Abstract:
In the process of mining across the overlying residual coal pillars in the lower coal face (referred to as crossing-pillar mining), the residual coal pillars are subjected to high supporting pressure, which may lead to disasters such as roof caving, pressure crushing, roadway damage and coal burst in the lower coal face. A three-dimensional similarity simulation experiment was carried out to study the movement patterns of the overburden and the load transfer characteristics of the coal pillars during crossing-pillar mining. The results show that: With the mining of the working face on both sides of the residual coal pillar, the stress distribution of the interbedded rock strata changes significantly, the angle of influence of the coal pillar stress is approximately 7° in unilateral mining, and increases to 39° in two-sided mining, and the working face starts to be affected by the concentration of stress in the coal pillar when it is about 32 m away from the residual coal pillar. After the working face of the lower coal seam enters the mining below the coal pillar, the coal pillar in the goaf gradually yielded and was unloacled. This results in the transfer of the overburden load to the complete coal pillar in front of the working face, leading to stress concentration, which led to the main key stratum instability induced by the fracture of the interlayer rock layer when the working face was advanced to 5m from coal pillar, and the intense ground pressure appeared.