远场高位厚硬岩层破断运动机理及响应规律研究

Study on mechanism and response of fracture and movement of the far-fieldhigh-position hard-and-hick stratum

掌握远场高位厚硬岩层破断运动规律对于地表剧烈沉降、强矿震等灾害安全防控具有重要作用。以营盘壕煤矿2201、2202工作面为研究背景,建立远场高位厚硬岩层破断力学模型,采用符拉索夫厚板理论分析白垩系砂岩组破断运动规律及其影响因素,并通过地表沉陷、微震响应规律进行验证分析。得出如下结论:(1)针对白垩系砂岩距煤层远、厚度大、整体性好的赋存特征,建立了远场高位厚硬岩层破断力学模型,采用符拉索夫厚板理论解算出了高位厚硬岩层初次破断临界力学条件。(2)随着抗拉强度增大,厚硬岩层破断悬露长度依次呈现缓慢增长、线性增长和指数型增长特征;随岩层厚度增大,厚硬岩层破断悬露长度近似呈现指数型增长;随着倾向悬露长度(工作面宽度)增大,厚硬岩层破断悬露长度呈现先增大后逐步减小的变化趋势。(3)营盘壕煤矿2201工作面推采过程中,厚硬岩层不会发生破断;当2202工作面推采至960 m左右时发生竖向“O-X”破断;随着工作面继续推进约188 m,厚硬岩层将发生周期性破断。(4)地表沉陷监测结果表明,2201工作面推采期间地表沉降值整体较小且无较大变化,以小能量微震事件为主;2202工作面推采期间地表下沉依次经历了缓慢下沉阶段、急剧下沉阶段、稳定阶段,大能量强矿震频率明显增大,大能量矿震发生位置与地表沉降最大值区域重合度较高,均处于“O-X”破断区域;地表下沉速度在距开切眼960 m处达到最大值9.87 mm/d,并诱发了“6·8”强矿震事件,验证了远场厚硬岩层破断规律的正确性。

Mastering fracture and movement of far-field high-position hard-and-thick strata plays an important role in safety prevention and control of disasters including severe surface subsidence and strong mine seismic events.The fracture mechanical model of high-position hard-and-hick strata is established based on the panels 2201 and 2202 in Yingpanhao Coal Mine.The fracture and movement of the Cretaceous sandstone formation and its influencing factors are analyzed by using the theory of Vlasov thick plate,which is verified and analyzed by surface subsidence and microseismic events.The conclusions are as follows:①In view of the occurrence characteristics of Cretaceous sandstone group that is far away from the coal seam,with large thickness and good integrity,a high-position hard-and-hick strata fracture mechanical model is established.And the critical mechanical conditions for the first fracture of high-position thick-and-hard rock stratum are calculated by Vlasov thick plate theory.②With the increase of tensile strength,the fracture overhang length of hard-andhick stratum slowly grow,linearly grow,and exponentially grow;As the thickness of the stratum increases,the fracture overhang length of the thick and hard rock stratum increases exponentially;With the increase of the overhang length along the dip(width of panel),the fracture overhang length of thick and hard rock stratum increases first and then decreases.③During the extraction of panel 2201 in Yingpanhao Coal Mine,the hard-and-hick stratum did not break;And when the panel 2202 advanced about 960 m,the vertical“O-X”fracture occured;When the panel continues to advance about 188 m,the hard-and-hick stratum breaks periodically.④The monitoring results of surface subsidence show that the surface subsidence value of panel 2201 is small as a whole,and there are many small energy micro-seismic events.The surface subsidence of panel 2202 has experienced slow subsidence,rapid subsidence and stable stages in turn,and the frequency of high-energy mine seismic event has increased significantly.The location of the high energy mine seismic events and the area of the maximum surface subsidence are highly coincident,both in the O-X break area;The surface subsidence velocity reached the maximum of the 9.87 mm/d at 960 m away from the setup room,inducing the“6·8”strong mine seismic event.The above phenomenons verified the correctness of the far-field thick and hard rock stratum fracturing behavior.The research results of this paper have guiding significance for the study on the fracture of thick and hard rock stratum and disaster pre-control under similar engineering geological conditions.