To study the behavior of soft clay under cyclic train loads, a series of non-destructive tests on remolding hollow cylinder samples is conducted using hollow cylindrical apparatus. Most of the tests are in the heart-shaped stress path and some are in the round stress path as assistant. The strain characteristics of non-coaxiality under the two kinds of stress path are compared with each other. The effects of vibration cycle times N on non-coaxiality and the influence of frequency f on the shape of curves between non-coaxial angle ? and major principal stress directional angle ?? are studied. The analysis of mechanism is carried out and the test results under the other dynamic stress level are compared with the former tests. In addition, a simplified model of relation between ? and ?? taking no account of f is established. The research shows that during any cycle of ?? , the relations between ? and ?? under the two stress paths have their own characteristics. And unit deviator strain increments caused by deviator stress increments (d? /ds) under the two stress paths at the same dynamic stress level are different from each other. However, during some section of ?? , the d?/ ds under the two stress paths are close to each other. The impacts of N on ? and d?/ds under the heart-shaped stress path are slight. d?/ds is much larger in the angle section [30°, 40°] of ?? than the other section during any vibration cycle time. The curves between ? and ?? fluctuate violently with the f increasing.

Not only hydrate amount but also occurrence habits of hydrate in sediments influence the mechanical characteristics of gas hydrate-bearing sediments (GHBS). In constitutive models proposed recently, however, the influence of occurrence habits is not considered. Based upon the influence mechanism of occurrence habits of hydrate on mechanical behaviors of GHBS, a novel concept, called effective saturation of hydrate, is proposed to address the influence of occurrence habit of hydrate. Referring to the statistical damage constitutive model for GHBS by previous researchers, a statistical damage constitutive model considering occurrence habits of hydrate is developed. In this model, the strengths of microelements for GHBS are assumed to obey the Weibull distribution, and the strength of microelement is calculated using the Drucker-Prager strength criterion. A modified empirical formula of elastic modulus is suggested to consider the effect of hydrate saturation and testing confining pressure. Meanwhile, the relationships between model parameters m and F0 , hydrate saturation sh and confining pressure?3 are analyzed; then the fitting expressions are furtherly proposed. Finally, it is demonstrated that this model can simulate well the stress-strain curves of GHBS, and has capacity of reflecting the stiffness, strength and softening characteristics of GHBS.

The wall-paintings of Mogao Grottoes have suffered from cracks initiated under the influence of external micro-vibration environment for a long time. Therefore, it is necessary to study the mechanism of crack initiation in the wall-paintings, which provides scientific basis and technical support for the wall-paintings protection and repair. Tensile strength is obtained by experiments of four-point bending on the plaster ground of the wall-paintings. Digital image correlation technique is used to measure the strain variation and distribution in real time. Besides, the crack initiation on the plaster ground is analyzed when tensile damage occurrs to obtain the strain limit of the wall-paintings. Moreover, the influences of initial flaw, loading method and fatigue cycle number on the bearing capacity and the strain limit of the specimen are studied. The results show that the initiation of cracks and even their development to some extent will not affect the bearing capacity of the grottoes wall structure. The initial flaw of the plaster ground can increase the risk of cracking around the flaw. Fibers such as hemp improve the plaster ground with better plasticity and durability, and reduce cracks within the fatigue limit. In order to avoid crack occurrence, maximum normal strain of the plaster ground should be strictly controlled less than 0.40%.

The lateral dynamic characteristics of a pipe pile in a viscoelastic soil layer are investigated. The soil is simulated using three-dimensional viscoelastic theory; and the pipe pile is modeled as an Euler-Bernoulli beam. The governing equations of the outer and inner soil are uncoupled without utilizing potential functions. The solutions are obtained by separate variable method. The lateral displacement of the pipe pile is derived based on the continuity conditions between the pipe pile and the soils. The lateral dynamic complex impedance of the pipe pile is determined. The proposed solution can be reduced to a solid pile solution. The proposed method is validated by comparing the calculated results with existing solutions. Parametric studies are conducted to study the influences of the moduli, densities of the outer and inner soil as well as the pile length on the complex impedance.

Undrained cyclic triaxial tests are conducted on Zhanjiang structured clay under different static deviatoric stresses. The internal connection among dynamic deformation, dynamic pore pressure, dynamic strength and structure characteristics are studied. It is shown that the sudden destruction of structured clay under dynamic loads exhibits a feature of brittle failure; and the higher the static deviatoric stress, the smaller the failure strain. The trend of critical dynamic stress with deviatoric stress first increases and then decreases, and the critical dynamic stress has a peak value as the deviator stress decreases. There exists a threshold for the influence of static deviatoric stress on the dynamic characteristics of structured clay. If the static deviatoric stress is below the threshold, the deformation of the clay is restrained as a result of the improvement of the critical dynamic stress and the dynamic strength by the compaction effect of the static deviatoric stress. With the increasing of static deviatoric stress, however, the critical dynamic stress and dynamic strength decrease due to the damage of soil structure. The dynamic pore pressure of structured soil is slower than that of general soil, thus, and it drops after soil fails. The initial shear stress can increase the dilatancy.

Undrained and drained monotonic as well as undrained cyclic torsional shear loading tests are carried out on saturated Nanjing sand at various relative densities in a hollow cylinder apparatus. The test results indicate that the phase transformation line appears to be independent of drainage conditions, but is lower when relative density is denser under monotonic torsional shear loading. In the cyclic torsional shear loading tests under undrained condition, as to the loose specimen, the excess pore pressure and the torsional strain increase rapidly when the stress path approaches the phase transformation line defined under monotonic torsional shear loading with identical initial conditions, which lead to specimen in instable state. Subsequently, initial liquefaction occurs. For the dense specimen, it shows cyclic mobility when the stress path approaches the phase transformation line defined under monotonic torsional shear loading with identical initial conditions. With the loading going on, the stress path presents a series of papilionaceous overlapped hysteresis loops with the border of failure line. At the moment, the excess pore pressure fluctuates around a nearly constant value and cumulative pore pressure no longer increases. The phase transformation line defined under cyclic loading appears to coincide with the phase transformation line defined under monotonic loading, which seems independent of the relative density.

For interlayer staggered zones revealed in Baihetan large-scale hydropower station, a preparation method of reconstituted specimens is explored to reflect in-situ stress of these zones with an alternative method of super particle processing. Meanwhile, the pre-consolidation pressure and consolidation time are controlled by the static loading. Based on unconsolidated and undrained triaxial tests on reconstituted specimens from the interlayer staggered zone under either different pre-consolidation pressures or different high confining pressures, in combination with tests of mineral composition analysis and scanning electron microscopy (SEM). The mechanical deformation characteristics of interlayer staggered zones under different pre-consolidation pressures are discussed in detail. Under different confining and pre-consolidation pressures, deviatoric stress-axial strain curves of interlayer staggered zones reconstituted specimens exhibit strain hardening, and the plastic failure shows as the waist-drum shape. Under the same pre-consolidation pressure conditions, the failure stress, deformation modulus and Poisson’s ratio increase with the increase of confining pressure, and the expansion effect is highly obvious. However, under the same confining pressure, the failure stress, deformation modulus and Poisson’s ratio gradually increase with the increase of pre-consolidation pressure, while the Poisson’s ratio decreases slightly. The cohesion decreases and the internal friction angle increases respectively, with consolidation pressure enhancing. The qualitative and quantitative microstructure analysis further reveal that the plastic deformation of the interlayer staggered zone, as rock materials containning fragments, mainly resulted from particle breakage and directional arrangement under high stress. Therefore, the pre-consolidation pressure is an important factor affecting the characteristics of the interlayer staggered zone.

Aquitard is an important part of the subsurface aquifer system. Hydraulic parameters of an aquitard, including the vertical hydraulic conductivity Kv and elastic specific storage Sske, are of great importance for the investigation of land subsidence and groundwater resources evaluation. An analytical solution for the flow in an overconsolidated aquitard is derived in dimensionless form under the condition of drawdown in adjacent aquifers fluctuating cyclically with time. The theoretical curve of cumulative deformation of the aquitard versus time is further derived in dimensionless form as well. Due to the low permeability of the aquitard, its deformation lags behind water level changes in adjacent aquifers. The relationship between the time delay in deformation and half cycle of aquifer drawdown is derived. Then a new method is proposed for estimating Kv and Sske. This method can be applied to an overconsolidated aquitard demonstrating elastic deformation. Before using the new method, the half cycle of cyclical aquifer drawdown and the time delay in aquitard deformation should be determined according to observed extensometer and hydrograph data. The new method is applied to obtain Kv and Sske of the second aquitard at the f10-7 extensometer site in Shanghai area. Field test results demonstrated that Kv and Sske are, respectively, 4.12×10-10 m/s and 1.07×10-4 m-1. The results are verified to be reliable.

Saturated sand in liquefied state exhibits the characteristics of a non-Newtonian fluid, while it is difficult to obtain a stable liquefied state using a conventional dynamic test. A sample mixing plastic sand and the sodium chloride solution of equal density is prepared to obtain a stable state of almost zero effective stress. According to the theory of low Reynolds number flows around a sphere, the test device for flow characteristics of saturated suspended plastic sand is developed based on the particle image velocimetry (PIV) technology. A half sphere on the inner wall of the transparent model box is embedded in the saturated suspended plastic sand, and it can move in a vertical direction. The movement of the particles around the half sphere which recorded by a PIV device indicates the flow characteristics of the plastic sand in a almost zero effective stress state. The apparent viscosity of the plastic sand is obtained by measuring the movement velocity and force applied on the half sphere. The test results show that the saturated suspended plastic sand is a non-Newtonian fluid, and it can be used as an equivalent material of liquefied sand. Same important concepts, including the zero-velocity bounding line, shearing zone, shearing angle and height of the shearing zone, are proposed based on the micro investigation on the pulling ball tests. The shearing angle of the shearing zone increase with the ball’s velocity increasing. The influencing zone in the direction of dragging ball can be described in the height of the shearing zone. The minimum distance between the ball center with the bounding wall of the model box should be larger than six times of the ball diameter. The hole below the moving ball is due to the high apparent viscosity of the saturated suspended plastic sand. The moving velocity of the ball or pipe in the dragging tests should be as low as that satisfying the theory of the low Reynolds number flows.

When the compacted bentonite is inundated in distilled water, the effective stress on montmorillonite particles is equal to the external load applied; in salt solution, the effective stress incorporates the osmotic stress due to the osmotic suction of pore water. In addition, the relationship between void ratio em and the effective stress p of montmorillonite in compacted bentonite is found to satisfy a fractal relationship, which can be used to calculate the swelling deformation. Base on the dispersion and fractal characteristics of bentonite particles in salt solution, the expression of osmotic stress is derived, and the formula for effective stress on bentonite particles is developed. The swelling deformations of GMZ01 and MX-80 bentonites are calculated by incorporating the fractal model into the effective stress. Comparison of the experimental results available in the literature and the estimated value shows a good consistence. It is shown that the swelling deformation of bentonite can be expressed by a unified curve of em-p in distilled water or salt solution with different concentrations, implying that the proposed effective stress represents the actual force condition. The fractal model offers a good approach to expressing the swelling characteristics in salt solution.

Coal and gas outburst is one of the most serious disasters in coal mining. In recent years, with the increasing of mining depth, the in-situ stress and gas pressure increase, and thus the coal and gas outbursts occur more and more frequently. At the same time, the in-situ stress in coal changes with mining activities; the “three zones” are formed, i.e, stress relaxation zone, stress concentration zone and original stress zone in the areas in front of the heading face and the working face, which brings more difficulties to the prevention and control of coal and gas outburst. Tianfu Sanhui No.1 mine is selected as an analysis example. The process of gas outburst is physically simulated according to the similarity theory, and the temporospatial evolution of gas pressure is discussed. It is shown that the development of outburst is a process of coal breakage in the cavity wall, which starts from the start part to the surrounding, with a relative intensity of 8.79%. Pulverized coals are thrown out intermittently and the gas pressure rise up and down in many times. The gas pressure close to the outburst mouth has a large change up to 69.2%, while it declines sharply with a short period at first then fall slowly to the atmospheric pressure far away from the outburst mouth. The isobaric surface distributes at the spherical center of outburst mouth during outburst. The gas desorption area expands outward with the shape of spherical shell and the expansion speed of spherical shell is about 130 mm/s, and the gas gradient nearby is greater.

The deviation of water flow from Darcy’s flow law and the influence of stress history on the settlement of soil have been recognized by many researchers, but the theory of consolidation with the considerations of non-Darcian flow and stress history was rarely reported. Based on Terzaghi’s consolidation theory and classical Hansbo’s flow model, a nonlinear model of consolidation is developed by considering different settlement characteristics of soil with different stress states and time-dependent load in practical engineering. The finite difference method is adopted to obtain numerical solutions for this model. Based on the reliability of numerical solutions, the influences of non-Darcy flow on consolidation behavior of over consolidated soil and the influences of stress history on over consolidated soil with non-Darcy flow are intensively analyzed, and similarities and differences of consolidation behaviors are compared. The results show that the consolidation rate of over consolidated soil with non-Darcian flow is slower than that with Darcy’s flow. In addition, the consolidation rate evidently decreases with an increase in the value of m or i1. Among different stress states of soil with non-Darcian flow, the consolidation rate of over consolidated soil is the fastest, and the final settlement of over consolidated soil under external load is the smallest. When non-Darcy flow in an over consolidated soil layer is considered, a large preconsolidation pressure and a small rebound- or recompression-index always result in a rapid consolidation rate and a small final settlement.

Uniaxial compression experiment is carried out on the cemented waste rock backfill of which the framework particles satisfy Talbol grading theory by MTS815 rock mechanics testing system and homemade device. The influences of Talbol index, initial porosity, type and content of cementitious material on the characteristics of strength and deformation of backfills are analyzed. The results show that the uniaxial compression strength, elastic modulus and deformation modulus of backfill increase first and then decrease with the increase of Talbol index. By adopting the quadratic polynomial to get the relations between the uniaxial compression strength of backfill and the framework grain Talbol index, it is concluded that when the Talbol index n is 0.45, the optimization of the strength and deformation characteristics can be achieved. Uniaxial compressive strength of backfill generally declines as the initial porosity increases and also can be affected by the pore distribution. When the uniformity of pore distribution is poor, it will cause the experimental results some differences. The strength of backfill, which meets the Talbol distribution, will increase as the glued performance of cementitious material improves. Among those materials, the uniaxial compression strength of backfill bonded with cement can be over 6 times higher than that of the specimen bonded with clay. In addition, the strength of backfill can be increased by the content of backfill enhanced. And in this way, the pore compaction stage in its stress-strain curve can be shortened.

The pre-bored grouting planted nodular pile is a type of composite pile foundations which consist of a precast pile and the cemented soil surrounding the pile. A simplified approach to calculating the settlement of a single pre-bored grouting planted nodular (PGPN) pile in homogeneous soil is proposed based on the ideal elastoplastic model; and the composite modulus of the PGPN pile is adopted in the calculation process. In addition, the varying modulus along the pile shaft and the function of the enlarged pile base are also considered in the calculation process. The settlement calculation approach of the PGPN pile in layered soils is then proposed based on the calculation approach in homogeneous soil. The proposed calculation approach is validated by comparing the calculated load-displacement curves of the test piles to the measured load-displacement curves. The skin friction of the PGPN pile is close to the skin friction of the precast pile foundation, demonstrating that the frictional capacity of the cemented soil-soil interface of PGPN pile is better than the frictional capacity of the pile-soil interface of the bored pile.

The failure process of granite plate with a hole at its center is examed under uniaxil compression using three-dimensional digital image correlation (3D-DIC) technique. The obtained evolutions of displacement field and strain field not only reflect the basic law of internal crack initiation and propagation but also reproduce the compression (parallel to the loading direction), stripping (vertical to the loading direction), expansion and spalling (vertical to the specimen surface) of the observation surface. The main findings are: 3D-DIC technique demonstrates its unique advantage in geotechnical experiments. The evolution of strain field during rock destruction is able to reflect the basic law of crack initiation and propagation which in turn can be observed by analyzing full strain contours. The evolution of crack is characterized with nonlinearity. The X-shaped local failure bands, forming slightly before rock destruction, eventually evolve into a macro-destruction zone, whose location is collectivelly controlled by the direction of load, the structure and interior heterogeneity of rock. It is effective to study the mechanism of rock deformation by using 3D-DIC technique, which can provide an important reference for the research on the macroscopic and mesoscpic.

The aim of this paper is to improve the control theory for the rheological behavior of the surrounding rock around roadway. Based on the theory of viscoelasticity and nonlinear optimization principle, a time-dependent viscoelastic model of coupling action between the surrounding rock mass and the anchorage body is developed considering the space effect of tunnel face advancement; and then an optimization model of roadway support is established. The influences of the support time, the thickness of anchor, the original rock stress and the road radius on the deformation of surrounding rock mass are analyzed; and then the optimal design parameters of the roadway support are discussed in detail by a case study. The results show that the support time, the thickness of anchorage body, the original rock stress and the road radius have certain impacts on the stability of tunnel. With the increases of the roadway support time, the original rock stress and the road radius, and the decrease of the thickness of the anchor body, the displacement increases. The optimal design parameters of the roadway support are obtained; when the force acted on the support body reaches a critical state, the thickness of anchorage body decreases with the support time elapsing, and when the thickness of anchorage body is smaller, they show an approximately linear relationship with time.

Traditional plastic dilatancy models are based on coaxial plastic flow rule when describing relations between the stress ratio and plastic strain increment, in which stress-dilatancy behavior of soil only depends on stress ratio. A large number of test results show that the stress and strain are non-coaxial during plastic flow under complex stress conditions involving principal stress rotation; so the non-coaxiality cannot be ignored when analyzing stress-dilatancy behavior of soil. In order to investigate the effects of non-coaxiality on the stress-dilatancy behavior of sand under complex stress conditions involving principal stress axes rotation, a series of fixed principal stress axes shear tests and pure principal stress rotation tests and combined loading tests are conducted on the saturated sand using a hollow cylinder apparatus. The test results indicate that the stress-strain non-coaxiality would result in the deviation between the stress-dilatancy curves and Rowe-line under different stress paths, which can be modified through the Gutiereez’s modified dilatancy equation by introducing a non-coaxiality factor. In this way, Rowe’s stress-dilatancy equation can be made more applicable to loadings involving principal axes stress rotation.

To explore the effects of rock block proportion (RBP) and the shape on the mechanical properties of cemented soil-rock mixture (CSRM) that widely exists in nature, a series of large scale triaxial tests is conducted in laboratory. Firstly, specimens of soil-rock mixture mixed with cement and without cement are compared to demonstrate that soil-rock mixture is necessary to be further divided into CSRM and uncemented soil-rock mixture. Then, contrast tests are designed and performed on CSRM specimens with different RBPs and rock block shapes. Finally, the effects of RBP and shape on the mechanical properties of CSRM are analyzed. The results indicate that CSRM specimens with 3% cement exhibit evident strain softening band and localized shear band, whose strength and modulus are greatly increased compared with those of specimen without cement. Under given conditions, peak strength and brittleness index both decrease with increasing RBP. With 40% RBP, the peak strength of CSRM specimen with gravel blocks is slightly lower than that of CSRM specimen with pebble blocks; while the residual strength is slightly greater. With 70% RBP, no matter the peak strength or the residual strength of CSRM specimen with gravel blocks is greater than those of CSRM specimen with pebble blocks, especially under higher confining pressure.

To investigate the influence of soil particle size on geogrid-coarse soil interface cyclic and post-cyclic shear strength behavior, a series of large scale direct shear tests, cyclic shear tests and post-cyclic direct shear tests is conducted through a large-scale direct shear device. The influence of cyclic shear history on interface shear behavior is studied according to the comparison and analysis of the results obtained from direct shear tests and post-cyclic direct shear tests. The results show that, in direct shear tests, the interface apparent cohesion and friction angle both increase with soil particle size increase. In cyclic shear tests, the shear strength tends to harden under different particle sizes; for the same amplitude of cyclic shear displacement, the smaller the particle size is, the faster the hardening rate of interface is. After subjected to cyclic shear, the ratio between residual shear stress and peak shear stress of interface decreases; and the peak apparent shear stress increases insignificantly.

Currently, it is is difficult to obtain the expensive rate of expansive soil simplely and rapidly. Generally, the expensive rate can only be obtained through indoor test. It is shown that the internal structure will be changed with water swelling by previous experiments about the electrical characteristics of expansive soil in laboratory. The change of internal structure can lead to the change of resistivity. Resistivity, expensive rate and other related performance experiments are performed by using Hefei expansive soil. The resistivity index is used to predict the water swelling characteristics of expansive soil. It can be found that the expansive rate increases with the increase of initial resistivity and decreases with the increase of the overlying load. In addition, the vertical resistivity exhibits a linear increase with real-time expansion rate until the soil resistance rate reaches pore fluid resistivity. The previous experimental studies of our research group about resistivity characteristics of expansive soil are used to analyze and contrast. It can be found that expansion characteristics of expansive soil have a good fit with resistivity properties. Hence, the resistivity can be used to predict expansion rate. As the corresponding expensive rate is a dimensionless index, through the normalization of cohesive soil resistivity and regardless of the influence of the porosity, the relationship between dimensionless integrated resistivity index Er and the expensive rate is developed. The conclusions can be used for the expansion rate prediction of expansive soil.

The hydro-mechanical coupling is the basic characteristics to the unsaturated soil, especially to the one which consists of clay particles. Pore structure of clay is sensitive to the water content; and the pore size distribution (PSD) changes at every moment during drying process. The evolution laws of microstructure under the hydraulic path are first summarized based on experimental results. Subsequently, a novel model is developed by relating the pore-size distribution to the void ratio. According to the model, the PSD can be transformed from the initial PSD through three steps: translation, scaling and dispersion. The quantity of displacement and scaling are linear with void ratio; and the dispersion is exponential attenuation with void ratio. Finally, the model predictions are compared with experimental measurements in the literature, showing that the new model is capable of describing the microstructure evolution of unsaturated soil during drying process.

To investigate the feasibility of bamboo geogrid in reinforcing the filling embankment of Bazhong-Nanchong expressway in Sichuan Province of China, the mechanical behaviours of fresh bamboo geogrid are analyzed based on the laboratory tensile and bending test results. The results show that bamboo geogrid can match the traditional geogrid in mechanical performance, and meet specification requirements. Based on above test results, the bamboo with 2-year-old or older is selected as auxiliary reinforcement material. Laboratory direct shear test is conducted to exame the interface properties of bamboo-reinforced soil. It is that the arrangement of bamboo strips in geogrid is relatively optimal when orientations of bamboo’s green and yellow surfaces alternate one by one, and the corresponding interface friction coefficient reaches 0.32. The friction coefficient of interface between soil and bamboo pieces reaches 0.35 in the laboratory pull-out tests. The knitting process of bamboo geogrid and the construction technology for the reinforced filling embankment in this study are beneficial to practical engineering.

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Through simple calculation of the normal stress on slip surface and the Mohr-Coulomb strength criterion, various calculation parameters are introduced and the stresses on slip surface are properly assumed, from which the limit equilibrium solution for three-dimensional slope stability is derived based on the static equilibrium conditions that three-dimensional sliding body satisfies Meanwhile, in stability analysis of three-dimensional slope, the direction of shear stress on slip surface is also assumed based on the previous research results, and the nonstrict method, quasi-strict method and strict method are adopted for three-dimensional slope stability analysis. By comparing with the classical results, the proposed method is validated, and the differences among various methods are analyzed. It is shown that the nonstrict method yields the smallest factor of safety, i.e., a conservative result; the quasi-strict method is similar to the strict method, yielding reliable results in calculating the safety factor of slope. In the proposed method, reasonable assumptions are made for the stresses on slip surface, and the simple solution process can be easily implemented into a computer code.

Based on the survey of Gongjiafang, Maoping and Shennüxi bank slopes, there are five stages of disintegration evolution of the quasi-earthy bank slope of Three Gorges Reservoir identified during impounding. These five stages are the formation of bank slope, the development of joint fissures, the formation of argillation interlayer and the quasi-bank slope, the disintegration of the bank slope by impounding, and the follow-up disintegration. On the basis of above disintegration evolution process, a physical model and a mechanical model are developed for the quasi-earthy bank slope disintegration from the viewpoint of fracture mechanics. The stress expressions and formulas of stress intensity factor are developed by considering five different working conditions at different storage levels in the mechanical model. Through the preliminary discussion, some conclusions are drawn as follows. The reservoir storage has a significant effect on the disintegration of the quasi-earthy bank slope. The stress intensity factor of rock block decreases with the increase of the water level. When the water level reaches a level of 4.49 m, fractures in the upper of rock block turn into the bottom, and the of stress intensity factor of rock block increases with rising water level. At the beginning of water storage, the development of fractures is dominated by the gravity of rock block, while the uplifting of water level stabilizes the rock block. The fractures controlled by gravity in the upper gradually change into the fractures governed by buoyancy in the lower part of rock block. The sectional dimension of rock blocks has the significant effect on the disintegration of the quasi-earthy bank slope. Fracture strength factors in the upper of rock block grow with the decrease of ratios of width to height; when the ratios of width to height decrease, fracture strength factors in the lower of rock blocks increase with the increase of the storage levels.

Uniaxial compressive strength, rock quality designation (RQD) and statistics data of joints survey are used as input parameters to construct probabilistic models based on mechanical tests and field surveying data from Muliashi Open Pit. These probabilistic models are well fitted by using the chi-square test. From the generalized Hoek-Brown criterion, the probabilistic distributions of strength and deformation parameters of jointed rock mass are obtained by using the stochastic analysis in the MATLAB program and Monte Carlo method. Spearman’s rank correlation coefficient is applied to analyze the correlations between strength parameters and each input parameters. Based on the practical slope engineering, the slope stability is evaluated from the perspective of failure probability. The proposed method comprehensively considers the uncertainty and variability of jointed rock mass parameters, and can provide a valuable reference for safety decisions of practical engineering projects.

Effects of three types of loading, i.e. concentrated loading, plate loading and flattened loading, on the macroscopically mechanical behaviors, tensile strength and cracking processes of Brazilian disks are numerically investigated. The effect of tensile strengths of materials is presented for three kinds of loading types. In addition, the modified coefficients of tensile strength at different loading angles are presented for the flattened Brazilian discs. A continuum-discontinuum method which combines the Lagrangian element method, the deformational discrete element method and the fictitious crack model is adopted. The method can be used to simulate the deformation in the elastic stage and actual cracking of materials. It is found that the flattened loading easily leads to a crack at the center of Brazilian disc, while the concentrated loading or plate loading most likely results in shear failure. When the disk failures at the center, the numerical solution of the concentrated loading is closest to the calculated tensile strength, followed by the plate loading mode, and finally the flattened loading. The materials with low tensile strength normally leads to cracking at the center of the disk for any loading type; otherwise, there is shear failure at two loading ends of the disc. After the disk centrally cracks, a great number of microcracks coalesce to form a band that continuously propagates along the loading direction, and meanwhile the failure is accompanied by stress wave generation and propagation.

The method to calculate the safety factor of slopes was implemented into a three-dimensional (3D) limit equilibrium model in the open source geographical information system (GIS) GRASS GIS. The Hovland method was exploited to evaluate the slope stability of specified or randomly selected ellipsoidal slip surfaces. The spatial plane projection theory was applied to calculate cell areas of the sliding surface, which increased the computational efficiency. By considering the relationship between the main slope sliding direction and the inclinations of cells, the expression of safety factor was proposed for cells in the sliding surface, which was used to distinguish between positive values and negative ones. Furthermore, the sliding surface was expressed by a triangulated irregular network (TIN) model which was obtained by utilizing constrained Delaunay triangulation method and mesh optimization algorithm. Thus, the shortcoming of the Grid model for accurately representing the sliding border was substantially improved. The safety factor calculated by the TIN sliding surface was closer to the exact solution than the Grid model at the same resolution condition, which demonstrated that the computational precision was obviously enhanced. Finally, the proposed method was verified by the modules programmed in Python language, which was further applied to some typical case studies. It was shown that the safety factor of cells lower than 1.0 represented the unstable region and that greater than 1.0 indicated the resistance slide area in the slip surface. The results can provide an essential basis for the development of landslide treatment measures.

Determining ultimate bearing capacity problem is of great importance in design and construction of the subgrade above void. The limit damage state of subgrade is numerically simulated by using upper bound finite element method. Firstly, the basic principles and calculation process of the upper bound finite element method are briefly introduced. Secondly, reasonable calculation assumption is proposed; and then a numerical model that can take various factors into consideration is established. Thirdly, the upper-limit solutions of ultimate bearing capacity under various conditions are calculated by using upper bound finite element method; and the bearing capacity coefficients Nc, Nq, N? are computed by using the formula of ultimate bearing capacity, as Tergaghi suggested; and then their influencing factors are analyzed. Finally, based on the large amount of energy dissipation and velocity field pattern analysis, three typical failure modes are presented and their influencing factors are analyzed. It is shown that Nc and Nq increase with the increasing of internal friction angle of ? , and when ? is larger, N? is positive number, and increases with the increasing of ? ; Both Nc and Nq increase with the increasing of the ratio of viod roof thickness and footing width H/B; and when ? is smaller, N? decreases with the increase of H/B. When ? is larger, N? increases with the increasing of H/B; and Nc、Nq and N? both decrease with the increase of D/B. The subgrade above void has three typical failure mechanisms: punching failure mode, punching shear press failure mode and Prandtl failure mode.

To deduce the real mechanical parameters of 300 m super-high arch dam inversely based on the various observation data during construction period, is of great engineering and research significance. In this paper, an inversion hybrid model of super-high arch dam is proposed based on simulating stress during construction period, which aims to deduce the real mechanical parameters inversely based on the vertical compressive deformation of dam and foundation detected in the period of construction. The practicality and feasibility of this model are validated by an case study of Xiluodu super-high arch dam. The elastic modulus of the dam body is inverted based on the observation of precise leveling instrument during construction, and the deformation modulus of its foundation is inverted according to the observation of multi-point extensometer during construction. The results show that the values obtained by the inversion hybrid model agree well with the actual measured elastic modulus and deformation modulus. The results in this current paper can provide research references for similar problem of super-high arch dams.