双轴压缩状态下岩体水力劈裂试验研究

Experimental Study on Hydraulic Fracturing of Rock Mass Under Biaxial Compression

针对水利工程中的岩体水力劈裂问题,采用自制水密封装置和水压加载系统,以水泥砂浆作为类岩石材料,基于不同轴压组合,开展双轴压缩状态下的岩体水力劈裂试验,研究了不同轴向压力对水力劈裂发展过程的影响.试验结果表明:双轴压缩状态下岩体顺缝向轴压可放大高压水流劈裂破坏能力,顺缝向轴压与临界劈裂水压呈负相关关系;垂缝向轴压可较强抑制裂缝扩展,垂缝向轴压与临界劈裂水压呈正相关关系;双轴压缩状态下,加载水压历时曲线呈M形,水力劈裂破坏具有非瞬时性;水力劈裂发展过程可分为弹性变形、缝端损伤区发展、劈裂破坏、持续变形开裂和完全破坏等5个阶段.

Aiming at the problem of hydraulic fracturing of the rock mass in engineering,the hydraulic fracturing test of rock mass under biaxial compression is carried out by using self-made water sealing device and hydraulic loading system.The cement mortar can be viewed as a rock-like material in this test.The influence of axial pressure in different directions on the hydraulic fracturing process is analyzed.The results show that the axial pressure in the parallel fracture direction can amplify the splitting and destruction capability of high-pressure water flow and it promotes the crack opening,while the axial pressure in the vertical fracture direction can strongly suppress crack propagation and it is positively correlated with the critical water pressure.Under the condition of biaxial compression,the water pressure duration curve is M-shaped and the hydraulic fracturing failure is non instantaneous.The hydraulic fracturing process can be divided into five stages,i.e.elastic deformation stage,fracture zone development stage,splitting failure stage,continuous deformation and cracking stage after splitting,and complete failure stage.