Research on Overburden Movement Characteristics of Large Mining Height Working Face in Shallow Buried Thin Bedrock

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.

Study on the Pressure-Bearing Law of Backfilling Material Based on Three-Stage Strip Backfilling Mining

“…The SBM technology is, thus, a potential solution to the above challenges.In recent years, research on strip backfilling mining of small and medium-sized mines in China's northern Shaanxi province has been gradually increasing [16][17][18][19][20][21]. Several scholars have studied the stability of coal pillars and overburden in SBM [22][23][24][25]. Zhang et al, among others, put forward the concept of green mining technology for "mining, selecting, and filling + X" in coal mines [26], which provided strong technical support for the so-called green coal mining.…”

Research on the Roof Advanced Breaking Position and Influences of Large Mining Height Working Face in Shallow Coal Seam

“…The average buried depth of the 2-2 coal seam is about 95 m, the mining height is 6 m, and the hydraulic support model is ZY12000/28/63D. In the middle of the 22201 working face, the cores are drilled to the roof coal and overlying strata mainly measured the compressive strength, tensile strength, elastic modulus, and Poisson's ratio of coal rock mass, experimental results, as shown in Table 2 [32]. In order to observe the whole process of roof advanced breaking position of the 22201 working face in mining.…”

“…Every observed station is including three drilling holes, which are drilled into the roof as shown in Figure 5a. By the drilling peep and the mechanical multi-point displacement meter, the breaking position of the roof is observed [32].…”

“…(2) Starting weighting: when the working face advances to 2-4 m from the advanced breaking line, the main roof structure M block starts to rotate, and the advanced breaking line extends downward to the EIR, so the stability of the immediate roof reduced. The same time, the support capacity of the structure and the stability of the roof structure are reduced, and the pressure of the support on the measured in the 22201 working face rises and starts to come [32], as shown in Figure 10b. In the same way, when the main roof is first period caving, the roof is broken at 5-8 m ahead of the rib, and the roof with horizon of 16-20 m, as shown in Figure 9a.…”

“…A short cantilever beam-hinged rock beam structure of a fully mechanized mining roof with a large mining height is proposed to determine the working resistance of the support [27]. Other scholars have also studied the roof structure of the LMH stope [28][29][30][31][32]. However, there are few studies on the roof advanced breaking position of LMH working face in shallow coal seam.…”