近距离下煤层综放面覆岩结构特征及运动演化规律

Characteristics of Overlying Rock Structure and Movement Evolution Law of Fully Mechanized Top-coal Caving Face in Close Distance Lower Coal Seam

针对近距离煤层开采时存在的上、下位基本顶特殊地质条件,运用“三带”理论分析了上煤层采后覆岩结构特征,得出下位基本顶周期来压步距22.09 m,上位基本顶处在弯曲下沉带不发生破坏。建立了下煤层开采时基本顶结构力学模型,计算得出下煤层开采时上位基本顶的周期来压步距31 m,下位基本顶二次破断步距12 m,下位基本顶两次周期来压后会发生上位、下位基本顶同时来压,从而在工作面表现出“强-弱-弱-强”的循环来压现象。矿压监测结果表明,工作面确实出现“强-弱-弱-强”的周期来压现象,在强周期来压时需要提前加强工作面支架稳定性控制以保障工作面安全生产。

In view of the special geological conditions of the upper and lower basic roof existing in the mining of close coal seams,the structural characteristics of the overlying strata of the upper coal seam after mining are analyzed by using the"three zones"theory,and it is concluded that the periodic weighting step of the lower basic roof is 22.09 m,and the upper basic roof is in the bending subsidence zone without damage.The mechanical model of the basic roof structure during the mining of the lower coal seam is established.It is calculated that the periodic weighting step of the upper basic roof during the mining of the lower coal seam is 31 m,and the secondary breaking step of the lower basic roof is 12 m.After the two periodic weighting of the lower basic roof,the upper and lower basic roof will be pressurized at the same time,thus showing a"strong-weak-weak-strong"cyclic weighting phenomenon in the working face.The monitoring results of mine pressure show that the periodic weighting phenomenon of"strong-weak-weak-strong"really occurs in the working face,and stability of the support needs to be strengthened in advance to ensure safe production in the working face during strong periodic weighting.