Abstract
Mining in close distance coal seams (CDCSs) is frequently associated with engineering disasters because of the complicated nature of stress distribution within CDCSs. In order to establish a layout of a roadway to minimize the occurrence of disasters associated with mining CDCS, here the spatial and temporal evolution of stress distribution during the multiworking face mining of a CDCS was explored through numerical simulation based on the engineering and geological conditions of the Nantun Coal Mine. The numerical simulation results indicate that, after the extraction of adjacent multiple working faces, the spatial distribution of stress can be characterized with areas of increased, reduced, and intact stress. The superposed stress of inclined seams that are very close to each other propagates through coal pillars in the bottom floor, and this propagation follows neither the line along the axis of the coal pillar nor the line perpendicular to the direction of the floor. It instead propagates along a line angled with the axis of the coal pillar. The roadway can be arranged in the area with reduced stress, to improve its the stability. Based on the computed spatial and temporal evolution of stress, an optimized layout of roadway was proposed. This layout features a reasonable interval between the mining roadway and a minimal proportion of increased stress areas along the mining roadway and is aligned with geological structures.
Highlights
In recent years, as China’s energy demand has continued to grow, coal mining activities in the country have continued to expand [1]
close distance coal seams (CDCSs) are coal seams that are in close proximity to other seams, i.e., the distances between the different coal seams are very small [2, 3]. e mining of CDCSs has been accompanied by frequent disastrous phenomena, such as large deformation of surrounding roadways, rock bursts, and coal and gas outbursts. ese phenomena are related to the multidimensional and dynamic redistribution of the stress of roadways in lower coal seams
According to the research results of Suchowerska et al [15] and Zhang [22], the factor that has the greatest influence on the stress distribution of the lower coal during multi-coal mining is the safe coal column left after the upper coal is mined, mainly manifested as the significant change in vertical stress, and with the change of the inclination of the coal seam, the stress distribution in the lower coal will be more complicated. erefore, based on the abovementioned research results, this paper focuses on the stress distribution in the coal seam after the vertical stress and the lateral stress are superimposed when the coal seam is mined at a close distance
Summary
As China’s energy demand has continued to grow, coal mining activities in the country have continued to expand [1]. Adhikary et al presented the results of a numerical simulation of the surface subsidence induced by multiseam longwall mining, obtained using both two-dimensional (2D) and 3D versions of a Cosserat continuum-based, finite element code called COSFLOW. Zhu et al studied the influence of vertical stress distribution to pillar stability during the extraction of a lower coal seam, using a 3D finite element model [17]. Zhang et al utilized borehole imaging technology and a 2D numerical model to analyze the fissure evolution and distribution characteristics of both coal and rock, following the extraction of a lower coal seam [18]. Rough the description of the geological conditions, setup of the numerical model, and analysis on the evaluation of the general trend of stress redistribution, an optimized roadway layout for the lower coal seam is presented Based on the geological and mining conditions of Nantun Mine, a 3D numerical model was built to study stress distribution during CSCD mining. is model was used to explore the spatial and temporal evolution of stress during CSCD mining. rough the description of the geological conditions, setup of the numerical model, and analysis on the evaluation of the general trend of stress redistribution, an optimized roadway layout for the lower coal seam is presented
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