刘得潭　沈振中

摘要：许多水工建筑物建于基岩上，天然岩体大多存在节理裂隙，在高水压力作用下易发生水力劈裂破坏。

为研究裂隙岩体的水力劈裂特性，以水泥砂浆代替岩石、制作预制裂缝试样，研制了高压水密封装置和水压力加载系统，开展了不同缝长和缝宽的砂浆试件水力劈裂试验研究，测定了预制裂缝起裂临界水压力、水力劈裂临界水压力，分析了两者关系，提出了预测表达式。试验结果表明，试件水力劈裂临界水压力为0.441～1.542 MPa，相同条件下，试件水力劈裂临界水压力与初始缝长及缝宽呈负相关关系；预制裂缝起裂临界水压力与水力劈裂临界水压力比值为61.57%～64.17%，与预制裂缝初始缝长和缝宽无关。应用应力强度因子计算公式，综合试验结果，分析得到了考虑预制裂缝宽度影响的裂缝起裂临界水压力和试件水力劈裂临界水压力的计算表达式。

关键词：裂隙岩体；水力劈裂；预制裂缝；临界水压力

中图分类号：TV36文献标志码：A文章编号：

16721683（2018）02014006

Abstract：

Many hydraulic structures are built on bedrocks，and most natural rock masses have joint fissures，which are prone to triggering hydraulic fracturing phenomenon under high water pressure.In order to study the hydraulic fracturing characteristics of fractured rock mass，we prepared specimens with precast cracks using cement mortar as a substitute material of rock mass.We developed a water pressure loading system and a water sealing device，and used them to test the hydraulic fracturing of cement mortar specimens with different initial precast crack lengths and widths.We determined the critical water pressure of precast crack initiation and that of hydraulic fracturing of the specimens. The relationship between the critical water pressure of precast crack initiation and that of hydraulic fracturing was analyzed， and the predictive formulas for the critical water pressures of precast crack initiation and hydraulic fracturing were proposed.The test results showed that the critical water pressure of hydraulic fracturing of the specimens was 0441 MPa1542 MPa.The critical water pressure of hydraulic fracturing would decrease as the initial precast crack length and width increased when the other factors remained unchanged.The ratio between the critical water pressure of precast crack initiation and the critical water pressure of hydraulic fracturing was 6157%6417%，and it was independent of the initial crack length and width. Based on the stress intensity factor formula and the experimental results，we obtained the calculation formulas for the critical water pressure of precast crack initiation and hydraulic fracturing of the specimens with consideration to the influence of the width of the precast cracks.

Key words：

fractured rock mass；hydraulic fracturing； precast crack；critical water pressure

巖体经过长期地质构造作用，含有很多微观甚至宏微观上的节理、孔隙及裂纹等。水的渗入使得裂缝内的水压值增大，增加了裂缝尖端应力集中的程度，可造成裂缝发生扩展、贯通出现水力劈裂现象[12]。

目前，很多学者在岩石水力劈裂方面进行了深入的研究。Hayashi[3]在03 m×03 m×03 m立方体安山石岩块表面钻一直径10 mm的圆孔，以黏性稠油为液体进行三轴水力劈裂试验，得出裂缝重新开裂的临界孔压经验公式；Papanastasion和Thiercelin[4]通过试验，研究了岩石塑性屈服和剪胀对水力劈裂裂缝的张开和扩展的影响，定性的分析了裂缝尖端在水力劈裂作用下的力学上和结构上的反应；……