以绿色中砂岩为研究对象,综合采用室内试验、数值模拟及理论分析方法研究了机械胀裂作用下岩石单孔及多孔预制裂缝的起裂及扩展规律。结果表明:与无预制裂缝试样相比,裂缝起裂压力降低53%以上,理论模型与数值模拟及室内试验结果吻合较好;多孔条件下裂纹的贯通压力随孔间距和围压的增加而增大,且其降低率随围压的增大逐渐降低同时不受孔间距的影响;起裂压力随着围压的增加逐渐升高且孔距对其无影响;多孔机械胀裂裂纹扩展过程可划分为裂纹萌生、裂纹扩展和贯通3个基本阶段,上述胀裂过程是在相邻钻孔产生的峰值拉应力相互干扰下导致的。研究结果对煤矿坚硬顶板水力压裂、膨胀剂致裂及定向爆破致裂等工程具有一定的指导意义。
Taking green medium sandstone as the research object, indoor experiment, numerical simulation and theoretical analysis methods were comprehensively used to study the initiation and propagation laws of single-hole and multi-hole prefabricated cracks in rocks under mechanical expansion cracking. The results show that: The crack initiation pressure is reduced by more than 53% compared with that of the unprepared crack specimens, and the theoretical model coincides well with the results of numerical simulation and indoor tests; the penetration pressure of cracks under multi-hole conditions increases with the increase of hole spacing and peripheral pressure, and its reduction rate gradually decreases with the increase of peripheral pressure while it is not affected by the hole spacing; the crack initiation pressure gradually rises with the increase of peripheral pressure, and the hole spacing has no effect on it. The multi-hole mechanical expansion crack extension process can be divided into three basic stages: crack initiation, crack propagation and penetration, and the above expansion process is caused by mutual interference of peak tensile stresses generated by neighboring boreholes. The results of the study are of guiding significance to the engineering of hydraulic fracturing, expansion agent fracturing and directional blasting fracturing of hard roof slabs in coal mines.
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