Abstract
One of the main difficulties in longwall mining (LM) is the movement of mining equipment from one panel to the next panel during mining process. The shields of the LM face may be damaged by the collapse of the roof in shallow coal seam under the “Goaf-Roof-Coal” (GRC) structure, especially when moving the shields from the current panel to the next panel. In order to solve this problem, the stability mechanism and its control factors during the LM equipment removal were investigated by using comprehensive methods including theoretical analysis, numerical simulation, and field validation based on the working conditions of Panel 31102 in Liangshuijing Coal Mine. The numerical simulations demonstrate that four different failure zones, shear failure zone, tension failure zone, partly elastic zone, and plastic failure zone, appear around the area due to the position of rock and the arrangements of the supports. The shear failure zone, which is controlled by shield working resistance and roof supporting strength, is the main cause of the failure in the removal area. To minimize the shear failure zone, several measures such as optimizing the end position for LM face, decreasing the width of removal area, and increasing the amount of cable support were taken to ensure the stability of surrounding rock in removal area, which have successfully controlled the damage of roof and equipment in Panel 31102. The field observation confirms that the proposed stability mechanism and control measures are effective under GRC structure.
Highlights
It is necessary to move the equipment from the current working face to the one at the end of excavation in longwall mining (LM) face [1]
It is necessary to move the equipment from the current working face to the one at the end of excavation in LM face [1]. If this process is not designed and implemented properly, it will significantly affect the productivity of the LM face and even cause damage of mining equipment and serious safety problems [2]. e removal area is prepared by cutting the coal without advancing the shields [3]. is space is difficult to remain stable due to high stress and deformed rock strata
Some scholars put forward a concept of yield mining, which controls the face advancing speed to control roof movement [6,7,8]. e slower the advancing speed is, the smaller the periodic roof weighting interval is. e reasonable advancing speed is used so that the roof can be in steady state instead of periodic roof weighting when the working face advances to the stopping line. erefore, the removal area can be set at a relatively stable position
Summary
It is necessary to move the equipment (i.e., shields, armoured face conveyor, shearer, etc.) from the current working face to the one at the end of excavation in LM face [1]. E removal area is prepared by cutting the coal without advancing the shields [3]. These waste rocks contribute to the instability of the removal area; on the other hand, these waste rocks are compacted gradually and, as a result, can provide support to the roof structures. E waste rocks in goaf form a GRC structure around the removal area where different elements, including shields, rock bolts, or cables, play different roles in maintaining the stability of removal area. These waste rocks contribute to the instability of the removal area; on the other hand, these waste rocks are compacted gradually and, as a result, can provide support to the roof structures. e waste rocks in goaf form a GRC structure around the removal area where different elements, including shields, rock bolts, or cables, play different roles in maintaining the stability of removal area. erefore, the purpose of this study is to investigate the structure stability through theoretical analysis and study the failure mode and support mode by numerical simulation
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