Mechanism and Control Technology of Rockburst Induced by Thick Hard Roof and Residual Coal Pillar: A Case Study

Abstract

Rockburst caused by the fracture of thick hard roof and the instantaneous instability of residual coal pillar seriously jeopardize the deep coal mining safety. This study takes Boertai Coal Mine, Shendong, China, as the engineering background, in which dynamic instability mechanisms of the gob-side roadway surrounding rock are analyzed by integrating field research, theoretical analysis, and numerical simulation. The results show that the overlying residual coal pillar, side abutment pressures, and front abutment pressures together induce high static stresses in the surrounding rock of the gob side roadway, with peak values exceeding the in situ stress by one order of magnitude. High stresses accumulated in the goaf-side roadway surrounding rock can easily induce dynamic disaster. With the working face advanced, overburdens are caved in succession, resulting in a continuously decreasing of the overlying residual coal pillar width, once the working face entered the influence area of the residual coal pillar. As the morphology of abutment pressure in the residual coal pillar changes from “unimodal distribution” to “bimodal distribution,” the residual coal pillar gradually changes from elastic state to plastic state. When the width of the overlying residual coal pillar is less than the critical width, the thick hard roof and residual coal pillar structure (THRRCPS) lose stability suddenly, resulting in strong dynamic load on the surrounding rock of gob-side roadway. In order to prevent the rockburst of the gob-side roadway under the influence of THRRCPS, regional and local prevention measures are adopted to mitigate the accumulation of stress in the thick hard roof and gob-side roadway surrounding rock by hydraulic fracturing technology and large diameter pressure relief drilling hole.

Investigation into Pressure Appearances and Hydraulic Fracturing Roof-Cutting Technology in Mining Working Face under Residual Pillars: A Case Study

“…However, DHF can be used to control the propagation direction of hydraulic fractures by grooving specified rock formations [36]. Another method is to construct directional drilling according to the position of hard rock and then use hydraulic fracturing [40,46,47]. In future studies, the directional hydraulic fracturing scheme for roofs above residual coal pillars should be studied, and the control effect of HF and DHF on strong mining pressures should be comparatively analyzed.…”

“…Zhang et al [39] concluded that roof cutting with a vertical hydraulic fracture at a specified position, also known as fixed-length roof cutting, can reduce the support load and keep the immediate roof intact. Liu et al [40] proposed a directional hydraulic fracturing roof-cutting technology for controlled rock bursts induced by thick, hard roofs and residual coal pillars under repeated mining in close coal seam groups. Gao et al [41] presented a method for subjecting hard roofs to ground fracturing in the Datong mining area in China, and physical simulations were used to study the control effect of ground fracturing on strata structure and energy release.…”

Analysis and Prevention of Rock Burst Risk of Working Face under the Influence of Continuous Irregular Triangular Coal Pillar Stress Concentration Area

“…18 Liu et al analyzed the mechanism of rock burst induced by a thick and hard roof and residual coal pillars through field investigations, theoretical analysis, and numerical simulations based on the engineering background of the Shendong Buertai Coal Mine. 19 Regarding research on rock burst prevention and control methods, Gao et al studied the seismic isolation technology and implementation method of a deep rock burst roadway and effectively protected the stability of the structure of the rock surrounding the roadway through dual protection means of isolation and shock absorption. 20 Xu et al studied the dynamic response characteristics of the surrounding rock and support system of a roadway under different vibration intensities and proposed the full anchor cable yield support technology, which effectively controls the stability of the rock surrounding the roadway under dynamic rock burst.…”

“…Wang et al studied triangular coal mining technology and roof control technology for the problem of coal resource waste caused by coal pillar areas with irregular boundaries and triangular coal pillars . Liu et al analyzed the mechanism of rock burst induced by a thick and hard roof and residual coal pillars through field investigations, theoretical analysis, and numerical simulations based on the engineering background of the Shendong Buertai Coal Mine . Regarding research on rock burst prevention and control methods, Gao et al studied the seismic isolation technology and implementation method of a deep rock burst roadway and effectively protected the stability of the structure of the rock surrounding the roadway through dual protection means of isolation and shock absorption .…”

A Prediction Approach Based on Clustering Reconstruction for Abnormal Mining Pressure of Longwall Face under Residual Coal Pillars

“…In the process of multi-coal seam mining, after the upper coal seam is mined, a large amount of coal pillars are often left behind [1]. When the lower coal seam mining face advances into the influence range of the mining area, the roof structure collapses again, and the thick and hard suspended roof breaks and fails under the additional stress of the residual coal pillar [2]. The special coal-rock occurrence conditions and repeated mining disturbance cause abnormal mine pressure, and there is a hidden danger of cutting the roof pressure on the hydraulic support of the mining face.…”