浅埋煤层群覆岩与地表裂隙发育规律和形成机理研究

Research on overburden and ground surface cracks distribution and formation mechanism in shallow coal seams group mining

浅埋煤层群高强度开采对地表的损害严重。为了研究煤层群开采裂隙(缝)发育规律和形成机理,以陕北典型浅埋煤层群开采为工程背景,采用物理模拟、数值计算和现场实测相结合的方法,得出覆岩裂隙主要为采空区边缘向上发育的上行裂隙和垮落区内的离层裂隙。地表裂隙(缝)主要为开切眼和停采线永久边界裂隙、随工作面推进周期性出现的平行裂缝、沿工作面间的煤柱边界裂隙。沿工作面间的煤柱边界裂隙的分布长度最大,是地表裂隙控制的主要对象。煤层群下煤层工作面来压步增大18%～30%,下煤层开采地表下沉系数有所减小。煤层群重复采动后边界裂隙最发育,且受上下煤柱位置的显著影响。通过合理布置煤柱,可以降低煤柱导致的应力集中,减轻不均匀沉降和地表裂缝发育。

In order to study the coal mining cracks(or fissure) formation and development mechanism, taking the typical shallow coal seam group mining in Northern Shaanxi as the engineering background and using the method of physical simulation, numerical calculation and field measurement, it is concluded that the mining induced cracks in overburden are mainly the upward cracks along the gob edge and roof separation cracks in the caving zone. The surface cracks are mainly the permanent boundary cracks of open cut and stop mining line, periodic parallel cracks along with mining face and sectional coal pillar boundary cracks. The coal pillar boundary cracks which are the longest in distribution is the main object of the crack control. Under the coal seam group mining, the roof caving step increase by 18%-30%, and the subsidence coefficient of the ground surface is reduced. After the repeated mining of the coal seams, the boundary cracks are easily developed and are influenced by the position of the upper and lower coal pillars. By reasonably arranging the coal pillars, the stress concentration caused by the coal pillar can be decreased, the uneven surface subsidence and cracks can be reduced.