Advanced Materials Research Vols. 243-249

Abstract: The high cut slope of reservoir-bank road and city buildings are mostly earth-rock mixture after excavation. The strength behavior of the gravelly soil is important for mechanism of landslide triggering and soil erosion in Badong high cut slope. With the impact of rainfall, the water content of gravel soil increases, and the water table changes, this eventually affects the mechanical properties of gravel soils. Taking high cut slope which formed in the course of relocation in Three Gorges Reservoir as its background, the paper selected the gravel soil of typical high cut slope in Badong new town; and through on-site survey, analysis of geological conditions, indoor large-scale direct shear test, combined with laboratory test results, it discussed the influence of high cut slope gravel soil shear strength parameters by different water content of sample. At the end of this paper, it draws some beneficial conclusions.

Abstract: Aiming at problem of low coal mining rate and environmental pollution by gangue, replacement mining technology of source recovery by excavating large span roadway and backfilling with gangue is put forward in this paper. Then combined control technology of roof cable truss and coalside cable-channel steel is applied to support the large span roadway, its control mechanism is discussed and the combined support scheme is defined by way of numerical simulation. Besides, according to the practice production condition, the replacement system which consists of gangue pretreatment, transport and replacement is established, achieving harmonic extraction of resource recovery and environmental protection and providing scientific basis and technological means for resource recovery under other geological conditions.

Abstract: An unequal interval grey model GM (1,1) was established according to the variation characteristics of sequence data about the bearing capacity of overlength piles, and a difference equations was usually adopted to replace the grey differential equation for determining the system parameters of the model; however, great errors would occur when the model thus established was used to predict the bearing capacity of overlength piles, that is, the prediction results would be overestimated or underestimated. In order to improve the prediction accuracy of the model, we established an error objective function based on optimization theory in this study, employed the method of nonlinear least squares to identify the system parameters in the grey differential equation for the bearing capacity of overlength piles, and built an optimization-based grey optimization model. The model system built with optimization method was used to predict the bearing capacity of overlength piles, and the predicted values fit the test values well. In addition, the model system had a higher accuracy, compared with the grey difference model built with difference method; therefore, the model system built with optimization method could provide reference for prediction of the bearing capacity of overlength piles.

Abstract: In this paper the dynamic property (shear modulus and damping ratio) of cement-stabilized soil is studied with using the resonant column test. The amount of cement admixed, the magnitude of confining pressure, and shearing strain amplitude are the parameters considered. Test results show that the maximum shear modulus of cement-stabilized soil increases with increasing confining pressure, the minimum damping ratio decreases with increasing confining pressure. The shear modulus of cement-stabilized soil decreases with increasing shearing strain while the damping ratio increases with increasing shearing strain. In the paper the relationship of shear modulus versus shearing strain is fitted into the Ramberg-Osgood equations using regression analysis.

Abstract: The impact of the cold-side temperature and moisture to frost heave were obtained by studying frost heaving test in open system. Frost heave ratio increased linearly with the decrease of cold-side temperature and moisture. Frost heave force increased with the decrease of cold-side temperature and increase of moisture. In addition, the soil physical properties variation laws was gained during freezing in the test, like moisture and dry density. By analysising the test data of frost heave ratio and frost heave force, the relationship between frost heave ratio and frost heave force were acquired. The results had important practical value and theoretical significance to the freezing shaft sinking and artificially freezing techniques applied in urban underground engineering.

Abstract: Cemented sand and gravel (CSG) is a new type of dam materials. It not only can reduce the waste of resources and environmental pollution, but has the merits of both gravel and concrete. In this study, Cemented sand and gravel specimens with three cement ratios were compacted at optimum water content and cured for 14 days. Based on the consolidated drained shear triaxial tests, the mechanical properties of different proportion of CSG are studied on shear failure mode, stress-strain relationship, shear strength. Research results showed that, with the increasing of the content of cement, the peak and residual strength of CSG were improved, but the failure strains were decreased. In addition, CSG material behaves distinctly softening.

Abstract: It is necessary to study the mechanic behavior of underground pipelines during the excavation of the foundation pit, because the excavation will inevitably endanger the nearby underground pipelines. Three factors include the depth of underground pipelines, the distance from the pipeline to the foundation pit and ground load are considered to conform comparative analysis, in order to study the variaty on the stress and deformation of the underground pipelines. The foundation surporting type and the soil layer distribution are also considered during the numerical simulation. The results show that the distance between pipeline and foundation has more influence on the underground pipelines than other two factors, the damage most likely occurred in the bottom right in the pipeline near the foundation pit.

Abstract: Hypoplaticity and Nader hypoplastic model are introduced. Based on finite element stress-strain analysis of Nader hypoplastic model, slip surface stress method in the slope stability is provided. The factor of safety of the slip surface is defined as the ratio of the critical shear intensity during failure to real shear stress and the critical slip surface of slope is ascertained with pattern search method. The clay slope with a weak foundation layer and clay slope with a foundation layer including a thin weak layer under the plane strain condition are analyzed. The results are shown that the shapes of critical slip surface and the magnitude of factor of safety are obtained by this method.

Abstract: In order to reveal the mechanism of deformation, disintegration and failure of shallow landslides of coal measure soil, through contact elastic-plastic FEM with shear strength reduction, the paper analyzes shallow landslides stability, calculates shallow landslides safety factors, and reveals the mechanism of deformation, disintegration and failure of shallow landslide of coal measure soil. The results are shown as follows: during shallow landslides of coal measure soil, the displacement of sliding mass sliding along sliding surface, the plastic strain of sliding mass and sliding mass sliding state along sliding surface don’t change simultaneously; adopting contact elastic-plastic FEM algorithm may better reflect the actual state and sliding process of shallow landslides of coal measure soil. It can help faithfully reflect real situations of shallow landslides like deformation, disintegration and failure of shallow landslide of coal measure soil, and it may afford one method that can be used as a reference of the stability analysis, accurate evaluation and forecast of this type of landslide.

Abstract: Multi-scale science is the challenge and opportunity of science in the 21th century, and turbulence of liquid and fracture of solid will be the classical problems of multi-scale mechanics. The failure process of brittle materials displayed a multi-scale mechanics feature that amounts of micro damages grow large trans-scale and nonlinear and evolve to a macro catastrophic transition in the end. So, the concepts of scale and hierarchy of material are inescapable in strength theory to be used explaining solid fracture, it is the main puzzle of the strength theory at present. In the paper, in order to show the phenomena of multi-scale fracture, numeric method is used to simulate the failure process of brittle material, during which micro cracks initiate, grow large, aggregate and in the end form a run-through fracture band in the sample. The result of the numeric simulation shows that the micro cracks of a meso-scale size initiate due to tensile strain and the sample of a macro-scale size breaks down due to tensile-shearing strain under uniaxial tensile or due to compression-shearing strain under uniaxial compression. It powerfully disabused the puzzles in teaching strength theory of brittle material. The further discussion concluded that for a brittle material grain of meso-scale size, the theory of Maximum Tensile Strain is reasonable in explaining the strength, as for a brittle material sample of a macro-scale size, the mohr-columb theory is reasonable for its strength owing to the two important factors of cohesive strength and friction factorwere introduced.