Applied Mechanics and Materials Vols. 256-259

Abstract: Based on the tensile feature and rupture mechanism, the point interpolation meshless algorithm of smeared crack model is proposed. When the displacement of crack opening and the fracture energy are smeared into the node influence area, the calculation results vary with the size of the node influence area which is called size effect. According to the conversation law of fracture energy, the solution of size effect of simulation of tensile crack process using the blunt crack band model is proposed and verified through a numerical test of concrete three-point bend beam.

Abstract: The principal stress axial would cyclic rotate when the moving pressure passed. In order to analyze long-term settlement of the ground subjected to traffic loading, the simplified method based on explicit model for predicting the accumulative deformations is usually preferred. The traditional model could not reflect the phenomenon of principal stress rotation. After the axial stress controlled equation and circumferential shear stress controlled equation were derived, A series of consolidated undrained cyclic shear tests were performed under the condition that the general shear stress value was constant and the principal stress angle was rotating. The explicit pore pressure model reference was verified to calculate the accumulative pore pressure caused by the principal stress axial cyclic loading.

Abstract: Alternate Room-Pillar Mining Method with Ascending Backfill is now used in deep mining of Sanshandao Gold Mine. In mining practice of the metal mines, the widths of the room and pillar vary from 6m to 15m. In order to improve the production capacity and solve the deep mining safety problems, a fuzzy optimization model containing 11 evaluation indexes was built to choose the optimal structural parameters among 8m×8m, 8m×10m, 10m×10m, 10m×12m and 12m×12m. The fuzzy comprehensive evaluation results prove that the optimal stope structural parameter is 10m×10m for safety and high efficiency mine operation.

Abstract: The shear strength properties of bulky rock material were studied by the fractal geometry theory. The results show that: (1)The research indicates that the fractal dimension D can be a quantitative parameter of the particle composition of bulky rock material.and there was a clear linear correlation between the D and particle size distribution when bulky rock material was at good gradation.(2) Curve of stress-strain relationship had no obvious peak strength and it was strain-hardening. Gfailur and fractal dimension D have a obvious negative exponent relation while bulky rock material at the good gradation.(3) There was a negative exponent relation between φ and D at good gradation,but relationship of c and D was relatively disperse.

Abstract: In order to investigate stress-dependent soil water characteristic curve of recompacted expansive soil and the changes of soil-water characteristic under vertical stress in terms of soil fabric and pore size distribution, pressure plate tests scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) tests were conducted on a recompacted medium-expansive clay. The test results show that under an applied vertical stress, the air-entry value of a SDSWCC was greater than that of SWCC obtained under zero stress. No distinct hysteresis within a dry-wet cycle of SDSWCC could be found. The change of SWCC of the expansive soil under the applied stress could be mainly attributed to the rearrangement of aggregate and the compression of pores in the soil.

Abstract: The shear strength of expansive soils is now a key geotechnical problem. The water content and dry density of expansive soils have deep effect on its shear strength. For analyzing the detail relationship of the water content, dry density and shear strength of this special soil, direct shear test was carried out with the samples from Xinxiang in middle line of South to North water diversion project. The results indicate that both of the cohesion and friction angle grow with dry density and decrease with initial water content. Applying the linear regression calculation, we obtained mathematical expressions which reveal the variation of shear strength with the dry density and initial water content of Xinxiang expansive soils.

Abstract: Flexible supporting is a kind of treatment more reasonable than rigid supporting for dealing with the landslide of expansive soil cut slope. Base on flexible supporting treatment mechanism, a corresponding finite element calculation method is established. Take into consideration reasonably the expansion force, use nodal force to simulate interaction between the geotechnical grille and expansive soil. Calculation results agree with the actual situation, and have provided a theory basis for flexible supporting reasonable size of design.

Abstract: Interfacial slip in rock was studied utilizing digital image correlation method (DICM). Notched rock specimens consisting of a natural interface under three point bending were employed for researching the characters and mechanisms of the interfacial slip. The displacement and strain fields on the surface of specimen were measured accurately by DICM. The experimental results show that the interfacial slip can change the crack extension direction and mode. The results are helpful in researching the mechanism of interfacial slip and practical applications in rock fracture problems.

Abstract: To solve the bearing capacity of foundation soil problem, through theoretical analysis and proof, a new method used to calculate bearing capacity of foundation soil is proposed, and the solving potential sliding curve and corresponding analytical program is devised. A continuous stress field of foundation soil is gained, by using the analysis of elastic-plastic finite element analysis of foundation soil for differ load; the numerical integration is used to make sure of the potential sliding curve, the most dangerous potential sliding surface, and the stability factor. The method has a rigor basis. Through many examples and engineering tests, the proposed method has good comparability with other method, and it can take into account many influence factors, such as the width and embedded depth of foundation, soil gravity, layered soil and etc, and it can also trace the trend of soil failure development and make clear the failure mechanism of foundation soil.

Abstract: The discrete element method (DEM) has been recognized as an effective tool to simulate soil–tool interactions. In this study, a saturated sand cutting model is developed using a commercial DEM software, Particle Flow Code in Two Dimension (PFC 2D). In the model, soil are defined as particles with the basic PFC 2D model, full coupling with a deformable fluid. The mechanical interactions between particles and also between particles and the walls are modeled by sprints, dash-pots and friction sliders. The properties of the material and interactions (Poisson’s ratio, shear modulus and density, coefficients of restitution, rolling and static friction) relate to the particle properties and not to the bulk properties. Such quantitative and qualitative models are essential for improving the design, selection and use of water saturated sand cutting implements, in different field sand under different conditions. This paper describes a numerical experimental investigation of the failure characteristics of two-dimensional water saturated sand cutting. Comprehensive simulated tests were carried out on sandy loam using a box apparatus and two model plane blades of rake angles 30º, 60º and two angles of friction 32º,42º, respectively. Besides, there are two extreme densities of the sand, compacted and loose. These factors should provide a basis for the reliable prediction of the failure type.