We used the key stratum theory to establish a more realistic thin-plate mechanical model of elastic foundation clamped boundary and study the fracture mechanism of overlying strata during longwall mining. We analyzed the fracture characteristics and factors affecting fracture of the key stratum combined with the Mohr–Coulomb yield criterion. Besides, we used numerical simulation methods to verify the evolution pattern of the overlying strata fracture. The results show that the fracture mechanisms of the elastic foundation clamped structure’s key stratum varied depending on the position under longwall mining. The advanced coal wall area of the upper surface is a compressive-shear fracture. The center area of the lower surface is a tensile fracture. With the increase of the excavation length and the load of the key stratum, the central area and the advanced coal wall area of the long side are fractured before the advanced coal wall area of the short side. With the increase of flexural rigidity of the key stratum, the advanced coal wall area of the long side fractures before the central area and the advanced coal wall area of the short side. With the increase of the foundation modulus and the advanced load of the key stratum, the central area fractures before the surrounding advanced coal wall area. The advanced influence distance was positively correlated with the key stratum’s flexural rigidity and advanced load and negatively correlated with the foundation modulus and excavation length. The advanced influence distance was not affected by the load of the key stratum. The numerical simulation results show that, with the increase of the mining area, the fracture trace of overlying strata in goaf extended to the coal wall’s interior. The fracture range of overlying strata is larger than that of the miningd: area. This study has a practical value for water disasters, gas outbursts, and rock strata control.

中文翻译：

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长壁开采上覆地层断裂机理

运用关键地层理论，建立了更真实的弹性地基夹边界薄板力学模型，研究了长壁开采过程中上覆地层的破裂机理。结合Mohr-Coulomb屈服准则，分析了关键地层的裂缝特征及影响裂缝的因素。此外，我们采用数值模拟方法验证了上覆地层裂缝的演化模式。结果表明，弹性地基夹层结构关键地层的断裂机制因长壁开采位置的不同而不同。上表面超前煤壁区为压剪裂缝。下表面的中心区域是拉伸断裂。随着开挖长度的增加和关键地层荷载的增加，长边中心区和超前煤壁区先于短边超前煤壁区压裂。随着关键地层抗弯刚度的增加，长边超前煤壁区先于中心区断裂，短边超前煤壁区先于中心区破裂。随着地基模量的增加和关键层的超前荷载，中心区先于周围超前煤壁区破裂。超前影响距离与关键地层的抗弯刚度和超前荷载呈正相关，与地基模量和开挖长度呈负相关。超前影响距离不受关键层负荷的影响。数值模拟结果表明，随着采区面积的增加，采空区上覆地层破裂痕迹延伸至煤壁内部。上覆地层的裂缝范围大于开采区的裂缝范围。该研究对水灾、瓦斯突出和岩层控制具有实用价值。