高构造应力区大采高覆岩灾变规律实验研究

Experimental research on catastrophic mechanism of overburden strata with high excavation height in high tectonic stress zone

在褶皱区开采覆岩受高构造应力的条件下,开采煤层上覆坚硬岩层断裂与开采范围属于非线性问题。为研究该条件下覆岩灾变规律,应用材料力学的弯曲梁理论,对相邻坚硬岩层建立简化的力学模型,推导出其势函数的表达式,运用尖点突变模型得到其发生破断的充分必要条件。通过实测的地应力,求得该矿坚硬岩层的极限断裂距为280 m;在实验室条件下采用围压加载模拟支架进行物理相似模拟实验后发现,在留设10 m煤柱条件下,坚硬岩层极限破断距为340 m。运用FLAC^(3D)数值模拟,得出在同样地质条件下,当留设0,10 m煤柱时,复合关键层的极限破断距分别为280,345 m。研究结果表明高构造应力条件下,复合关键层的断裂是矿井冲击矿压灾害的源头,断裂距越大其聚集的能量越大,因此在矿区开采中应尽量使用窄煤柱或无煤柱开采,减少坚硬岩层的断裂能量的释放。

Under the circumstance with high tectonic stress in folded region, overlying hard strata fracture and mining scope are nonlinear. For the catastrophic mechanism of overburden strata, the simplified mechanical model of the adjacent hard strata was established through the application of bent beam theory in material mechanics, and the potential function was elicited. Besides, necessary and sufficient condition of hard strata fracture was obtained through applying cusp mutation model. Limit fracture spacing of hard strata was 280 m in in-situ stress monitoring. A physical simulation experiment with simulated support under confining pressure was carried out and the limit fracture spacing was 340 m when the width of coal pillar was 10 m. The limit fracture spacing of the compound key strata was 280 m and 345 m respectively, which was found in the numerical simulation（FLAC3D） of the circum stances where the width of coal pillar was 10 m and 0 m. The results have indicated that the longer limit fracture spacing of compound crucial strata is, the larger energy releases. Therefore, coal excavation with shallow coal pillar and without coal pillar would be valuable for reducing energy release from hard strata fracture for mining safety.