高强度开采覆岩岩性及其裂隙特征

Lithology and fissure characteristics of overburden in high-intensity mining

为分析高强度开采工作面覆岩岩性及其裂隙特征,以高家梁煤矿20313工作面为研究对象,分析了工作面顶板含水层赋存情况,通过试验获取了砂质泥岩顶板细观结构和矿物组分及物理力学性质,采用相似模拟试验、理论分析、CAN-Ⅱ大地电磁探测仪和现场调查综合分析了工作面开采后的覆岩破坏情况。结果表明:工作面顶板砂质泥岩随着与煤层距离的增大,颗粒间接触逐渐由点-点、点-面接触转变为线-面、面-面接触,且颗粒体积有增大趋势;由煤层至地表,抗拉(压)强度减小,断裂后接触面积更大,且遇水后颗粒体积膨胀,挤压颗粒间的孔隙,孔隙通道减小,降低宏观通水性;覆岩及地表裂缝以张开、闭合、压实的过程重复向前发展,虽然覆岩含水层及隔水层产生了破坏,但裂隙宽度较小,地表没有出现明显的塌陷裂隙;工作面开采后覆岩内会形成稳定的压力拱结构,覆岩破坏不会与地表裂隙贯通,地表潜水不会直接与井下工作面贯通。采动后工作面断层上盘侧岩层整体上破坏更严重;在断层下盘侧,虽然采动后CAN型综合值云图内出现了较多环状闭合曲线,但仍有平滑层状曲线包裹,说明采动覆岩的连续性分布较好,岩层内裂隙发育程度低;20313工作面开采后地表多以细小拉伸或挤压裂缝为主,裂缝数量较少,基本上所有裂缝经历了"张开—扩展—闭合"完整发育过程,裂缝发育周期最长的为15 d,最短为7 d;裂缝宽度最大为6.3 cm,台阶落差最大为8.7 cm,地表植被生长及分布情况与开采前基本一样,说明工作面开采的安全性及地表生态基本不受影响。高强度开采覆岩裂隙发育特征得到了大量理论与试验研究,物探法是开展覆岩裂隙现场探测最方便、快捷的手段,提高物探仪器对覆岩裂隙探测的敏感度及物探结果解释的准确度是物探法探测覆岩破坏得以推广的技术前提。

To analyze the lithology and fracture characteristics of overburden in high-intensity mining face,focusing on 20313 working face in Gaojialiang Coal Mine,The distribution of roof aquifers were analyzed.The microstructure,mineral composition,physical and mechanical properties of sandy mudstone were obtained by experiments.Physical test,theoretical analysis,magnetotelluric detection and field survey were used to analyze the overburden failure.The results show that with the increase of the distance from the coal seam to the sand mudstone of the working face,the contact between particles gradually changes from point-point and point-surface contact to line-surface and surface-surface contact,and the volume of particles tends to increase.From the coal seam to surface,the tensile (compressive) strength decreases,the contact area after fracture is larger,and the volume of particles expands after water encounters,the pore space between particles is squeezed,the pore passage is reduced,and the macroscopic water permeability is reduced.Overburden and surface fissures develop repeatedly in the process of opening,closing and compacting.Although overburden aquifers and impermeable layers have been damaged,the width of fissures is small,and there are no obvious collapse fissures on the surface.After mining,a stable pressure arch structure will be formed in overburden.Rock fissures will not connect with surface and the surface water will not directly connect with underground working face.The destruction of strata on the side of the upper wall of fault is more serious.On the lower side of the fault,although there are many circular closure curves in the nephogram of CAN,there are still smooth layered curves wrapped up,which indicates that the continuous distribution of mining overburden is good and the development degree of cracks in the strata is low.After mining in 20313 working face,most of the surface cracks are mainly tension or compression cracks,and the cracks is few.All cracks have undergone a complete development process of “opening-expanding-closing”.The longest development period is 15 days,the shortest is 7 days;the largest crack width is 6.3 cm,and the largest step drop height is 8.7 cm.The growth and distribution of surface vegetation are basically the same as before mining,which indicates that the safety of mining and surface ecology are not affected.A large number of theoretical and experimental studies have been carried out on the development characteristics of overburden fissures in high-intensity mining.Geophysical prospecting is the most convenient and fast method to detect the in-situ overburden fissures.Improvement on the sensitivity of geophysical instruments to overburden fissures detection and the accuracy of interpretation of prospecting results are the technical prerequisites for the popularization of geophysical prospecting to detect overburden fracture.