Abstract
It is well accepted that faults have significant impacts on the safe production of underground coal mines; however, the fault-slip mechanism during longwall mining through a fault still needs to be investigated. In this study, the distribution of microseismicity events during panel mining through a fault is analyzed, and 3-dimensional fast Lagrangian analysis of continua was used to study the mining stress distribution and fault-slip behavior under the two different mining directions, i.e., mining the panel through the fault from the footwall, or mining the panel through the fault from the hanging wall. The research shows that when the panel is mined through the fault from the footwall, the shear displacement of the fault is significantly greater than those created by mining the panel through the fault from the hanging wall. Under the two mining directions, the variation behaviors of the normal stress and shear stress on the fault are quite different, and fault-slips mainly occur in fault areas where the normal stress decreases. When mining the panel through the fault from the footwall, the slip mainly occurs in the coal-seam roof fault, and when mining the panel through the fault from the hanging wall, the slip mainly occurs in the coal-seam floor fault. According to the variations in the normal stress and shear stress of the fault during the period of mining the panel through the fault, the mechanism of the fault slip can be divided into three categories. 1: Normal stress and shear stress decrease abruptly, but the reduction of the normal stress is greater than that of the shear stress. 2: The normal stress is continuously reduced, the shear strength of the fault is decreased, and the shear stress is suddenly increased. 3: Both the normal stress and the shear stress increase, but the increase in the shear stress is greater than that of the normal stress. These research results can provide a reference for the layout of panels and for fault-slip-induced disaster prevention under similar conditions.
Highlights
With the rapid development of the Chinese economy, the coal demand and production capacity continue to grow, and the world’s coal production reached 5,481 million tons in 2017
After the panel is mined through the fault, the total energy of the daily microseismicity events on that day reaches 23
The study shows that the count of daily microseismicity events and the total daily microseismicity energy increase significantly when the panel is mined from L = 40 m to L = 0 m, and the count and energy level of the microseismicity events on the roof are much larger than those of the microseismicity events on the floor
Summary
With the rapid development of the Chinese economy, the coal demand and production capacity continue to grow, and the world’s coal production reached 5,481 million tons in 2017. Of this amount, 2,541 million tons of coal was produced in China, accounting for 46.4% of the world’s total coal production. China’s annual coal consumption accounts for 50.7% of the world’s total coal consumption, making it the largest coal consumer in the world [1]. With the continuous deepening of the coal mining depth and the continuous expansion of the production scope, the geological conditions of coal mines are becoming increasingly complex.
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