Abstract
The roof fracture is the main cause of coal mine roof accidents. To analyze the law of movement and caving of the roof rock stratum, the roof subsidence displacement, rock stratum stress, and the rock stratum movement law were analyzed by using the methods of the particle discrete element and similar material simulation test. The results show that (1) as the working face advances, regular movement and subsidence appears in the roof rock strata, and the roof subsidence curve forms a typical “U” shape. As the coal seam continues to advance, the maximum subsidence displacement remains basically constant, and the subsidence displacement curves present an asymmetric flat‐bottomed distribution. (2) After the coal seam is mined, the overburden forms an arched shape force chain, and the arched strong chain is the path of the overburden transmission force. The farther away from the coal seam, the smaller the stress concentration coefficient is, but it is still in a high stress area, and the stress concentration position moves toward the middle area of the goaf. The stress concentration in front of the coal wall is the source of force that forms the abutment pressure. (3) Above the coal wall towards the goaf, a stepped fracture was formed in the roof rock stratum. The periodic fracture of the rock stratum is the main cause of the periodic weighting of the working face. Understanding the laws of rock movement and stress distribution is of great significance for guiding engineering practice and preventing the roof accidents.
Highlights
China is a country with large coal production, and its coal production accounts for about half of the world’s total production. ere are six major disasters occurring in coal mines, namely, gas explosion, water inrush, roof caving, coal-gas outburst, transport, and poisoning
(2) After the coal seam is mined, the overburden forms an arched shape force chain, and the arched strong chain is the path of the overburden transmission force. e farther away from the coal seam, the smaller the stress concentration coefficient is, but it is still in a high stress area, and the stress concentration position moves toward the middle area of the goaf. e stress concentration in front of the coal wall is the source of force that forms the abutment pressure
The roof accident accounted for 13.79% of the total accidents, and the death rate accounted for 14.98%, as shown in Figure 1. e roof fracture is the main cause of the coal mine roof accidents. erefore, it is of great theoretical and practical significance to study the laws of the movement of the roof above the coal seam for preventing and controlling the occurrence of roof disasters
Summary
China is a country with large coal production, and its coal production accounts for about half of the world’s total production. ere are six major disasters occurring in coal mines, namely, gas explosion, water inrush, roof caving, coal-gas outburst, transport, and poisoning. Zhao and Liu [2] based on the engineering geology conditions of remaining face 3101 in Shenghua Mine in China analyzed the roof fracture and instability features of the roof caving zones through physical simulation, theoretical analysis, and field measurements He et al [3] built the structural and mechanical models to explore the mechanism of the new approach. Wang et al [19] studied the height of the mininginduced fractured zone above a coal face by PFC and similar material experiment; there was little analysis of the rock stratum motion law of the overburden after coal seam mining, especially the stress and displacement of the rock stratum. With an overview of the previous studies found that there are few studies which used particle flow code and similar material simulation test to analyze the laws of movement and fracture of the roof rock stratum in the longwall mining. With an overview of the previous studies found that there are few studies which used particle flow code and similar material simulation test to analyze the laws of movement and fracture of the roof rock stratum in the longwall mining. erefore, this paper uses PFC2D software and similar material simulation test to establish the analysis model of longwall mining. e roof subsidence displacement, rock stratum stress, and the rock stratum movement law will be analyzed. is research will provide more information about rock stratum movement laws for engineers
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