洞周岩体内裂纹水力劈裂临界水压分析计算

水力劈裂是深埋隧洞施工涌水重要因素之一，对其破坏机制研究是岩土工程界的热点课题。根据裂纹面的应力状态，从断裂力学角度将岩体的裂纹扩展分为拉剪复合扩展和压剪复合扩展。应用地下岩体复合失稳扩展判据分别推导出两种破坏模式的临界水压计算公式，并对其随裂纹在隧洞洞周围的位置、方位变化规律进行分析。分析结果表明，在发生拉剪复合扩展情况下，裂纹方向与最大地应力方向平行时，最易失稳扩展；在压剪复合扩展情况下，裂纹与最大地应力夹角约介于30°～75°之间时，最易失稳扩展。

Analysis and calculation of critical internal water pressure in fracture of surrounding rock of tunnel during hydraulic fracturing

Hydraulic fracturing is one of the important affecting factors in water inflow out of deep-buried tunnel construction. Its failure mechanism is a hot topic in geotechnical engineering fields. Based on stress states in rock fracture surface and fracture mechanics, fracture propagating models comprise tension-shear and compression-shear mixed fracturing. Using crack propagation criterion for mixed fracture model, calculation formulae of critical internal water pressure of two kinds of failure models are obtained respectively; and the affecting laws of fracture location and direction are studied. This study shows that fracture is most easily to propagate when it is parallel to the direction of maximal in-situ stress under tension-shear mixed model. For compression-shear mixed model, fracture is most easily to propagate when the angle between of fracture direction and maximal in-situ stress is within range of 30°and 75°.