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Experimental studies on influence factors and mechanism of critical water pressure of hydraulic splitting in rock mass
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摘要: 为了研究材料强度、初始裂缝开度、初始缝长和轴向压应力对岩体水力劈裂临界水压力的影响，采用水泥砂浆作为岩体相似材料，进行岩体水力劈裂试验，探讨其水力劈裂破坏机理。试验结果表明，岩体水力劈裂临界水压力与材料强度和轴向压应力存在正相关关系，轴向压应力较材料强度对水力劈裂临界水压力影响大；水力劈裂临界水压力与初始裂缝开度、初始缝长呈负相关关系，初始缝长对水力劈裂临界水压力敏感性比初始裂缝开度大。随着缝内水压的增大，岩体初始裂缝的裂尖扩展，裂隙水流渗入到损伤劣化区，在裂隙水流的双重力学作用下，损伤区裂隙、孔隙扩展贯通形成宏观裂缝，宏观裂缝在缝内水流双重力学作用下，裂尖应力强度因子超过断裂韧度，岩体失稳破坏。Abstract: In order to investigate the impacts of material strength, initial crack opening, initial slit length, and the axial compressive stress on the critical water pressure for hydraulic splitting of the rock masses, the cement mortar is selected as the substitute material for a rock mass, and it is subjected to hydraulic splitting tests to examine its hydraulic splitting mechanism. The experimental analysis results indicate that a positive correlation exists between the critical water pressure for the hydraulic splitting and the material strength and the axial compressive stress of the rock mass. The axial compressive stress is found to have a larger impact on the critical water pressure for the hydraulic splitting than that of the material strength. However, the critical water pressure for the hydraulic splitting has a negative correlation with both the initial crack opening and the initial slit length, with the latter being more sensitive to the critical water pressure for the hydraulic splitting than the former. When the water pressure in the rock cracks increases, the tip of the initial crack expands and allows more fissure water to infiltrate the damaged and degraded zone. Under the dual mechanical effects of fissure water, the fractures and pores in the damaged zone expand and interconnect to form macrocracks. These macrocracks are in turn subjected to similar dual mechanical effects. Eventually, the stress intensity factor at the tip exceeds the tenacity of the cracks, resulting in destabilization and destruction of the rock mass. Under the action of the double mechanics of water flow in the rock, the stress intensity factor of the crack tip exceeds the fracture toughness, and the rock mass is unstable.
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Key words:
- rock mass /
- hydraulic splitting /
- critical water pressure /
- double mechanical effects
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图 4 D-2-3试件水压及轴压加载过程
Figure 4. Process of water pressure and axial loading on D-2-3 specimen
图 5 部分试样水力劈裂破坏形态
Figure 5. Fracture morphology of hydraulic splitting of some specimens
图 6 水力劈裂临界水压力与材料强度关系
Figure 6. Relationships between critical water pressure of hydraulic splitting and material strength
图 7 水力劈裂临界水压力与轴向压应力关系
Figure 7. Relationships between critical water pressure of hydraulic splitting and axial compressive stresses
图 8 初始裂缝开度和初始缝长与水力劈裂临界水压力关系
Figure 8. Relationships among critical water pressure of hydraulic splitting and initial crack opening and slit length
图 9 裂缝扩展过程中水流双重力学效应
Figure 9. Double mechanical effects of water flow during crack propagation
表 1 试件基本参数及试验结果
Table 1. Basic parameters and test results of specimens
方案 编号 试件尺寸 初始裂缝开度b/mm 初始缝长a/mm 数量/个 抗拉强度ft/MPa 轴压/kN σz/MPa Pc/MPa A A-1 150 mm×150 mm×150 mm 2 50 3 1.09 0 0 0.915 A-2 150 mm×150 mm×150 mm 4 50 3 1.09 0 0 0.695 A-3 150 mm×150 mm×150 mm 6 50 3 1.09 0 0 0.441 B B-1 150 mm×150 mm×150 mm 2 40 3 1.09 0 0 1.541 B-2 150 mm×150 mm×150 mm 2 50 3 1.09 0 0 0.915 B-3 150 mm×150 mm×150 mm 2 60 3 1.09 0 0 0.582 C C-1 150 mm×150 mm×150 mm 2 50 3 1.17 0 0 1.067 C-2 150 mm×150 mm×150 mm 2 50 3 1.66 0 0 1.551 C-3 150 mm×150 mm×150 mm 2 50 3 2.31 0 0 2.000 D D-1 150 mm×150 mm×150 mm 2 50 3 1.66 0 0 1.551 D-2 150 mm×150 mm×300 mm 2 50 3 1.66 4.5 0.2 1.764 D-3 150 mm×150 mm×300 mm 2 50 3 1.66 9.0 0.4 1.934 
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