Sponsor(s): China Coal Society
12 issues per year
Current Issue: Issue 07, 2019
Journal of China Coal Society, the 1st in the field of mining engineering, promotes the development of coal theory and practice, as well as academic exchanges at home and abroad to accelerate the transformation from scientific research to real productive forces. It is supervised by China Association for Science and Technology and sponsored by China Coal Society. Launched in 1964, it aims at providing key topics of coal scientific research and mining development. Its scope covers coal geology, geochemistry, geophysics, mineralogy and coal seam formation and evolution; petrophysics of coal; organic matter-rich shales, including mineralogy, formation, transport and storage of gases in coal and shales; unconventional energy systems (e.g. oil shales, shale gas, and other carbon-based fuels); ore deposits of materials and rare metals in coal and coal-bearing strata; and groundwater management. The journal is included in CA, JST, EI, CSCD.
Fan Baoying, Xu Shengyang, Zhu Shuangcheng
Construction and application of overburden damage and aquifer water loss model in medium-deep buried coal seam mining in Yushen mining area
Journal of China Coal Society,2019,Vol 44,No. 07
Overburden deformation caused by coal seam mining is the main cause of water loss from aquifers. This paper aims at the problem of limited research on the water loss law of aquifers under the influence of mining medium-deep coal seams in Yushen mining area. According to the geological and hydrogeological structure characteristics of overburden rock of the main mining seam in Yushen mining area, the authors summarize and put forward the “lateral direct drainage and vertical gradual leakage” combined water-loss model of aquifers under the influence of damage and deformation of overburden in medium-deep seam mining. On the platform of COMSOL Multiphysics numerical analysis software, the method of constructing numerical analysis model of deformation of overburden and water loss of aquifers in medium-deep coal seam mining is put forward. (1) With the rock mechanics module of the software, the coupling relationship of overburden mining stress, porosity, and permeability is established under the condition of coal seam mining. The displacement and deformation of each subdivision node of overburden in the sagging zone are simulated and the change of mining permeability coefficient is calculated. The Mohr-Coulomb plastic failure criterion is used to identify the range of a water-conducting fracture zone under mining disturbances. (2) The secondary subdivision mesh under mining deformation is formed by relying on the auto-subdivision function of large deformation geometry in COMSOL software. (3) According to the transformation characteristics of groundwater flow between aquifers and water-conducting fractured zones, the range of a mining-induced aquifer fractured zone is numerically treated as Darcy flow boundary, and the mining permeability coefficient is re-input in the Darcy flow analysis module. Finally, with Caojiatan Coal Mine in Yushen mining area as an example, an analysis model of deformation of overburden and water loss of aquifers in coal seam mining on a working face scale is established. The simulation results show that the maximum height of the water-conducting fractures is 128 m under slice mining (5 m in mining height) of the 2 −2 coal, which develop into the aquifers of bedrock of Zhiluo and Yan’an Formations, resulting in 35.84 m 3/h of total water loss, and the lateral direct loss and the vertical loss are 23.17 m 3/h and 12.67 m 3/h respectively, which has little influence on the loose aquifer. The maximum height of the water-conducting fractures is 202 m under the condition of full-seam mining (10 m in mining height), which develop into the weathered strata with well water abundance, resulting in 130.31 m 3/h of total water loss. Moreover, the lateral and vertical water loss increase to 92.65 m 3/h and 37.66 m 3/h respectively, which has great influence on the loose aquifer.
Numerical simulation of zonal disintegration of surrounding rock at arched tunnel under progressive excavation and different internal frictional angles
Journal of China Coal Society,2019,Vol 44,No. 07
Zonal disintegration is a phenomenon in which the alternated regions of fractured and intact rock masses appear in the surrounding rock at great depth; this is completely different from the traditional understanding on the failure characteristics of the tunnel surrounding rock. A full understanding on the development of zonal disintegration in different surrounding rock can provide a foundation for its control and application. Excavation of a tunnel will lead to a rush of rocks in the vicinity of the working face into the tunnel. Therefore, the stress state of planes orthogonal to the tunnel axis is not a plane strain state, but a three-dimensional state. With the heterogeneous strain-softening model where the Weibull distribution function is introduced based on the strain-softening model in FLAC 3D, the effects of the internal frictional angle on the pattern of zonal disintegration are studied, and the distribution of the shear strain increment, minor principal stress, and major principal stress are investigated when the tunnel nearly penetrates the numerical model where a U-shaped tunnel is progressively excavated. The following results are found. The low internal frictional angle leads to a serious failure of the tunnel surrounding rock, a full development of shear zones, and an apparent zonal disintegration. Zonal disintegration appears after the tunnel surrounding rock is subjected to a certain failure. The mechanism of the zonal disintegration can be summarized as follows: Under stresses and excavation, at planes going through the tunnel axis, the randomly distributed defects develop into (conjugated) shear zones, and at planes orthogonal to the tunnel axis, the isolated annular fracture zones can be formed. At planes going through the tunnel axis, the present results are qualitatively consistent with the previous experimental results. According to the present research, at different planes orthogonal to the tunnel axis, zonal disintegration is different, which means that it is not necessary to choose the unified tunnel support parameters. For example, at some positions where zonal disintegration is obvious, the lengths of rock bolts should be extended, and vice versa.