深井巨厚覆岩邻空采动强矿震孕育发生机理

Occurrence mechanism of strong mining tremors under mining near goaf in deep mine with extremely thick strata

矿震是深部矿井开采必然出现的动力现象,针对鄂尔多斯矿区白垩系巨厚覆岩邻空采动强矿震频发的现状,采用地面离层探测、地表岩移监测等技术,结合Reissner厚板理论与相对矩张量反演方法,分析了工作面邻空采动下白垩系巨厚覆岩破断运移特征,研究了工作面实体煤阶段向邻空回采阶段过渡区域频发矿震震源破裂模式的演化规律,揭示了白垩系巨厚覆岩深部煤层邻空采动强矿震孕育发生机理。结果表明:综放工作面实体煤回采阶段,白垩系巨厚覆岩无明显裂隙产生,地表沉降稳定,沉降量最大为0.23 m;邻空回采阶段,裂隙发育高度最大至煤层上方444.8 m处白垩系巨厚覆岩,强矿震震源处地表总是最先达到最大沉降,强矿震发生前地表最大沉降量快速增加,较1个月前监测最大沉降量增大超60%,表明白垩系巨厚覆岩破断运动为强矿震动力源,强矿震扰动作用下,巨厚覆岩失稳引起地表再次快速沉降。白垩系巨厚覆岩初次破断步距为307.7 m,与工作面实际推进度基本吻合,佐证了强矿震由白垩系巨厚覆岩初次破断诱发;巨厚覆岩破断厚度增大,其初次破断步距增幅逐渐变缓;工作面面长增大,巨厚覆岩初次破断步距线性增长,巨厚覆岩初次破断形式由横“O-X”形转变为竖“O-X”形。邻空采动下,白垩系巨厚覆岩下岩层逐级向上破断,岩层自下而上破断诱发矿震震源主导破裂模式由压缩、剪切破裂向压缩、张拉破裂转变;随着邻空工作面采空范围进一步增大,裂隙扩展至白垩系巨厚覆岩后,不稳定巨厚覆岩张拉破断是诱发“8·20”强矿震的根本原因。研究结论可为深部矿井巨厚覆岩邻空采动强矿震的防控提供参考。

Mining tremors is an inevitable dynamic phenomenon in deep mine mining,in view of the current situation that strong mining tremors occurs frequently in the Erdos mining area under mining near goaf in deep mine with extremely thick strata,we used techniques such as ground detection holes and surface stratum movement monitoring,combined with Reissner Thick Plate Theory and the relative moment tensor inversion method,to study the characteristics of strata rupture transport and the evolution of rupture-induced mining tremors source rupture pattern at the working face,and revealed the occurrence mechanism of strong mine tremor in deep coal with the Cretaceous extremely thick strata under goaf mining.The results show that:during the in the retreating period with no goaf nearby,ex-tremely thick strata has no obvious fissures and the surface settlement is stable,with a maximum settlement of about 0.23 m;during the In the retreating period along with goaf,the fissures develop to a maximum height of 444.8 m above the coal seam in the extremely thick strata,and the surface always reaches the maximum settlement at the source of the mining tremor first,and the maximum settlement of the surface increases rapidly before the strong mining tremor occurs,which is more than 60%higher than the recent one.This indicates that the fracturing and movement of the extremely thick strata was the source of the strong mining tremor and that the instability of the ex-tremely thick strata caused the surface to settle rapidly again as a result of the disturbance of the strong mining tremor.The initial fractur-ing step of the extremely thick strata is 331.82 m,which is consistent with the actual advance of the working face,and supports that the strong mining tremor was induced by the initial fracture of the extremely thick strata;the initial fracturing step increases gradually with the increase of the thickness of the extremely thick strata;the initial fracturing step increases linearly with the increase of the working face length,and the initial fracture of the extremely thick strata transforms from horizontal“O-X”shape to vertical“O-X”shape.The bottom-up rupture of the rock layer induced by the bottom-up rupture of the mining tremors source changed from compressional and shear rupture to compressional and tensional rupture;with the further increase of the mining area of the working face,the fissure extended to the ex-tremely thick strata,and the tensional rupture of the unstable extremely thick strata was the root cause of the“8•20”strong mining tremor.The findings of the study can provide references for the prevention and control of strong mining tremors under mining near goaf in deep mine with extremely thick strata.