浅埋煤层沟谷区高位关键层破断动载机理及应用

Breaking dynamic load mechanism and application of high key strata in gully area of shallow coal seam

针对西部沟谷地形易发生动载矿压的问题,通过相似模拟、理论计算分析、现场实测,对复合关键层下工作面过沟谷区强矿压显现特征进行分析与对比,构建了复合关键层下沟谷区上坡段失稳结构模型,推导了上覆岩层移动过程中高位关键层回转变形与滑落失稳初次破断步距计算公式。研究表明:工作面过沟谷区域高位关键层缺失的上坡段时极易发生剧烈的切顶、压架、台阶下沉等动载现象。沟谷区上坡段先发生回转变形失稳,随后破断块体形成的链式结构发生滑落失稳冲击下部工作面造成强矿压显现。通过构建连续沟谷区高位关键层非均布载荷梁结构力学模型基本单元,计算得出初次回转变形与滑落失稳破断步距分别为27、142 m,与1305-2工作面过第一条沟谷距谷底145 m处发生压架的位置较为吻合。结合高位关键层破断动载机理提出了过沟谷地形动载矿压综合防治措施并应用到朱家峁煤矿开采中,计算得出1305-2工作面过第二条沟谷与1307-2工作面分别于147、126 m处发生剧烈来压,对计算的危险区域采取水力压裂等防治措施,防治效果良好,为过沟谷地形开采时动载矿压防治提供了理论依据。

This study is aimed at tackling problems induced by dynamic loads on coal rock in western gully areas through multiple research methods including similar simulation,theoretical calculation analy⁃sis,and field measurement.Specifically,the characteristics of intense mining pressure on the working face across the gully area under composite key strata were comparatively analyzed.On this basis,a structural instability model of the uphill section in a gully area under composite key strata was construc⁃ted,and the calculation formulas of the rotation deformation of high key strata and the initial fracture step of sliding instability during the movement of overburden were derived.The research results indicate that when the working face passes through the uphill section of high key strata in a gully area,severe dy⁃namic loading phenomena such as roof cutting,support crushing,and step sinking are likely to occur.Initially,rotation deformation instability occurs in the uphill section of the gully area,followed by the sliding of chain structure formed by broken blocks,which further affects the lower working face and ulti⁃mately results in intense mining pressure.By constructing the basic unit of the structural mechanical mod⁃el of the non⁃uniform load beam at high key strata in the continuous gully area,the step distances for ini⁃tial rotation deformation and sliding instability were calculated to be 27 m and 142 m,respectively,which is consistent with the actual support crushing accident that occurred at 145 m away from the bot⁃tom of the first gully when the 1305⁃2 working face passed there.Subsequently,combined with the fail⁃ure mechanism of high key strata under dynamic loads,comprehensive prevention and control measures for mining pressure in valley terrains under dynamic loads were proposed and applied to Zhujiamao Coal Mine.According to the calculation results,severe mining pressure is likely to appear in the 1305⁃2 and 1307⁃2 working faces at distances of 147 m(when it passes the second value)and 126 m,respectively.Hydraulic fracturing and other prevention and control measures were carried out in these calculated haz⁃ardous areas,and the effect turned to be excellent.This study provides a theoretical basis for the preven⁃tion and control of dynamic load mining pressure in valley terrains.