岩石裂纹水力劈裂分析与临界水压计算

水力劈裂是深埋隧洞施工涌水或高压隧洞洞周岩体开裂渗漏的重要因素之一,对其破坏机理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断裂及压剪复合断裂。应用工程近似裂纹失稳准则,分别推导出两种破坏模式的临界水压计算公式,并对其随裂纹方向及地应力侧压系数变化规律进行分析。结果表明,当侧压力系数等于1.0时,临界水压并不随裂纹的方向而变化;在拉剪复合断裂模式下,裂纹与主应力方向平行时最易发生水力劈裂;在压剪复合断裂模式下,当压剪断裂参数与裂纹面间摩擦系数之差大于零时,其规律性与拉剪复合断裂模式基本一致;但当其差值小于零时,裂纹与最大主应力夹角呈45°及135°时最易发生水力劈裂。

Analysis of hydraulic fracturing and calculation of critical internal water pressure of rock fracture

Hydraulic fracturing is one of important effect factors in water gushing out of deep-buried tunnel construction and cracking and seepage of high head tunnel .Its failure mechanism study is a hot topic in geotechnical engineering fields. Based on stress state in fracture surface and fracture mechanics, the fracture propagation is divided into tension-shear and compression-shear mixed cracking. Using fracture propagation engineering criterion, calculation formulae of critical internal water pressure of two kinds of failure model are obtained respectively; and its effect laws as fracture direction and lateral geo-stress coefficient are studied. The study shows that critical internal pressure of two kinds of model is not varied as fracture direction changing when the lateral pressure coefficient equals 1.0. Under tension-shear complex model, fracture is most easily fracturing when fracture direction is parallel with direction of principal stress. Under compression-shear mixed model ,distribution law of critical internal water pressure is same as tension-shear complex model when ( ) large than 1.0. But fracture is most easily fracturing when ( ) less than 1.0 and fracture direction are 45°or 135°angle with principal stress.