Instability Control of Roadway Surrounding Rock in Close-Distance Coal Seam Groups under Repeated Mining

Abstract

In order to solve the problems of roadway stability and easy instability under repeated mining of close-distance coal seam groups, the mechanism and control technology of surrounding rock instability under repeated mining were studied via indoor testing, field testing, physical similarity simulation experiment, and numerical simulation. The results show that the surrounding rock of roadway has low strength, low bearing capacity, and poor self-stabilization ability, and it is vulnerable to engineering disturbances and fragmentation. Affected by the disturbance under repeated mining, the roadway surrounding rock cracks are developed and the sensitivity is strong, and it is prone to large-scale loose and destroyed. The location of the roadway is unreasonable, and the maximum principal stress of the roadway is 3.1 times of the minimum principal stress, which is quite different. Thus, under a large horizontal stress, the surrounding rock undergoes long-range expansion deformation. On the basis of this research, the direction and emphasis of stability control of roadway surrounding rock under repeated mining of coal seam groups in close-distance are shown. A repair scheme (i.e., long bolt + high-strength anchor cable + U-shaped steel + grouting) is proposed, and reduces the risk of roadway instability.

Study on the Mechanism and Control of Strong Rock Pressure in Thick Coal Seam Mining under the Goaf of Very Close Multiple Coal Seams

“…The predicted coal reserves of Xinjiang are 2.19 trillion tons, accounting for more than 2/5 of the national coal resources [1,2]. The very close coal seams in each mining area in Jiangxi account for about 1/4 of the recoverable reserves and involve more than 100 mines.…”

Study on Failure Characteristics and Control Technology of Roadway Surrounding Rock under Repeated Mining in Close-Distance Coal Seam

“…Meanwhile, the grouting bolt to strengthen shallow broken surrounding rock and hollow grouting anchor cable to strengthen deep cracks combined with double anchor mesh shotcrete support were proposed to fully mobilize the self-supporting ability of the surrounding rock. In addition, Xiong et al [11] illustrated the stress distribution of the floor under the repeated mining and the staggered arrangement of the roadway in the lower coal seam. Zhang et al [12] illustrated that the lower coal mining roadway was prone to instability under the action of the low support strength of the roadway, the over-speed mining and the vertical arrangement of the upper coal seam roadway.…”

Study on Mechanical Characteristics and Failure Modes of Coal–Mudstone Combined Body with Prefabricated Crack

“…Therefore, the mechanical behaviors and failure laws of the coal and rock mass mainly depend on the distribution and development of cracks, which can cause serious engineering disasters, such as rib spalling, roof falling, rock burst and landslides [1][2][3][4][5]. In recent decades, gaining a comprehensive understanding of the mechanical behaviors of coal and rock masses with various faults (e.g., pre-existing cracks or holes) has been attractive [6][7][8][9][10][11][12][13]. Specifically, experimental tests had normally been performed on pre-existing cracks in rock to illustrate mechanical behaviors [14][15][16][17].…”