Chai Jing, Liu Yongliang, Gao Shigang, Yang Jianfeng, Zhang Dingding, Du Wengang, Ma Chenyang, Han Zhicheng
College of Energy Engineering, Xi'an University of Science and Technology, Xi'an, 710054, China.
Shendong Coal Group Corporation Limited, China Energy Group, Shenmu, 719315, China.
Sci Rep. 2022 Oct 5;12(1):16620. doi: 10.1038/s41598-022-21066-x.
The reserved thickness of top coal has an important influence on the stability of a large section open-off cut under gob in the thick seams slicing mining. The destabilization extremum conditions of the open-off cut top coal were derived from by elastic-plastic theory, and the optical fibre sensing technology was utilized to monitor the top coal deformation law with different thicknesses (3, 3.5, and 4 m) in the physical similar simulation experiment in the paper. The results show that the top coal thickness is greater than 3.4 m without tension cracks. In the vertical direction, the top coal of the large open-off cut is divided into mining and excavation disturbance zones under the influence of the upper slice coal mining and the excavation disturbance. In the direction of the span of the top coal can be divided into the roof fall risk zone and the warning zone. The deformation changes from exponential to linear to logarithmic in the roof fall risk zone, and it changes from linear to logarithmic in the roof fall warning zone as the number of excavations increases. The sinking amount in the two zones is smaller as the thickness of the top coal becomes larger. It is comprehensively determined that the thickness of the top coal of open-off cut is set as 3.5 m, the stability is moderate, and the field application shows that the integrity of the top coal is good after support, and the maximum off-layer value is 6 mm, which can satisfy the production requirements.
厚煤层分层开采采空区下大断面切眼稳定性受顶煤预留厚度影响显著。基于弹塑性理论推导了切眼顶煤失稳极值条件，并运用光纤传感技术，在物理相似模拟试验中监测了不同厚度（3m、3.5m和4m）顶煤的变形规律。结果表明，顶煤厚度大于3.4m时无拉裂现象。在垂直方向上，受上层煤开采及掘进扰动影响，大断面切眼顶煤分为采动扰动区和掘进扰动区。在顶煤跨度方向上可分为冒落危险区和预警区。冒落危险区内变形由指数变化转为线性变化再转为对数变化，冒落预警区内变形随掘进次数增加由线性变化转为对数变化。两区内下沉量均随顶煤厚度增大而减小。综合确定切眼顶煤厚度为3.5m时稳定性适中，现场应用表明支护后顶煤完整性良好，最大离层值为6mm，可满足生产要求。
