厚松散层薄基岩坚硬顶板工作面覆岩破坏电法监测

掌握导水裂缝带发育高度对于厚松散层薄基岩煤矿工作面安全开采具有重要的意义。在煤层采动影响前,在工作面巷道向煤层工作面顶板施工1个仰孔,布置孔中电极电缆,形成钻孔电法监测系统。在巷道中连接并行电法仪器和钻孔电缆,数据采集方式称为AM法。随采煤工作面位置逐渐接近并进入钻孔控制范围,监测电极电流值和视电阻率值发生变化。结果表明:对潘北煤矿厚松散层薄基岩坚硬顶板工作面电法监测显示,弯曲下沉带电极电流值和视电阻率值较为稳定,受采动影响程度较小;导水裂缝带内,电极电流值明显下降,视电阻率值明显升高;顶板高度0~40 m采动超前影响范围可达410 m左右;工作面坚硬顶板砂岩地层为控制覆岩破坏的关键层,采空区上方坚硬顶板岩层垮落滞后工作面9~16 m;工作面导水裂缝带高度为37 m,导水裂缝带未发育到基岩面,风化砂质泥岩裂隙在采动应力作用下存在闭合现象。

Electrical monitoring of overburden failure in hard roof working face with thick loose layer and thin bedrock

It is of great significance to grasp the development height of water conduction fracture zone for safe mining of the working face in thick loose layers and thin bedrock coal mines. Before the influence of coal seam mining,a lift hole was constructed in the roadway of the working face to the roof of coal face,and the electrode cables in the holes were arranged to form a borehole electrical monitoring system.Parallel electrical instruments and drilling cables were connected in the roadway,and AM method was employed as the data acquisition method. With the position of coal mining face gradually approaching and entering the drilling control range,the changes of electrode current and apparent resistivity were monitored. The results of electrical monitoring on the working surface of the hard roof of thick loose layer and thin bedrock in Panbei Coal Mine show that the electrode current values and apparent resistivity values in curved subsidence zone are relatively stable and are less affected by mining;in the water-conducting fracture zone,the current value of electrodes decreases significantly and the apparent resistivity value increases accordingly. At the roof height of 0 ~ 40 m,the influence range of mining advance can reach 410 m or so;the hard roof sandstone stratum is the key stratum to control the overburden rock failure,and the hard roof rock stratum above the gob collapses and the working face is 9-16 m lagging behind;the height of the water-conducting fracture zone in the working face is 37 m,the water-conducting fracture zone does not develop to the bedrock surface,and the weathered sandy mudstone fractures are closed under the action of mining stress.