针对窑街三矿“三下”厚煤层压覆资源的安全开采问题,采用了下行分层膏体充填开采方法,通过构建膏体充填体假顶力学计算模型,得到了其厚度与极限强度关系式。利用尖点突变理论的势函数,推导了充填体假顶总势能,探究了充填假定的稳定性。采用FLAC3D数值计算软件,建立了下行分层膏体充填开采数值计算模型,研究了充填体假顶的移动变形特征。研究结果表明:充填体假顶的极限强度与其厚度呈幂函数负相关。充填体假顶厚度为3.2m时,其极限强度为4.9MPa,当充填体假顶厚度大于3.2m后,其极限强度逐渐稳定于2.9MPa。充填体假顶的总势能满足失稳判别式Δ≥0,不会发生突变失稳破坏。充填体假顶与下分层充填体的最大主应力均为1~2MPa,小于其极限承载的抗压强度,且塑性区出现在下分层充填体层位,充填体假顶未发生剪切或拉伸破坏,所受的拉应力稳定于0.65MPa,远小于充填体的许用拉应力。现场实测表明:下分层充填开采时,充填体假顶下沉量与上、下分层充填体的压缩量累计仅为75mm。因此,在上分层充填体假顶的基础上开采下分层,充填体假顶能够承受上部围岩所施加的覆岩荷载,保证其自身稳定性,不会发生破断失稳,从而保证窑街三矿“三下”厚煤层压覆资源的安全开采。

In order to address the problem of safe mining of the “three underground”(meaning the min- ing areas are arranged under buildings, railways and water bodies)thick coal seam overlying resources in the third Mine of Yaojie, we adopt the mining method of downward stratified paste filling. First, by constructing a mechanical calculation model for the false roof of paste filling, we could obtain the rela- tionship between its thickness and ultimate strength. Then, the total potential energy of the false top of filling body was derived by using the potential function of the cusp catastrophe theory, and its stability was explored. In the end, by using FLAC 3D  numerical calculation software, the numerical calculation model for the downlink layer paste filling mining is established, and the deformation characteristics offalse top of filling body were studied. The results show that the ultimate strength of the false roof of the backfill is negatively correlated with its thickness as a power function. When the thickness of the false roof of the filling body is 3.2 m, its ultimate strength is 4.9 MPa. and when the thickness of the false roof of the filling body is greater than 3.2 m, its ultimate strength gradually stays at 2.9 MPa. The total potential energy of the false roof of the filling body satisfies the instability criterion Δ≥0, and the sud- den instability failure will not occur. The maximum principal stress of the false roof of the filling body and the lower layered filling body are both 1-2 MPa, which is less than its compressive strength of ulti- mate bearing. And the plastic zone appears in the lower layered filling body, and the shear or tensile fail- ure of the false top of the backfill does not occur. The tensile stress is stable at 0.65 MPa, which is far less than the allowable tensile stress of the filling body. The field measurements show that,the sinking of the false roof of the filling body and the cumulative compression of the upper and lower layered filling bodies is only 75 mm during the excavation of the lower layered filling. Therefore, on the basis of the layered filling false roof in the upper strata, the lower strata are mined, and false top of filling body can bear the overburden load that the upper surrounding rock exerts, ensuring its own stability and preventing fracture instability, and keeping the safe mining of the “three underground” thick coal seam overlying resources in the third Mine of Yaojie.