivity at initial stage are larger than 11.5 and 0.09 s/m respectively, cement treated soil starts to get strength. After that, the strength grows with the increase of pH value slowly. However, when pH value reaches 11.8, the strength grows with the increase of pH value rapidly. Characteristics of relationship between electrical conductivity and strength can avoid inaccuracy and risks brought by using single chemical index to determine the unconfined compressive strength. These results can provide a test basis for the judgment of the strength of cement treated Shanghai clayey soil.

In order to study anisotropic properties of schist in Shiyan area, Hubei province, uniaxial compressive tests on cubic samples and Brazilian tests on disk samples of Wudang chlorite schist were carried out. The anisotropic strength and fracture characteristics of samples under different loading states were discussed, the mechanism was revealed. The results show that: Wudang chlorite schist shows obvious anisotropic properties; the strength parallel to foliation is higher than the vertical direction. The special orientation bunch structure and the weak cementing strength between foliations caused the different fractures and mechanisms along different directions. Under compression stress, tension-split along foliations and rod press-bent failure are easily caused by Poisson effect; and tension-shear failure is easily caused under vertical direction compression. There is strength consistency in the same direction, for the compression strength and tension strength parallel to foliations are higher than that vertical to foliations. As the tension stress between foliations is extremely low, tension-split failure and tension-shear failure are easily caused with a small angle to foliations under splitting load; so tension failure along foliation should be avoided as far as possible. The results can be referenced for reinforcement and water-proof treatment of tunnel and slope projects.

The loess with low viscosity and large number of powder particles, has weak-cemented and more frame-holes microstructure, which could lower its dynamic strength and induce large seismic subsidence deformation under dynamic loading. It brings some challenges technology problems for foundation treatment in engineering construction. The acidified modification method is through by changing the loess microstructure from base to reduce its dynamic deformation and collapsibility. The modification method is by adding below, the boron chemical compound, the main materials can produce strong dispersed and cemented effect, light calcium carbonate, to adjust the original loess particles size gradation, and the diluted phosphoric acid, to adjust the original loess pH value. Moreover, through contrasting the seismic subsidence test and others by different ingredients, then analyzing its microstructure and energy spectrum before and after modification, the best proportion of ingredient is determined. The study results show that the acid-modified method can change the loess microstructure and reduce the seismic subsidence conefficients effectively. In addition, the all modified adding materials have non-toxic, and have no pollution to the soil.

Based on the shear creep curves of gray marbles contain green schist weak structural plane, using rock biaxial rheology testing machine, the long-term strength and accelerated creep properties are studied. On this basis, a new nonlinear shear rheology component is proposed. When nonlinear rheological model component serial connected with Nishihara model, a new nonlinear visco- elastoplastic shear rheological model can be built to fully describe the shear creep properties of greenschist weak structural plane. Using complete accelerative rheological curve, the nonlinear visco-elastoplastic shear rheological model is carried out the identification, and the correlative parameters of nonlinear rheological model such as viscoelastic modulus and viscosity etc. are also gained. The comparison between the rheological model and experimental result shows that the nonlinear rheological model is right and reasonable.

In order to know about the joint effect on the unloading triaxial rheological rules of pelitic siltstone, step unloading triaxial rheological experiments with the same initial confining pressure were carried out under different deviatoric stresses. The precast method of joint specimen and the test process are introduced; then the variance law of axial and lateral rheological strains of joint specimen under different deviatoric stresses is investigated. The results show that the axial and lateral rheological strains of jointed specimen increase with the decrease of confining pressure; and the increasing tendency of jointed specimen with the dip angle ? of 0°is the steepest; and followed by jointed specimen with the dip angle ? of 60°; and is rather gentle with the dip angle ? of 40°. Meanwhile, the effect of joint on the variance tendency of axial and lateral rheological rates is analyzed; and the unloading rheological failure mechanism of specimen with different joint inclinations is also discussed in detail. Based on the experimental results, the unloading triaxial rheological law of joint pelitic siltstone is mastered, so as to bring important reference for the establishment of rheological constitutive model of joint rock mass and the identification of parameters.

The effects of size and embedment depth of underreamed ground anchor under vertical pullout on its bearing capacity characteristics were researched through 25 model tests. The test results exhibited two different modes of underreamed ground anchor depending on depth/diameter ratio, namely shallow and deep underreamed ground anchor. During pullout, the two type underreamed ground anchors experienced several phases, such as soil elastic deformation, shear failure on normal anchor section-soil interface, soil elastoplastic deformation phase and shear failure as well. And they manifested general shear failure and local shear failure. In comparison between underreamed ground anchor and normal tension-type anchor, the test results indicated that in ultimate bearing capacity, bearing capacity ratio and safety, underreamed ground anchor had substantial superiority in comparison with normal tension-type anchor. In order to improve the bearing capacity, expanding diameter of underreamed section had more obvious advantages. Furthermore, there was an optimal diameter of underreamed section by the bearing capacity ratio analysis. So it is highly recommended to seek an optimal dimension of underreamed ground anchor to get more economic benefits in practice.

Model tests are conducted to research the effect of cyclic loading frequency on bearing capacity of suction anchors with taut mooring systems under combined inclined static and cyclic loads at the optimal loading point. Following conclusions are obtained. The failure modes of suction anchor are vertical pullout if the direction of cyclic load is the same as that of the static load. The cyclic average displacement of the anchor is decreased with the cyclic loading frequency; but the influence of cyclic loading frequency on the cyclic average displacements become weak with the number of cycles. As the frequency varied from 0.1 Hz to 0.01 Hz, the cyclic bearing capacity decreases 8% and 4% respectively when the numbers of cycles to failure are 100 and 1 000; but the cyclic bearing capacity just drops 1% when the number of cycles to failure is up to 2 000 and then the effect of the frequency on bearing capacity can be neglected.

Based on the traditional cement-treatment and lime-treatment methods, the stabilizers by using high volume low-calcium fly ash, lime and cement are proposed, in order to improve the strength and durability of marine sediments and to achieve the resource utilization of marine sediment and low-calcium fly ash. A series of laboratory tests were performed to investigate the variation of compaction characteristic, strength property, water stability and durability of solidified marine sediments. The experimental results show that the addition of designed stabilizers causes a decrease in optimum water content and a very slight increase in maximum dry density compared to untreated sediments. The elastic modulus, unconfined compressive strength and tensile strength increase to different levels, while the strength and elastic modulus increases more significantly with higher cement content and longer curing time. The water stability can be greatly ameliorated after solidification treatment compared to untreated sediments. Finally, the strength performance of solidified sediments could be significantly decreased by water immersion damage and thawing-freezing cycles, and the unconfined compressive strengths of designed materials are decreased by about 22% due to the thawing-freezing cycles.

In seasonally frozen soil region, the physico-mechanical properties of subgrade soils with different states (plasticity index, confining pressure, etc.) will change after freeze-thaw cycle during the traffic operation; but the study of effects of freeze-thaw cycle is not extensive and intensive and can not provide accurate data to support the roadbed design in roadbed design of seasonally frozen soil region. So this change has not been taken into account. Three subgrade soils with different plasticity indices are selected from seasonal frozen soil region. Static triaxial test is executed on the samples exposed to 0-7 times closed-system freeze-thaw cycles under different confining pressures. Elastic modulus is obtained from the line segment of deviator stress-strain curve. The results show that the elastic modulus increases with confining pressure increase for the same kind of soil under the same freeze-thaw cycles. Elastic modulus with the same confining pressure decreases with the of freeze-thaw cycles; Under the same confining pressure and the same freeze-thaw cycles, elastic modulus increases with the plasticity index. The exponential function is adopted for multiple nonlinear fitting. The relationship between elastic modulus and confining pressure, plasticity index, freeze-thaw cycles is obtained and shows a good correlation.?

The dispersive clay is a special soil which has low erosion resistance ability, impermeability, and high dispersion in pure water; it would cause serious harm to water conservancy construction. There have been many results on identification and modification of dispersive clay; but study of dynamic characteristics of dispersive clay is seldom reported in the newspapers. By using the DTC-199 dynamic torsional shear instrument to study the dynamic shear modulus of a kind of dispersive clay coming from a rolling soil dam in Ningxia. By changing the initial conditions such as moisture content, dry density and confining pressure and so on, to study its dynamic characteristics and its variation rules of dynamic shear modulus in different experimental conditions, then to compare and analyze the results. We can get that: dispersive clay’s dynamic shear stress-strain relations conform Hardin-Drnevich hyperbolic model; controlling the initial conditions, as other condition is the same, the lower moisture content, the greater dynamic shear modulus; the greater dry density is, the greater dynamic shear modulus is; the higher confining pressure is, the greater dynamic shear modulus is. Initial shear modulus and the maximum dynamic shear stress change as the same way. Dynamic shear modulus become smaller as dynamic shear strain increases. Compared with ordinary clay, the moisture content has greater impact on its strength and deformation.

The influences of cross-cracks on the jointed rock mass failure modes and mechanical properties were studied. The brittle jointed rock mass specimens with cross-cracks were simulated by similar material. There were 20 groups of jointed rock mass similar material specimens in which the angle between main crack and loading direction and the angle between main crack and secondary crack were taken as changing parameters. The specimens of jointed rock mass similar material were tested to obtain the influences of cross-cracks on jointed rock mass failure modes and mechanical properties. The test results show that when the angles between main crack and loading direction are 0°and 90°, the failure modes of specimens are mostly shear type failure propagating from the secondary crack; when the angles between main crack and loading direction are 30°and 45°, the failure modes of specimens are mostly shear type failure propagating from the main crack; when the main cracks are at same angle, the strength of most jointed rock mass similar material specimens with cross-cracks is higher than the strength of specimens with single crack; the post-peak stress-strain curve descending slopes of most jointed rock mass similar material specimens with cross-cracks are steeper than the slopes of specimens with single crack; the specimens have low strength when the angle between main crack and secondary crack is about 45°, and the specimens have high strength when the angles between main crack and secondary crack are about 30° or 90°.

Governing equation has significant effects on the results of fluid flow through rough joint. In order to investigate flow through a rough joint, Navier-Stokes equation, Stokes equation, Reynolds equation and cubic law, which are commonly used in analyses of flow through a rough joint, are firstly introduced and their applicability are evaluated. And Reynolds equation is chosen as the governing equation, a void model is established to analyze fluid flow through a rough joint. Then taking artificial rock joints as objects, laboratory flow tests are first performed and the flow rates through joint derived from void model under the same boundary conditions are also predicted after obtaining the joint aperture distributions. Three other models including void model taking cubic law as governing equation, Cubic law referred to the whole joint surface and Su B.Y. empirical modified cubic law are also applied to predict the volumetric flow rates through joint samples. The predictions of four models are compared with experimental observations. It is found from the comparisons that flow rates derived from void model based on Reynolds equation agree well with experimental observations; while the predictions of other three models have large discrepancy from experimental observations. According to the comparison, Reynolds equation is able to predict flow rates through rough joint exactly. In addition, tortuosity phenomenon of flow through joints can also be derived from the distributions of volumetric flow rates vectors, which provides a theoretical basis for investigating the influences of tortuosity on flow rates in a rough joint.

Considering the interaction between soil and foundation, an investigation is put into rocking vibrations of a rigid circular foundation on the poroelastic soil excited by incident Rayleigh waves based on Biot’s dynamic theory. The free field, rigid-body radiation field and rigid-body scattering field are introduced in order to consider the scattering phenomena caused by the existence of the foundation. Using the Hankel integral transforms, the governing equations of the soil are solved. Combining with the mixed boundary-value condition at the interface between the soil and the foundation, expression of the rocking dynamic amplitude of the foundation under the action of the Rayleigh waves is obtained. Influences of the Poisson ratio, the mass of foundation, the boundary drainage, the permeability of soil on rocking vibrations of the foundation are determined through numerical calculation. Computed results show that pore water in the soil has weakening effect on rocking vibrations comparing with that in elastic half-space. And the weakening effect depends upon the boundary drainage and permeability of soil.

In the literatures, there are two major forms of expressions of the effective stress and the pore pressure coefficient B controlling the deformation of saturated geomaterials. In order to discriminate and analyze their rationality, the relationship is investigated between the volumetric compressibility coefficients of the solid phase and the skeleton subjected to both hydrostatic pore pressure increment and net cell pressure increment under an undrained condition. Also investigated are the volumetric deformation increments of the liquid phase, the solid phase and the skeleton induced by the hydrostatic pore pressure increment and the net cell pressure increment. The problems existing in the derivation procedures of the two forms of expressions of and B are pointed out. Based on the equivalence relations of the deformations under undrained and drained conditions, new expressions for the effective stress and the pore pressure coefficient B are established.

The geotechnical prestressed anchorage techniques have been widely used in the traffic, hydraulic and construction engineerings. But the engineering practice has shown that the prestressed anchorage cable/bolt could happen to fail because of the special service environment and condition, such as the long-term moist environment and the effect of high-tension stress. Based on the present related experiment results, and through the comparison and analysis of the principal factors that can influence its service life, it is shown that the stress corrosion of rod body materials is the basic factor that determines its service life under normal use conditions of geotechnical prestressed anchorage structures. Utilizing the model test which can forecast the long term prestressing force variation by combining the rheological mechanics with the actual monitoring data and the quantificational formula of the development rule of the stress corrosion established from the indoor accelerated corrosion test and the related field-testing data, the method of forecasting service life for the geotechnical prestressed anchorage structures is presented, which utilizes the ultimate bearing capacity of rod body material as a criterion. This method can guide the risk prevention and treatment of the prestressed anchorage system. Finally, the research result is applied to an actual engineering; and the service life of the project is put forward.

With soil body adopting the hyperbolic hardening model and cement-soil pile wall and anchors elastoplastic one, the influence of anchors’ diameter and length on the supportive structure has been calculated and analyzed. The results show, on the condition that the diameter reaches over 400 mm, such effects in the saturated soft clay as replacement, occupation and reinforcement are obvious; thus distinctively controlling the coping’s horizontal displacement and settlement of the soil mass behind the retaining wall; while less than 200 mm, all the functions vanish thus lowering the active reinforcement. As the anchor’s length arrives at 1.6 times as long as the excavation depth, the coping’s horizontal displacement and soil mass’s settlement behind the retaining wall would be under control in the efficient way, while exceeding that all the effects are not that clear. Compared to the monitoring data from the same foundation pit, calculated and measured values bear great repeatability and regularity.

Former researches indicate that the distribution of debris flow velocity is laterally asymmetrical. Due to a lack of a theoretical basis on it, velocity and load have to be calculated on uniform state advised by current design regulations when the debris flow dam and drainage canal are designed. It is different to the practical status, which may lead to the engineering failure due to the poor partial stability. Therefore, based on deposition-erosion equilibrium, isotropic fluid hypothesis and reasonable simplification for debris flow's gully cross-section, the nonlinearity features of debris flow velocity's lateral distribution was proposed by deducting the deducing process of the velocity calculation formula at any cross-section. With the instance analysis of debris flow mitigation and control work at earthquake-stricken areas in Lixian, Sichuan province, we found that the debris flow velocity at channel line is triple the one at either side, and conducted the structural optimization design for debris dam on the premise of ensuring its function, reducing the risk of the dam break and instability of debris dam, which would rise the dam stability coefficient by 20%, and save the engineering cost by 5%.

Casing is a weak part of underground gas storage during its operation period, which will be influenced by kinds of stochastic factors. In this paper, failure modes and failure criterions of casing and cement sheath are discussed firstly; then a three dimensional calculation model including casing, cement sheath and wall rock is established based on Jintan underground gas storage in Jiangshu province. Stochastic characters of geometrical size, load and material parameters of the casing system are analyzed, which are applied to the safety analysis. Then, failure probability and sensitive factors are calculated based on Monte Carlo method. At last, the simulation result is proved by a three dimensional geological model experiment. The research results indicate that the influences of the randomness responding to factors on casing reliability are different. Thickness of casing, inner diameter of casing, operation pressure and thickness of cement sheath are sensitive factors of casing-cement and wall rock system．Moreover, different factors have different effects on reliability. The reliability of casing decreases as storage pressure decreasing. And the reliability of cement sheath decreases as storage pressure increasing. More attention must be paid because failure probabilities of casing are high when the gas pressures of storage are extremely high or low. The gas extraction rates determined by the volume convergence law of the caverns will not influence the safety of casing-cement and wall rock system.

Large long-term tunnel settlements are generally observed after the completion of shield tunnel construction in soft clay. It is well-recognized that significant tunnel settlements may pose a threat to the serviceability and safety of underground metro systems. However, the mechanisms of the observed large long-term tunnel settlement in soft clay are still not fully understood. Measured tunnel settlements of a metro line in Shanghai from 1999 to 2007 are studied. Several possible causes, especially secondary compressions of clay and sand layers due to groundwater mining, are investigated based on laboratory test and field monitoring results. Noticeable secondary compression of Aquifer IV was found in some areas in Shanghai. The compression of Aquifer IV, especially the secondary compression due to groundwater mining is one of the principal reasons for long-term tunnel settlement. Controlling groundwater mining in Aquifer IV is vital to minimize large tunnel settlement in Shanghai.

Based on earthquake damage investigation after the Wenchuan Ms8.0 earthquake, it is discovered that the phenomena of site amplification effects on ground motion were very obvious both in the mountainous area of southeastern Gansu province and the Loess Plateau areas. Combining with the borehole exploration, site seismic response analysis of the typical loess tableland at Pingliang City, Gansu province is carried out applying the dynamic finite element method of two dimensions linearly equivalent for dynamic response numerical calculation; the local amplification effect of the loess tableland is studied as well. The results show that there are seismic amplification effects at loess tableland; and acceleration, velocity and displacement increases with increase in tableland height gradually. Moreover, the low frequency components become more abundant and the high-frequency components are absorbed with increase in tableland height. The long-period components of acceleration response spectrum have increased gradually as well. The numerical results are basically consistent with the earthquake damages, so as to have certain scientific significance for the reasonable seismic fortification in loess regions.

The method of slope stability analysis based on the assumption distribution of normal stresses over the slip surface is a progress of limit equilibrium theory. To obtain a reliable safety factor, it is essential to analyze the composition and assumption pattern of normal stresses over slip surface of slope which are dependent upon the body and inter-slice forces. Examples are given to analyze the distribution and contribution components of normal stresses over the slip surface under different assumptions of inter-slice forces. The results show that: Contribution component of slide body forces (including slope external forces) is dominant; and inter-slice forces are smaller contribution component. The safety factor is insensitive to the distribution of normal stresses over the slip surface. So, it is not necessary to demand for the accordance between assumption normal stresses distribution and real normal stresses distribution over the slip surface. Then, the assumption distribution of normal stresses over the slip surface could constitute by the contribution component of body forces, chosen as the kernel function, and the contribution component of inter-slice forces which could be approximated by a modifying function with two undetermined parameters. The research results have disciplined the assumption patterns of normal stresses, and have practical and theoretical value.

Based on the background of ultra-small spacing tunnels of Nanjing Metro and combined with the existing research results as well as domestic and international codes, a method of blasting technology using in small spacing later tunnel is studied in order to keep the security and stability of the antecedent line. Using modern information technology theory as the basis and making full use of on-site monitoring, the vibration velocity of particle in antecedent tunnel can be monitored and analyzed for vibration reduction and vibration isolation during the blasting. The final results show that the blasting design parameters such as optimized footage driving cycle, the maximum loading dose and the time difference of sectional blasting are reasonable during the construction. The blasting design did not affect the safety of the antecedent tunnel. While through the three dimensional numerical simulation, after observing the variation of particle vibration in antecedent line over time, we find that the maximum vibration velocity meets the relevant codes; and the optimized blasting design is reasonable. Through numerical analysis, we find that the tangential and centripetal vibration velocity in tunnel side wall are much faster than the vibration velocity in arch springing, the effect in antecedent blasting surface is slight greater than the rear lining; and the surface vibration of lining in left tunnel which near blasting point is greater than the surface in blasting point. The research results to the construction of this protect provide a scientific basis and technical guidance for similar future tunnel blasting excavation engineering and construction methods in theory.

In-situ vibration test of non-embedded pile-board subgrade needs to be carried out because this structure’s dynamic characteristics are quite different from normal subgrade. DTS-1 dynamic test system is used to test the vibration response, internal force and settlement of a subgrade section in Zhengzhou-Xi’an Passenger Dedicated Line. Result shows that sympathetic vibration will not happen in range of exciting frequency, and subgrade settlement mainly happens on loading plate and will be basically stable after 0.7 million times’ loading with a final settlement of 1.0mm after 1 million times’ loading. Comprehensive dynamic stiffness is related to thickness of board, span, piles and soil, which can provide well vibration characteristics and long-term dynamic stability for the combining structure of pile-board structure, subgrade and foundation.

It is proved that the statistical parameters of a random response can be directly expressed in terms of transfer function; and then a transfer function-based stochastic seismic response analysis is made on Baihetan underground caverns. The seismic reliability of underground caverns is also discussed. The results indicate that in addition to stochastic seismic response of the caverns, spectral characteristics of seismic response and seismic response estimations can be conducted at the same time, which leads to a more profound point of view in comparison with conventional methods. Results of stochastic seismic analysis and transfer function-based estimation are well consistent with the results of numerical computation. The theory of excursion failure criterion is firstly applied to provide a new approach to consider the randomness of earthquake loading in stochastic seismic response analysis of underground caverns.

The theoretical solutions of elastic multilayered road structures under dynamic double-circular loads are derived using the transmission-reflection matrix (TRM) method and the superposition principle. By employing inverse Hankel transformation, the numerical results are obtained. The transmission-reflection matrices of elastic layered structure are of small size and free of any numerically unstable exponential terms which may greatly increase its efficiency and accuracy in applications. As a result, the TRM method can be valid for the large layer thickness and high frequency cases. The presented methodology is validated by comparing solutions with laboratory model tests. Some numerical results are presented and used to analyze the influence of pavement thickness and modulus on the vertical stress and displacement. The research results can be for reference in design of the road pavement and subgrade.

The study on representative element volume (REV) attracts attentions in geotechnical engineering. The inherent complexity (stochastically distributed fracture network) highly attributes to the existence of REV. A new method, which comprehensively considers the fracture features of the rock masses, is built based on 3D fracture numerical network modeling. Subsequently, volumetric joint count calculation is applied to determine the REV size. 3D fracture numerical network is modeled; and the network is divided by cubes with augmented sizes. The cubes are numbered, and the fracture parameter central point number is confirmed. On the assumption that the parameter is an attribute of the rock masses, the volumetric joint count can be confirmed; and the mean value can be applied to determine the RVE size based on the convergence state. This paper comprehensively considers the fracture features of the rock masses; and the REV model is built based on volumetric joint count determination. A conclusion is drawn that REV size is 4 times larger than the average trace length.

Stability analysis of goaf group is a complicated geological problem; there is some “group effect”. An accurate grasp of cavity shape, size and its change is the premise to this problem. In the engineering background of Shirengou iron mine, using the cavity monitoring system (CMS) to detect the goaf group precisely. Then the cavity model and geological model of the mine are constructed using the 3Dmine software based on the detection results. A method of constructing numerical computing model with the coupling of 3Dmine and FLAC3D is put forward. The stress and strain fields are analyzed according to the simulation calculation results; and the “group effect” is discussed. The research results show that the “group effect” increases the stress and strain larger than the single goaf; and this effect is not only simple addition but improve the goaf’s hazard grade. This paper combinates the advantages of CMS, 3Dmine and FLAC3D, and provides a new and effective way for numerical simulation research on the stability of rock engineering.

As the parameter assignment methods for inhomogeneous rock have the characteristic of randomicity, the coefficient of variation of the random parameters is defined as inhomogeneity degree of the rock. The computational formula of inhomogeneity degree for the method of Weibull distribution is discussed; and the comparative analysis with shape parameter is pursued. And the computational formula of inhomogeneity degree for rock mineral cell unit is discussed. In addition the influences of inhomogeneity degree on mechanical property of inhomogeneous rock simulation model which bulit by each of these two methods are researched by numerical experimentations. The study results indicate that the difinition of inhomogeneity degree is logical and it can describe the degree of inhomogeneity of rock models which are bulit by different parameter assignment methods. The mechanical properties of inhomogeneous rock are affected by the mechanical properties of cell unit and the inhomogeneity properties of rock and the ultimate strength of the rock will be weakened because of inhomogeneity. For different inhomogeneity rock models, the influence of the inhomogeneity degree on the ultimate strength of rock can be described by the same function relationship which is linear function.

An enriched radial point interpolation meshless method(X-RPIM) was presented for the linear elastic fracture problem. In order to represent the discontinuous displacement field along crack face and stress singularity around the crack tip, enriched functions were added in the approximation of traditional radial point interpolation meshless method (RPIM) based on the ideas of partition of unity. The merit of presented method is that the shape functions have the properties of Kronecker δ functions, which would make the essential boundary be implemented easily. The construction of discontinuous approximation function, the discrete format of governing equation and the evaluated process of the mixed-mode stress intensity factors by using the J integral method are introduced in detail in X-RPIM. The impact for the computational results of stress intensity factors using different integral domains of crack tip is discussed. Analyses of numerical examples demonstrate that the enriched radial point interpolation meshless method can effectively solve fracture problem, and has practical merits for modeling crack growth problem.

The problem of failure of soil is generally studied by shear band. The lunar environment is quite different from the earth such as Anhydrous, low gravitational fields, and very low atmospheric pressure etc.; and the internal friction angle of lunar soil is quite large. In this paper, particle rolling resistance and Van der Waals forces between lunar soil particles are taken into consideration in the new lunar soil contact model. With this model several flexible boundary biaxial compression tests are simulated by distinct element method (DEM). The results show that the formation of shear band is characterized with both strain localization and the pure rotation ratio (APR) localization; and the lunar environment has a significant influence on failure modes of samples, such as inclination and thickness of the shear band. The influence of lunar surface environment on the mechanical properties of lunar soil should be taken into account in lunar exploration.

Back analysis of displacements of excavation involves the coupling of numerical model and optimization method, which is computationally intensive and inconvenient. This paper proposes a multiple response surface method (MRSM) for back analyzing displacements of excavation. MRSM uses quadratic polynomial to express the implicit relationship between the horizontal displacements of the underground diaphragm wall and the soil elasticity modulus at different depths of the underground diaphragm wall of the excavation; and based on that, the back analysis of the elastic modulus of the excavation is undergone with the displacement observation. This method uncouples the numerical model and optimization method so as to attain a higher calculating efficiency. Using spreadsheets makes computational process more convenient. This method is utilized in the back analysis of two excavation cases. We can get convergence result by only three-step iteration in case 1. The predicted trend of the horizontal displacement of underground diaphragm wall is coincided with practical data. The predicted depth of the maximum horizontal displacement approaches the actual measurement. Engineering application cases prove that the MRSM is reliable in displacement back analysis in excavation construction with its features of convenience, high calculating efficiency and accuracy.

Super long bored piles are friction piles; thus establishing the appropriate pile-soil interface shear model is the key to reasonable and effective simulation analyze the load-movement characteristics of the pile. According to working trait of the super long bored pile shaft friction (? ) with the increasing of pile-soil relative movement (w), ? - w relationships are divided into the hardening and the softening types. Furthermore, the mobilized patterns of the pile shaft friction are divided into three types: the full hardening mobilized pattern, full softening mobilized pattern and hardening-softening mixed mobilized pattern. Hardening type and softening type pile-soil interface shear models are established for super long bored pile. The pile-soil interface shear models are introduced into FEM software using subroutine FRIC of ABAQUS. Single pile simulation example shows that the interface shear models are implemented in ABAQUS successfully. FEM simulation of field test piles is carried out using the established pile-soil interface shear models. The simulation results are similar to the measured results. It is shown that the established pile-soil interface shear models and FEM simulation have the rationality and feasibility to calculate the load-movement behavior of super long bored pile.

CO2 storage in deep saline aquifers is considered to be an imperative practical mean for reducing greenhouse gas emissions. Injectivity is one of key factors for determining the feasibility for storage of CO2 in a brine field. Research into the injection rate variation rules and the measures to improve is of great value. Many saline aquifers have relatively low permeability which limits the injection rate of CO2 to the aquifers. In this paper, numerical simulation studies of carbon dioxide storage in brine-saturated reservoirs have been conducted to investigate the approaches for enhancing injectivity through changing the fluid salinity in aquifer, using horizontal well or longer injection screen, and introducing hydraulic fracturing for storage aquifer improvement. Changing fluid salinity can be implemented through injecting a slug of fresh water prior to commencement of CO2 injection. Setup of the models is loosely based on the hydrogeological conditions in Ordos basin. Modeling results indicate that these approaches can effectively improve the injectivity. Use of horizontal well and hydraulic fracturing shows obvious injectivity enhancement. The effect of changing salinity could be more significant when the initial salinity of aquifer is high. The findings may provide helpful hints to the CO2 geologic sequestration in saline aquifer in Ordos basin or similar areas.

Jacket platform suffers the wind, waves, earthquake and other lateral loads; while the stability of platform has strict requirements for pile foundations. Therefore, studies of the behavior and deformation mechanism of pile foundation under lateral loads are of great significance. A new test system has been developed to simulate the response of pile foundations subjected to lateral loads. The system consists of a jacket platform test model subsystem, an electric servo loading subsystem, a sensor and data acquisition subsystem, and a vibration test subsystem. It can be used to study the deformation mechanism of pile foundations, the response of soil around pile foundations and the vibration characteristics of jacket platform subjected to lateral impact, static and cyclic loads. The test results show that the system can simulate pile-soil interaction and vibration characteristics of jacket platform effectively.