A large number of rockburst cases happened in deep tunnels of JinpingⅡhydropower station revealed that the slab failure of surrounding rock has a strong relationship with rockburst. Model specimens that meet the architectural feature of slab failure are made by using high-strength gypsum. Instability destruction process, strength and deformation characteristics, crack propagation signature of model specimens are researched under the condition of one lateral side restraint uniaxial loading mode. The results show that (1) the instability destruction process of the slab model specimens shows the characteristics of strain rockburst. A typical failure process can be described as follows: initiation and propagation of extension crack from the tip of pre-existing fissure, splitting into slabs, flexure deformation of slabs, buckling of slabs and ejection of slices. (2) The peak strength, elastic modulus of model specimens containing one, two and three pre-existing fissures show a steady decline law, but the peak axial strain decreases and then increases. (3) The emergence of extension crack will result in: a sudden change of the lateral strain near the tip of adjacent fissures and a significant increase in the amount and the rate of lateral deformation of the specimens. (4) Due to the affect of the free surface, extension crack will enter into unstable propagation stage in a short time after its initiation from the tip of pre-existing fissure that near the free surface of specimens and this will lead to the overall instability of the model specimen. At last, acoustic emission characteristics of specimen in the overall stage of compression deformation are analyzed. The research results are of important significance for the reveal of the instability destruction law of slabbing surrounding rock and the rockburst formation mechanism of deep tunnel in hard rock.

In order to understand the shear properties of salt rock under compression-shear state, the compression-shear test and acoustic emission test on salt rock at different insertion angle are designed. The characteristics of damage mechanics and acoustic emission signal for salt rock specimens at different shear angles are studied. In addition, considering the condition of compression and shear, the shear damage model with respect to shear stress and normal strain is established based on general dynamic model. Test results show that, with increase of placed angle, the mechanical characteristics of salt rock shift from plasticity for main features gradually to brittleness for main mechanical features; while the placed angle increases, the peak shear stress of salt rock decreases; the overall capacity of bearing load also shows declined trend; the capacity for deformation weakens with angle increasing and the capacity against deformation with angle increasing strengthens firstly and weakens lastly, reaching the maximum while angle of 45 degree. The acoustic emission test shows that, due to its own structure and damage features, the signal of salt rock under compression-shear state is comparatively apparent; while placed angle is 55 degree and 65 degree, the AE count of specimens in yield stage fluctuates more violently; and the process of break is also more fast; while placed angle is less than 45 degree, the AE count increases gradually; and the peak generally appears near the peak stress.

By improving the critical slip field of slope, the numerical simulation method of bank collapse is proposed, considering lateral erosion and bed degradation. To avoid the unrealistic estimation of pore water pressure distribution, the method proposed here is to couple riverbank stability with groundwater flow simulation, and apply this to deal with the conjunction effect of river stage and groundwater flow. Numerical simulations of clay and silt bank collapse with representative parameters are carried out. With continual lateral erosion and bed degradation, stability of riverbank has dynamic changes. Modes of bank collapse of different soil riverbanks are also discussed. The results show that steep clay riverbanks fail along an almost planar failure surface which passes through the toe of the bank; and a gentle silt riverbank, exhibits a curved failure surface for which may occur partial collapse during rapid drawdown of river water level.

By using equivalent rock mass(ERM) technique, the ERM models containing diverse joint dip angle and connectivity rate are constructed, in which the joint and rock block are represented by smooth joint model and bonded particle model, respectively. Combining with test result, the effect of joint connectivity rate on strength, fracture mechanism and energy evolution of rock mass under the condition of uniaxial compression, is quantitatively investigated from meso-mechanical viewpoint. Research shows that when an angle presents between joint and load direction, rock mass behaves as the tendency of coalescence failure along the connecting direction of rock bridge. Especially with joint dip angle α of 30° and connectivity rate L of 0.8, rock mass exhibits composite coalescence failure of rock bridge. Under the condition of the joint dip angle α of 30°, with increase of joint connectivity rate, rock mass exhibits the following mechanical behaviors: (1) The peak compressive strength continually decreases. (2) The amount of microcracks decreases, but the ratio of tensile microcracks increases. Meanwhile, microcracks gradually generate on the rock bridge line between different level joint tip. (3) The occurrence time of acoustic emission (AE) event during the entire loading stage gradually disperses. The amount of AE event as well as the distribution range, mean value and standard deviation of fracture magnitude decreases. (4) The peak strain energy as well as the post-peak change rate of strain and kinetic energy reduces. The growth of post-peak frictional energy slows down. The required work supplied by exterior to destroy the specimen reduces.

On the basis of systematic analysis of the material composition and destabilized mechanism of debris landslide induced by water，the dynamic action of unloading and loading and its response law of groundwater in the process of the dynamic stability evolution of the slope are systematically analyzed. The unloading-loading response ratio parameter to evaluate the laws of the dynamic stability of the landslide evolution and destabilized features are analyzed and put forward from the viewpoint of the nonlinear system dynamics. This paper firstly proposes that the monthly change of groundwater table can be taken as the unloading- loading parameter of debris landslide and its displacement velocity and acceleration rate can be taken as the response parameter to unloading-loading are proposed. Thus, the dynamic displacement parameters and dynamic prediction model of the unloading-loading response ratio of the groundwater table are determined. Meanwhile, the quantitative relationship between unloading-loading response ratio and damage variable & the stability coefficient and the criterion of displacement response ratio to unloading-loading are determined by using the theory of damage mechanics and the damage variable parameters of slope. Finally, taking the typical debris landslide of the Three Gorges Reservoir region—Xintan landslide for example, the calculation of unloading-loading response ratio of monitoring points of Xintan landslide is completed by using the dynamic displacement prediction models of the groundwater. The computed results show that the curves of unloading-loading response ratio of monitoring points basically agree with the dynamic evolution law of the slope stability. The results of the study show that the parameter proposed in this paper is a kind of effective dynamics appraisal parameter of displacement in the stability of landslides induced by water and it can be used to make real-time monitoring warning and evaluation on the dynamic stability of this kind of landslides.

In this study, the continuum-discrete coupling method is be used to an open-pit iron mine slope in Hebei province. The deformation and stress characteristics in the typical across-section of the slope excavated in the difference time steps are simulated in combination with the strength reduction method. Continuum and discrete region are analyzed with FLAC and PFC procedures respectively. Emphatically in terms of the data consistency for continuum-discrete models, the relations of shear strain increment formation, development with local displacement, the force and displacement transformation process of continuum and discrete media, meso-crack of discrete media and plastic deformation of slope mass and so on, the applicability of the continuum-discrete coupling method are studied. Based this method, the instability mechanism of the slope is illustrated from macro and micro aspects. The results show that, stress and displacement of slope in the continuum and discrete region maintain a superior consistency in the process of computation, showing the continuum-discrete coupling method is applicable to slope stability analysis; the varition of shear strain increment acting as slope instability criterion is controlled by horizontal displacement of rock or/and soil mass; the meso-crack mechanism can characterize macro plastic deformation effectively; the change of contact force chain direction between soil particles is the driving factor of displacement and deformation of soil mass.

In recent years the multicomponent reactive transport model is widely used in earth science and environment field; however, some difficulties lie in its solution. To enhance computational efficiency a decoupling approach is advised to simplify the model. A decoupling approach is presented for heterogeneous media and used to solve the model in this situation. The whole domain is divided into several subdomains according to the reactions that may occur; and the corresponding decoupling matrix is obtained. The concentration boundary between sub-domains is set so that the models in each subdomain can be connected and solved together. A test of reactive transport in one-dimensional heterogeneous domain where reactions followed local equilibrium assumption is taken as an example. The model is solved by proposed method and by PHAST separately; and the corresponding results are compared. The results show that the concentration evolution and distribution solved by decoupling approach has a good agreement with ones solved by PHAST, so as to show that the proposed method has a good applicability.

This study investigates the physico-mechanical properties, as well as the microstructural characteristics of the reactive magnesia (MgO)-activated ground granulated blast-furnace slag (GGBS) stabilized kaolin clay via a series of Na2SO4 solution soaking durability tests. For the purpose of comparison, the cement stabilized kaolin clay is selected as a control sample. The results show that the mass loss of GGBS-MgO stabilized soil is 0.25 times lower than that of PC stabilized soil soaked for 120 days. The unconfined compression strength (qu) of GGBS-MgO stabilized soil has a significant increase of as much as 20% at the early stage. Furthermore, qu of GGBS-MgO stabilized soil is 15% to 80% higher than that of PC stabilized soil. The results of X-ray diffraction analysis show that the GGBS-MgO stabilized soil has higher peak of calcium silicate hydrate (C-S-H) and lower peak of AFt relative to the PC stabilized soil. The scanning electron microscopy test shows the morphological characteristics of ettringite(AFt) in these two types of stabilized soils are different. For the PC stabilized soil, the AFt exists in the form of swelling aggregates. Unlike PC stabilized soil, the AFt of GGBS-MgO stabilized soil is in the fine small form and exists between the soil particles, which can promote the filling of large pores, leading to a higher resistance to the sulfate attack.

Triaxial compression creep tests on the quartz–mica schist from Danba, China, are carried out to illuminate the schist’s anisotropic creep characteristics. Samples are divided into two sets by the axial load direction, which is perpendicular or parallel to the rock bedding plane. Creep tests under different confining pressures used the multistage loading mode, which shows the creep variation of the quartz–mica schist, including instant deformation, attenuation creep, stable creep, and acceleration creep. A creep model with the Kachanov creep damage rule is adopted to describe the acceleration creep stage, and to estimate the rock creep parameters of the quartz–mica schist. The good agreement between the fitting and test curves indicates that this model can suitably describe the creep properties of a quartz–mica schist. Long-term yield strength, fracture morphology, instantaneous deformation parameters, and steady-state creep strain rate based on the results from the two sets of tests show that there are significant anisotropic creep properties in the quartz–mica schist. The relatively higher strength, shear modulus, bulk modulus, and viscosity of these samples, in which the bedding plane is perpendicular to the axial load, show that these samples perform better in terms of anti-deformability and damage resistance compared with the parallel sample set. The samples in which the bedding plane is perpendicular to the axial load mainly have shear failure modes; the other sample set show lateral expansion when the samples are damaged. The instantaneous deformation and stable creep rate of both test sets increase with increase of stress level.

Soil is a granular medium and its strength and deformation characteristics show a strong particle size effect. On the basis of their connection characteristics and the ratio of micro-forces and gravity, soil particles are decomposed into matrix particles and reinforcement particles. In addition, a soil cell element that can describe the internal material information and particle characteristics of soil is constructed; and a soil cell element model that can characterise the particle size effect of soil is proposed. A series of direct shear tests on saturated and remoulded soil is conducted to study the particle size effect of soil and to quantitatively determine the strain gradient and intrinsic length scale of soil. The results show that the shear yield stress of soil increases with an increase in the volume fraction of the reinforcement particles and effective strain gradient, and has an approximately linear dependence on the volume fraction of the reinforcement particles. Moreover, the relationship between the shear yield stress of soil and the effective strain gradient can be presented as a parabolic function. The size of the reinforcement particles has little influence on the shear yield stress of soil. The experimental data can be well fitted to the cell element model.

Based on the problem to water load acted on the tunnel structure because of seepage after excavating, this paper uses the theoretical method on complex variable function to establish the seepage model considering the reinforced area, and the study obtains the seepage analytical solution considering the influences of the permeability and thickness parameters of reinforced area. One hand, the research indicates that the hydraulic gradient of the reinforced area will be amplified when the seepage capacity weakens; on the other hand, the hydraulic gradient is also amplified when the reinforced area is increased, but the effect of seepage capacity on the hydraulic gradient is more significant than the reinforced area. So the effect of the permeability of reinforced area on the seepage force in the surrounding ground is the main cause, and the effect of the thickness of reinforced area is much slighter. It can be seen that the thickness is just satisfied with the relative requirements. The compare between analytical solutions and numerical solutions proves that the analytical solutions are rational.

Considering that the shapes of particles have an important impact on the mechanical properties of the coarse aggregate, this paper proposes a new method for characterizing particle shapes. The method randomly selects a series of points on ellipse; then those points are connected to form polygon particles. The new method can represent more types of particle shapes than old method that access points on the circle, applies more broadly, can characterize the narrow flat particles. In addition, a new algorithm of particle delivery is proposed, which is to reduce the particle; then the reduced particles are put to the given area randomly. After the particle was meshed by triangular element, the reduced particles was enlarge to the original size. Afterwards, using finite combined finite-discrete element method(FEM/DEM) to calculating equilibrium state, a sample that meet given void ratio was generated. Then the particle generation algorithm above and FEM/DEM was combined, the FEM/DEM method is applied to coarse aggregate numerical simulation, the analysis shows, FEM/DEM is a great way to study the mechanical properties of coarse aggregate. The complex particle shape can also be modeling simply, because the particles was meshed into the triangle finite element, complex contact judgments and the contact force calculation can be transformed into a standard uniform contact judgments and contact force calculations between triangles, all calculations can be standardization and unification. At the same time, particles can be deformed, the concept of stress and strain that belong to the continuum mechanics was still retains, rather than PFC which stress and strain of a point was expressed indirectly by the measuring circle. Finally, by confined compression test numerical simulations of coarse aggregate show enormous potential of the proposed set of solutions in the simulation coarse aggregate.

Based on the derived equations of overlying strata subsidence and infinitesimal surface stretching, two-dimensional and nonhomogeneous distribution model of delamination fracture rate, broken fissures rate and total fracture rate of the overlying strata in the combustion space area of underground coal fire is constructed. And through a case study, it is found that the fracture field of overlying strata is the vertical discontinuous, anisotropy and heterogeneous porous media composed of delamination fracture field and broken fissures field. Some conclusions are drawn as follows: (1) The fissure rate in the surrounding of overlying strata is large; and the internal region is small. (2) With the decrease of depth of overlying strata, fissures growth extent reduces gradually. The maximum value of delamination fissure rate successively reduced from 0.36 to 0.20, 0.14, 0.12; and the maximum value of broken fissure rate successively reduced from 0.32 to 0.11, 0.05, 0.02. (3) There is a mutational point of the vertical variation of fissure rate in the central area of overlying strata. (4) The distribution of fissure rate in the surrounding of overlying strata is led by broken fissures, but the internal region is led by delamination fissures. Finally, an indirect measurement method of overlying strata fissures has been proposed on the basis of the infrared thermal image analysis technology. And the high reliability of the model was confirmed by this method.

Triaxial soaking test system is developed; and test samples could be soaked to different saturations. Microstructures of Q2 loess of different saturations are observed by environmental scanning electron microscope (ESEM) and their mechanical behaviors are investigated through unsaturated triaxial tests. ESEM tests show that inter-aggregate pores of Q2 loess mainly consist of those that induce moderate or slight hydro-collapse. Confining pressure held constant, ration of inter-aggregate pores of larger size decreases with saturation; while that of inter-aggregate pores of 10-20 ?m increases. Results of unsaturated triaxial test show that stress-strain curves of Q2 loess of different saturations are all slightly strain-softening, and could be divided into three phases: rapid increase of deviatoric stress with axial strain, slight increase and slight decrease of deviatoric stress to a constant with axial strain. Relation between microstructure and mechanical behavior of Q2 loess after soaking is analyzed. A microstructural parameter is introduced that relates microstructure and mechanical behavior. A constitutive model of Q2 loess is established preliminarily considering influence of microstructure.

Pressures around tunnels are the priority of the design and construction of underground excavations. One of the designs for Badaling underground station of new Beijing-Zhangjiakou intercity railway utilizes a large span single arch excavation method. In this design, the excavation span is approximate 45 m. Traditional methods to predict the rock mass pressures around tunnels are not suitable for the case in Badaling underground station because of the large span. Instead of the traditional methods, numerical simulations can provide a more accurate result but with a more complex and non computation-efficient process. Comparing the differences between various traditional calculation methods and numerical simulation method, a rapid estimation method of rock mass pressures for deep and large-span underground excavations is proposed based on the Q system. The newly proposed method introduces the factor of span into the original Q system. Comparison of surrounding rock pressures between estimated and monitoring results of underground structures with different spans shows that this method could provide engineers and designers with a quick way to predict rock mass pressures in the design and construction stage of underground excavations as well as researchers with a reference guide.

Considering the supercritical CO2’s characteristics of low viscosity and no surface tension, it is expected to be a new type of fracturing method for unconventional oil and gas reservoir. In this paper, we finally build the initiation pressure models for supercritical CO2 fracturing through the establishment of pressurization rate model of fluid in the wellbore, and compare with the breakdown pressure of water and liquid CO2. The results show that: the breakdown pressure of supercritical CO2 fluid is 20.5% less than liquid CO2 fluid, which is 75.5% less than conventional hydraulic fracturing breakdown pressure, which shows that breakdown pressure is significantly affected by the low viscosity and low pressurization rate of supercritical CO2. The error of this model is only less than 3% compared with experimental data in the literature, so as to indicate that the model can provide guidance for the prediction of supercritical CO2 fracturing initiation pressure.

Classical Nishihara model is difficultly to describe the nonlinear acceleration rheological properties of rocks. According to Riemann-Liouville fractional calculus theory, by replacing a Newton dashpot and viscoplastic dashpot in classical Nishihara model with fractional dashpot and nonlinear viscoplastic body(NVPB) model, a modified Nishihara model is proposed and a three-dimensional constitutive equation is deduced in the case of constant stress creep state. The rheological stage decomposition- particle swarm optimization(PSO)-simulated annealing intelligent algorithms is used for data inversion on existing experimental data. The results show that the model can effectively reflect the three-stage creep characteristics of rock. Through sensitivity analysis, it is found that the nonlinear gradual process and acceleration stage of rock are controlled by order of fractional derivatives and rheological index respectively. Furthermore, it is pointed out that the classical Nishihara model is a special case of the modified Nishihara model.

Considering the geological formation characteristics of bedded salt rock in China, triaxial compression tests were carried out on samples of bedded model material. The influences of interface inclination on stress-strain curves, compressive strength, elastic modulus, stress decreases after the peak stresses and damage modes of samples of bedded model material are discussed; and theoretical analyses are carried out on the damage modes of samples with varying inclinations. Testing results and theoretical analyses show that: (1) The triaxial compressive strength increases firstly and decreases afterwards as the interface inclination increase; and it reaches the minimum and the maximum when the interface inclination is 60°and 90°, respectively. (2) Its elastic modulus increases as the inclination increase with the increasing trend slow at the start of inclination increasing, and then fast when the inclination gets near 90°. (3) The Stress decreases after peak stresses lessen firstly and increase afterwards as the interface inclination increase; and it reaches its minimum and maximum when the inclination is 30°and 90°, respectively. (4) As the interface inclination increase, damage modes show the law of damage from conjugate shear damage(the interface inclination is 0°), shear failure along the poor-strength surface(the interface inclinations are 30°and 60°) to shear and local splitting failure(the inclination is 90°). (5) The top and bottom of the storage are of high-strength but high brittleness; and measures should be taken to control their displacement and deformation; and the waist and adjacent places of the storage(30°and 60°of the storage) are of low strength and high plasticity; and careful design should be adopted for its shape and running pressure. Theoretical analyses are carried out on the results of the triaxial compression experiments, so as to offer a certain reference to further analyses of storage stability in bedded salt rock areas.

Parameter values adopted in railway engineering analysis at present are generally obtained through triaxial tests, whereas the remarkable difference between the actual stress path during train passage and the loading path in cyclic triaxial tests may lead to inaccurate predictions and even engineering problems. Published researches show that the actual stress path probably contains principal stress rotation(PSR), which has a sisgnificant influence on the mechanical response of soil. However, the conventional approach, i.e. cyclic triaxial test is not efficient in simulating this complicated stress path involving PSR. Instead, hollow cylinder test with cyclic shear stress has been proved to be an excellent selection for PSR study. In order to obtain reliable stress path for guiding hollow cylinder tests, three-dimensional calculation for a certain urban railway is carried out; and the distribution regularity of cyclic stress amplitudes, cycle numbers and PSR under train loads is analyzed. Furthermore, a series of cyclic torsional shear tests on hollow cylinder samples is employed to simulate the complex stress path and to research the deformation and pore pressure accumulation properties of saturated soft clay. Considering stress in foundation soil decreasing along with the depth increasing, various cyclic stress amplitudes corresponding to different depths are adopted in this experiment study. Three-dimensional calculation shows that the major principal stress axis will rotate from -90° to 90° during the train loading passage as well as the number and amplitude of stress waves reduce gradually with the increase of depth. It is also shown that both PSR and stress are quite sensitive to train loads as the upper soil element can identify a single wheel load while the lower soil element can just identify a bogie and even the whole train load. And through the cyclic torsional shear tests, it’s obvious that the rotation of principal stress can promote the accumulation of pore pressure and strain in soft soil foundations significantly; and in the case when vertical cyclic stress amplitude equals to 15 kPa, the pore pressure and strain in cyclic torsional shear test are 77% and nearly 50% higher than that in cyclic triaxial test respectively. What’s more, as the cyclic stress amplitude increases, the gap of cumulative pore pressure and strain between that two types of tests will enlarge further, which may even result in essential difference that samples in triaxial tests show only small strain whereas failure in torsional shear tests.

In order to investigate the shear yield characteristics of structured granite residual soil, a series of conventional triaxial drained tests are conducted on the undisturbed granite residual soil, remolded soil and cemented residual soil. From the test results, some insights can be obtained as follows. For undisturbed granite residual soil and cemented residual soil, the bond yield point during shearing could be identified on the curve of the normalized tangential stiffness versus axial strain in log-log scale. The consolidation pressure has a significant influence on the shear yield characteristics of undisturbed granite residual soil and cemented residual soil during shearing; the bonds inside structured soil tend to be damaged relatively more seriously as is higher; accordingly the initial normalized stiffness will be smaller at the beginning of the shearing process; and the axial strain at the bond yield point will also be smaller. Besides, it can be concluded that once excesses a critical value, the bonds inside soil will be damaged totally; in this case, there will be no bond yield occurring during shearing; and the curves will be coincided with the ones of remolded soil. For remolded soil, no bond yielding is observed during shearing, the curve is nearly constant with no dependence of the value of .

In order to investigate the dynamic response of hard crust under the low embankment of soft subsoil, the road system on soft subsoil is simulated into pavement – subgrade – hard crust – soft subsoil layers of structure. The pavement, subgrade and hard crust are regarded as three elastic layers resting on a poroelastic porous medium simulation. Solution is derived by using the integral transform model, the dynamic stiffness matrix for the pavement; subgrade, hard crust and soft subsoil are set up respectively. The dynamic response equations for the layer which considered the effect of vehicle load are obtained by integrating the overall dynamic stiffness matrix of structure. On this basis, numerical results are derived through the inverse fast Fourier transform (FFT) method and used to analyze the influences of thickness, modulus and Poisson ratio of hard crust on stress dispersion. It is shown that the existence of the hard crust weakened the vertical dynamic stress of soft foundation greatly and increased the range of diffusion. And the responses of soft subsoil are very sensitive to the change of thickness and modulus. Therefore, it can be concluded that the dynamic response of traffic load is significantly diffused by hard crust.

Considering the insufficiency of the present theory of rock damage model, this paper presents that the rock damage can be divided as damage materials and the rock microdefects caused by the materials damage on the basis of the study of the mechanism of rock deformation and the process of rock damage. Then a new definition of rock damage and impact factor γ between the damage materials and the microdefects is presented. Meanwhile, ascertain parameters, the basic properties of γ, and a rock damage model is established according to micro rock force analysis. Furthermore, a statistical constitutive model is established by introducing the statistical damage theory and lucubrating the relationship between effective stress and normal stress. The model well reflected the strain- softening characteristics of rock and strain- hardening of rock and had the definite physics meaning parameters. Therefore, it is easy to be applied. Finally, the model is proved to be rational and feasible by comparing with the existing research results and measured data.

Pile diameter optimization is an important part of piled raft foundation analysis for the purpose of minimizing the differential settlement. Based on a general analysis method of piled raft foundation, this paper proposed a pile diameter optimization model with the genetic algorithm. The optimization model contains an objective function of differential settlement and other nonlinear constraints. Detailed process steps are listed. Implementation of pile diameter optimization is illustrated by an example, with a contrast before and after the optimization of foundation settlement, pile load distribution, raft bearing ratio, shear and bending moment of the raft. The influences of raft thickness, piled foundation parameters and soil parameters on the optimal diameter are also studied by parameter analysis. Results show that piled length and soil property have a significant impact on radius optimization than pile body material properties and raft depth.

Dynamic compaction method is widely used for its high efficiency in foundation treatment. But the vibration caused by dynamic compaction will threaten the surroundings especially the structures around. Base on the fact that the tamping energy is approximately divided into vibrational energy and plastic work of soil, the formula of plastic work is derived according to the proposed ellipsoid partition model of dynamic compaction, and the inversion method of the energy efficiency is given by monitoring the information such as depth of tamping pits；also the inversion formula is derived. According to the ellipsoid distribution hypothesis of the affected zone and compacted zone, associated with the monitoring data of the depth of tamping pits, the calculation method of compacted scope and affected scope is given. Finally, under the background of the Beijing Garden Expo Park backfill soil reinforcement project, the compacted scope and affected scope as well as energy efficiency of dynamic compaction are calculated and inversed according to the field monitoring information. The result shows that the method in this paper can not only inverse the energy efficiency and calculate the compacted scope and affected scope, but also provide a reference to estimate the effective number of tamping in the design of reinforcement scheme. By comparing the analytical results with the foundation testing results, the effectiveness and practicability of the method in this paper are verified.

According to the engineering geological characteristics of bedding rock slope in Puli-Xuanwei Expressway in Yunnan province, the structural planes are divided into four types based on their formation mode. A home-made loading device is used to test the compression strength and shear strength of structural planes under natural conditions; and strength parameter values are obtained by least square linear fitting method, structural surface shear strength parameter values are obtained. By contrasting the equivalent shear strength of Mohr-Coulomb method based on JRC-JCS, the results basically agree with each other; and the feasibility of the device is verified. Considering filling thickness, moisture content of filler and other factors based on different types of slope structural planes, the shear strength parameters is obtained through several shear tests. The results show that the values of shear strength parameters in saturated state are smaller than that in the state of nature, meanwhile c increases and ψ decreases gradually with the increase of filling thickness. The test results provide reference data for correct evaluation of the characteristics of structure planes and stability calculation of the rock bedding slope in the next stage. This research results provide a simple test method for the choice of strength parameters relative to structural planes in the test field.

In order to govern the disasters produced by induced rockburst in roadway, the dominate relationship between static stress and dynamic stress of induced rockburst in roadway is expounded based on the mechanical mechanism. The mechanism of Induced rockburst occurred in roadway is revealed; and the expressions of maximum principal stress and minimum principal stress superimposed by quadratic stress field of surrounding rock and different kinds of stress waves occurred in coal roadways are obtained by superimposing the quadratic stress field of surrounding rock and the dynamic stress produced by hypocenter. Given the two aspects of high stress difference and bump-prone of roadway surrounding rock, a judgment method of induced rockburst occurred in roadway is put forward. As a result, the rockburst and burst range can be judged out directly when occurring in specific depth of the roadway, the hypocenter locating in certain place and generating a certain amount of stress wave. The mechanism of wide-ranging burst produced nearby the roadway group is explained; and the reason why the heading face in a coal mine in Shandong province occurred rockburst is analyzed successfully. The research results provide a theoretical basis for analyzing the risk of induced rock-burst, and a technical way to governance induced rock-burst.

A series of uniaxial compression tests is carried out on the gypsum specimens with different fracture types, including single fracture, two coplanar fractures, T-shape and X-shape cross-fractures, through the electrohydraulic servo machine RMT-150C. Then, influences of fracture types on failure modes and strength characteristics are investigated. The experimental results show that: (1) The failure mode is initial fractures propagation for all the specimens with different fracture types, which means that the relationship between failure mode and fracture type is not obvious. (2) The fracture type can affect the uniaxial compressive strength (UCS) of specimens significantly, with the fracture type transfer from single fracture to the X-shape cross-fractures, the UCS increase gradually; and the total acoustic emission energy of fracture specimens initiation and unstable increase too. Furthermore, the mechanism of how the fracture type affects the UCS is studied preliminarily. The research results can reflect the influence laws of different fracture types on the stability of rock mass.

Two Cam-clay models, including the original and the modified, were established on phenomenon of the conventional triaxial tests on normal and lightly over consolidated soils. That is to say the initial stress state of the triaxial sample is isotropic other than anisotropic. Application of the two models on the intact soil in K0 consolidation inevitably leads to systematic errors that could not be ignored. Based on the relationship between K0 line and isoclinic line for the intact soil, the Cam-clay model and modified Cam-clay model for the intact soil were constructed by circumvolving the two models along a special line. The improved model can reflect the structure and anisotropy of intact soil due to K0 line taken as the axis rather than the isoclinic line in principal stress space. Experimental data verify that, the improved model can describe the yield and strength characters of the intact soil more reasonably than two Cam-clay models.

The stress-deformation law and the structure-soil interaction of chair-shaped pile(CSP) retaining structure on soft-rock steep slope under stepwise loading on the subgrade surface are studied by large-scale model test. According to the experimental conditions and stress states, the design and calculation method of CSP are proposed. The test results show that the spatial structure properties of CSP can efficiently control the deformation and reduce the pile stress; the bending moments of main and side piles have little differences; the maximum bending moment is located at the slope surface; and the pressure of pile side rock is related to the deformation of piles and the deformation modulus of rock. The toppling failure of CSP would not occur generally; and the shallow layer failure is the main failure of soft-rock slope. Based on the analytical solution of elastic foundation beam, the change and distribution rules of internal forces of CSP could be described well. The study results have a good reference value to correctly analyze the anti-slide mechanism, design and calculation of CSP retaining structure.

Water has softening, dissolving and water wedging effects on rocks. To study the energy mechanism of rock with different moisture contents, the conventional triaxial compression tests on sandstone with five moisture contents are conducted using MTS815 rock mechanics test system. The results show that, with the increase of moisture contents, the increase rate of total energy absorbed by rock and its amount decrease. The increase rate of elastic energy decreases with the increase of moisture content, but their release rates differ slightly. The energy storage limits decrease with the increase of moisture content. The dissipated energy causing rock failure decreases as the moisture content increases, but the increase rates of ante- and post-peak dissipated energies are roughly identical. The proportion of dissipated energy to total energy can reflect the status of internal damage of rock, the variation of the proportion with time can be divided into four stages, i.e., gradual increase, decline, stable increase again, sharp growth. With the increase of moisture content, the concentration degree and intensity of acoustic emission energy gradually decrease. The total acoustic emission energy decreases as the moisture content increases. It is shown that the energy storage capacity and strain energy release ability of rock reduce with the increase of moisture content, meanwhile its plasticity is enhanced and brittleness is weakened.

Reservoir permeability is a most important physical parameter. It is also the basis for the development of oil and gas. In recent years because of the shale gas, tight sand gas and other unconventional oil and gas development, the need for ultralow permeability (<0.1×10-3 μm2) measurement is increasing. However, the test methods and instruments are challenging, which is difficult for the development of unconventional oil and gas research. At present, China mainly uses pulse decay method for ultralow permeability testing in oil industry. The test accuracy, stability, and test cycle of pulse-decay method are still insufficient. It is very important to explore high-precision ultralow permeability method. This paper presents and analyzes the steady-state method, pulse-decay method and periodic oscillation method to measure permeability in the laboratory. The contrast application in ultralow permeability measurements are also made in an example rock with the three methods. The results show that compared to the steady state and pulse decay method, periodic oscillation method has good stability, high accuracy and short time. We propose to apply the oscillation method for ultralow permeability tests. In this paper, the equipment requirements and data processing methods of periodic oscillation method are also discussed. Fast Fourier transform (FFT), cross spectral method and other signal processing methods are introduced to improve signal to noise ratio. That is to improve the accuracy and stability of ultralow permeability measurement.

In order to study overriding and cutting off coupling effect in process of joint shear, the joint three-dimensional models which have asperities of different combinations of height (h) and angle (?) are made for, conducting model shear tests. The test results confirm this coupling effect. The joint shear movement characteristics are analyzed; and a ratio of cutting off area Sj to shear area S, i.e. K, is proposed to present quantitative characteristics for the degree of coupling effect. In different dominant effect, the K changes between 0-1. Meanwhile, a shear strength formula which is involved in the coupling effect of overriding and cutting off is established to help valuating effect rule of joint shear strength. The results show not only that shear strength is largely determined by overriding friction when the K is low for hard rock with large compressive strength and for slightly undulated joint surface, but also that it is largely determined by strength of the rock material when the K is high for soft rock with small compressive strength and for roughly undulated joint surface.

How to meet the settlement requirements both within construction process and post-construction and to improve impermeability of embankment is a key technology in building the passenger dedicated line in collapsible loess area. On the basis of the subgrade structure with lateral-constraint and seepage control, the effects of lateral-constraint and seepage structure in high speed railway subgrade on improving the seepage property of foundation soil in collapsible loess area are researched. Lime-soil compaction pile and cement-soil compaction pile with different pile spacing are adopted as lateral seepage control structure for indoor model test. According to different fillings of compaction piles and pile spacing, the change of moisture content of the foundation soil in different position and depth is measured. It is concluded by comparative analysis that setting compaction piles has a significant effect on the lateral seepage control compared with natural foundation. And with the spacing decreasing, the change of moisture content of the foundation soil decreases gradually, which means the slower the flowing speed, the better seepage control effect. In terms of the two kinds of compaction piles mentioned above, cement-soil compaction pile has a better effect on seepage control than lime-soil compaction pile. The research results can provide a reference for similar projects.

Roadway excavation and mining underground coal mine is a process of unloading confining pressure. Compared with the conventional triaxial compression test, the coal rock showed different mechanical properties during unloading confining pressure. Based on two kinds of stress paths the conventional triaxial and unloading confining pressure tests, it is found that both the conventional triaxial or unloading confining pressure test, the coal sample caused by high confining pressure are greater strain and more intense failure. In the case of the same initial confining pressure, compared with the conventional triaxial test, unloading confining pressure tests peak secant modulus is smaller, secant Poisson’s ratio is larger; coal sample failure more intense when unloading confining pressure, the lateral strain is larger, and the axial strain but little difference. By unloading confining pressure effect coefficient analysis, it is found that the higher the initial confining pressure and the greater the rate of unloading confining pressure, the unloading confining pressure effect coefficient of coal sample is smaller, the more easily failure of coal sample, the secant modulus under high confining pressure decrease is consistent. Conventional triaxial and unloading confining pressure test failure process of energy change of anthracite analysis show that: the faster the rate of unloading confining pressure, the limit stored energy of coal samples is smaller, more easily instability and failure to verify the unloading confining pressure effect coefficient analysis results. In high confining pressure, coal sample failure requires more energy under conventional triaxial tests and unloading confining pressure test, reveal that higher confining pressure of coal sample, the stronger failure.

Many electric transmission tower footings built on the slopes in mountainous area, it is necessary to study the additional stress distribution of slope foundation. In this paper, model tests and numerical experiments are used to research the influence on stress distribution and diffusion regularity of the additional slope foundation induced by the distance from the top of the slope. Results of the model test show that the distance from the top of the slope has a great impact on the additional stress in soil. Additional stress increases with the increase of the distance from the top of slope and has obvious asymmetry on both sides of the foundation when it is less than the safe distance. Additional stress gradually stabilized, close to the level ground state when the distance from the top of slope is more than the safe distance. When the distance from the top of slope is 0.3 m, additional stress in shallow soil is close to 50% of the plane foundation condition, the influence of additional stress in soil slope is very significant; and traditional additional stress calculation method is not applicable to slope foundation. In the small distance from the top of slope conditions, the additional stress is small; but the corresponding ground deformation is greater; it is proved that the traditional layerwise summation method is not suitable to calculate the deformation of the foundation in the slope. Otherwise, it will affect the safety of engineering. In the case of foundation stability meet the requirements, it is recommended that the minimum distance from the top of slope is not less than the safe distance.

The holes caused by dissolution in red-bed soft rock are well developed in Chengdu. Submerging test, leaching test and dissolution test are performed with the samples of red-bed soft rock form different depth of Bandao City in Chengdu. Then the influencing on the environmental water and the erosion degree of soluble components in red bed soft rock containing saline deposit under different processes are analyzed after observing the dissolution characters and behaviors of rock sample under different environmental waters. The results show that the content of gypsum in red-bed soft rock rises with the depth increase. The causticity of rock and environmental water is significantly enhanced; the soluble components of red-bed soft rock dissolve and drain gradually under water, so as to turn to pore enlargement, permeability enhancement, strength reduction and lost of integrity; the acid environmental water makes the calcium carbonate cement drains faster and does great damage to the connection of structure, so as to influence the strength of red-bed soft rock obviously. The compressive strength, wave velocity of the rock are tested after submerging test, leaching test and dissolution test. The test results show that the uniaxial compressive strength of the soft rock reduces obviously after corroded by sulfuric acid. The uniaxial compressive strength reduces for 76% from 8.5 MPa to 2 MPa. The wave velocity in the rock also reduces for 40% from 2 204 m/s to 1 355 m/s. Meanwhile, the pH value of the rock reduces from 8.77 to 7.29 and its conductivity increases from 55 μs/cm to 1 100 μs/cm.

The scientific assessment of impact of tunnel engineering factor on groundwater environment is a technological problem to tunnel builders. The study of tunnel engineering factors on groundwater resources loss and level change is theoretical basis of scientific assessment of groundwater environment. Based on 350 km/h high-speed railway double line tunnel of grade V surrounding rock, the authors analyze the relationship between groundwater loss and level change with time. The authors further study the impact of multiple engineering factors on groundwater environment. The factors mainly include groundwater buried depth and tunnel construction method and construction time and shotcrete thickness and shotcrete anti-penetrability performance and shotcrete cracking leakage and strata grouting reinforcement method and grouting anti-penetrability performance and grouting range and partition wall. Finally, the authors suggest technical measures to protect groundwater environment during both construction stage and operation stage.

For the current technical code for building pile foundations(JGJ94-2008), the comprehensive coefficients of shaft/tip resistance for rock socketed pile are used to calculate the bearing capacity of the rock-socketed part. The method is easily to be used and is meaningful for the engineering application, while the values of the comprehensive coefficient are not very reasonable. Based on the data about 20 pile tests of 4 background projects, the FEM is used to calculate the comprehensive coefficient for rock socketed pile. And a value table are presented, which is more detail than the standard table; in which the relationship among comprehensive coefficient, rock property and depth-diameter ratio of rock-socketed pile is given. It is shown that the calculation results of using the comprehensive coefficient proposed herein is more closer to the measured value than the calculation results of using the comprehensive coefficient of the current code.

The maximum collapsing depth of collapsible loess ground is closely related to the neutral point position of pile foundation. In order to solve the problem of improper pile foundation design, the accurate determination of the collapsing depth is of key importance. Based on a systematic analysis of experimental results obtained from Ningxia, Guyuan series of pile foundation and Heping town in Lanzhou ground treatment test and other area immersion test, the relationship between the maximum collapsing depth and neutral point position of pile foundation is revealed. The research results can be divided into the following four points. 1) Because of the limited vertical penetration depth of the homogeneous loess in the field immersion test (generally 20-25 m), the maximum collapsing depth is limited as well. The collapse coefficient in indoor test cannot be directly adopted to evaluate the collapsing depth. 2) The recommended values of the collapse coefficient or dead weight collapse coefficient varying with the region and the collapsing depth are given. Meanwhile, the depth modification coefficient and earth immersion probability coefficient are suggested to be introduced into calculating collapsing depth and their reference values are provided as well; the difference between the indoor and outdoor can thus be effectively decreased. 3) The maximum collapsing depth calculated in indoor test is some kind of over conservative, the adverse effects of negative skin friction are overly exaggerated in most actual projects, rendering the smaller design load-carrying capacity. 4) When the depth of the neutral point of the pile foundation is less than 20-25 m and maximum collapsing depth is smaller than 20 m, the neutral point should be determined by the evaluation depth. The estimation method of negative skin friction is provided and It could be more appropriate if the negative skin friction of foundation pile is set as 20-35 kPa.

Pile-raft composite foundation is one of traditional soft ground treatment methods for embankment (such as high-speed railway embankment, etc.) settlement control. However, the researches focused on dynamic responses influenced by different vibration waveform loads are relative little. Large-scale model tests on single pile-raft composite foundation in sand are carried out. The accumulated settlement, pile end and pile side soil dynamic stress ratio, acceleration and speed are measured; and the mechanisms of pile-raft composite foundation influenced by vibration waveforms are briefly discussed and analyzed. The test results show that the accumulated settlement influenced by the M wave is slightly larger than that influenced by the sine wave; while the pile end and pile side soil dynamic stress ratio influenced by the M wave is slightly smaller than that influenced by the sine wave. The acceleration and speed along the pile-raft system are increased with the increasing of loading frequency and loading amplitude. The related research results provide a reference for the theoretical analysis and calculation of pile-raft composite foundation.

On the basis of Coulomb’s concept that the active earth pressure against the back of a retaining wall is due to the thrust force exerted by a sliding wedge of soil between the back of the wall. Considering an inclined rough retaining wall under the general conditions such as curvilinear fill, cohesive soil and uneven surface load, the functional extreme-value isoperimetric model about active earth pressure is deduced based on the force equilibrium equations of the sliding mass. Then the problem of active earth pressure is transcribed as the functional extreme-value problem of two undetermined functions by means of Lagrange undetermined multiplier. According to Euler equations, linear sliding surface function and linear normal stress function are obtained. Combined with the boundary conditions and transversality conditions, the problem of active earth pressure turned to be the solution of a one-dimensional equation. The magnitude of active earth pressure calculated by variational method is the same as that of Coulomb’s theory; and the location of application point of earth pressure is not always at 1/3 height of the retaining wall by case studies. In addition, curvilinear fill and uneven surface load also have significant effect on the magnitude and the location of application point of active earth pressure.

For thorough research of the anti-seepage problem in terms of seepage flux and seepage stability due to the geosynthetic clay liner(GCL) defects, the seepage physical test method for the simulation of GCL with defects in dam anti-seepage hydraulic projects is established by means of developing the seepage experimental apparatus consisting of pressure control system and model test system. Factors which affect the joint impermeability of dam soil and GCL with defects are preliminarily discussed according to the seepage test of GCL with different defect conditions. The results show that the hole-defect’s size can be more sensitive to the impact of overall permeability of GCL with defects and soil than the defect rate. The main sensitive factors for defect’s healing capacity include hole-defect’s diameter and GCL specifications (material’s own performance). Therefore, two following points should be considered in the projects: (1) the hole-defect’s diameter should be less than 0.5 cm in the projects, the ones larger should be repaired; (2) make sure the GCL interface is smooth and flat in case that the local defect rate becomes more than 0.5%.

Full-scale static load tests of four sets of uplift piles with side-grouted are carried out in the project of Shanghai Hongqiao Comprehensive Transportation Hub. Curves of side resistance and relative displacement relationship (?-w curve) of all soil layers in the pile range are derived based on the measured data. Firstly, make every soil layer τ-w curves of the full-scale test and the ?-w curves from the direct shear test normalized, in which the normalized parameters are the ultimate side resistance and the corresponding critical relative displacement of pile and soil. Secondary, a hyperbolic function is used to fit the normalized data; and then a unified ?/?ult-w/wult function curve is obtained. Finally, the unified fitted curve is applied into load-transfer method, and the pile head load-displacement relation, pile axial force and side friction distribution curve along the pile depth under different test load levels are gotten easily, so as to use it to predict bearing capacity and deformation properties. It is meaningful in the theoretical analysis and practical engineering.

Wedge model has been widely used in the calculation of the limit supporting pressure of shield tunnel excavation face due to its simple and intuitive, but the determination of sliding face dip angle is a complex question, current research on this aspect is relatively less, especially under the condition of facing-slope. Therefore, the article established a new model that considering longitudinal gradient of shield tunneling through introducing the longitudinal slope angle ? on the basis of the trapezoidal wedge model, and deduced the calculation formula of the limit support force of excavation face in this case. Through the data analysis of the calculated value of the support pressure of excavation surface, the article founds that the value of angle ? only affect much more by angle ?, the effects of the soil cohesion c, soil density ?, tunnel diameter D, depth of shield H and additional pressure of earth’s surface q on the value of angle α is less. Under the condition of c is considered, the value of angle ? will decrease gradually with the value of c increases, and the value of angle ? will only change small around a constant value when the value of c, φ and D is fixed. Meanwhile, the value of angle ? will increase gradually as the value of D increases. We can take no account of ?, q and H when calculate the value of angle ? for it’s less effects. Finally, a calculation formula of sliding surface dipping angle is obtained based on the regular pattern, so as to simplify the solving process.

The high-intensity mining face has complex strata behaviors and high propensity to support crushing, roof falling and other disasters. To theoretically explain the characteristics of strata behaviors in high-intensity mining, the general characters of high-intensity mining and its influence on strata behaviors are analyzed first. Then taking the roof’s first caving for example, based on the plate structure theory and the rock mechanics testing, a formula of first caving interval under different advancing speeds and with different face lengths is derived; and the impact mechanism of working face length and advancing speed on working resistance of support is also explained. The results show that, working face length affect the stress distribution of roof while advancing speed change bearing capacity of roof; the shorter the working face is and faster the advancing speed is; the greater the roof’s first caving interval is. In most of high-intensity mining, the working face length is more than 200 m. At this point, strata behaviors are mainly affected by advancing speed instead of face length. Thus, the roof’s caving interval and working resistance of support in high-intensity mining face are bigger than the general, and easier to support crushing, roof falling and other disasters.

Based on the wave propagation equation in unsaturated soils, four kinds of body waves i.e. one is S wave, and other three are P waves, P1 wave, P2 wave and P3 wave, according to the wave velocity are found in unsaturated soils through theoretic deduction. Analytic expressions for wave velocity and attenuation are proposed. Numerical analysis about the relation between the wave velocity, attenuation and the void ratio and Lame constants are carried out. The results show that with the increasing of void ratio, the velocity of P1 wave and S wave become enhance; and the attenuation of three kinds of P waves becomes great, especially for P3 wave. Almost the velocity of P1, P3 and S don’t change with the changes of Lame constant , and the velocity of P2 wave become a little faster with the increasing of Lame constant Almost the attenuation of P2 wave and S wave don’t change with the Lame constant . The attenuation of P1 wave and P3 wave become smaller with the increasing of Lame constant Almost the velocity of three kinds of P waves don’t change with the variation of Lame constant , but the velocity of S wave becomes faster with the increasing of Lame constant . Almost the attenuation of P2 wave and S wave don’t change with the variation of the Lame constant . The attenuation of P1 wave and P3 wave decreases with the increasing of Lame constant , especially for P3 wave.

For the disorderly distributed nonlinear problems of groundwater flow field and its parameters, the migration of pollutants cannot obey the convection-dispersion equation. For this reason, what abnormal change would happen during the migration of Sr and U in nonhomogeneous media is the premise to provide the groundwater pollution forecasting methods and models. To this end, based on the investigation, we use the analysis methods to design model system for experimental study. Results show that the migration curves of nonhomogeneous test column and the homogeneous one are significantly different in the overall features. For the migration and environmental effects, the impact of the lenticular and blind-hole-type nonhomogeneous is a double-edged sword.The advantage is the reducing of pollution intensity, and the disadvantage is that the pollution action time is extended. Preliminary laboratory tests indicate that the pollution intensity may decreased by 10%-30%; however, the pollution action time is 3-5 times longer. In addition, we explain the migration curve mechanism of the so-called twin peaks and multi-peak, which are people concerned about.

The research subject is silty clay found along the Jilin–Huanggang Expressway. Soil samples mixed with different amounts of lime are subjected to static triaxial test and freeze-thaw cycle tests indoors. The aim is to investigate the effects of 0, 2, 4, 6, 8, 10, and 12 freeze-thaw cycles on the strength of lime-treated silty clay. The research results indicate that the stress-strain relationship curve of such clay is the strain-softening type; and its peak-value strength increases with confining pressure increase. Compared to lime-treated silty clay, the decrease rate in peak-value strength of silty clay is faster. After four freeze–thaw cycles, the peak-value strength began to stabilize. The decrease rate in sheer strength of lime-treated silty clay after being subjected to the freeze-thaw effect is slower than that of silty clay. Shear strength even increases with confining pressure increase. Under the condition of same confining pressure, the elastic modulus of lime-treated silty clay gradually decreases with increase of number of freeze-thaw cycles; and basically stabilized after four freeze-thaw cycles.

The X-section cast-in-place concrete pile (XCC pile) is a new shaped pile. The pile-soil interactions are influenced by the cross-sectional geometry. The load transfer mechanism of the XCC pile dependent on the cross-sectional geometry has been derived by means of equilibrium analysis. However, the mechanical response of the vertical shearing coefficient, governing the pile-soil interactions, for the cross-sectional geometry have not been fully understood. This paper represents the effects of the three geometrical parameters (the diameter of the surrounding circle R, the distance between two adjacent cutting circulars 2a and the central angle of the cutting circle ?X) of the X-shaped cross-section on the vertical shearing coefficient. Comparative analyses between the XCC pile and circular pile of the same cross-sectional area are carried out. It is found that the pile-soil interactions vary with the changes of the geometrical parameters. Influenced by the cross-sectional area, the pile parameter and the vertical sharing coefficient, the axial force increases with the increasing of R and ?x, but decreases with the increasing of 2a. In addition, the axial force of XCC piles is always smaller than that of circular piles of the same cross-sectional area.

The studies of, creep and damage of fine sandstone under step loading of pore water pressure are carried out by triaxial compression creep tests using the coal and rock computer controlled rheological testing machine RLW-2000 M. The highlights include studies of volumetric strain(rate) and equivalent pore volume(rate) evolution curves of rock creep under different stepwise loadings of pore water pressure. In addition, evolutions of rock creep curves are analyzed. The results show that the creep curves are consistent with three stages in typical creep process. The evolutions of pore volume are consistent with three stages in damage process of the microholes under stepwise loading of pore water pressure. The theoretical analysis of creep curves by Nishihara model was validated by experiments.

As is well-known, the effective vertical stress of surrounding soil element of pile foundation is not identical to the dead weight of overburden soil plus the applied surcharge load. This is because the vertical shearing is developed on pile-soil interface due to the large pile-soil relative stiffness. The analytical solutions for the effective vertical stress, the unit positive (negative) shaft resistance, the total shaft resistance and the axial force (dragload), subject to axial and surcharge loads, are derived by means of equilibrium analyses. Those solutions are calibrated by the reported test result of a single pile in saturated clay. It is shown that those solutions are reasonable and it is necessary to consider the vertical shearing of pile-soil interface. Under the surcharge load, the vertical shearing weakens the effective vertical stress, the unit negative shaft resistance and the dragload. The negative shaft resistances at the pile tip of the cases ? = -0.01, -0.02 and -0.04 are reduced to 91%, 83% and 71% that of the case ? = 0, respectively. Meanwhile, the induced dragload at the pile tip of the cases ? = -0.01, -0.02 and -0.04 are reduced to 93%, 87% and 76% that of the case ? = 0, respectively. The dragload is reduced slight smaller than the negative shaft resistance since it is also controlled by the cross-sectional geometries. This indicates that pile settlement is always overestimated independent of the vertical shearing.

Significant climatic warming is in progress and causes degradation of permafrost and stability of superstructures. Especially under the more complex climate, frequently ultra weather and climate, the progress of bearing capacity in frozen ground is becoming more complex. taking a single pile in representative humid permafrost in Qinghai-Tibet plateau for example, considering the pile exposed in the air absorbs solar radiation, permafrost phase-change, natural air convection and global warming, the sensitivity of pile vertical bearing capacity to short-term climatic anomaly in permafrost regions is analyzed using finite element method. The numerical results show that the pile bearing capacity become lower under the short-term warmer climate because the decrease of adfreeze strength between pile and frozen ground, and no change of adfreeze area. The decrease influence is not fade away in the next years. The warmer climatic make the more decrease of bearing capacity. Under the colder climatic alternates with warmer climate, the pile bearing capacity is changed with outer air temperature, and regain normal after the climaticanomaly.

Shear characteristic of base material soil-rock interface plays a key role for long-term stability of ecological slope protection system. Related research on this can provide necessary basis and guidance for resolving the substrate failure and improving the ecological protection technology. The self-made in-situ shear apparatus is used in the field shear tests of 4 groups of base material soil-rock interfaces with different roughnesses. Experimental results show that shear stress-displacement of the base material soil-rock interface is characterized by typical shear softening, including 4 stages of initial linear elastic deformation, elastic plastic deformation, the post-peak softening and residual shear deformation. Under the test conditions, it is found that the peak shear strength increases fast when the arithmetic average deviation of asperity (Ra) is about less than 4 mm. For the higher Ra, the increasing gradient shows a slower trend. Residual shear strength, peak shear displacement and shear displacement stepping to the residual stage show the nearly linear positive correlation with Ra. Therefore, for a specific implementation of ecological slope protection, the reasonable control of slope surface roughness will contribute to increasing the peak and residual shear strength of soil-rock interface, so as to improve the deformation performance and the long-term stability of the protection system.

Predicting the behavior of driven piles is a key issue in practical engineering, particularly in major bridge, wind turbines, harbor and offshore engineering applications where the piled foundations are widely used to underpin the superstructures and the pile capacity is seldom determined from pile load tests. Numerous methods exist for calculation of axial pile capacity in clay, including four design methods, namely Furgo-96, NGI-99, ICP-05 and UWA-13. However, application of the latter in mainstream civil engineering sector has been relatively slow, possibly because of the small number of high quality, full scale, case histories available to demonstrate their potential benefits. Thus, it is necessary to collect a more comprehensive database to evaluate the performance of the four design methods objectively and to assist designers in the selection of the most appropriate method. A new ZJU-ICL Clay database with 89 high-quality pile load tests is formed by expanding the major databases with new available pile load tests. Database assessment of these four methods and evaluation of the predictive performance by using mean ? and coefficient of variation COV are presented.

As a common foundation form, prestressed thin concrete (PTC) pipe pile composite foundation holds high practical value and excellent application prospect. In actual projects, the determination of the additional stress distribution of underlying stratum in composite foundation is the emphasis and difficulty. Hence, the study of the properties of stress dispersion of PTC pile composite foundation is of great significance. Three sets static load tests on composite foundations with different cushion thicknesses are designed and conducted in Tianjin soft soil area. Based on the static loading tests, the bearing characteristic of the PTC pile composite foundation are studied. The effect of cushion thickness on the bearing capacity is also studied. The numerical simulation method about PTC pile composite foundation is established and verified through the static loading tests. Through the numerical simulation method, the additional stress dispersion behavior of composite foundation in different geological conditions is studied and the scope of diffusion angles is determined. The influence of geological conditions, pile depth and the external load on the diffusion angles are indicated and the influence laws are carried out. The analysis results can be a good reference to the engineering practice.

Although numerical simulation is the prominent method for calculating earth pressure on the foundation pit, it is not handy to do calculating whenever and wherever possible as analytical solutions do. An analytical solution of earth pressure is performed to estimate the mechanical response of backfilled openings, emphasize the effect of load transfer along the interface at the corner of foundation pit. The arc between adjacent corners of pit is formed as parabolic whose original rake ratio at corner can be determined as a function of friction angle in soil. Based on the formation of stable arch in soil, a sliding block behind retaining structure can be determined as a parabola prism truncated by sliding plane. Finally, a formula of active earth pressure is deduced in light of limit equilibrium theory. The results indicate that the arching effects developed in the backfill greatly influence the resultant force on the supporting structure. The analytical results are compared to experimental ones and the discussion that follows highlights some of the key factors influencing the resultant force on the supporting structures.

Geddes’s method is widely applied to estimate the settlement of pile group in China with its simple principle and easy realization. However, Geddes’s method has its own obvious shortcomings. The influence of pile diameter is not considered in Geddes’s method which can produce great stress concentration on the pile tip. Moreover, the distribution of shaft resistance of long piles under vertical working load is quite different from the suggested one of Geddes’s method. In order to solve these problems, based on Geddes’s method, a modified assumptions is presented, i.e. the end resistance uniformly distribute on the pile tip and the shaft resistance distributes on the side surface of the pile. Mathematical integration and Gauss integration are applied to estimate additional stress in the soil, which can significantly decrease the influence of stress concentration. Meanwhile, calculation formula of additional stress in the soil of bilinear distribution pattern is deduced by the combination of Geddes’s method. Case studies show that the settlement predicted by modified Geddes’s method is smaller than that predicted by Geddes’s method.

In the construction of the foundation engineering, the settlement and stability of the upper structure is directly affected by the compaction quality of the earth-rock filling embankment; so how to effectively evaluate the compaction quality of earth-rock filling embankment is the key technical problem to be solved in the process of the construction quality control. A theoretical model of the compaction quality detection by wave-electricity coupled method is constructed based on the wave propagation characteristic and electrical resistivity characteristic of the soil and stone; and then the fast detection method of the compaction quality of embankment is put forward based on the theoretical model. By the engineering application, fluctuating signals in the filling embankment is collected by the surface wave method; and the wave velocity is analyzed based on the frequency dispersion of the surface wave. The electrical resistivity is tested by the direct current survey. The relationship between the wave velocity and compaction degree and the relationship between the electrical resistivity and the water content are established by analyzing of the wave and electricity characteristics of the compaction specimen. And the evaluation model of the filling embankment compactness is set up based on wave-electricity coupled method. At last, the compaction quality of embankment is evaluated comprehensively. The results show that the model considering the wave and electricity characteristic of the soil and stone, and the parameters of the wave and electricity characteristic is easy to test, and the model is simple in calculation, and this wave-electricity coupled method is convenient for rapid detection

Model tests have been conducted on a single pile and pile group in sand under both compressive and tensile loadings. Axial forces, loads and displacements at the pile head, and pile tip resistance were measured. Experimental results show that the compressive group pile effect coefficient ? is greater than 1. The optimal pile spacing is 4D(D is pile diameter), at which η is about 1.2. The pile tip resistance coefficient is greater than the lateral friction coefficient . The pile tip resistance coefficient reaches maximum at the spacing of 5D with a value of about 1.3. The lateral friction coefficient is about 1.2 at pile spacing of 3D, but it decreases with the increasing of pile spacing. Different from the results revealed by previous theoretical analysis, the test results show that the pullout group effect coefficient is greater than 1, due to sand densification during pile driving. The optimal pile spacing is between 4D-5D, with a maximum coefficient of about 1.2. The group coefficient is close to 1 when the pile spacing is greater than 7D and the group pile effect can be ignored.

For shallow tunnel under unsymmetrical pressure with fault, the surrounding rock failure caused by fault diastrophism is a process from anamorphic to mutational with characteristics of discontinuous changes and sharp jump values. Therefore, the surrounding rock failure modes can be analyzed by catastrophe theory. Taking the tunnel portal across fault facture zone of Shanghai-Kunming passenger dedicated line Changsha-Kunming Hunan CKTJ-IX section as the engineering background and according to the surrounding rock instability, the mechanical model for tunnel across the fault is established; the total potential energy function of fault surrounding rock system is built; and the standard type of catastrophe model and the bifurcation set equation are obtained. The time-dependent function of vault settlement deformation is transformed into Taylor series to build the criterion of tunnel surrounding rock stable state for the fusion of catastrophe model and monitoring data. The research results show that the time-dependent function of vault settlement deformation can be converted into the catastrophe model of surrounding rock instability. The surrounding rock instability based on the catastrophe criterion is identical to the actual damage of surrounding rock. The composition of criterion is simple. It has strong practicability for judging the stability of shallow tunnel under unsymmetrical pressure with fault. There is a certain correlation between the value of the criterion and surrounding rock damage degree.

A dynamic evaluation of landslide sliding surface strength parameters approach is proposed to analyses the stability of large-scale landslides which are controlled by groundwater fluctuations within the slide. The proposed approach utilizes a dynamic model in conjunction with stress state to describe the strength parameters of the sliding surface. Both experimental and theoretical analyses are carried out. Subsequently, three-dimensional numerical modelling of the landslide is carried out to explore the influence of three-dimensional sliding surface geometry and groundwater level fluctuations on sliding surface strength parameters. Simulations of the slide suggest that the approach proposed can describe the strength parameters of Badi landslide. In addition, simulations indicate that groundwater has not significantly influenced on sliding surface strength parameters under situ stress state.

For the tunnel general sections, seismic damage types appeared in Wenchuan earthquake. In order to improve aseismatic performance of tunnel general sections in high intensity earthquake area, by analyzing the seismic survey data of general sections of highway tunnel in Wenchuan earthquake, seismic damage analysis is concluded. The results show that the seismic damages of tunnel general sections occurred mainly in the soft rock of uniform section, the soft rock part of soft and hard surrounding rock and the defect section. Through three-dimensional finite difference numerical simulation and analysis of typical field damage, seismic damage mechanism of highway tunnel general section is studied. The seismic damage mechanism of surrounding rock uniform general section is understood; namely there is almost no seismic damage in the hard rock tunnel general section damage, while the seismic damage is more serious in the soft rock tunnel general section; lining structure is greatly influenced by the seismic inertia force, and forced displacement comes second. The seismic damage mechanism of the soft and hard surrounding rock general section is revealed, that is, the seismic damage occurs mainly in the soft rock part of soft and hard surrounding rock; the main influence factor is the forced displacement, closely followed by seismic inertia force. The seismic damage mechanism of the defect of general section is disclosed, namely the seismic damage is mainly caused by the seismic inertia force, and forced displacement has little effect. These research results can provide reference for the seismic fortification of highway tunnel general section in high intensity earthquake area.

Selecting any one bracing plane on a pile as the research object, according to set up a bracing (or anchor or bolt) and excavation to the bottom of foundation pit, the force balance equation and the displacement coordination equation is established. Then through the collaborative working among the ring beam to them , the research object is extended to the entire bracing plane, to consider the excavation process, internal bracing to be set and soil-pile-ring beam interaction bracing plane displacement and force equations is derived. And then using FORTRAN language to solve the program, the horizontal displacement and internal force will be calculated to the ring beam and any section of the pile body to foundation pit excavation to bottom. Through a case study, it is shown that the calculated ring beam(pile top) displacements are consistent with monitoring results; and internal forces for some piles are consistent with calculated results by the references [1]. Finally, the proposed method is proved to be reasonable and feasible.

Seepage analysis of a hydropower station is extremely important in design stage; however realistic results is difficult to obtain for the comlexity of the seepage situation. A comprehensive exposition of the seepage analysis process is given based on Aqing hydropower station. Contents including the familiar with the project overview and hydrogeological conditions, a clear analysis of the task, the model generalization and mesh generation, the selection of material parameters, the selection of computing solutions and the determination of boundary conditions, the result analysis, scheme comparison, parameters sensitivity analysis, are introduced step by step. To well done each step makes great sense to fully understand the real seepage situation in the engineering project and a reasonable design for anti-seepage and drainage system. It is not necessarily that the discharge of the greatest section of the dam will be greater than that of sections at the bank. The total discharge may also greater than the product of the length of the dam axis with the discharge at the greatest dam section.

Compared with the common soils, frozen soils have unique engineering properties. After the pile foundation was constructed in regions with polygonal permafrost, the frozen soil and pile sustain the load as an integral due to the cementing effect between pile and surrounding frozen soil in the refreezing process. In order to obtain the properties of capacity and deformation before and after refreezing process, two 15 m testing piles were constructed in Daxinganling, China. Temperature monitoring system was adopted to record the temperature change in refreezing process. Based on the monitoring results, self-balanced static load test was conducted to determine the bearing capacity, tip and lateral friction within different stratus. The results show that the frozen soil was -1.9°C after refreezing. The capacity is 1.42 times of that before refreezing, and the tip friction is 1.49 times of that before freeing, which consisted about 12.98% of the total pile capacity. The average increment in pile lateral friction is 40.3%. This paper can serve as an evidence for the pile design and construction in permafrost areas.

The construction of high gravelly soil corewall rockfill dams on thick overburden layer has developed rapidly in recent years. At the same time getting a clear understanding and a reasonable numerical simulation method of the deformation law is an important problem. The factors that affect the deformation of rockfill dams are many-sided and complex. The measured results of deformation are very significant for the above problems. Based on the monitoring data of Yaoji dam, a 100 m level gravelly soil corewall rockfill dam on thick overburden layer, and combined with the actual construction process and reservoir impounding process, the dam deformation, gravelly soil corewall deformation are analyzed. Maoergai dam has high similarity with Yaoji dam in the height of dam, the depth of overburden, the width of valley. Comparative analysis of these two dams’ monitoring data is also conducted. Based on the analysis, some clear understanding of the deformation law of this kind of dam are obtained. The influence of wetting deformation, creep deformation, construction and impounding method is learned, so as to provide reference for modeling and predicting deformations of similar projects.

The soft soil in coastal area will be affected by the long-term immersion of the brine, in order to obtain the evolution law of mechanical properties with time, on the basis of the main composition of the brine content and preparation of the brine solution. Selection of Tianjin binhai new area of soft soil, mixed with 15% cement for maintenance. In order to illustrate the effect of salt solution immersion, the salt water and fresh water soaking two way contrast test are carried out. Unconfined compressive strength test results show that the improvement of soft clay after fresh water solution and salt solution immersion in 3 days, reached its maximum intensity difference; 7 d and 28 d curing age sample are respectively 0.40, 1.28 MPa. Then, using the Seep/W and GEOSTUDIO CTRAN module to simulate the process of salt ion in brine immersed specimens, it is found that salt solution ion in sample 2-3 days after, internal migration into the 5 mm under sample surface area, tends to steady. The results of numerical calculation is consistent with the experimental phenomena.

The strain of pipe section of the immersed tunnel engineering in Zhejiang province is monitored by the fiber grating sensor. The sensor type selection, installation and on-site installation scheme are introduced. The testing data is analyzed and the section measured strain values of the measuring-point changing with time and the influence of tidal load on monitoring results are studied. The measured strain values are compared with the theoretical value according to the modified model for the theoretical calculation of the pipe strain. The results show that pipe strain stabled basically after the end of the year in the construction; and the strain regularity with time is related to the pipe location and the pipe ends joint; the tidal load impacts on pipe strain within the range of 0.8%-12%, and closely related to the joint form; when both ends of the pipe sections are flexible joints, the strain regularity and the tide level showing a strong correlation; correlation is not obvious when it is rigid joints; pipe strain theory calculated and measured values are close, with some reliability.

Excavation beneath the original basement can effectively utilize the underground space, which is one of the popular ways to improve the parking problem in the dense urban areas. Excavation beneath the original basement will change the behavior of original pile. If the excavation depth exceeds a certain value, it may lead to buckling instability of the original piles due to the reduction of ground confining pressure around piles. In this paper, a theoretical analysis is performed to estimate the bucking critical load and the effective length of a single pile. At first, the scheme of floor-addition of basement is briefly introduced with the case of Zhejiang Hotel Extension Project. Secondly, the total potential energy of the pile-soil system under the condition of excavation beneath the original basement is set up based on the Winkler elastic beam theory. Finally, the expressions of critical load and effective length of single pile are deduced by using the minimum potential energy principle. Based on the proposed theory, the influence factors of critical load, including half-wave number n and excavation depth, are analyzed. It is shown that the buckling critical load of pile shaft converges with an increase in half-wave number n; by increasing the excavation depth, the buckling critical load decreases rapidly. The proposed theory may provide guideline to estimate the supported pile behavior of excavation beneath original basement under existing buildings.

According to the characteristics of long span underground engineering’s complex structure and high safety risk, the paper establishes a synthetically evaluation system by theoretical analysis, numerical simulation and experience evaluation. Through a variety of plastic mechanical calculation method, the Caquot formula, Fenner formula, modified Fenner and Kastner formulas are applied to project practice; select one method is most suitable analyze way for large span structures in hard rock. Using Q system and engineering analogy, determine the supporting parameters of anchor bolt in large-span underground engineering. The length of anchor bolt depends directly on the excavation span in Q system, at same time we can get support parameters of shotcrete. By analyzing the same level span underground works, determined that cable length should longer than 40% of the underground work’s span. Through the three-dimensional discrete element to evaluate the stability of supporting structures. In numerical calculations, rock strength criterion can be defined by the strain-softening model of HB. Constitutive relations of structural surface can use ideal elastoplastic model in Mohr-Coulomb strength criterion. After applying three rows of prestressed-cables at the upper side wall, the of deformation of side wall is significantly reduced. At the same time, the number of potential instability surrounding rock mass and scope are effective significantly controlled. By stress analysis of supporting structure，it is show that the 60% of the anchor’s axial force is between 2.0-2.25 MN; the underground engineering has a good safety. Through the synthetically evaluation system including plastic area analysis, numerical simulation and experience analysis, the formation of three-in-one evaluation system is reached. This system can be used for large-span support structure’s rationality evaluation. Through the analysis, The supporting design scheme can effectively deal with the failure phenomenon of rock block stability risk. In local lowly safety parts, anchor and anchor-cable stress level is comparatively high, can reduce the anchor-cable’s pretension force and increase the number of random anchor.

For Guocun coal mine, Yuzhou city, the goaf surface has formed 1 700 m long and 400 m wide moving basin; the goaf overlying rock mass is a typical "three zones" (in break, crack and bent zones) in South-to-North water diversion project. High precious monitoring networks are installed to research the goaf deformation characteristics during construction. The monitoring results indicate that the surface moving is over before construction. The surface moving in grouting area is obviously because of grouting; and the surface moving tends to stable after grouting. The deformation and stress of channel and goaf in three working conditions no-leakage, common-leakage and severe-leakage are simulated by FLAC3D. The vertical displacement and effect depth increase with leakage become more serious but added value decreases; the maximum value is 5.5 cm; effect width is symmetrical along the channel and increases uniformly; horizontal displacement increases and added value increases, while the maximum value is only 7 mm.; grouting redistributes stress field and there is stress concentration at both ends of goaf area; during leakage working conditions there is no effect on goaf area from water and channel load.

Impact roller(IR) compaction has been widely used for ground improvement in highway, airport engineering at home and abroad. The IR applies high energy to the ground and densifies deeper than conventional static and vibrating rollers and has the virtues of saving construction period and cost. As a result, attentions from academic circles and engineering circles have been drawn gradually. However, the theoretical research of IR compaction technique is inadequate and far behind its engineering practice. To promote reasonable application of IR compaction technique, a laboratory study based on self-devised impact roller simulation device was carried out to investigate effects of mass of impact wheel and towing speed on the effectiveness of IR compaction. The impact load form and the transmission and attenuation of impact energy in dry sand during IR compaction were also investigated. The results of laboratory cone penetration tests show that both mass of wheel and towing speed have significant influence on the IR compaction effectiveness. The effectiveness of IR compaction is better when heavier wheel is used and can be increased significantly by increasing the mass of impact wheel. There is an optimum towing speed to achieve the best effectiveness of IR compaction. The results of stress measurement in tests show that the impact load is a transient single pulse and the load distribution is not uniform with higher values in the centre of impact contact area. It also can be found that the impact energy mainly transfers in vertical direction in form of transient single pulse and attenuates quickly in form of negative power function.

During the operation of the Three Gorges Project, a large number of retrogressive landslide geological disaster occurred due to the combined effects of reservoir water levels and rainfall, making the retrogressive landslide occupies considerable proportion in reservoir landslide. Through studying formation mechanism of the reservoir retrogressive landslide, according to the deformation and failure mode, the retrogressive landslide is divided into traction district (initial slide district) and passive traction district, and analyzing the interdependence between traction district and passive traction district during the evolution process of retrogressive landslide. For its interaction of mechanical of characteristics, a reasonable physical and mathematical mechanical calculation model is established; and thrust calculation formula of retrogressive landslide is derived preliminarily to provide reasonable design thrust for anti-slide pile design. Taking the Three Gorges Reservoir Area Zhujiadian retrogressive landslide for example, on the premise of determining exist thrust between traction district and passive traction district, by thrust calculation shows that: derivation formula to calculate the design thrust of traction district sliding body is bigger than calculated the design thrust of traction district sliding body separately, compared traction district sliding body and passive traction district sliding body are regarded as the overall sliding body calculation design thrust smaller, it is show that the method of calculating the thrust for anti slide structure design can achieve both safety and economy effect, so as to provide new ideas for the design of retrogressive landslide.

The weak geologic body existing in the dam foundation is one of the key factors influencing the safety of the dam. The determination of reasonable mechanical value for the weak rock mass is the base for the stability analysis and evaluation of safety. To reasonably determine the deformation modulus of the broken rock mass distributing in the dam foundation at the left bank of Xiangjiaba hydropower station, experiments such as MTS 3-axial servo test, in-situ conventional bearing plate test and large-scale bearing plate test are performed. The values of deformation modulus of the broken rock mass obtained by the above mentioned experiment methods are less than 1.0 GPa. The measured values of deformation modulus of the broken rock mass with covered rock layer are greater than the experimented results without overlying rock mass. It indicates that the experiment values of deformation modulus obtained by different experiment methods are different from each other due to difference of stress status during experiment process. Based on analyzing of the intrinsic reasons leading to the difference of the tested deformation modulus, and considering of the actual force state of broken rock mass in the dam foundation, a reasonable value of deformation modulus is proposed.

Instability of slate slope，that is more common in slope engineering, often accompanied by toppling deformation, occurred frequently due to the unique structure of slate. The instability characteristics of slate slope subject to rainfall infiltration are studied by analyzing the instability phenomenon of the right dam foundation slate slope in Miaowei hydropower station; then the stability theory is used in the instability mechanism of slate slope, and combining the engineering practice with stability theory subsequently. Finally, the key measures for preventing instability phenomenon are proposed and used in the subsequent engineering. The results show that the slate joint characteristics, slope excavation ratio and rainfall infiltration are the key factors influencing the stability of slate slope; reinforcement is needed first to prevent rainfall infiltration and, have a good design of waist reinforcement. The slate slope in Miaowei hydropower station after reinforcement is safe and withstand the impact of flood and blasting, so as to prove that the instability causes of slate slope and reinforcement measure are well analyzed. That are useful for the similar slopes when they are need to reinforcement or deal with the instability.

In order to solve the technical difficulties to reinforce the deep marine soft soil foundation that including walkway network, the reinforcing technology by plastic drainage plate and sand column combined with surcharge preloading is proposed to reinforce the large scale complex deep marine soft soil foundation. The mechanical behaviors of the reinforced soft soil foundation during embankment filling and preloading are studied including the surface settlement and deep settlement characteristics, the excess pore water pressure dissipation mechanism, and the horizontal displacement law by field tests. The results show that the construction method used to reinforce the deep marine soft soil foundation has achieved good reinforcing effects. The settlement of the deep marine soft soil foundation accomplished mostly during the period of filling and preloading, which effectively reduce the post-construction settlement and construction period. The results provide an important reference for the reinforcement of the complex deep marine soft soil foundation. The settlement versus time curve of the marine soft soil foundation treated with plastic drainage plate and sand column combined with surcharge preloading is multistage development model. The settlement at the site reinforced by sand column is less than that at the site reinforced by plastic drainage plate. Meanwhile, the excess pore water pressure at the site reinforced by plastic drainage plate is greater than that at the site treated with sand column. The drainage effect of the upper soft soil is significantly superior to the lower. The top soil of the soft foundation under surcharge preloading would move to the treated area; while the soft soil below the surface 3 m would be pushed outside the region treated with plastic drainage plate and sand column.

The long piles of the ocean oil platform are usually manufactured as the integration of several segments which have to be assembled one by one during installation. During pile driving, excessive pore pressure will build up in such a high level that hydraulic fracturing in the soil round the pile may take place, which will cause the soil to consolidate much faster during pile extension period. Consequently, after pile extension, the soil strength will recover to some extent and the driving resistance will increase considerably, which makes restarting driving the pile very difficult and even cause refusal. A drivability analysis method for judging the risk of refusal by estimating the blow counts after pile extension is proposed, penetration GRLWEAP software is used to calculate the subsequent piling hammer the required number of hammer, in which the regain of soil strength is considered via the fatigue factor β. A case study is made using the proposed method, so as to prove the feasibility and applicability of the method.

Based on the horizontal static load tests on 57 single-piles of 12 sites in Shanghai, the bearing capacity of single pile under the action of horizontal load is studied. According to the test data, the effects of different pile diameters, and different loading methods and grouted pile stress characteristics of prestressed hollow are explored. For the architectural engineering, the larger pile diameter or the pile diameter enlarging top within a certain range are suggested to optimize the design of horizontal bearing capacity of singe pile. The loading test is suggested by the single cycle constant speed horizontal loading method; the safety of prestressed hollow core can be used as filling pile top horizontal bearing capacity. The study results will be useful for the design of lateral bearing capacity of single pile.

Bearing capacity evaluation is important for existing bridge piles with potential defections. As the pile loading tests and high strain tests are not allowed to perform for some bridges in service, a bearing capacity evaluation method for bridge piles is proposed. This method is based on the measured dynamic stiffness of piles and can be used for evaluating large quantities of piles, according to the following three steps: pre-analysis, general investigation measurement and verification. Combined with a practical engineering that evaluation of a great many piles for a long highway bridge, dynamic measurement for 680 bridge piles are performed by impulse transient response method. Detail statistics for dynamic stiffness of the bridge piles is performed. Combined with the assistant low strain dynamic measurements, the pile bearing capacities are calculated; and reinforcement suggestions for piles are proposed. Finally, in order to validate the estimation method, 80 pile samples are selected to perform the core drilling analysis. Results show that: for integrated piles, the obvious positive correlation can be found between dynamic stiffness and bearing capacity of piles; moreover, the values of dynamic stiffness have good reliability for evaluating the bearing capacity of large number of piles when they bear the similar design loads. By analyzing drilling core samples, it is proved that the evaluation method proposed has good reliability.

Pile foundation construction may have passive effects on the adjacent tunnel; and it makes the settlement and horizontal displacement of the tunnel increase slowly and makes the surrounding soil disturbance. The field measurements are carried out. The results show that the settlements and horizontal displacements of tunnel increase slowly; the pile surrounding soils are disturbed. The correspondent cross section has the maximum segment displacement. The settlement and horizontal displacement of the segments decrease with distance between the piles and the tunnel. The settlements are probably 0.5 times of horizontal displacement-based segments. Soil horizontal displacement moves to direction of the tunnel in one burial depth of the tunnel, while moves to the other direction beyond the burial depth. The test of pile practice shows that it is possible that soils can be cutting by all the steel casing pipe wall spiral; and it has better early warning and controlling construction risk for information monitoring of tunnel and surrounding soil layers during construction. The conclusions can provide the guidance of similar projects and for references.

By using finite element method, a series of parametric studies is performed for the maximum wall deflection induced by excavation in soft clay. Five main parameters effecting deformation i. e. excavation depth(H), excavation width(B), system stiffness(S), axial stiffness of the supporting structure(Sa), ratio of the average shear strength over the vertical effective stress , are analyzed. Based on the results of parametric studies，a simplified calculation method for maximum wall deflection is proposed using multiple regression. The proposed method is verified through several case stdudies. The proposed method can be used to preliminarily predict and also check the final results of design.

Static drill rooted pile (SDRP) is a compound pile consisting of soil-cement and prestressed pipe pile. For the purpose of knowing the deforming performance under lateral load, three sets of amount six piles static tests are carried out. The first set is 600- 750 mm SDRP (pipe pile diameter 600 mm and drilling diameter 750 mm); the second 800- 900 mm SDRP (pipe pile diameter 800 mm and drilling diameter 900 mm); and the third bored piles with diameter 1 000 mm. The second set is of very close in geometry size but different materials with the third set, and the first set is of same materials but different geometry size with the second set. Three findings are carried out after comparing lateral deformation ratios and lateral loads to deformations and deformation gradients, which are firstly bored pile is better than SDRP in the elastic stage but gradually reversed in the subsequent stages, secondly SDRP is stronger at deformation resilience than bored pile, and thirdly pile’s lateral deformation is nearly linear to sectional bending stiffness in the elastic stage. In order to promote lateral load-bearing capacity in elastic stage, the better way was substituting bored pile to SDRP with same diameter but not enlarging SDRP’s diameter.

The uniaxial compressive strength(UCS) of rocks is the crucial parameter in the design stage of rock engineering. Direct determination of the parameter is expensive, time-consuming and troublesome. The most widely used indirect determination method to predict the UCS is the point load test. Based on detailed analysis of the available experimental data of igneous rock published on the international journal, the shortcomings of the existed empirical equations are as follows: (1) Most of the equations overestimate the UCS with increasing point load strength index , especially for the power function. (2) The lower limit boundary suggested by ISRM (American Society for testing and Materials) still overestimates the UCS. To assess the UCS of rock in a between way, a new empirical parabolic equation eq. (1) is suggested and the application scope is 0.0 MPa < <15.0 MPa.

Deep foundation engineering is increasing in northwest China. The anti floating and durability for deep foundations problem research is a blank. This paper effectively solved the anti floating and durability problem by introduction of large diameter bag pile technology to comprehensive renovation project of Xining Railway Station. The 6 piles are selected to conduct on-site single pile load test; it is shown that the maximum load weight is 9 060 kN, Using MATLAB to fit out the three prediction function models of uplift ultimate bearing capacity curve; and using PLAXIS to simulate for different grades of pile soil load displacement. The study results show that the hyperbola and exponential function models to predict ultimate bearing capacity of uplift pile are appropriate; similar foundation prediction of large diameter corrosion deformation of uplift pile ultimate load corresponding standard limit displacement should be reduced from 0.030D to 0.025D. The ultimate friction based only on physico-mechanical characteristics of soil to determine the anti pulling pile surrounding soil is not enough; the influence of different buried depths of similar physico-mechanical characteristics of soil should be considered.

The engineering application of prestressed concrete pipe piles has developed rapidly in China at present, and the products have enormous quantity and wide applications. Their bearing properties, design, construction and testing should be taken attention seriously. This paper summarizes and analyzes the developmental history of prestressed concrete pipe piles, the current situation of pipe pile application and some problems which we often encounters in engineering application of prestressed concrete pipe pile. Combined with national codes, industrial standards, and the measured data in engineering test of prestressed concrete pipe pile, this paper comparatively analyzes the conditions for the application of prestressed concrete pipe pile, the bearing properties on pipe piles shaft, and the construction quality management of prestressed concrete pipe pile in depth. Through the analysis of several engineering example, this paper summarizes some implementation notes. in the engineering application of prestressed concrete pipe pile. This paper gives some prevention measures of reducing the quality accidence in the prestressed concrete pipe pile engineering, and makes some recommendations on the application of security, economy and rationality in prestressed concrete pipe pile.

Based on statistics of lateral load test data of 56 prestressed high-strength concrete(PHC) pipe piles in Fuzhou area, the horizontal bearing capacity of PHC piles in Fuzhou area is studied by combining m-method recommended by China’s technical code for building pile foundation. The range of m value for different soil around piles in Fuzhou area is confirmed by comparing back analysis value based on lateral load test data of different types of piles with value recommended by the code. The applicability of two kinds of mechanical models recommended by the code are validated by comparing with the bending moment curve simulated by the ABAQUS finite element software. The results show that the m method is applicable in calculating horizontal bearing capacity of single PHC pile in Fuzhou area. Physical and mechanical properties of overlying fill soil have an evident influence on the horizontal bearing capacity of PHC piles in silt. It’s applicable to adopt the "tip of pile supported in the bedrock surface or soil" model recommended by the code’s appendix to calculate horizontal bearing capacity of PHC piles in Fuzhou area.

To study the propagation of seismic wave caused by pile-well blasting on the natural slope nearby, field test of vibration velocity is carried out during the excavation of pile-well blasting. Two measuring points are set on the step adjacent to the pile-well, one is on the foot of the slope, another is on the edge of step. The results show that the radial, vertical vibration velocities and the main frequency of measuring point on the edge of step have an increasing trend than ones on foot, slope effect appearing. While it has a decreasing trend in the tangential direction, illustrating that the changes of vibration velocity and frequency of blasting seismic wave are in consistency; and the amplification effect of blasting seismic wave has directionality; among them the vertical is the main. Slope effect explains the amplification effect of blasting seismic waves on the edge of step reasonably. Meanwhile, the analysis of blasting seismic wave frequency of "whiplash effect" verifies the reasonability of the slope effect.

Based on the rule that the moment of piles under horizontal load decreases suddenly along the depth, the top of pile was designed as steel pipe piles having good bending properties and the rest of it was designed as PHC pile having weak bending properties, and chosen desired location to connect by welding and so on. Hammering test, horizontal bearing capacity test and bending properties test were carried out; and then compare compressive stress, tensile stress and horizontal bearing capacity with allowable value. Test results show that material composite pile gives full play to material properties, especially performing well at the aspect of horizontal bearing capacity; and the connection has a good performance. The study results can provide new ideas and test basis for the improvement of piles.

Considering the interaction between basement rock and pile, a procedure for computing uplift capacity of uplift pile with constant section is deduced according to power function slip surface premise and based on limit equilibrium method. Based on the report of skin friction experiment of pile in soft rock, it is taken that the power function slip surface of pile is close to experiment when the coefficient N = 0. Meanwlile the comparison between theoretical predictions and experimental data indicates the accuracy of the computing formula. According to this computing formula, it is proposed that the coefficient of interaction between soft rock and pile should take 0.7-0.8 discount of coefficient of rock’s internal friction angle and cohesion c. The relation between the internal friction angle , cohesion c and uplift capacity of short uplift pile in soft rock is revealed, where the uplift capacity is enhanced with increasing of the internal friction angle ?, cohesion c of soft rock and cohesion c is more efficient.

Methane hydrate bearing sediments(MHBS) are usually found undersea, which is generally categorized into different types, i.e. bond, pore-filling and so on. The mechanical properties of MHBS will be deteriorated as methane hydrate (MH) dissociates and many marine accidents will be caused; thus a lot of attention has been attracted in investigating MHBS properties changes during exploitation. A newly proposed 2D temperature-water pressure-mechanical bond model is implemented into PFC2D, the commercial software of the distinct element method (DEM), to simulate the dissociation of MH by thermal recovery and depressurization using soil in good exhaust and drainage conditions. By comparison with laboratory test results, it is validated that the newly proposed model is applicable to simulate the mechanical behavior of MHBS. At the same time, the micromechanical properties are also analyzed. With temperature increasing during thermal exploitation, the anisotropic degree of total contact distribution increases; the amount of bond contact, whose principal direction is horizontal all the time, decreases and the amount of unbonded contact, whose principal direction is vertical all the time, increases; the value of averaged pure rotation rate (APR) and its concentration degree increases all the time. With back (water) pressure decreasing during exploitation by depressurization, the total contact distribution changes from isotropic to anisotropic with a vertical principal direction, and the value of APR is small and uniformly distributed. After the recovery of back water pressure, the sample is damaged further, and the anisotropic degree of total contact distribution increases. Besides, the value of APR increases and the concentration degree of positive and negative value increases.

It is shown that sand has significant viscous properties related to loading rate. The stress-strain curve will jump abruptly upon a sudden change in strain rate. This strain rate effect will gradually fade as loading progresses. The TESRA (Temporary Effects of Strain Rate and its Acceleration) model which highlights the strain rate as the core variable rather than the conventional time variable is used to consider the viscous properties of sand. The dynamic relaxation-finite element method (DR-FEM), which has a high reputation in solving highly nonlinear geotechnical boundary value problems, is chosen as the numerical method. Return mapping method is used for stress update during the calculation. The laboratory tests on sandy foundation under variable loading rates were then simulated numerically by the nonlinear finite element method. The simulated results reproduced reasonably the load-settlement relations under loading conditions such as the changes of loading rate，creep and stress relaxation; and it also performed the decaying of viscosity as the loading progressed. Comparisons are made between test and simulated results to present the viscous properties of sandy foundation. The results also validated the rationality of the proposed nonlinear three-component visco-elastoplastic model for sand.

The jointed rock mass is the most common kind of rock in the practical engineering, therefore the jointed rock’s mechanical response and failure process under dynamic loading such as earthquake and explosion is crucial to the safety of the relevant engineering. Based on the finite element stress analysis and the microscopic damage mechanics, numerical code RFPA2D is developed to simulate the failure process of intermittent jointed rock mass subjected to dynamic loading. The failure characteristics of intermittent jointed rock mass with different numbers of joints, different joint discontinuity degrees and different joint dip angles under different amplitudes of stress wave are studied respectively. The numerical results show that the failure process and failure extent of intermittent jointed rock mass is closely related to the parameters of joints and amplitudes of stress wave. Under the same dynamic loading, with the increase of the number of joints, fragmentation degree of the rock mass and stress wave energy grows clearly at first, but to a certain number, the fragmentation degree and stress wave energy tends to be stable gradually. When the joint discontinuity degree is little, the fragmentation degree of rock mass is low and the failed units uniformly distributed from top to bottom relatively. With the increase of the length of joint, the fragmentation degree of rock mass becomes more and more serious, and the failed units mainly appear in the rock above the joint. When the joint dip angle is little, the upper rock is fractured more obviously and easy to form new cracks relatively. With the increase of the joint dip angle, the damage range expanded, and the rock mass is more difficult to form new cracks. Besides, the fracture effect of rock mass with a joint dip angle of 45°-60°,is the best. The more amplitude of stress wave is, the more serious the fragmentation degree of rock specimen is. When the amplitude of stress wave reaches a certain value, multiple cracks will be formed near the joint and extend upward and downward, which will cause the rock mass to fully fracture. Finally, the damage of rocks with different joint discontinuity degrees is compared with the damage of split Hopkinson pressure bar test. This method is proved to be reasonable and reliable by the similar conclusion.

On the basis of reliability index of homogeneous embankment slope calculated with Monte Carlo method, the influences of critical slip surface searching strategy and stability analysis methods on slope reliability computation are analyzed; and the variation characteristic of slope failure probability with the variability of geotechnical parameters is discussed. The results show that: (1) Failure probability calculated by the critical slip surface searching approach of “overall slope” is slightly larger than by “global minimum”; but there is little substantial influence on analysis of slope stability. (2) The variability of geotechnical parameters is the main factor affecting the slope reliability; and the reliability index decreases sharply with increasing variability of parameters. (3) There is nearly same curve shape but various horizontal position of probability density function of safety factor approached with different stability analysis methods; and it result in significant difference of failure probability; so the target reliability index of design should correspond to the adopted stability analysis method. The principle that safety factor value should be modified by considering the geotechnical parameter variability is put forward; it may provide improvement conception to the traditional slope stability analysis which obtained with the mean value of geotechnical parameters.

The contact pressure between soil and the flexible foundation under top uniform load is uniformly distributed. The additional stress of subsoil is large inside and small outside, which causes that the settlement of flexible foundation is also large inside and small outside. But the contact pressure between soil and the rigid foundation under uniform load is large outside and small inside, and the settlement is uniform. The thickness of the raft foundation of oil storage tanks is always large but not as large as that of the rigid foundation. So the distribution of the contact pressure is between that of the flexible foundation and the rigid foundation, and the settlement of the raft foundation is large inside and small outside. The authors adopt the UH model(the unified hardening model) as the soil constitutive model to simulate the soil deformation and research the sensitivity analysis of main influencing factors for the nonuniform settlement of the oil tank foundation. And the authors also research the influence of variable stiffness as on the nonuniform settlement.

Considering the uncertainty of soil parameters and soil strain softening characteristics, the reliability theory is used to establish the limit state equation of the slope progressive destruction, which is to calculate the slope probabilities for the partial failure and the progressive failure. The mode of failure considered here is that failure initiates within an assumed slip surface in the ‘weakest’ segment and progresses outwards from that segment along the slip surface. The reliability analysis method of the slope progressive failure can well reflect the partial slope body failure including its emergence, extension and its influence on the entire slope reliability. Then we can determine the most realistic failure propagation path and provide a theoretical basis of slope stability analysis. The example shows that the partial failure probability of each segment along the slip surface is not equal. Initiating from the eighth segment, the failure passes up at first and then down to the toe, which is different from the traction type failure, initiating from the toe and passing to the top, and the passage type failure, initiating from the top and passing to the toe.

This paper presents a semi-numerical and semi-analytical solution to the problem of an Euler-Bernoulli beam on multilayered isotropic elastic soils by the coupling of the finite element method and the boundary element method on the basis of the cooperation of the vertical displacements and the frictionless contact at the soil-beam interface, where the subgrade is assumed as a multilayered isotropic elastomer, the finite element method is applied to model the beam and the boundary integral method at the soil-beam interface. Then a corresponding program is compiled on the basis of the present theory. By comparing the solutions of this paper with the existing solution, the accuracy of the present theory is verified. The responses of elastic beams on both layered foundation model and the equivalent homogeneous one are further analyzed and compared. The results show that the characteristics of the beam on layered foundation model differ greatly from those of the beam on equivalent homogeneous foundation model; so layered foundation beam model should be adopted in practical engineering.

In order to study seepage mechanism of soil, there are some basic assumptions, the soil is saturated, and flow is laminar in the process of seepage. Based on lattice Boltzmann method at the representative elementary volume(REV) scale, the mesoscopic seepage numerical model of soil under pressure is established, considering the effects of macroscopic statistical parameters, i.e. porosity, permeability and effective viscosity coefficient. The D2Q9 model is applied for the discrete velocity direction. In the macroscopic boundary condition, it is impermeable in the left and right sides; and it is controlled by pressure in the upper and lower boundaries, which is decided by setting different density. And the non- equilibrium extrapolation scheme is used in the microscopic boundary. The porous media is set to be fluid in the study region by letting 1.0 and , the corresponding program is compiled to verify the Poiseuille flow. Combined with an example, the influence of porosity, permeability and seepage pressure on the seepage velocity driven by pressure is discussed for soil, and the results of this paper are in good agreement with that calculated by Darcy’s law. Therefore, lattice Boltzmann method at the REV scale could effectively simulate the seepage characteristics of soil, and it provides a new research approach for further study of seepage mechanism.

Stability and failure mechanism of shallow tunnel under surcharge loading is studied. The program is compiled based on finite element upper bound theory with rigid blocks translatory moving elements to obtain upper bound solution of critical surcharge coefficients and rigid block movements failure mechanism. Comparing with current results of rigid blocks upper bound solution and finite element upper and lower bound solutions of limit analysis, it is proved that the proposed upper bound solution is reliable. The results show that: critical surcharge coefficients increases with increment of soil internal frictional angle and ratio of depth to diameter of tunnel C/D; and decreases with increment of soil weight and cohesion factor ; C/D and have great influence on tunnel failure mechanism. Failure area expanded when C/D increases; as internal frictional angle increases, failure mechanism composed by rigid moving blocks mutually split up significantly. In contrast, influence of on failure mechanism is comparatively less potent. The proposed solution obtained for finite element upper bound method with rigid blocks translatory moving elements is accurate. Obtained failure mechanism composed by rigid moving blocks is presented as slip-lined shape, which precisely indicates characteristics of failure mechanism for unstable tunnel.

This paper aims at investigating the potential benefits of using new generation of reinforcement, horizontal-vertical reinforcement(H-V), to improve the bearing capacity and reduce the settlement of shallow foundations on soils. Finite element simulations of model tests were carried out to develop an understanding of influences of horizontal-vertical reinforcement on the bearing capacity, settlement, stress distribution, lateral displacement and the friction on the surface of reinforcement in horizontal-vertical reinforced soil foundation. Load-settlement response of strip footings on horizontal-vertical reinforced sand beds obtained from the numerical simulations are compared with the corresponding experimental results and the match is found to be good. The numerical simulation results show that the inclusion of horizontal-vertical reinforcement will redistribute the applied load to a wider area, thus minimizing stress concentration and achieving a more uniform stress distribution. The redistribution of stresses below the reinforced zone will result in reducing the consolidation settlement of the underlying weak sand soil, which is directly related to the induced stress. It also can be seen that the vertical inclusions of H-V reinforcement offer a strong passive resistance in the vicinity of the load, which prevents the sand particles from moving and rotating. Thus, it can be concluded that beside the tension membrane reinforcement mechanism, the vertical elements of horizontal-vertical inclusions kept the sand from being displaced under the applied load and redistributed the surcharge over a wider area. The horizontal-vertical reinforced base acts as a mattress to restrain the soil from moving upward/downward outside the loading area, redistributes the footing load over a wider area, and reduces the settlement, thereby increasing the shear strength of the composite system, which in turn substantially improves the bearing capacity of a sand bed reinforced with horizontal-vertical inclusions. In addition, failure mechanisms for horizontal-vertical reinforced soil foundations are proposed based on the finite element simulations and the results of experimental study on model footing tests conducted by the authors. Based on the beam on elastic foundation theory, vertical stress formulas that incorporate the contribution of reinforcements are then developed for horizontal-vertical reinforced foundations. The parameters such as the width, the length and the total depth of horizontal-vertical reinforcement were investigated. The predicted vertical stress values are compared with the results of finite element simulation on horizontal-vertical reinforced foundation. Good agreement is observed.

There are more shield tunnellings near the pile of the bridge in the downtown, the problem of the effects of shield tunnelling on the nearby piles of the bridge need to be studied. The numerical analysis method is used to study this problem. And than a numerical analysis model is established. The settlement of the pile, the lateral displacement of the pile and the settlement of the ground induced by the shield tunneling are analyzed. The settlement of the pile, the lateral displacement of the pile, the settlement of the ground during the shield tunnelling and after the tunnel crossing the pile is in controllable. The results of the numerical analysis and the results of monitoring are compared; and the results are similar to each other, so as to show the reliable of using the numerical analysis method to study the effects of the shield tunnelling on the nearby piles.

Under the multifield coupling of temperature, crustal stress and gas pressure, a coal-gas experimental device with microscopic observation has been developed to reveal the significance of the coal-gas reaction for the extraction of coal-mine gas. ECBM and the sealing of carbon dioxide in deeper coal seam, and to observe more accurately the dynamic process of coal-gas interaction under multifield coupling from a micro perspective. The microscopic-observing experimental device consists of sealed container and clamping device, pressure system, temperature-field system and microscopic-observing system. Combining with image processing techniques, the device is able to directly observe the slight changes caused by the interaction between coal and different kinds of gases under multifield circumstances. After performing adsorption-swelling deformation experiment of gas and carbon dioxide under conditions of no-stress loading, the same temperature and air pressure. Results show that: (1) The sample experienced three deformation stages in the two gases about rapid growth, slow growth and balance, which is similar to the adsorption isotherm curve. (2) The sample use time to achieve saturation adsorption in CO2 condition is shorter than it in methane. (3) The sample’s maximum longitudinal stain in CO2 condition is about 0.5%, which is the three times of the value in methane at the same conditions (0.15%). It indicates that the device has features of simple structure, high visibility and accuracy.

Dynamic centrifuge modeling has become a generally domestic and international acknowledgement of advancement and effectiveness in geotechnical earthquake engineering. However, its realization of superiority is inseparable from reliable measurement techniques. The common failure forms of node-oriented measurement techniques in dynamic centrifuge modeling are summarized, including discussing three types of conventional node-oriented transducers for pore water pressure, acceleration and displacement to increase reliability of test results by optimizing design and improving measurement. Via separable configuration, the emergency capability and controllability of pore pressure transducer are enhanced while the saturation quality and rate of porous stone using new technique of vacuum deionized-water saturation are advanced. The workability of accelerometer with utilization of core element increased rises using a type of separable configuration; and a rubber cover seal technique is established to reduce probability of settlement and inclination during seismic loading. A combined measurement technique of accelerometer and displacement transducer is proposed, be able to gain high accuracy of internal lateral soil displacement variation with better flexibility of placement.

The scientific and perfect early warning system for tunnel structure health monitoring has not been given by domestic and overseas; so the efficacy coefficient method is introduced to complete weighted comprehensive of multiple sensors monitoring data obtained from the health monitoring system to realize real-time warning or evaluation of the tunnel structure stability. Combining with the characteristics of health monitoring system, the method using support degree of the sensor monitoring data at the same time to determine the early warning index system (the optimal fusion data set) is proposed to solve the difficult problem of selecting index system in efficacy coefficient method. The three-scale method is chosen to determine the index weight which effectively overcomes the disadvantage of the 1-9 scaling method which has strongly subjectivity and the poor consistency judgment matrix. Applying the proposed method to the warning system of Wuhan Yangtze River tunnel health monitoring, firstly the monitoring data of which the support degree are greater than 0.1 is selected from the four surface strain gages and the six surface joint gages to constitute the early-warning index system; then the three-scale method is used to determine the index weight; finally the total efficacy coefficient value is calculated to complete tunnel early-warning; and the early warning results are in conformity with tunnel actual operating conditions; so the efficacy coefficient method has a good applicability in early warning of tunnel structural health monitoring.