Abstract
To explore the impact of lateral stress concentration in interlayer rock stratum on the exploitation of protected coal seam, a field experiment was carried out in a multi-seam mining structure. Lateral stress redistribution and interlayer rock failure behavior were surveyed. Then an assistant numerical investigation was implemented to evolve the effect of liberated seam mining and its influence on stress reconstruction in surrounding rock mass. The cause of lateral stress concentration and its impact were discussed finally. Key findings turn out that a certain lateral stress increases in interlayer rock stratum and concentrates on its lower region. Lateral stress concentration and interlayer rock failure are interactional. The former is an inducing factor of the latter; the latter promotes the increase of concentration degree. Extent of lateral stress concentration increases to the maximum as seam distance is about 50 m. But the efficacy of liberated seam mining decreases as the seam spacing gets larger. Protected seam mining is then classified based upon the impact of lateral stress concentration, which helps to prevent the rock burst hazard and then to achieve a reliable mining in deep mines.
Highlights
Many geological hazards distinguished from the conventional ones occur gradually in the underground coal mines with the increase of mining depth [1,2,3], for instance, the high temperature, high ground pressure, seismic hazard, and rock burst
Observation results of lateral stress redistribution and interlayer rock failure behavior in these boreholes are shown in Figures 3 and 4
It indicates that lateral stress redistribution in the stress relaxation zone of interlayer rock mass is greatly influenced by the mining activities in liberated seam
Summary
Many geological hazards distinguished from the conventional ones occur gradually in the underground coal mines with the increase of mining depth [1,2,3], for instance, the high temperature, high ground pressure, seismic hazard, and rock burst. Multi-seam coal mining is treated as an effectively precautionary approach for the deep geologic hazard prevention, especially, for the rock burst [5,8,9]. It changes the initial distribution of in-situ stress, improves the plastic deformation of coal and rock mass, weakens the stress concentration in mining region and makes the subsequent seams easier to be extracted [10]. In deep coal mining, some unnatural accidents occur occasionally during the exploitation in protected seam These accidents delay mining schedule and injure the workers in the worse cases. In this study, aiming at the lateral stress changes in interlayer rock stratum, the authors carried out a field investigation in a deep underground coal mine, explored the lateral stress redistribution and interlayer rock failure behavior, discussed the mechanism and impact of lateral stress concentration, which provides the necessary theoretical and practical experience for deep multi-seam coal mining in rock burst prevention
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