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Liu Y.,National Key Laboratory of Gas Disaster Detecting | Liu Y.,China Coal Technology and Engineering Co. | Liu Y.,Chongqing University
Procedia Engineering | Year: 2011

Through the experiments investigation on complete stress-strain of coal and the permeability of coal under different stress and gas pressures, the rules of permeability of coal samples under different conditions and the corresponding permeability evolution equation were established. The results show that the permeability of coal samples under certain gas and axial pressure will exponentially decrease when the confining pressure increase. The gas flow in coal has significant Klinkenberg effect. As the volume stress increase, the scope of Klinkenberg effect can also become larger. The relationship of confining pressure & permeability and gas pressure & permeability were obtained by fitting experimental data. Base on permeability test of complete stress-strain, we recognized that the curves between gas permeability and strain under different confining pressure have the similar change trends. Changes of permeability are closely related to the damage evolution of coal. According to the characteristics of permeability curves, considering the integrated effect of confining pressure, axial compression, and gas pressure, the permeability evolution equations of complete stress-strain was established with effective stress. © 2011 Published by Elsevier Ltd. Source


Zhang S.-T.,China Coal Technology and Engineering Co. | Zhang S.-T.,National Key Laboratory of Gas Disaster Detecting
Procedia Engineering | Year: 2011

The calculated methane content keeps away from real loss methane content with the increasing of loss time and initial desorption velocity data. Small size coal sample's methane absorption and desorption experimental study is carried out under the condition of a certain methane adsorption balance pressure and constant temperature, which the small size coal sample is collected from different coal mines. The experimental data is studied with the methane desorption law of Sun Chong-Xu formula (Q=ati ). Relations among coal sample's methane desorption quantity, exposure time and methane desorption velocity are studied. Then eigenvalues (i) in desorption law (Q=ati) of coal samples with different exposure time is calculated. So the same group coal samples' Eigenvalues calculated with different exposure time are studied. This study provides according for small size coal sample's methane loss value accurate calculation. © 2011 Published by Elsevier Ltd. Source


Wang B.,National Key Laboratory of Gas Disaster Detecting | Wang B.,China Coal Technology and Engineering Co.
Advanced Materials Research | Year: 2014

In order to better implement ratio production of coaly similar material, make use of research results of existing similar materials, consult domestic and foreign documents, and combined with the needs of their own experiment, determine the requirements for coaly similar material, propose a selective condition of similar raw materials, and according to the condition determining a selective content and range of similar raw material. Compared with the advantages and disadvantages of uniform design method and the orthogonal experiment design, put forward the corresponding experimental design, and its uniform dispersion was studied, the research show that the use of uniform design method that used in the ratio and manufacture of coaly similar material, which is very reasonable, its research results provide the basis and foundation for the future experimental research of similar material. © (2014) Trans Tech Publications, Switzerland. Source


Dai L.C.,National Key Laboratory of Gas Disaster Detecting | Dai L.C.,China Coal Technology and Engineering Co.
Advanced Materials Research | Year: 2014

In order to study the coal and gas outburst similar simulation experiment, coal similar material was made up based on the similarity theory. Based on the previous similar material study, the cement, sand, water, activated carbon and coal powder was selected as the raw material of similar material. Meanwhile similar material matching program with 5 factors and 6 levels was designed by using Uniform Design Method. And the physical and mechanical properties of the similar material compressive strength was measured under different proportions circumstances. The relationship between similar material and the raw materials was analyzed. The results show that choosing different materials can compound different similar materials with different requirements. And the water-cement ratio plays a decisive influence on the compressive strength of similar material. The compressive strength of similar material decreases linearly when the water-cement ratio increases. © (2014) Trans Tech Publications, Switzerland. Source


Jin H.-W.,National Key Laboratory of Gas Disaster Detecting | Jin H.-W.,China Coal Technology and Engineering Co.
Meitan Xuebao/Journal of the China Coal Society | Year: 2012

In order to study the form and reason of coal damage during the developing process of coal and gas outburst, some experiments were performed to study the breakage characteristic of suddenly exposed gassy coal, simulations of the outburst developing process were also performed in various conditions with a simplified outburst model, and a mathematical model for coal and gas development was built. The results show that the main form of coal damage is spall fracture, the speed of damage propagation is very fast(greater than 1 m/ms), and there is no violent pulverization damage in the initial stage of outburst development. An unloading wave will occur after the sudden unload of coal wall, and it may be reflected by the restrained coal when propagating into coal body, the incoming wave and reflecting wave interact to produce a tension area and thus lead to tensile failure of coal, which is the reason of fracture initiation during the developing process of outburst. Even if there is no ground stress, sudden exposedness of a coal wall may also induce unloading wave that propagates into deep area, and thus induces spall fracture of coal. Source

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