Abstract
The overburden movement of the large mining height working face of shallow buried thin bedrock (SBTB) is a complex engineering problem with “time-space-intension”, which is of great significance to realize efficient and safe mining in the northern Shaanxi mining area. Based on the research object of No. 22201 working face in Zhangjiamao Coal Mine, the roof structure characteristics of large mining height working face in SBTB are researched by field drilling measurement, laboratory test, physical and numerical simulation. The results show that: (1) Based on the measured data of the drillholes, it is concluded that under the mining conditions of SBTB with large mining height, the roof movement is ahead of the weighting of the working face, and the working resistance has a significant time effect. The advanced movement distance is about 20 m, which can be used as an early warning index of the weighting. The lag movement distance in the roof with horizon of 30 m is two periodic weighting intervals, which are about 26 m. (2) The first weighting interval of the working face is 32 m. The roof first break has obvious step sinking phenomenon, and the measured surface appears at a position 45 m away from the transport slot. It is statistically concluded that the periodic weighting interval is 9.5~16.5 m, the average weighting interval is 13 m, which is equivalent to the periodic dynamic crack spacing of the surface. (3) The results of field measurement and physical simulation show that the breaking angle of the roof of the No. 22201 large mining height is about 66°, and the periodic stepping distance of the T-junction suspension area is 6~8m. Along the strike of the working face, the roof breaking is mainly arc arched. The research results ensure the safe and green mining of shallow coal seam.
Highlights
Shallow coal seam is characterized by shallow buried depth, and it is divided into typical shallow buried coal seam and near shallow buried coal seam [1,2]
The practice of mining in shallow coal seams shows that the dynamic surface of the working face is obvious during the mining process [1,7,8], and the roof is performed to strong mining pressure such as step sinking [9,10,11,12], especially in the special geological conditions such as thin bedrock [13], gully terrain [14], concentrated coal pillars [15,16,17,18], surface subsidence [19,20,21] and water protection mining [22,23,24,25,26]
Through the field drilling measurement, combined with the displacement observation and drilling peeping results, it is concluded that the horizon of 0~10 m above the roof can monitor the displacement of roof advance movement, during the period of the weighting of large mining height
Summary
Shallow coal seam is characterized by shallow buried depth (less than 100~150 m depth), and it is divided into typical shallow buried coal seam and near shallow buried coal seam [1,2]. The practice of mining in shallow coal seams shows that the dynamic surface of the working face is obvious during the mining process [1,7,8], and the roof is performed to strong mining pressure such as step sinking [9,10,11,12], especially in the special geological conditions such as thin bedrock [13], gully terrain [14], concentrated coal pillars [15,16,17,18], surface subsidence [19,20,21] and water protection mining [22,23,24,25,26]. With the improvement of comprehensive mechanization technology of large mining height, it has been widely popularized and applied in China, especially the Shenfu. With the improvement of comprehensive mechanization technology of large mining height, it has been widely popularized and applied in mining is widely in recent
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