vacuum loading mode are generally not considered in Traditional vacuum preloading method in the reinforcement of soft soil. This paper carried out indoor model test, it tested four groups of the flow mud soil samples the water content of which is 100%, the vacuum loading mode are -80 kPa, -60 kPa→80 kPa, -40 kPa→-80 kPa, -20 kPa→-80 kPa, Water, settlement and lateral deformation was monitored during the loading of the sample in the course of the test, and changes of the water content, plasticity index and vane strength was studied after the test. The test results showed that: (1) Vacuum loading mode significantly effects on consolidation of dredger fill flow mud. (2) Soil settlement is largest and strength is highest when the initial vacuum value of -20 kPa better than the others; soil settlement is smallest, and strength is lowest when the initial vacuum value of -80 kPa better than the others. (3) From the distribution characteristics of the plasticity index, soil particles move with water in the soil discharge, initial vacuum load value larger this trend is more obvious; the part of the soil particles will accumulate around of plastic vertical drain and so as to reduce soil permeability; severe cases will affect soil consolidation of follow-up. Finally, it is recommended that a lower initial load mode to loading in the flow mud vacuum consolidation process.

Chromium is a trace element and toxic effect will be caused by excessive intake of chromium. Factors including the concentration of Cr(III), reaction time, reaction temperature and pH value were studied to investigate the adsorption behavior of loess soil towards Cr(III). The researches indicated the adsorption speed is very fast; the adsorption capacity of Cr(III) on loess soil is very big; and the adsorption test results can be well interpreted by three isotherm models, i.e. Freundlich and Dubinin-Radushkevich (D-R) models. The thermodynamic analysis indicates that the adsorption process of Cr(III) on loess soil is spontaneous, and higher temperature is benefit to the adsorption process. Higher temperature leads to higher adsorption capacity; higher initial concentration of Cr(III) leads to higher adsorption capacity too; pH value has great influence on the removal efficiency of Cr(III) from aqueous solution, and Cr(III) can be nearly completely removed at pH>6. X-ray diffraction spectra and Fourier transform-infrared spectra were used to further discuss the adsorption mechanism of Cr(III) on loess soil; and the analysis indicates that the clay minerals such as kaolin and quartz and organic matter in loess play important roles in Cr(III) removal.

The shear stress of a rock joint is composed of three components triggered by anti-shear effect, dilatancy effect, and frictional effect under normal load and shear load; but the three components will not exert their maximum at the same point in the shear process of a rock joint. Firstly, the five main engineering geological properties of rock slope joints are analyzed in detail, which will provide engineering conditions for the component constitutive model. A component constitutive model of rock joints is presented and its characteristics are as follows: (1) The coupling effect between dilation and shearing is considered. (2) The component constitutive model has obvious physical meanings. (3) Each component is composed with a simple function, so segmental fitting functions are not needed. Furthermore, based on the component constitutive model of rock joints, the concept and solving principle of dual safety factors for jointed rock slope are put forward, which will directly show the physical process from shear failure to residual strength. The three components’ contribution to the slope stability is clarified by a calculation example.

In order to research the tensile properties of compacted clay, a conventional triaxial test apparatus was modified to a uniaxial tensile apparatus for clays, by which clay samples can be extended and the stress and corresponding strain of the samples can be measured directly. A series of laboratory tests were conducted to investigate the tensile properties of compacted clay. The tested clay samples have various moisture contents (from 16% to 24%) and various dry densities (from 1.29 g/cm3 to 1.65 g/cm3), which have impacts not only on the tensile strength of samples, but also on the pattern of tensile stress-strain curves. It is found that there are three patterns of stress-strain curves for the tension of clay soil, i. e. strain-softening, strain-hardening, and strain-strengthening, corresponding to the increasing tensile strength and failure strain. The tensile strength of compacted clay approximately increases with its dry density and decreases with its moisture content linearly. With the increasing dry density and decreasing moisture content, the pattern of stress-strain curves of the clay samples changes from strain-softening to strain-hardening, then to strain-strengthening pattern. The tensile rate has obvious effect on the measured tensile strength and the pattern of stress-strain curves. For the samples with identical dry density and moisture content, lower tensile rate results in smaller measured tensile strength and strain-softening stress-strain curves; and higher tensile rate causes greater measured tensile strength and strain-strengthening stress-strain curves.

Dynamic triaxial test in laboratory is the main approach to investigate the dynamic residual strain (seismic subsidence) of natural loess under seismic loadings. How to reasonably apply the little test data in laboratory into the quantitative evaluation of dynamic settlement in loess field is one key problem within the practice of geotechnical earthquake engineering. Based on a magnitude estimation model for dynamic residual strain of natural loess, which comprehensively considers the critical influence parameters of the dynamic subsidence, consolidation stress, structure strength, spatial volume property and seismic loadings, the authors propose a probability-based evaluation method for ground settlement of natural loess under seismic loadings by means of theoretical analysis methods of probability statistics and Monte Carlo simulation. For the application of this new probability-based evaluation method, here, we provide one practical case on a typical loess field. The relevant Chi-square test show that frequency features of the four critical parameters influencing dynamic residual strain of natural loess determined by the above-mentioned theoretical model could be described by normal distribution. In order to minimize the uncertainties (scattering and randomness) of physico-mechanical property of the soil, furthermore, Monte Carlo simulation technique is adopted to extend the laboratory data into huge numbers. Then the corresponding huge numbers of dynamic residual strain of natural loess in the case field calculated by the evaluation method could be used to analyze the probability features of dynamic settlement behaviors of the loess ground. According to occurrence probabilities of different magnitude-grades of dynamic settlement, we could acquire the detailed behaviors of dynamic residual strain of natural loess in the target field under seismic loadings. The probability distribution reveals that the quantitative evaluation method reported here can obviously decrease the influence of parameter uncertainty associated with the soil. Meanwhile, those probability characteristics of dynamic settlement in the example field accord with the existing basic-behavior knowledge of dynamic residual strain of natural loess under seismic loadings. These results mean that the probability method could provide a better/reasonable reference not only to understand dynamic settlement behaviors of natural loess ground under seismic loadings, but also to select the proper treatment method for the potentially dangerous ground.

Size effect of tunnel deformation has been studied in this paper based on the deformation mechanism of different structures of rock mass. Size effect on deformation of rock mass surrounding tunnels closely relates to deformation mechanism of rock mass. Deformation mechanism of surrounding rock, which is intricate and diverse because of structural planes in the rock, includes material deformation and structural deformation. Size effect of deformation also reflects in the material deformation and structural deformation. Material deformation of surrounding rock varies directly as cross-section dimension of tunnels. Size effect of structural deformation is much more intricate. On the one hand, cross-section dimension of tunnels affects structure type of surrounding rock which closely relates to deformation mechanism; while amount of deformation provoked by different deformation mechanisms varies a great deal. On the other hand, in a same surrounding rock, amount of deformation provoked by an identical deformation mechanism also varies with size of tunnels. In the massive surrounding rock, for example, immobile rock surrounding tunnels will convert into movable rock in company with increase of cross section dimension of tunnels, and sliding or rolling deformation occurs sequentially. In the layered surrounding rock, bending deformation of rock stratification varies directly as the square of cross-section dimension of tunnels.

For sedimentary soil which completes the consolidation due to the gravity of the overburden, the value of its modulus is directly related to the value of pre-consolidation pressure. The main factors of constitutive relation for geotechnical material are first analyzed, considering its changes with depth and volumetric strain. Secondly, pile foundation stability problem’s solving format is established for the finite element calculation, considering horizontal load and downstream scouring. Finally, based on the analytical results of the downstream erosion and contact force of different-plane-position pile due to asymmetric horizontal loads, the stress concentration and flexion instability and overall stability are analyzed for group pile foundation in large and complex engineering, considering synergism in the system of piles and soil and pile cap, so as to provide a method for quantitative calculation.

Based on the non-Darcian flow in soft soil and nonlinearity during the process of consolidation, the governing equation of one-dimensional nonlinear consolidation was derived according to continuity condition of one-dimensional consolidation. Solutions for this question were obtained by adopting a semi-analytical method, and were verified by comparing with the results by finite difference method. Finally, the difference of consolidation behavior between non-Darcian flow and Darcy’s law and influence of distribution types of dead-weight stress on consolidation rate were emphatically analyzed. The results show that the rate of nonlinear consolidation will be slowed down when non-Darcian flow is considered; and the larger the exponent and threshold hydraulic gradient are, the slower the rate of nonlinear consolidation is. Furthermore, this retardation of nonlinear consolidation with non-Darcian flow will be more noticeable with an increase of thickness of soil layer and a decrease of external loading. The rate of nonlinear consolidation with linear distribution of dead-weight stress is faster than that with uniform distribution; and the difference between them will diminish with increasing the external loading and decreasing the thickness of a soil layer.

In unsaturated soils with high saturation, gas phase is disconnected, and the occluded gas pressure may change and affect the soil behavior. The properties of unsaturated soils with high saturation are first discussed; and then a constitutive model is developed within an existing constitutive framework of unsaturated soils by using the principle of generalized effective stress. This model takes into account the effect of gas diffusion, with a hardening law accounting for the effect of occluded gas pressure change. To validate the new model, the modeling results are compared with the experimental results available in the literature and the simulated results of existing models. It is shown that this model performs better than existing models, especially for the unsaturated soils at high saturation.

To improve the accuracy of microseismic source location, the application scope, the advantages and disadvantages of traditional and improvement algorithms in locating solving were comparatively analyzed based on the simulation experiment. The influence of unknown variables, sensors’ density and P wave velocity on the location algorithms were studied respectively. Based on the advantages of the simplex and the global convergence characteristics of the simulated annealing, it was proposed that taking the steady simulated annealing-simplex algorithm located the microseism. The study shows that this algorithm is a simple estimation in advance by steady arithmetic without directly searching for the seismogenic moment. The searching steps can be greatly reduced and the location accuracy and convergence velocity can be improved. So the microseismic focus can be effectively located with less sensors without being affected by the initial velocity. Taking the artificial blasting location test experiment of a mine as an example, the errors of both the location accuracy and objective function for the simulated annealing-simplex, the steady simulated annealing-simplex and the other algorithms were specially analyzed. It is widely believed that applying the nonlinear least square algorithm can get reliable results when there are more sensors and better information of P wave. The errors of three-dimensional location and objective function of the other location algorithms are basically the same. But the objective function error of the steady simulated annealing-simplex algorithm is the minimum; and the stability is the best. So this algorithm with higher reliability and stability has obvious advantages; and it can be widely used for the microseismic location in mines.

Considering the non-homogeneity and anisotropy of soil mass, according to the shape of rapture surface of anchor cable and nonlinear failure criterion, a formula of ultimate pullout force of anchor cable, considering the non-homogeneity, anisotropy, nonlinear failure characteristics and many other factors, is deduced based on limit equilibrium principle. Theoretical calculations are conducted to analyze the influences of non-homogeneity parameters, anisotropy parameters and nonlinear parameters on ultimate pullout forces of anchor cables. The results reveal that, with the increase of non-homogeneity parameters, the ultimate bearing capacity of anchor cable increases; but with the increase of anisotropy parameters and nonlinear parameters, the bearing capacity of anchor cable decreases; the rupture width expands with the increase of non-homogeneity parameters and anisotropy parameters, which provides a certain reference for the design of anchorage body.

In order to study the influence of zinc ions on the compressibility of remolded bentonite, a series of tests including one-dimensional compression, free swelling ratio, physicochemical property, and scanning electron microscopy were performed on artificially prepared bentonite of high water content with different concentrations of zinc ions. Test results indicate that, when the vertical load is lower than a critical value of 200 kPa, the void ratio and compression index of the contaminated bentonite will decrease with the increasing concentration of zinc ions under a constant vertical load. However, if the concentration of zinc ions is greater than a threshold value of 0.02 mol/L, there will be little change in void ratio of bentonite; and the compression index will just decrease a little. As the vertical load is greater than 200 kPa, basically the void ratio of bentonite will not be influenced by the physicochemical property of the pore fluid but only be determined by vertical load. In addition, experimental analysis shows that as the concentration of the zinc ions increases, pH value of the pore fluid and specific surface area will be decreased; but the particle diameter will be increased. Furthermore, the dispersed structure of bentonite will be gradually destroyed; clay mineral flakes will form big aggregates; and large inter-aggregate voids will come into being due to the zinc contamination.

The blasting seismic wave is simplified reasonably. Based on wave function expansion method, the dynamic stress concentration factor equation of tunnel surrounding rock and lining under the blasting seismic wave is deduced in infinite rock. Combining with a typical case, the influences of the main frequency of the blasting seismic wave, geometric parameters and the physico-mechanical indices of tunnel surrounding rock and lining on dynamic stress concentration factor in the different positions of tunnel are analyzed. The analytical results show that the trend of dynamic stress concentration factor of different direction stresses with the main frequency of the blasting seismic wave are different at different positions. The dynamic stress concentration factor caused by the blasting seismic wave with low main frequency of the blasting seismic wave is larger, which is unfavorable for blasting vibration resistance. The influence trend of tunnel geometric parameters on the dynamic stress concentration factor of tangential stress of tunnel surrounding rock and lining is different. The elastic modulus of tunnel lining has a greater effect on dynamic stress concentration factor than the Poisson’s ratio. The tunnel surrounding rock with larger Poisson’s ratio have the effect of blasting vibration resistance, but the effect is limited.

In order to explore influence of engineering blasting on rockbolt and shotcrete, cement mortar and glass fiber reinforced plastics are used to simulate the rock and rockbolt respectively; and some 2.5 m×1.8 m×2.1 m rockmass models are built. By model test, construction process is simulated according to similarity. Vibration characteristics of rockbolt and shotcrete structures near the explosion source are studied under cut blasting load. Strain waves were obtained from the measured rockbolts at different setting condition. Test results show that: (1) For end-anchored rockbolts, vibration waveforms and deformation pattern are different between the anchoring segment of rockbolts’ middle and the free segment of its tail. And vibration amplitude of anchoring segment is relatively larger than free segment. (2) Without shotcrete and prestress, strain wave on free segment of bolt tail shows better law and lasts longer. (3) Vibration frequency and amplitude of rockbolt decay distinctly with the distance from the working face; but duration of rockbolt slightly increases with the distance. By time-frequency analysis of stains waves basing on wavelet transform, it is found that: (1) For vibration energy of rockbolts close to working face is large; but vibration energy distributes widely and duration is limited. (2) For the more distance rockbolts, although vibration energy is less, vibration energy is more concentrated and vibration lasts more time. The two different vibration energies cause different damage patterns for the rockbolt and shotcrete structure. Tests and practices show that blasting vibration can easily cause damage in shotcrete and failure to rockbolts near the explosion source. Steel fiber concrete has a better anti-dynamic performance and is helpful to shotcrete near explosion source when subjected to blasting. Adjusting the support process is an effective method to decrease blasting effect.

Structural characteristic is an important basic property of natural loess. The authors have developed an artificial preparation of structural loess, improved the deficiencies of the original true triaxial apparatus and carried out the true triaxial tests of artificial structural loess. The results show that the method of artificial structural loess is reasonably reliable. At the same time, the variation of failure strength and residual strength of structural loess under complex stress conditions is analyzed. When the confining pressure is less than the structural strength of the structural loess soil, the stress-strain curves is softening, and on the contrary hardening. Mohr-Coulomb strength criterion is better to describe the residual strength variation of structural loess and significantly worse to describe the peak breaking strength variation of structural loess.

A new fractal description method for three-dimensional roughness characteristics of rock joint is proposed and researched. Firstly, based on the scanning data of joint surface morphology, the joint surface is reproduced in the discrete form of triangular nets; and then the calculation method of 3D root mean square resistance angle is established. Secondly, fractal theory is applied to propose a new fractal description method to describe 3D roughness characteristics of rock joint on the basis of 3D root mean square resistance angle. Finally, the new method is used to characterize the roughness of natural basalt joint and tensile granite joint. Research results show that the new method can well reflect the 3D morphology of joint and it can also describe the anisotropy of roughness. Research results offer the foundation for further studying the shear strength and shear constitutive law of rock joints.

For heap leaching of uranium ore, the seepage of the leaching solution in the uranium ore heap has significant effect on the leaching behavior. Therefore, it is important to study the permeability characteristics of the uranium ore heap. In the present work, ten groups of samples with different particle size distribution fractal dimensions were prepared using the fragmented uranium ore for heap leaching taken from a uranium mine in South China; experiments were conducted to obtain the permeability and the flow state index of each sample using the self manufactured apparatus for liquid saturated seepage experiment; analyses were made for the effect of the particle size distribution fractal dimension on permeability of the samples; and support vector machine (SVM) was used to establish the SVM models for predicting the permeability and the flow state index, respectively. The results show that, under laboratory conditions, the liquid saturated seepage in the uranium ore heap for heap leaching follows non-Darcy exponential law with flow state index ranging from 1.1 to 1.5; the permeability decreases gradually with the increase of the particle size distribution fractal dimension; and the SVM models for predicting the permeability and the flow state index can give the predicted results with relative errors of less than 8% and 7%, respectively; so as to satisfy the requirements for engineering application.

Using large-scale shearing device, isotropic consolidated-drained triaxial tests under different confining pressures are performed for three relative densities overburden material of Shuangjiangkou earth dam. The dilatancy of coarse-grained materials is investigated; the relationship among dilatancy, relative density and confining pressure are discussed; and applicability of dilatancy equation of modified Cam-clay model and Rowe dilatancy equation for coarse-grained soils are tested. It is found that the confining pressure and initial density influence dilatancy evidently; that is, under low confining pressure coarse-grained soils are characterized by volumetric dilatancy; and with the increasing of confining pressure they exhibit volumetric compression. The increasing of density results in the increase of dilatancy. Phase transformation stress ratio is an important factor affecting dilatancy, which exhibit increasing with the increase of density and linear decrease with the increase of confining pressure. According to the test data, a relationship formula among dilatancy ratio and relative density and confining pressure is obtained. Dilatancy equation of modified Cam-clay model cannot reflect the dilatancy; and Rowe dilatancy equation can reflect the dilatancy of the coarse-grained materials; but when confining pressure is higher it underestimate the compression during compression stage and overestimate the dilatancy during shearing stage.

In order to study the soil fracturing grouting pressure under asymmetric loads, based on the cavity expansion theory and unified strength theory and considering the influence of the asymmetric loads, the analytical solutions of stress fields and displacement fields in the plastic regions surrounding slurry bubble, as well as the radius of plastic region and limit expansion pressure are deduced. The solutions are validated through the engineering example. The results show that grouting pressure considering the symmetrical load is larger than that considering the asymmetric loads, which indicates that the radius of plastic region are underestimated in the analysis of grouting under the symmetrical load. For the cylindrical cavity expansion and the spherical cavity expansion, where K0 is less than 1, the starting fracturing pressure increases with the increment of K0; while the radius of plastic region significantly decreases with the increment of K0. Where K0 is greater than 1, the starting fracturing pressure decreases with the increment of K0, but the change of radius of plastic region is limited. Therefore it is important to estimate the initial stress conditions of the soil previously before the critical fracturing pressure. The results will improve theoretical basis for design and construction of fracturing grouting.

In the geological disposal of high-level radioactive waste (HLW), the performance of the cushioning material will improve when the bentonite is mixed with a certain proportion of quartz sand. A research on soil-water characteristic curves of compacted mixture of bentonite-sand for higher suctions is carried out through moisture balance method; and influences of temperature, sanding rate and dry density on water retention capacity of the bentonite-sand mixture are analyzed. The results show that the water retention capacity of the mixture decreases obviously with temperature increase. Within the controlled suction range, the influence of sand mixing ratio on the soil-water characteristic curve is evident when suction is low; Within the controlled suction range, the influence of sanding rate on the soil-water characteristic curve is evident when suction is low, and at high suction the effects gradually decreased. On the other hand, dry density almost has no effect on the soil-water characteristic curve. Empirical formulas for SWCCs of bentonite-sand mixed buffer/backfill material under conditions of different temperatures and sanding mixing ratio are proposed by fitting the experimental data; and SWCCs of this material with different temperatures can be thus predicted.

This paper pays main attention on the failure performance and excavation induced interaction of prestressed thru-anchor cable by a case study. In-situ investigation had shown that there were several failure formats of prestressed thru-cable in the Jinping II underground powerhouse. The observed proof also indicated that this kind of break of thru-cables belongs to tensile failure due to unloading deformation and time-dependent rheology of underground caverns. Thus, a new cell model is purposed to describe the interactive relation between thru-anchor cables and reinforced rock. This cable-rock cell model has special structure, i.e. an elasto-brittle cell is employed to representing the mechanical behavior of thru-anchor cables, and a viscoelastic Kelvin-Hooke cell is employed to representing the mechanical response of host rock. Based on this coupled model, several mechanical parameters which influence the cable’s load are discussed, including elastic modulus of cable, elastic modulus of rock, viscoelastic modulus of rock and coefficient of rock viscosity, etc. This discussion can help us to recognize the ambivalent relationship between thru-anchor cable and reinforced surrounding rock.

Despite increasing interests in various aspects of expansive soil behavior such as the structure of the expansive soil, properties of expansion and shrink, treatment measures, little is known about the nature and magnitude of secondary compression of the distinct sediment. However, long-term stabilization of subgrade and underground structures as tunnel excavation promotes the study of secondary compressibility of expansive clay. The secondary compression behavior of a typical expansive soil in Nanning was investigated. A series of long-term compressibility tests were conducted. The influence of compression pressure and water content on compression index Cc and coefficient of secondary compression Ca is discussed respectively as well as the relation between Cc and Ca. Moreover, the influence of precompression or lime-added dispose on secondary compressibility is studied to seek the best measure to reduce secondary compressibility. Some useful conclusions are drawn. The relation between Cc and Ca is linear. The secondary compressibility of Nanning expansive clay appears little compared with other clays. The secondary compression can be minished effectively by precompression or lime-added dispose. Specially, the secondary compressibility of lime-added expansive soil becomes less if precompressed simultaneously.

Rock mass surrounding the excavation also under the complex radial unloading and ring direction loading stress path due to the excavation, for which results in difference from that of rock mass strength，deformation property and failure mechanism. Aiming to the high in-situ stress characteristics of Jinping II hydropower station, four different stress paths are chosen as test schemes corresponding as the uniaxial compressive test, triaxial compressive test, unloading triaxial test and unloading confining – loading axial pressure full test under high stress conditions are carried out on the marble specimens from the drainage tunnel. The complete stress-strain curve，deformation properties，failure characteristics and limited energy storage are obtained under respective stress path. Some instructive conclusions are drawn from tests as follows: (1) The failure axial strain is generally small. Jinping marble is hard and brittle which more apparent under unloading conditions. (2) The axial strain, circumferential strain and volumetric strain value unloading confining – loading axial pressure full tests are generally higher in the unloading tests, peak strength conversely. (3) The deformation modulus is large and the peak strength is lower with larger unloading rate, the deformation modulus is lower and the peak strength is large with larger loading rate, the deformation modulus is lower and the peak strength is large with larger initial confining pressure. (4) The principally failure model is tension without confining pressure; shear failure and locally tensile failure with lower confining pressure; while shear failure shape is X or Y with higher confining pressure. (5) The rock specimens have the limited value of energy storage, which can be effected by various factors. Limited energy storage is large with high confining pressure and is lower with higher unloading stress rate. The results can offer valuable references in explaining the mechanism of rockbutst and solving underground rock engineering problems.

Mine backfill is an ideal approach to protect land resources, ecological environment, to achieve the mine mode of no-waste-discharged and eliminate the potential hazards. The unclassified tailings from a mine was used as experimental raw material, then the micro-mechanism of consolidating backfill body of super-fineness unclassified tailings and cementitious materials under different conditions by means of XRD and SEM were obtained after analyzing the physical and chemical properties, the chemical components and particle size composition of the unclassified tailings. The cementing agent type #1 and type #2 were taken to replace the regular cement and the uniaxial compressive strength (UCS) of backfill specimens were gained. The experimental results showed that the influence degrees of different cementing agents on the behaviors of UCS were different, when the external experimental conditions were same; and it almost obeyed the law: cementing agent type #1＞cementing agent type #2＞cement. The study also demonstrated that the performance of the cementing agent type #1 were better than the others; and its price was cheaper; therefore, it can reduce the cost of mine backfill. The increasing curves of UCS of backfill samples at different curing times were obtained and it showed that the increasing laws of UCS at different curing conditions were unanimous, in accordance with the exponential function growth curve, although the cementing agents type were different. The cement-sand ratio, slurry concentration and curing time exhibit a positive correlation with the UCS growth curve.

In deep tectonic stress area, shoulder bolt broken and failure phenomenon is prominent in coal roadway; and it’s easy to induce roof collapse accident. It is an immediate requirement to solve support failure problem. In view of “shoulder bolt breakage” in deep coal roadway under the action of tectonic stress, a mechanical analysis model of shoulder bolt is established to analyze the action of slippage of coal ribs along roof on bolts; and stress and deformation characteristics of shoulder bolt are gotten. Shoulder bolt breaking mechanism is discovered. Under slippage shear force produced by tectonic stress, bending deformation of bolt body happens; and the shear force of shoulder bolt is biggest in interface between coal seam and roof, where the bolt body is cut off easily. Focused on the problem of shoulder bolt breakage, “controlling and yielding coupling support” control technology is put forward. The research results have been successfully applied to engineering practice.

In the oriented perforation fracturing, current predicting initiation pressure just considers the naked borehole and neglects the effect of casing, which will lead to the greater errors in the engineering applications. Considering the effect of casing, wellbore stress models of directional well are obtained. According to tensile failure criteria, fracturing initiation pressure and angle models of oriented perforation well are presented. A software is developed, which includes the initiation prediction and perforation optimization of oriented perforation well. The software can predict the initiation pressure and initiation angle of oriented perforation fracturing considering the effect of casing, and optimize the perforation angle and length. Comparing to the actual initiation pressures, the maximum error of the prediction initiation pressures in the software is 4.33% and the predicting initiation angles are consistent with actual initiation angles, so as to prove the accuracy of fracturing initiation pressure and angle models. The models and software can offer instructions to the field fracturing and perforation optimization.

Soil arching is very important for analyzing the stress state of existing and widening embankment and differential settlement between piles (caps) and subsoil. In this paper, the behavior of soil arching is analyzed for a widening embankment which is supported by rigid piles with caps and reinforced by geogrid. Based on the test site of the widening expressway project, earth pressures on caps and subsoil at the bottom and at different depths to fill surface are investigated; and tensile strains of the geogrid are monitored too. Then stress concentration ratios and soil arching ratios are analyzed and compared with several current design methods, including the Guido method, the BS8006 method, the Kempfert method and the Low method. Results show that, a two-dimensional plane soil arching fill load distribution on caps and subsoil within a critical arch height which is deduced to be 2.0 m owing a ratio of 1.4 the pile clear spacing, and is consistent with BS8006. The Guido and BS8006 methods were too conservative on assessing tensile strain of geogrid; Except for the Guido method, all rest presented design methods underestimated the resistance from the compressible subsoil. So, further study and a better understanding of soil arching should be developed.

Pile-anchor retaining structure is widely used in foundation pit engineering and side slope engineering in many countries, especially in China and Japan. In contrast to strut, pile-anchor retaining structure has several typical features and advantages. It doesn’t occupy the internal space of the foundation pit and the project cost is much lower. With the technology of prestress, engineers can control the deformation of the retaining wall actively which is impossible in inner supporting structures. Accurate prediction of the lateral displacements of the retaining structure is very important in the design stage. An analytical evaluation model and several calculation assumptions of lateral displacements of pile-anchor retaining structure are set up according to measured data of several foundation pits from different cities in China. The deformation of the retaining wall under each external force is calculated. The expression of lateral displacement versus depth is solved by means of quasi-elastic summation; and the parameters are obtained from the stiffness equation of the anchors. The analytical evaluation of the lateral deformation curve is then completed. The simplified method is suitable for braced excavation with small displacement at the bottom of the retaining wall. The applicability of the proposed method is validated by practical engineering.

Analysis of earth surface displacement using GPS and deep focal mechanism show that present activity in the Shandong segment of Tan-Lu (Tancheng-Lujiang) fracture zone exhibit a clockwise compression-torsion characteristics in between the shallow earth crust and deep zone of the region after the 2008 Japan earthquake. Data was gathered from 25 in-situ stress sensors installed at varying intervals along the total depth of single 600 m borehole located inside a granite rich region at the northeast part of Shandong. Combined with in-situ stress data, core sampling of the structural features of shallow earth crust rock formations reveals that current horizontal principal stresses play a leading role in strike-slip fault activity. Moreover, measured maximum principle in-situ stress mechanics trend towards the east-west direction and reflects present compressive properties, with dextral slip activity, of the Shandong segment. Including pre-existing data of surface and subterranean experiments, this new data will allow us to open new research avenues for understanding the present active features of the Shandong segment of the Tan-Lu fracture belt.

The unconfined random field may lead to higher variability especially when the variability of dissolution foundation is high, and may lose the geological information and practice experience. So the Bayes constraint random field model is put forward. The constraint random field is built by introducing Bayes formula to modify the distribution characteristics of parameters of dissolution, to reflect the new geological and samples’ location information. Then the effect of the dissolution system in the dam foundation is studied through stochastic finite element method (SFEM). The results show that the space variability of dissolution can be considered more objectively by Bayes constraint random field model rather than the unconfined one; also, the variance of the structural responses can be reduced effectively. In the probability analysis process, the Monte Carlo response surface coupled method (MC-RSM) is recommended for the random simulation of complex engineering, which can reduce the simulation time relative to the direct Monte Carlo method which can only repeat the process of the same mechanical mechanism.

This paper aims at proposing a non-intrusive stochastic finite element method for reliability analysis of slope stability. A computer program for non-intrusive stochastic finite element method is developed. The non-intrusive stochastic analysis is achieved using the polynomial chaos expansion combined with SIGMA/W and SLOPE/W modules. The finite element method of sliding surface stress analysis is used to calculate the factor of safety of slope. The closed-form expressions of the first four statistical moments of factor of safety (mean, standard deviation, skewness, and kurtosis) and Sobol indices are provided using the coefficients of polynomial chaos expansion. A global parametric sensitivity analysis based on Sobol indices is carried out to identify input uncertain parameters that have the most contribution in the variability of factor of safety. An example of reliability analysis of homogeneous soil slope is presented to demonstrate the validity and capability of the proposed method. Also, a parametric study is performed to investigate the effect of variability and correlation of input parameters on the statistical moments of factor of safety and sensitivities of input random variables. The results indicate that the proposed non-intrusive stochastic finite element method can effectively evaluate slope reliability with a consideration of slope deformation. It is more efficient than the traditional Monte Carlo simulation method(MCS), which provides an effective way for reliability problem of complex slopes. The variability in shear strength parameters has a significant influence on the first four statistical moments, whereas the variability in unit weight almost has no influence on them. The mean value of factor of safety is slightly influenced by the negative correlation between shear strength parameters, whereas such negative correlation greatly influences the standard deviation, skewness, and kurtosis of factor of safety. The distribution of factor of safety is changed from approximate normal distribution to strong non-normal distribution as the negative correlation becomes stronger.

A block-discrete-spring model based on deformable discrete element method is established; this model would be applied to simulate the rock failure process. In this model, the theoretical basis is continuum mechanics and block element is divided into discrete spring system with specific physical meaning. The stiffness of the spring can be obtained from the energy functional. In this way, element deformation and stress would be calculated by spring stiffness directly and efficiently. In the case of rock mass slope under gravity, the elastic result achieved with this model is the same as that of traditional finite element method. (FEM). On this basis, Mohr-Coulomb criterion with a tensile cutoff which used to judge the failure state and broken direction is proposed and implemented into the block-discrete-spring model. After the internal failure face established, the element will be divided into two elements by means of cutting block; and double judgement including element boundary and element interior is adopted to realize the crack initiation and propagation, which could mitigate the effect of initial mesh. Finally, the rationality of the failure result calculated by block-discrete-spring model is approved by some cases including split test with flattened disk, uniaxial compression and three point bending. The results show that this method can well simulate the crack initiation and propagation under tensile, compressive and shear conditions, by which the rock failure process can be realized from continuum to discontinuum.

Research on mechanism of sand production has been the key topic to improve the oil production and reduce the oil extraction cost; however, current investigations are mainly based on rock macromechanical theory and methods; and these achievements cannot comprehensively reflect initiation and propagation of the sand production. Considering physical property of the sand reservoir and real characteristics of the perforation test, 3-Dimensional numerical model based on PFC3D under cylindrical coordinate system from a geomechanics prospective was established to research the fluid-solid coupling effect and the micromechanism of sand production. The comparison with theoretical results shows the feasibility of the forward 3-Dimensional micro numerical model; and the model could simulate the fluid flow and fluid-solid coupling effect in the process of sand production. Based on the above numerical model, simultaneously considering pressure gradient force and drag force, research on initiation and propagation of the sand production was carried out based on PFC3D considering different fluid flowing conditions. The figures about simulated stress distribution indicate that fluid flow affecting the sand mechanical characteristics should not be neglected during oil extracting; and under the same conditions, the greater the flow rate is, the more the bonds between the particles are; and the larger the sandstone plastic zone is, and also the greater the probability of the sandstone broke and sand production is. In addition, there were research achievements about the initiation and propagation of the broken parallel bond and magnitude of the particles rotation considering different cases. The figures show that under the same conditions, the larger the flow rate is, the greater the range of the plastic zone and the particle rotation was to result in more particles losing restraints; and also the more volume of the sand production. The above numerical results explained the same developing trend comparing the two kinds of figures about micro characteristics of the particles between the figures about macro stress distribution, and the results indicated that the forward micro numerical model could simulate the sanding mechanism and also provide a new thought to predict the sand volume and control the sand production.

The perilous rock is one of the typical disasters in the Three Gorges reservoir region; it can be classified as two types in views of perilous mode, i.e. falling perilous rock and toppling perilous rock. Crack propagation of control joint of perilous rock under loads is the key process in failure of perilous rock. In this paper taking the control joint in perilous rock as one crevice in a sample, to solve the moving discontinuities of joint propagation by extended element method and explore the crack propagation behavior of control joint of perilous rock under loads. The Taibaiyan cliff at Wanzhou is a representative case of massive perilous rocks in the area. Using this cliff as an example, the effect of joint location, obliquity and rock tensile strength on the failure mode and magnitude of safety factor were investigated. The results demonstrate that with the decreases of rock tensile strength, the perilous rock stability decreases; and with the decreases of control joint obliquity, the perilous rock stability increases. The destructive mechanism of two unstable modes for perilous rock is tension-shear. As opposed to toppling perilous rock, under the same conditions, the stability of falling perilous rock is even worse.

Green’s function method and "conformal mapping" technology are used to analyze interaction of an elliptical elastic inclusion and a crack at arbitrary position under incident SH-waves from above. The fundamental solution to the displacement field for elastic half space containing an elliptical inclusion while bearing a time harmonic out-plane line source load at any point was firstly constructed, namely the suitable Green’s function. Combined with “crack-division” technology, a beeline crack was then created to derive the displacement field and stress field of elastic half-space containing an elliptical elastic inclusion and a crack. Lastly, numerous numerical examples are given to discuss distribution regularities of dynamic stress concentration factor (DSCF) around the elliptical inclusion, the horizontal surface displacement and dynamic stress intensity factor (DSIF) at crack tip under different parameters, and the results demonstrate that variation of different parameters can bring certain effect on them.

Aiming at the continuous-discontinuous failure process of rock and soil materials in slope engineering, a novel deformable block discrete element method which combined spring element method(SEM) and discrete element method(DEM) together is presented. Compared with the accustomed element in traditional finite element method(FEM), the element in SEM is described as a spring system that contained some orthogonal generalized springs. This generalized springs are defined in 3D space, which means that each spring can has two or three spring stiffness. How to determine the generalized spring stiffness for continuous material is the difficult and most important in SEM. With the triangle element as an example, the basic theory of SEM is introduced in detail. Assuming the relationship between the generalized spring deformation and the element strain, the generalized spring stiffness can be obtained directly by comparing the elastic strain energy of the element and the elastic potential energy of the spring system. The Poisson and shear stiffness coefficients were defined as system parameters to describe the relationship between different generalized springs. The SEM can consider the Poisson effect accurately for any Poisson’s ratio material; and the result using SEM are the same with using traditional FEM. This method does not need to know the expression of the element-stiffness-matrix. It can be used in 4-node element; and the stiffness expressions of springs are given clearly. With the SEM used to compute the block deformation and the contact-spring used to calculate the interaction between blocks, the combined SEM/DEM program can be used to simulate the failure process of rock and soil material from continuous to discontinuous. The SEM and DEM are combined in the motion equation of each node in each element. The contact-spring in DEM satisfied specific strength criterion. When the contact-spring force exceeded its limit, the material became discontinuous from continuous. The combined SEM/DEM program is implemented easily in the continuum-based discrete element method(CDEM) program. The simulation of a homogeneous soil slope under gravity shows that the SEM is performed as good as FEM when using line elastic constitutive and reasonable when using Mohr-Coulomb strength criterion. The simulation of a bedrock and overburden layer slope shows that the combined program is suitable to simulate the slope failure process.

Based on the Bayesian theory, a probabilistic back analysis method using time-varying measurement data is established. The back calculated posterior distributions are determined using the Markov chain Monte Carlo method (MCMC) with the differential evolution adaptive Metropolis algorithm. In this paper, a case study of a well instrumented natural terrain is presented. The deterministic model for pore-water pressure evaluation is an analytical model. Field measurements of pore-water pressure are used to calibrate the unsaturated parameters of the deterministic model. Statistical properties of the posterior distributions are presented and discussed. It is found that the posterior standard deviations of the six parameters are all greatly reduced. The predicted and measured pore-water pressures during the calibration period and the validation period are compared. The coverage of the 95% total uncertainty bounds is estimated to be 0.964 for the calibration period, during which the field measured pore pressures are used to back analyze the input parameters. For periods 2 to 4 of the validation period, the coverage by the 95% total uncertainty bounds are 0.52, 0.79 and 0.79, respectively. These results indicate an overall good performance by the calibrated model.

The thermal parameters are vital to frozen soil temperature field prediction and stability analysis in cold regions engineering. According to the characteristics of the permafrost temperature field, the paper established permafrost one-dimensional phase change parameters estimation model. The model used nonlinear finite element method to compute the soil temperature field and based on a very fast simulated annealing (VFSA) algorithm to optimize the thermal parameters. VFSA is an artificial intelligence algorithm which is of high search efficiency, easy to realize and does not require derivative information of objective function. Besides, in order to overcome the difficulty of optimization of too many parameters, thermal parameters are grouped and optimized step by step considering the condition of parameters sensitivity and soil layers. As an example, the above approach is applied to a monitoring section of the Qinghai-Tibet Highway in permafrost regions to get frozen soil thermal parameters. Then, these parameters of the inversion results are used to predict the frozen soil temperature field. The analytical results of posterior variance test show that the predicted soil temperature is well in line with actual temperature field in shallow and deep layers, and not bad near permafrost table zone. It can demonstrate that the back analysis results are reliable and good accuracy. The method can be used in practical engineering.

Studying the dynamic process of the occurrence and development of ground surface subsidence disaster due to underground mining has important theoretical significance and engineering application value. Because of the complexity of the overlying strata and coal mining process, it is difficult to comprehensive study the strata movement and surface subsidence in the mining process. So，research the subsidence of surface observation spot is a starting point to study the dynamic surface subsidence in the coal mining process. It is discovered that the Weibull function can more accurately to fit and describe the subsidence curves of the observing spots in mining subsidence area through the study of subsidence time series of surface subsidence observing Points. It is discovered that the sinking processes of the subsidence observing Points in same subsidence area are independent in space and time through the study of the simulation of mining by the numerical analysis software FLAC3D. On this basic, the phenomenological model of the subsidence, curvature and slope curve of the section on subsidence area is established through combining the probability integral settlement curve model and the Weibull time sequence function of the surface subsidence of the observing points. Some mining area observation data proved this modeling and model is feasible.

Besides the interaction of the multiple stress superposition from piles shaft friction, pile bottom resistance and contact stress between low caps and soil, the clamping action makes the cap-pile-soil interaction more complicated in pile foundation with large pile diameter and small spacing. 3D finite difference program is employed to evaluate the pile-soil-cap interaction with the change of vertical load, while the pile spacing and pile diameter remain constant in the analysis procedure. Analysis is carried out to explain the interaction of cap-pile-soil from the following aspects such as the lateral friction of soil in each layer, load on the top of characteristic piles, load-settlement relationship, vertical displacement of soil between piles, etc. The results show that: the clamping action on the upper soil among piles will decrease, and the pile shaft friction in the upper part will increase when the load exceeds 117.8 MN which is slightly larger than Pu/2 (Pu means ultimate bearing capacity of piles group); the lower part of pile shaft friction shows a trend of decrease due to the influence of the multiple stress superposition, and the decrease trend in characteristic piles has different influence scope; the load, which makes settlement of piles group achieve 5% of pile diameter, can be regarded as the vertical ultimate bearing capacity of piles group, and it is reasonable; when the ratio of piles group’s settlement to pile diameter exceeds 1%, the proportion of the load carried by piles decreases because of the cap contribution.

A test system of double medium seepage characteristics which is composed of double medium test module, water cycle system control module and data collection module is developed. The test system solves the key issues of porous media and fissure medium simulation, boundary conditions simulation, the perfection of water sealing technique and water exchange information collection, etc., and it has the characteristics of that the fracture width can be adjusted, higher precision, higher automation and test data real-time automatic acquisition. The test system of double medium seepage characteristics is used to study the distribution of water pressure that based on the water exchange and the seepage field of double-medium model, as well as the hydraulic behavior of double medium model and percolation mechanism. Using the test system of double medium seepage characteristics carries on the double medium seepage characteristics test and making use of the methods of trend diagram intuitive analysis, range and variance analysis and F-inspection, we obtained that water exchange factor of pore and fracture double medium exert the effects on the water exchange of double medium model. The influence ability of water exchange factor of pore and fracture double medium which are in the order, from big to small, are fracture width, porous media permeability coefficient, pressure gradient and water temperature.