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顶板定向钻孔水压致裂工作面强矿压控制试验研究

Experimental study on controlling strong strata behavior in mining face by cracking roof with directional hole hydraulic fracturing

  • 摘要: 针对神东矿区布尔台煤矿42107工作面回采过程中频繁发生的强矿压显现问题,采用理论分析、数值模拟和现场实测方法,对井下定向钻孔水压致裂顶板厚硬关键层控制工作面强矿压显现进行了研究。研究结果表明:4-2煤层顶板厚度约22 m的粉砂岩亚关键层2是影响工作面强矿压显现的主要因素;理论分析通过顶板弱化降低亚关键层2的强度,在一定程度上能够削弱工作面强矿压;通过减小亚关键层2破断块体竖向节理的摩擦角以模拟顶板致裂效果,亚关键层2弱化改性后,42107工作面两侧的区段煤柱以及实体煤壁上的支承压力峰值显著降低,减小幅度约18.3%;实际在42107工作面顶板布置了3个定向钻孔,由该工作面内11台液压支架在致裂前后的工作阻力曲线得出,来压期间支架最大工作阻力由22 535 kN减小至19 599 kN,周期来压步距则由致裂前的21.0 m减小为致裂后的16.9 m,表明定向钻孔水压致裂覆岩关键层能够较好地控制工作面强矿压显现。

     

    Abstract: In an attempt to address the strong strata pressure problems frequently occurring during the mining process in No. 42107 working face of Buertai Mine of Shendong Mining Area, the studies was carried out to investigate the feasibility of directional hydraulic fracturing technique using theoretical analysis, numerical simulation and site measurement. The results show that strong strata pressure at working face is mainly cause by the 2.2-meters-thick siltstone, the No.2 key stratum located in No.4-2 coal seam roof. Theoretically, strong strata pressure can be reduced to some extent by lowering the strength of No.2 key stratum. By reducing the friction of vertical joints in No.2 key stratum , the authors were able to simulate the cracking effect, and the simulating results indicated that with the reduction of friction, the bearing pressure in the coal body drops considerably by 18.3% approximately. In real operation, three directional boreholes were drilled from coal seam into No. 2 key stratum at No.42107 working face and based on the working resistance curves generated by the 11 hydraulic supports both before and after the occurring of cracking, the average support resistance reduced from 22 535 kN prior to cracking to 19 599 kN after cracking, and the periodic weighting interval decreased from 21.0 m to 16.9 m. Those results imply that strong strata pressure could be controlled by cracking the key strata through directional hydraulic fracturing technique.

     

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