Papers by Author: Xia Ting Feng

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Authors: Ming Tian Li, Xia Ting Feng, Hui Zhou
Abstract: Based on the cellular automata of the plane truss structure, a 2D cellular automata model is presented to simulate the fracture of rock at meso-level. Cellular automata are made up of cell, states, lattice, neighbor and rule. Rock is divided into lattice in which each lattice point presents a cell. Each cell is assumed to connect with several cells, which are called as its neighbors, in virtue of truss elements. The truss elements can adopt some different simple local laws, i.e. constitutive law, which may be elastic or elastic-plastic and the simple fracture rule. It also can adopt different mechanical properties, which present their heterogeneity and anisotropy. This model can make full use of the advantages of cellular automata such as its intrinsic parallelism, localization and so on. In the meantime, as a powerful tool to analyze the nonlinear, complex system, cellular automata can be used to study the nonlinear, complex fracture process. The model is used to simulate the direct tensile of the rock plates, the complete fracture process and the stress-strain curves are attained which are accordance with the experiment.
Authors: Shui Lin Wang, Xia Ting Feng, Xiu Run Ge
Abstract: In finite element method, the order of complete polynomial of the interpolation function is related to the number of nodes in the element. This paper presents a four-node quadrilateral element with quadratic function on it. The presented displacement functions maintain C0-continuity. Meanwhile, the element stiffness matrix is derived from the displacement functions. Test problems show that high accuracy can be achieved by the use of the new displacement function on the element.
Authors: Guang Liang Feng, Xia Ting Feng, Zhou Neng Zhao, Guo Feng Liu, Ya Xun Xiao
Abstract: Tunnel collapse causes serious casualties and economic losses. One typical case analysis of a collapse in deep-buried tunnel based on microseismic monitoring is presented. The results show that the number of microseismic event keeps increasing and the distribution of microseismic events becomes concentrated in space domain gradually during collapse nucleation process. And average distance squared decreases gradually during the imminent period time just before the collapse. The failure evolution mechanism of the collapse is analyzed by moment tensor method. It is noted that the failure mechanism between this kind of collapse and immediate strain-structure rockburst is similar. However, the proportion of shear and mixed fracture for collapse is higher than immediate strain-structure rockburst. It due to the rich structure planes in collapse zone.
Authors: Hui Zhou, Jian Fu Shao, Xia Ting Feng, Da Wei Hu
Abstract: In this paper, a coupling constitutive model is proposed for anisotropic damage and permeability variation in brittle rocks before cracks fully coalesce. In this coupling model, an anisotropic damage model is employed to perform the mechanical analysis, and a statistical penetration model is set up to describe the effective porosity and permeability evolution in brittle rocks. For the coupling analysis, anisotropic damage model offers statistical penetration model the crack length in various directions, and statistical penetration model inversely provides anisotropic damage model with permeability of rock for coupling hydro-mechanical analysis. The proposed coupling model is applied to Lac du Bonnet granite, and generally a good agreement is obtained between numerical simulations and experimental data.
Authors: Cai Hua Liu, Cong Xin Chen, Xia Ting Feng
Abstract: A test apparatus was developed to study shear-flow coupling properties for a marble fracture with sand. Experimental tests include shear stress-flow coupling process and shear displacement-flow coupling process. The shear stress-flow coupling test results, revealed that mechanical aperture keeps constant during shear, and that hydraulic aperture and conductivity decrease almost linearly with increasing shear stress. The shear displacement-flow coupling test results showed that hydraulic behavior under shear displacement includes two phases. During the first about 0.05mm shear displacement, hydraulic aperture and conductivity decrease with increasing shear displacement, and mechanical aperture remains constant or increases only by several microns of magnitude. After shear displacement is up to about 0.05mm, the fracture dilates remarkably, and hydraulic aperture and conductivity increase with shear displacement increasing.
Authors: Xia Ting Feng, Shao Jun Li, Sih Li Chen
Abstract: Study of effect of water chemistry corrosion on strength and cracking characters of rocks is an important aspect to improve long-term stability of rock engineering and increase efficiency of geothermal and petroleum developing. This paper reviews new progress of study on this topic. It includes effect of water chemical corrosion on triaxial compressive strength, uniaxial compressive strength, shear strength, tensile strength, and cracking characteristics of rocks. The mechanism of water chemical corrosion is analyzed. The further study on this topic is also discussed.
Authors: Qiang Xue, Jing Wang, Xia Ting Feng, Xiao Li Liu
Abstract: Pavement straw composite fibers (PSCF), a new material, were independently invented and developed by blending agriculture waste straw and modified bentonite, as showed in this paper. The chemical corrosion properties of PSCF in different pH values were test in microscale, and digital imaging processing technology was adopted to analyzing quantitatively the physical and mechanical properties, including particle area, pores connectivity rate and compressive strength, before and after PSCF were corroded. Research results show that the particle area of acidified PSCF is smaller than that of alkalized PSCF, however, the fractal dimension of acidified PSCF is bigger than that of alkalized PSCF. The change of PSCF microstructure has significant effect on its macromechanics properties. The compressibility of acidified PSCF was obviously bigger than that of alkalized PSCF, so the strength of acidified PSCF decreased significantly with the acidifying time increasing. The main reason was gradually decreasing of the particle area, decreasing of the fractal dimension and the loose tendency of fibers particle distribution. The interaction between mineral composition of PSCF and hydrochemistry solution was the basic factors determining straw structural characteristics, and the physical and mechanical properties of PSCF were affected by its structural characteristics. The main process was that mineral compositions of PSCF were cemented by the corrosive action of hydrochemistry solution, or some compositions were dissolved and precipitated, the porosity and particle area of PSCF, the arrangement pattern of soil particles as well as other microstructures changed. And deformation properties of PSCF changed correspondingly with the change of PSCF structure shape. Moreover, the constitutive model of PSCF with effect of acid and alkali was presented according to test data of digital image. It provided reliable techniques to quantitatively evaluate the pavement performance of PSCF in micro and macro scales. Furthermore, the chemical corrosion theory was improved, and the reference for constitutive model research was provided.
Authors: Ying Hui Lv, Xia Ting Feng, Bin Yan
Abstract: it is already confirmed that the rock mechanical characteristics under unloading condition differ from those under load condition, and the excavation process should be considered to be a typical kind of unloading mechanical behavior. As thus, a series of representative unloading tests and shear strength tests about unloading cracks are performed on hard granite samples from the underground workshop excavation zone in Dagangshan hydropower station in western China, where the surrounding rock is affected by high geo-stress. Based on the tests results, some significant theory research is made.
Authors: Jin Hua Xu, Xia Ting Feng, Si Li Chen, Chen Yang Shi
Abstract: At present, waste rubber tires cause a significant environmental and human health problem. An innovative way to recycle used tires is that the waste tire rubber is used in Portland cement concrete as a portion of aggregates. In this paper, the crumbed tire rubber particles were used to replace fine aggregates, which includes two grain sizes, from 3 to 4 mm and 50-mesh.. The replacement levels were 0, 5, 10, 15, and 20 % by volume of the fine aggregates. Rubber concrete mixtures were produced according to mixture proportions design. The slump of fresh concrete and the unit weight of the nine mixes were examined. The mechanical properties investigation of harden concrete included determining the 28 days compressive strength and dynamic modulus of elasticity. The study demonstrated that 5 and 15 vol% replacements with rubber powder can meet fundamental engineering demands, although substituting part of fine aggregate with fine rubber powder deteriorated mechanical properties of concrete.
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