Coal wall caving mechanism of longwall large mining height stope in steeply dipping coal seams

Coal wall caving is a common mining technical problem for large mining height stope, and the caving feature and its occurrence mechanism are more complicated under steeply dipping condition. Through field measurement, numerical calculation and theory analysis, the caving features, influencing factors and the caving mechanism have been studied. The results have shown that coal wall caving of large mining height stope in steeply dipping coal seams has distinctive features, such as alternating evolution, different regional forms and so on. It also reveals that mining height, pseudo angle, mechanical properties of coal are all closely related to coal wall stability-within a certain range: the bigger mining height and pseudo angle, the lower the coal strength becomes, and the more probability and extent of coal wall caving accordingly increase. Working face 25221, with low strength coal walls, gangue, a large height, poor self-stability, and variable mining height and pseudo-angle, increases the roof pressure strength, coupled with the repetitive dynamic load disturbance and other internal and external factors, promotes the coal wall caving of large mining height stope in steeply dipping coal seams. © 2019, Editorial Board of Journal of Mining & Safety Engineering. All right reserved.