基于颗粒流的含交叉裂纹类岩石水力致裂细观机理研究

针对目前岩石在水力耦合作用下交叉裂纹扩展机理认识不足的问题,采用颗粒流软件(PFC2D)的平直节理接触模型和流域法,模拟计算含交叉裂纹的类岩石三轴压缩水力致裂过程,分析双向水平主应力差和主、次裂纹倾角对水力裂纹起裂、扩展及贯通的影响规律,并揭示其细观断裂机理。研究结果表明:数值模拟与试验结果吻合较好。当有或无水平主应力差时,水力裂纹沿着或偏离水平最大主应力方向扩展,与交叉裂纹贯通或不贯通,细观机理均为拉伸断裂。增加水平主应力差可明显降低临界水压力,易形成网状裂纹,有利于提高资源开采效率。

Mesoscopic mechanism of hydraulic fracture of rock-like material with cross crack based on particle flow code

In view of the lack in understanding the hydraulic fracturing mechanism of the natural rock with cross crack,the flat joint contact model of the Particle Flow Code(PFC2D)and the domain method are adopted to simulate the hydraulic fracturing process of the rock-like specimen with cross crack under triaxial-compression,and analyzes the influence of biaxial horizontal principal stress difference and the inclination angles of the principal and secondary cracks on the initiation,propagation and penetration of the hydraulic cracks.Research results show that simulation results are in good agreement with the test results.With or without horizontal principal stress difference,the hydraulic crack propgates along or deviating from the direction of the horizontal maximum principal stress,and connects or does not penetrate with the cross crack.The mesoscopic mechanism of hydraulic fracturing under triaxial-compression is tensile fracture.By increasing the horizontal principal stress difference,the critical water pressure can be significantly reduced and the network cracks can be easily formed,which is advantageous to improve the efficiency of underground resource exploitation.