窄柔模墙体沿空留巷围岩偏应力演化与控制

Evolution of deviatoric stress and control of surrounding rock at gob-side entry retaining with narrow flexible-formwork wall

为研究柔模混凝土巷旁充填下沿空留巷围岩偏应力的分布与演化规律,以山西吕梁贺西煤矿3301工作面沿空留巷为工程背景,采用实验室试验的方法确定了沿空留巷巷旁混凝土充填材料的单轴抗压强度,通过现场调研、理论分析、数值模拟和现场实测相结合的方法研究了本工作面回采过程中沿空留巷围岩偏应力和塑性区的分布及其演化规律,揭示了工作面回采扰动下沿空留巷围岩的非对称变形破坏机制。数值模拟研究结果表明:随着工作面不断向前推进,沿空留巷围岩偏应力以对称椭圆→非对称圆→窄“条带状”→宽“条带状”的形态进行演化,其塑性区呈现分区域扩展的动态响应特征,从而确定了超前与滞后采动区顶板、底板与两帮的影响距离;非对称分布的“条带状”偏应力峰值带呈现出由回采侧向实体煤侧偏转演化的趋势。基于工作面回采过程中沿空留巷围岩偏应力与塑性区的分布及演化规律,将沿空留巷围岩以偏应力峰值带与塑性区轮廓线为边界划分为2个区域,按围岩支护不同又将留巷围岩划分为实体煤帮A区、留巷顶板B区和柔模混凝土墙体C区,提出沿空留巷窄柔模墙体拉筋配合铁板加固辅以单体支柱护墙+巷内强力双排单体支柱+实体煤帮与顶板高强高预紧力非对称锚杆索的分区非对称耦合控制技术。现场工程实践表明,沿空留巷围岩控制效果良好。

In order to study the distribution and evolution law of deviatoric stress of surrounding rock at gob-side entry retaining under the filling of flexible-formwork concrete wall,taking the gob-side entry retaining of No.3301 working face in Hexi coal mine as an engineering background,the uniaxial compressive strength of roadside concrete filling body of gob-side entry retaining was determined by laboratory test.Deviatoric stress and plastic zone distribution and evolution law of surrounding rock at gob-side entry retaining in the mining process of the working face was studied by a combination of methods such as field research,theoretical analysis,numerical simulation and field measurements.The mechanism of asymmetric deformation and failure of surrounding rock of gob-side entry retaining under the mining and disturbance of the working face was revealed.The numerical simulation results show that the evolutional sequence of deviatoric stress distribution of gob-side entry retaining is symmetric ellipse,asymmetric circle,narrow“strip”,wide“strip”as the working face moves forward.The plastic zone presents a dynamic response characteristic of zonal expansion.And the obvious influence zone of the roof,the bottom and the two walls of the roadway in the advanced and the lag mining areas was determined.The asymmetrically distributed“stripe”deviatoric stress peak zone shows a trend of evolution from the mining side to the solid coal side.Based on the distribution and evolution laws of deviatoric stress and plastic zone of surrounding rock of gob-side entry retaining during the mining of working face,the surrounding rock was divided into two areas with the boundary of the peak of deviatoric stress and the contour of plastic zone.According to the different support of surrounding rock of gob-side entry retaining,it was also divided into the solid coal side(A),the roadway roof(B),and the flexible-formwork concrete wall(C).The zonal asymmetric coupling control technology was proposed and applied in the field test,which was named the narrow flexible-formwork wall reinforced with cable and iron plate along single-pillar wall+strong double-row single-pillar in the roadway+high-strength and high-preloading asymmetric anchor cable in solid coal and the roof of gob-side entry retaining.