强烈动压巷道水力压裂切顶卸压压裂时机研究

Study on fracturing timing of hydraulic fracturing top-cutting and pressure relief in roadway with strong dynamic pressure

水力压裂技术近年来越来越多地被应用于强烈动压巷道的卸压工程中。在强烈动压巷道水力压裂切顶卸压过程中,裂缝的扩展方向最终会与最大主应力方向保持一致,而最大主应力的大小和方向会因受到工作面回采超前应力的影响而改变,如何保证裂纹最终扩展方向和巷道轴线基本保持一致是确保卸压效果的关键。采用全钻孔注浆锚固的改进型空心包体应力计在晋城王坡煤矿3310回风巷进行了顶板三维应力随工作面推进演化规律实测及分析研究。研究结果表明:随着回采工作面的推进,煤柱侧15 m上方顶板三维主应力相对值在距工作面250 m处开始受到回采影响,三维主应力方位角和倾角在距工作面200 m以远就基本完成了调整。工作面侧15 m上方顶板相对主应力值在距工作面252 m处开始受到回采影响,三维主应力方位角和倾角在距工作面180 m以远就基本完成了调整,但在距工作面50 m以内由于受采空区影响,方位角逐渐出现逆时针偏转;巷道正上方顶板相对主应力值在距工作面164 m处开始受到回采影响,距工作面越近影响越显著,特别是在距工作面57 m以里影响更加剧烈。三维主应力方位角和倾角在距工作面140 m以远基本完成了调整,超前回采工作面140~80 m最大主应力σ1方位角和巷道轴向夹角(13°~20°)较小,为水力压裂的最佳时机,同时不影响回采巷道的超前支护施工。

Hydraulic fracturing technology has been used more in the project of strong dynamic pressure roadway in recent years.In the process of hydraulic fracturing top-cutting and pressure relief in the roadway with strong dynamic pressure,the fracture propagation direction is finally consistent with the direction of maximum principal stress,and the magnitude and direction of maximum principal stress will be changed by the influence of advanced stress in the working face.How to keep the final crack direction consistent with the roadway axis is the key to ensure the effect of pressure relief.In this paper,the 3D stress evolution law of roof with the advance of working face is measured and analyzed in the 3310 Return Air Roadway of Wangpo Coal Mine,China,by using the improved hollow inclusion stress meter with full bore grouting and anchoring.The results show that the relative value of principal stress at the roof 15 m above the coal pillar is influenced by mining at the distance of 250 m from the working face,and the azimuth and inclination of 3D principal stress are adjusted at the distance of 200 m from the working face.The relative principal stress value at the roof above 15 m of the working face begins to be influenced by mining at 252 m from the working face,and the azimuth and inclination of 3D principal stress are basically adjusted at 180 m from the working face,due to the influence of mined-out area,the azimuth gradually appears counter-clockwise deflection within 50 m from the working face.The relative principal stress of the roof above the roadway begins to be influenced by mining at 164 m from the working face,and the closer the relative principal stress is to the working face,the more significant the influence is,especially within 57 m from the working face.The azimuth angle and inclination of 3D principal stress have been adjusted at the distance of 140 m from the working face,and the angle betweenσ1 azimuth and the axial direction of the roadway is smaller between 140 m and 80 m,and is 13°-20°,which is the best time for hydraulic fracturing.At the same time,it does not affect the advance support installation at the mining roadway.