考虑裂隙附加水压的岩体断裂强度分析

修建大坝、隧洞等工程活动必将对其周围岩体产生扰动，导致赋存于岩体裂隙中的水产生附加水压，从而使岩体在扰动荷载和裂隙水压作用下沿裂隙面失稳扩展。首先基于夹杂理论，推导出扰动荷载所引起的裂隙附加水压的解析式，并应用数值分析进行验证，然后分析裂隙附加水压随岩石力学性质、裂隙形状以及裂隙倾角的变化规律。其次，应用岩石压剪断裂准则，推导出考虑裂隙附加水压的岩体断裂强度解析式。最后结合算例，进一步探讨了裂隙附加水压对岩体断裂强度的影响规律。结果表明，裂隙附加水压降低了岩体断裂强度，增大了岩体发生断裂破坏的倾角范围，使岩体更易于沿裂隙面发生水力劈裂失稳破坏；另外，岩石弹性模量、裂隙形状因子以及裂隙倾角对裂隙附加水压有显著影响，岩体断裂强度随岩石弹性模量和裂隙形状因子的增大而增大，且随裂隙倾角的增大，其增大的趋势更加明显。

Analysis of fracture strength of rock mass considering fissure additional water pressure

Disturbance induced by the construction of dams, tunnels and other engineering activities occurs in the surrounding rock mass and causes additional water pressure in the water of rock mass fracture. Thus, the unstable rock fracture propagates along the fissured surface under the disturbance load and fissure additional water pressure. Firstly, an analytical expression of fissure additional water pressure caused by the disturbing load is derived based on the inclusion theory, which is verified by numerical analysing. Then variation regularity of fissure additional water pressure is analysed under different rock mechanical properties, fracture shapes and inclination angles. Secondly, considering the influence of fissure additional water pressure, an analytical formula of fracture strength of rock mass is deduced by using the compressive shear fracture criterion. Finally, the effect of fissure additional water pressure on fracture strength is further investigated with an example. The results show that fissure additional water pressure reduces the fracture strength and increases the inclination angle range of fracture failure, which makes the rock mass more prone to hydraulic fracturing along the fissured surface. In addition, rock elastic modulus, fracture shape coefficient and inclination angle can have a significant influence on the additional water pressure. The fracture strength of rock mass increases with the increase of rock elastic modulus and fracture shape coefficient, and its increasing trend is more significant with the increase of fracture inclination angle.