This paper presents the experimental study of instantaneous strain-type granitic rockbursts. It uses the nondestructive acoustic emission (AE) testing method to monitor the rock internal damage during the simulation test. Using real-time waveform signals, we can plot the evolution of stresses and voltage signals in full time-domain. Combining with the cumulative AE energy curve, we can determine five key points which are the first inflection point A (positioned at initial load), the two turning points B and C (located at obvious rise ledges), the dramatic increasing point D and the final peak point E. The five points can be extracted and processed with the Fast Fourier Transform (FFT) in Matlab commercial software. The results indicate that the dominant frequency component of the granitic rock sample is 106 kHz at the initial loading stage. As the load increases, the frequency changes from low value to high value, the band of frequency becomes wider and wider, and the shape of wave changes from unimodal to multimodal. These frequency changes indicate the complicated frequency components and various fracture modes. At the time of rockburst occurring, the band of frequency becomes narrower and the shape of wave changes back to unimodal. The dominant frequency decreases to 106 kHz and equals to the initial value, which indicates a large amount of energy is released.

Seismic soil liquefaction problem in the soil site of nuclear power plants is a crucial point for the nuclear power plant siting. Therefore, it is urgent to develop a seismic soil liquefaction assessment procedure suitable for the soil site of nuclear power plants. The standard penetration test (SPT) and peak ground acceleration (PGA) based assessment method of soil liquefaction potential is reviewed. The basic principle to determine liquefaction triggering curve is proposed. Three corresponding liquefaction triggering correlations are derived respectively from the Idriss and Boulanger liquefaction case history database, the database of Chinese Code for Building Seismic Design and the two combined databases to reduce the possibility of mistaking liquefaction data points as no-liquefaction data points. The positions of the derived liquefaction triggering correlations are verified with respect to many factors including fines content, overburden stress and standard penetration test (SPT) procedures. In addition, the sensitivity of the database’s interpretation to a number of aspects and components of the analysis framework is examined. The results show these factors have a slight effect on the position of the proposed liquefaction triggering correlations. At last, the relationship among the nominal factor of safety and the probability of liquefaction as well as the probabilistic contours for the proposed liquefaction triggering correlation is given on the basis of Monte Carlo simulation, the weighted maximum likelihood technique and a weighted empirical probability approach. The soil liquefaction triggering correlations are proposed for the soil sites of seismic design categoryⅠ, Ⅱand Ⅲ of the structure, system and component of nuclear power plants, respectively.

This paper is about land reclamation with hydraulic fill. The hydraulic fill is treated with microorganism for enhancing its compressibility. It selects Aspergillus niger, Agrobacterium radiobacter and Bacillus licheniformis to do the experimental study. First, the changes of the consolidation characteristics of fill soil are examined after different microbial strains and culture mediums are added in the soil through consolidation test. Then some measures including determination of specific surface area of soil particles, chemical composition analysis and mineral composition analysis are applied to exploring the mechanism of modified hydraulic fill with microorganisms. The results show that: after the incorporation of microbial strains and culture medium mixed with the soil samples, the compression factors av1-2 of the soil samples show a decreasing trend and the largest drop is 29%; the compression moduli Es1-2 show an increasing trend and the biggest gain is 37%. The mineral composition of soil samples is essentially the same. The high valent cation content reduces significantly, which isn’t the main reason of the change of soil compression feature. The specific surface area of soil particles added with Agrobacterium radiobacter increases 49%. The specific surface area of soil particles added with Bacillus licheniformis increases 45%. The reason is that strains change the connection state of soil particles, and then lead to increasing of soil particles or the change of soil structure.

Stone column is one of the most commonly used techniques for soft soil improvement in practical engineering projects. The consolidation of the soil between piles is one of the most concerned problems. Studies on the problem under different conditions have been made great progresses. In this paper, the effects of column-soil modular ratio (equivalent to steady state stone column-soil stress concentration ratio) and area replacement ratio of stone column are considered. An equal strain assumption is assumed. As well as a general time-dependent loading is transformed into Fourier series to deduce the analytical solution of consolidation. The stress applied to column and soil at any time is gained respectively. The model gives reasonable modifications to existing theories. Comparisons with other methods demonstrate that the proposed solution is reasonable and accurate. The influence of area replacement ratio and column-soil modular ratio on the soil consolidation should be considered when their values are fairly large. Furthermore, this paper also analyzes the Carrillo hypothesis that vertical and radial consolidation can be considered independently. The result shows that the hypothesis is not accurate although the general trend holds true.

Large-scale triaxial tests on metamorphic soft rock embankment filler at Ankang west section of Shiyan-Tianshui expressway are conducted with double lines method respectively and under two kinds of densities. Variation of wetting strains (i.e., the differences between strains of dry and saturated states under the same vertical deviatoric stress) is analyzed. Results show that, there are two development stages of filler wetting strain curves. The positions of the change points of the two stages are closely related to the ratio of vertical deviatoric stress and confining pressure. Values of the wetting strain at change points on the curves of fillers with same density under different confining pressures are comparably consistent. They can become larger as the filler density increases. This indicates that the density and confining pressure have effects on both the magnitude and the rules of wetting deformation. Empirical formulas of wetting deformations and vertical deviatoric stress are put forward using the test results of three kinds of confining pressures. and the formulas are then verified with the test results of a new kind of confining pressures. These formulas can be applied to analyzing the laws of embankment wetting deformation in highway construction.

Due to waste accumulation and the capping weight of landfill, mechanical consolidation would happen in impervious barrier of the landfill liner under pressure. The chemical consolidation can also happen when the contaminant transports through the barrier. Then, the above effect of soil consolidation would not only induce contaminant advection, but also make the changes of its inherent transport property, such as soil volume and structural transformation. A hydro-chemo-mechanical contaminant transport framework is established, which is based on the mixture theory. It is able to describe systematically the coupling deformation under the hydro-chemo-mechanical effect, the water absorption and desorption, advection and diffusion. The influence of the hydro-chemo-mechanical coupling effect on the inherent transport property is considered with the changing of macroscopic pores. The contaminant transport is simulated using the coupling advection and diffusion flux. Then, the parametric analyses about consolidation load, diffusion-consolidation coefficient, coupling deformable effect, desorption effect and effective osmotic coefficient are progressed. The analyzing results indicate that if the difference between the adsorption water and free water in the soil of the landfill liner is larger, the more adsorption water would be desorbed. However, when the adsorption water is desorbed, the degree of soil consolidation would be changed with the soil characteristic which is hard or soft. If the overlying load is larger, the effect of limiting expansion of the macroscopic pore in the soil is larger. Subsequently, the velocity of contaminant transport would be reduced.

On the basis of the fracture failure mechanism and stress distribution characteristics of compressive-shear rock cracks under biaxial compression, this paper theoretically examines the influence of seepage pressure on the effective normal stress of preexisting crack surface. Then, a judging criterion is proposed for determining whether the seepage pressure is higher or lower. It considers the stress state of the effective normal stress of preexisting crack surface. Finally, the cracking law and characteristic of microcracks, generated at the tips of preexisting crack with different seepage pressures, are studied using the maximum circumferential stress criterion and sliding crack model. The results show that the optimal inclination angle of preexisting crack (on which the initial cracking strength of fissure body is the minimum) is directly related to the frictional coefficient of preexisting crack surface under biaxial compression. The optimal inclination angle of preexisting crack increases from 45° with the increasing of frictional coefficient of preexisting crack surface. When the seepage pressure is lower, the frictional coefficient of preexisting crack surface is weakened because of presence of seepage field. Furthermore, the optimal inclination angle of preexisting crack is close to 45°. On the other hand, the seepage pressure directly is applied to the surface of preexisting crack. Therefore, it just influences the initial cracking strength of fissure body. When the seepage pressure is higher, the stress state changes from compression-shear to tension-shear on the surface of preexisting crack. Because of the action of tensile stress, the initial cracking angle of microcrack generating at the tip of preexisting crack increases from 70.5° to 0° with the increasing of the value of KI /KII.

The engineering properties of newly hydraulic reclamation mud in liquid state are poor. Their bearing capacity is almost zero. After it is improved with vacuum preloading technology (VPT), its soil strength increases only a little and its effective depth is very small. A new idea of vacuum preloading combined with nonpolluting chemical reinforcement technology (VPCT) is proposed. Three kinds of vacuum preloading combined with chemical reinforcement technologies (VPCT1, VPCT2 &VPCT3) and one kind of chemical improvement technology (CT) are compared with VPT in laboratory tests. The test results show that: (1) when the effective chemical agent adding, the deposition of newly hydraulic reclamation mud finishes after a short standing time before vacuum preloading; (2) the effective chemical agent can promote the improvement effect; (3) in macrocosmic aspects, the mud of VPCT3 has uniform improvement, the clay content obviously decreases, the wet density is the biggest, the void ratio obviously decreases, and the unconfined compression strength is the biggest (66.7 kPa) which is 3.5 times that of VPT; (4) in microcosmic aspects, the mud of VPCT3 has the smallest total region (void) area, average perimeter, region(void) number, void ratio, porosity, and has good directionality, intimate contact with mainly surface-to-surface connection, and has most noticeable agglomerate phenomenon. Therefore, comparing with VPT, VPCT3 has the best effect for improving the mud. It is advisable & necessary that VPCT3 is further researched in field trial.

The current load transfer method does not consider the weight of pile shaft itself. When it is directly applied to calculating the settlement of super-long pile in the soft soil area, the computational accuracy can hardly meet the requirements of strict control criteria for post-construction settlement of high-speed railway. This paper considers the settlement calculation of both soil around pile due to dewatering and soil beneath pile tip using tip-resistance elastic model. The calculation method of dewatering-induced foundation pile settlement is proposed by modifying and solving the basic differential equation of load transfer method. The weight of pile shaft is combined. A hypothetic load transfer function of skin friction is included using Kedzi’s model. A case study is given. The theoretical solution and the FEM embedded with the hypothetic load transfer function are used. The skin friction, the shaft axial force and the foundation pile settlement are comparatively analyzed under either the action of upper load or the combined loading of upper load and dewatering. The additional vertical displacement of soil around pile due to foundation pile settlement is obtained using both the FEM and the theoretical calculations. The two results have slight difference. The rationality and correctness of the theoretical calculation are verified since its corresponding laws change almost in the same way as those of FEM.

This paper proposes a soil constitutive model suitable for geotechnical earthquake simulation. The Hardin curve of soil dynamic stress-strain relationship and its Pyke’s modification for irregular cyclic loading are used. The boundary surface is established on the deviatoric stress plane according to von Mises criterion. After connecting reverse loading point and the current stress point for boundary surface projection, a plastic hardening modulus is derived regarding projection ratio as hardening parameter. The specific increment formulation is given. This constitutive model is implemented by customizing the secondary development of materials in finite element method software ADINA and verified with dynamic triaxial test. The comparison of numerical simulation and test results illustrates that this constitutive model can truthfully reflect the stress-strain relation of soil. For seismic responses of a site, a 2D numerical simulation is executed using the boundary surface constitutive model in ADINA. The results are compared with those of SHAKE91 to illustrate the rationality of adopting this constitutive model to geotechnical earthquake engineering problems.

This paper is based on the findings of shaking table test of underground caverns and the similarity principle. Proportioning tests of similar materials of surrounding rock are performed by taking advantages of the combination of orthogonal experiment and secondary refinement test. Iron ore powder, barite powder and quartz sand are the main materials. Gypsum powder is glue. Glycerin is regulator. The density, compressive strength and deformation modulus of the similar materials are chosen as the four control indicators in the orthogonal experiment. The importance of each factor is obtained using polar difference analysis method. The design of the secondary refining experiment is decided with the orthogonal experiment results. Tensile strength is additionally tested in the secondary refining experiment. The similar materials that satisfy the similar relationship can be developed efficiently with the combining test methods. The variation between the proportion of similar material and the physical parameters and the efficient method of combination test can offer a reference to model test of the similar project in which proportioning test of similar material is also required.

Acoustic emission (AE) will evidently accompany in the process of deformation and grain crushing of the coarse aggregates. Monitoring the acoustic emission signal characteristics of the coarse aggregates under the action of external force can be used to study the crushing mechanism. This paper studies the acoustic emission characteristics of sericite schist coarse aggregates. It uses the coupled acoustic emission large-scale triaxial test apparatus to carry out the conventional consolidated drained triaxial tests, the constant volumetric stress p and the constant deviatoric stress q tests on sericite schist coarse aggregates. The acoustic emission signals are monitored. The test results show that the acoustic emission of coarse aggregates is mainly from the particle breakage, sliding friction and rolling friction. The activities of inter-particle sliding, rolling and particle breakage are severely affected by different confining pressures and different stress levels. So the proportions of frictional AE and fractured AE are different at different stress levels. Under the constant p stress path test, the inflection point of accumulative acoustic emission signals appears, which can judge the strain softening point. The acoustic emission during the constant q test is obviously lower than that during the constant p test. The growth rate of accumulative acoustic emission parameters is gradually increased with the volumetric stress increasing in the constant p test. However, the growth rate of accumulative AE parameters is gradually decreased with the deviatoric stress increasing in the constant q test. It can be deduced that the acoustic emission of coarse aggregates is greatly influenced by shear stress.

The rocking interaction between adjacent strip foundations is studied based on the elastic half-space theory. The interface between the foundations and the supporting medium is divided into a number of strip elements. Asymmetrical Green function of the displacement of elastic soil medium under harmonic uniform excitation is derived. The multi-value improper integral is precisely calculated by the piecewise integration method and Cauchy principal value integral. The coupling rocking impedances between soil and adjacent strip foundations are solved. The bending moments caused by the contact forces of Green function is added on each element. The analysis uses the fact that the displacement of a rigid foundation determines that of each element. Influences of calculating parameters of foundation and soil medium on the rocking interaction between two foundations are discussed in detail. The numerical results show that the rocking interaction between adjacent strip foundations should be taken into consideration when the spacing and width ratio S/L is less than 4.0. This method is simple, has a highly accurate, and can be used for the calculation at a high frequency range. The research results provide a theoretical basis for the study of soil-foundations dynamic interaction, and make it convenient for engineers to consider dynamic interaction between adjacent foundations in the seismic design of structures.

This paper attempts to make mechanical and permeability characteristics of cement bound coals closer to those of undisturbed coals. It uses triaxial servo-controlled seepage equipment for thermo-fluid-solid coupling of coal containing methane and selects cement as a binder. The triaxal compressive properties of cement bound coals with different binder ratios are compared with those of undisturbed coals. The characteristic values for the mechanical and permeability characteristics of the cement bound coals are evaluated quantitatively using Euclidean distance based similarity methods. The results show that: as binder ratios increase, the peak principal stress difference and the elastic modulus of the cement bound coal probably increase following a positive exponential function trend. Poisson's ratio decreases following a negative exponent function trend. As the binder ratio increases, the initial permeability and the minimum permeability of the cement bound coal have the decreasing trend of exponent function. The penetration rate of change is smaller and smaller. The permeability-axial strain curve is gentler. The mechanical and permeability characteristics of the cement bound coal with the cement binder ratio #IV are the closest to those of undisturbed coal. This type of cement bound coal can be used as the similar material for simulating the undisturbed coal.

This paper is to determine the spacing of cantilever piles for stabilizing slope more reasonably. The defects of existed analysis models for cutting slopes are discussed. A reversely trapezoidal compressed zone is assumed to present behind a pile. This zone is the arch foot related to soil arching on both sides of the pile. Some control conditions are given for calculating rational spacing between two adjacent piles. These conditions include (1) static equilibrium equation between slope thrust on the soil arching and resistance on its two end sections near the two piles, (2) strength principle of the point at internal edge of medial cross-section of the soil arching, (3) the strength condition of two end sections of the soil arch, (4) calculation width of the pile due to its spatial resistance effect and (5) compatibility of deformation between the pile and the behind soil. The equations to determine the spacing are given and can be solved with iterative and trial and error calculation methods. Results of an engineering example quantitatively show that the spacing between two adjacent piles nonlinearly increases as the cohesion or internal friction angle of soil behind piles increases. It nonlinearly decreases as the upslope landslide thrust on the piles increases. In addition, the effect of the cohesion on the spacing is more sensitive than that of the internal friction angle. The proposed method can be suitable for both cohesive and noncohesive soil.

The existing phenomenological constitutive model is hard to describe how the impurity content, temperature and strain rate affect the mechanical behavior of the salt rock. It is more difficult to explain its deformation mechanism. Salt rock mainly consists of halite crystal. The deformation mechanism of salt rock is controlled by the polycrystalline structure. Therefore, it is more appropriate to build the plastic constitutive model using solid dislocation theory for the description of the deformation of the rock salt. The mesoscopic mechanism of the plastic-creep is the coupling of dislocation sliding of inner crystal grains and dislocation climbing-sliding of boundaries and their interference surfaces of inner crystal grains. According to the above hypothesis, the relationship between the average scale of the subgrain (or grain) and flow stress, the mean density of dislocation of inner grains and evolution model of microscopic parameters (including dislocation, subgrain diameter and boundary width between subgrains) are obtained sequentially. Finally the meso-macroscopic deformation and then plastic constitutive equation of salt rock are established using Orowan’s law. The obtained equation can reflect the physical mechanism of plastic-creep deformation of salt rock and has an improved physical significance, comparing with traditional plastic constitutive model. This constitutive model could only be obtained through observation and research on mesoscopic structure of rock salt.

The coal-rocks contain gas are assumed as gas saturated isotropic homogeneous media. The physical equations, geometric equations, continuity equations and dynamic control equations about the coal-rocks are established using the mixture theory. The length of the gas suction hole is much larger than the diameter. The dynamic response of gas suction hole in the coal-rock due to the action of negative suction pressures during the suction process can be simplified into a two-dimensional initial-boundary problem. The theoretical solutions in frequency domain and time domain are respectively derived with Laplace transform and inverse Laplace transform. The parameters of coal rocks and gas in a mine of Henan province are taken as examples. The dynamic response near the hole wall is numerically calculated. The dimensionless radial displacements, radial stresses and circumferential stresses are analyzed. Finally, some conclusions are drawn as follows. The dimensionless radial displacements and stresses are mainly concentrated at a local area near the gas suction hole. The area increases with the suction time. Large and volatile circumferential stresses are generated at the hole wall. They increase as the negative suction pressures increase.

Soil-bags are a new earth reinforcement method and have been widely used in many projects including building foundations and slope reinforcement. A large number of researches on soil-bags show that soil-bags have significant vibration energy absorption effect. This paper investigates the effects of different soil fills in bags on vibration energy absorption. Cyclic simple shear tests are carried out on soil-bags filled with different soils and on soil-bags filled with soils that have different particle sizes, gradations and clay contents. The dynamic shear modulus and the equivalent damping ratios of the soil-bags and fill soils are analyzed. The test results show that the dynamic shear modulus of soil-bags are smaller and the equivalent damping ratios of soil-bags are higher than the fill soils. The dynamic shear modulus and equivalent damping of both the fill soils and the soil-bags are relatively higher in the cases that particle sizes of the fill soils are smaller, gradations are uniform and clay contents are larger. In general, the effects of the particle sizes and gradations of the fill soils are not pronounced on the equivalent damping ratios.

Sericite schist particles are easy to disintegrate. Their performance can decay and weaken easily under long term wet-dry cycle effects. Both California bearing ratio (CBR) test and resilient modulus test (MD) are carried out on sericite schist particles with different initial maximum sizes. The strength variable characteristic is gained. Meanwhile, the paper reveals the interior disintegrated mechanism joined with particle size distribution curves. The results show that sericite schist particles don’t disintegrate obviously any further after they are subjected to more than 10 times wet-dry cycles. Moreover, they disintegrate rapidly if their particle sizes are greater than 10 mm. They disintegrate slowly if their particle sizes are less than 10 mm. The initial maximum particle size ranges corresponding to the strength peak value are 5-10 mm and 10-20 mm for CBR test and MR test, respectively. Hence, the initial maximum particle size of 10 mm could be recommended as controlled size for using sericite schist particles as subgrade fills.

This paper analyzes the shear strength of the bolted rock joint contributed by the axial force and transverse shear force. The formula of the shear strength of a bolted joint with dilatancy is derived using the variational principle of minimum potential energy. The theoretical solutions are verified with the direct shear test of bolted structure. Then the shear strength of the bolted structure is contributed by the axial force and transverse shear force. It is analyzed with different rock mass strengths, bolt diameters, normal stresses and pre-stresses, using this theoretical method. All the relevant analyses show that the computed results agree well with the results of experiment. The shear strength of the jointed structure contributed by the transverse shear force is remarkable. When the bolt inclination increases gradually, the joint shear resistances contributed by the transverse shear force and the axial force increases and decreases respectively. When the bolt inclination is 120°－150°, the joint shear resistance contributed by the axial force is almost zero. The joint shear resistance contributed by the axial force decreases as the rock mass strength and normal stress increase. It increases obviously as the bolt diameter and pre-stress increase. The joint shear strength contributed by the transverse shear force increases as the rock mass strength and bolt diameter increase, but decreases slightly as the pre-stress increases.

This paper treats the ground soil as a saturated half space. It investigates the dynamic response of a generalized Gibson soil (whose shear modulus increases linearly with depth) subjected to an embeddd harmonic torsional load. It uses Biot’s theory of saturated soil and combines the characteristics of torsional vibration. It establishes the dynamic differential equations of generalized Gibson saturated soil. Using the technique of Hankel transform, it solves the differential equations. The tangential displacement and shear stresses in Hankel transform domain with several undetermined coefficients are formulated. Using the boundary conditions including the free surface at the top of the half-space, the tangential displacements near the loading area are continuous, the shear stresses near the loading area are discontinuous and the radiation boundary condition, the undetermined coefficients are solved. Then, the tangential displacement and the shear stress of the nonhomogeneous saturated soil are expressed explicitly in Hankel inverse transform. Selected numerical examples are presented. The numerical results reveal that in the same horizontal plane, both real and imaginary parts of the tangential displacement and shear stress show very significant fluctuations. In the vertical plane, the real parts of the tangential displacement and shear stress increase with depth in the zone above the loading surface, and decrease with depth in the zone below the loading surface. Besides, the influence range of the torsional dynamic load is about two times of the action radius to the loading surface.

A set of tests with the hollow cylinder apparatus are conducted to simulate the oblique incident seismic waves. Tests are performed with two cyclic stress components involving the horizontal shear stress (torsional shear stress) and the vertical shear stress (stress difference between vertical normal stress and horizontal normal stress) to show an elliptical shape in the orthogonal coordinates of stress difference and shear stress. Then the dynamic characteristics of saturated Fujian standard loose sand, consolidated under isotropic undrained condition and applied with cyclic oblique elliptic stress path, cyclic circular shear, cyclic torsional shear and cyclic triaxial path, are studied. The experiment results show that the development of elastic pore pressure can be classified as “sharp dropping type” and “sharp rising type”. The cumulative rates of excess pore water pressure under cyclic circular shear and under cyclic torsional shear are the fastest and the slowest respectively. The normalizing pore pressure is independent of inclination angle of the obliquity of elliptic path, but depends on the ellipticity of cyclic stress path and stress amplitude CSR. Experimental results also indicate that undrained dynamic strength of Fujian sand is closely related to cyclic stress path. The cyclic torsional shearing path and cyclic triaxial path have the highest dynamic strength. The strengths under standard inclined elliptical loading path and under cyclic circular path are lower and the lowest respectively. Approximate circular path can be generated with seismic wave in a particular incident angle. If seismic wave is regarded as vertical incident S wave, the soil liquefaction strength would be overestimated.

Limit equilibrium theory and variational method are combined to analyze ultimate uplift capacity of excavated foundation of transmission tower. A general shear failure for the soil mass around the tower is hypothesized. The soil stresses satisfy the yielding criteria of Mohr-Coulomb at limit conditions. The ultimate bearing capacities for different loading conditions can be estimated with this method. The effects of soil strength and embedment ratio on ultimate uplift of foundation under centric, eccentric and inclined uplift force are examined with a series of calculations. The influence coefficients of moment and horizontal force are proposed using a normalized processing. When the ratio of normalized moment to uplift force Nm is less than 0.4, the moment influence coefficient ? m declines rapidly with Nm. When Nm is more than 0.4, the decay rate of ? m becomes slow. Soil cohesion has more significant effects on ? m than the internal friction angle. The influence coefficient of horizontal loading ? h is affected by the soil strength and embedment depth simultaneously. The results show the values of ? h are smaller than those proposed in technical code. The accuracy and reasonableness of the method are verified by comparing test data with the results of formula in code. It can provide a reference for determining uplift capacity of outcrop foundations under eccentric uplift or horizontal force.

This paper uses a thermo-mechanical dispersion coefficient model in a small-scale aquifer to examine the advection- dispersion heat transfer process. Analytical solutions of advection-dispersion are derived and proved their correctness with experiment. The assessment results show that the coefficient of the thermal-mechanical dispersion of 1×10-2 W/(m?°C) can be selected as the critical point where thermal transport is affected. The distribution of thermal mechanical dispersion coefficients can be divided into non-ignorable triangular domain and ignorable polygon domain. The calibration scope of longitudinal dispersion degree of natural flow field is made clear in different aquifers. However, the research result of small scale thermal dispersion show that, under condition that the particle diameter and the seepage velocity are both at the upper limit, the maximum of longitudinal thermal dispersion degree is at centimeter order of magnitude, which is significantly different from the research result of thermal dispersion degree under outdoors of large scale conditions. This proves the existence of scale effect of thermal dispersion, and thus shows the direction of further research.

Sometimes, at the condition that a confined aquifer is not completely cut off, its pressure-relief can occur when dewatering via pumping is conducted to prevent the heave failure of pit formation above. Such pressure-relief can have negative effect on ground settlement considerable larger than that due to pit excavation. Therefore, such effect on the existing shield tunnel adjacent to the pit has to be considered. The effect is simulated with finite element method in this paper. The stress field of surrounding soil, the deformation and internal forces of the cross-sections of tunnel at different locations relative to the confined aquifer are analyzed. The results show that, when either most part of tunnel or the whole tunnel is located in the confined aquifer, its pressure-relief can cause not only overall upheaval or settlement, but also vertical convergence deformation of the tunnel. When the tunnel is located in the aquiclude above or under the confined aquifer, the pressure-relief only produces little influence on the tunnel deformation. However, when it is located in the upper aquiclude, the tunnel would exhibit obvious settlement due to the pressure-relief in the confined aquifer.

Field practice demonstrates that geological discontinuities such as joints, weak intercalations, as well as faults, are a key factor controlling result of presplit blasting operations. The influence of angle of geological joints is investigated using the software LS-DYNA 3D. The numerical simulation of the process of presplit blasting in jointed models shows that the existence of the joint in rock mass can affect presplitting blasting significantly. The joint absorbs stress wave energy and prevents the transmission of stress wave, also impacts presplitting fissure occurrence. The cracks near joints mostly run along the direction vertical to the joints and gradually connect with the joints. When the angle between joint and the direction of designed presplit is small, the zigzag-shaped cracks are likely to rise, but hardly to penetrate. With increase of the angle, the effect of the stress wave transmission over the joints, as well as the particle vibration velocity near the joints can increase, and the produced presplitting cracks are more likely to straightly penetrate from one to another along the designed presplit line. When the joints and the designed presplit line are perpendicular to each other, the stress wave transmission over the joints reaches maximum and the cracks are likely to be in the same line connecting the presplit holes. Thus it becomes less possible for the zigzag-shaped crack to occur. The effect of presplitting to crack occurrence is best

Differential weathering can cause unstable rock mass in rock slope with alternating strata. The alternating strata can be sandstone and mudstone and belong to the soft and hard rocks. The rock collapse damage is a common form of geological disasters. This paper uses unstable rock mass at Puerdu as case study. The calculation formula for the compressive stress of unstable hard rock block on the soft mudstone base is derived for the slope rock mass with cavity in the soft mudstone due to differential weathering. The stress increases as the cavity depth increase. According to the slope topography, geomorphology and characteristics of geological structure of unstable rock blocks at Puerdu, two kinds of four unstable rock mechanical models due to differential weathering are established. The first type is the type of mudstone base fracturing damage and rotational damage unstable rock block whose main control fissure connectivity rate is equal to 1. The second type is the type of falling and toppling of unstable rock block whose main control fissure connectivity rate is less than 1. The rock strength theory is used to derive the quadratic parabolic Mohr strength envelope equation for sandstone at the study area. The limit equilibrium theory and Mohr strength theory is used to deduce the collapsing damage and judgment expression of four kinds of unstable rock blocks under the gravity, earthquake force and fissure water pressure. The critical collapse boundary equation is derived for the unstable rock mass at the study area. The relationships among rock cavity depth, thickness, height and the main control fissure depth are also derived. Those results provide an intuitive and reliable basis for the prediction and judgment of stability and collapse of the unstable rock mass.

Due to the highly developed natural fractures and horizontal beddings in shale reservoirs, it is possible to generate complex volume fractures during hydraulic fracture treatment. In order to investigate the propagation process of complex fracture network, a three dimensional finite element model for volume fracture propagation of hydraulic fracture in shale reservoirs is built using fluid-solid coupling basic equations in porous medium and basic theory of damage mechanics. The numerical simulation results are in good accordance with laboratory experiment of shale fracture propagation, which prove the reliability of the numerical model. After a series of numerical simulations, some conclusions are drawn as follws: (1) The horizontal beddings can open and form horizontal fractures in hydraulic fracturing. They can intersect with vertical fractures and finally generate complex volume fracture network. (2) As the horizontal stress difference increases, the length of stimulated reservoir volume (SRV) can increase and the width can decrease, which means the ratio of length to width of SRV can increase. The length is the distribution distance of volume fracture along horizontal maximum principal insitu stress. The width is the distribution distance of volume fracture along horizontal minimum principal insitu stress. (3) As the pump rate of fracturing increases, the SRV length can decrease, width can increase, and the ratio of length to width of SRV can decrease accordingly. (4) When the residual tensile strength of the natural fracture becomes stronger, the width of SRV can decrease, the length and the ratio of length to width of SRV can increase. Research results can offer some references for hydraulic fracture design and operation of shale gas in China.

For slope failures on reservoir, we can’t only see the damage from their deformation and failure, but also think about the disaster from the tsunami caused by them. This paper attempts to obtain the law about spread and attenuation of the reservoir tsunami caused by slope failure. It uses the software of FAST (Fast Assessing System for Tsunami) and GEO-WAVE to numerically simulate such tsunami. It selects the slope #4 at Gongjiafang on the Three Gorges reservoir as the actual case. The simulation area is about 23 km long and 10.4 km wide and the reservoir water levers are 175 m, 156 m and 145 m respectively. Figures about the tsunami are gained with the numerical simulation. The pictures of wave probes are charted with calculation and analysis of data processing module. Comparative analyses of simulation results under the three water levers are given. As water lever decreases, the largest wave height and the largest climbing height have an increasing tendency, but the time of wave damaging the passage gets shorter. The largest wave height has a distribution rule that the shape in middle of river is concave and the shapes on both sides of river are protuberant. The rapid attenuation area of impulse wave distributes in the region at a distance of 1 km from the source point. The higher is the wave height of source point, the more is the drop height of impulse wave in unit length. Because the waves can be superposed near bank, it is suggested that boats must speed through along the middle of the reservoir river immediately when they are near the slope #4.

In order to study destruction law of aquiclude under the action of mining and seepage, this paper carries out the experiments of solid-liquid coupling similar simulation and the theoretical analysis of soil damage. The experimental results show that, in use of method of long wall mining in the interval mining, the combinatorial key stratum in shallow coal seam breaks into the fracture zone, and aquiclude breaks into the bending subsidence zone. The mining method can change the stratum moving destruction law and restrain the development of caving fissure into aquiclude, and avoid the connect with the bending subsidence zone. The method can achieve the purpose of protecting water-isolating capacity. Theoretical analysis of soil deformation and failure reveals that span of soil layer is span of the combinatorial key stratum breaking. The fractured water-conducting zone cannot be produced when the span doesn’t reach the limit deformation span in bending and sinking failure process. The mining practice has proved that water leakage doesn’t appear in the mining site after mining. The method is successfully used in a number of mining face exploitation to achieve water protection mining.