基于应变的脆性岩石破坏强度研究

在三轴压缩条件下，岩石类材料的破坏具有延性破坏和脆性破坏2种类型。岩石发生破坏的机理是构成岩石的矿物颗粒之间发生相对位移。一般而言，岩石在力的作用下发生拉或剪破坏，在破坏发展过程中，哪一种破坏类型取得优势地位，岩石最终便以那种形式破坏。最大拉应变准则能够解决岩石拉破坏问题，但不能解释破裂角的存在。岩石为各向异性体，应变主轴不同于加载轴，因此，不能用加载轴上的应变来描述岩石的强度。考虑3个方向拉应变的应变强度准则能够描述岩石的强度，也能够在一定程度上描述破裂角的变化。理论分析和室内试验证实了这一结论。并且随中间主应力的升高，应变破坏准则的变化与岩石抗压强度、最大拉应变准则的变化具有相同的规律。

STUDY OF FAILURE CRITERION FOR BRITTLE ROCKS BASED ON STRAINS

When rock-like materials are tested under triaxial compression,two kinds of failure may happen,that is,ductile and brittle failures. The essential reason for rock failure is the relative displacement among mineral particles making up rock. Generally,rock failure can be either tensile or shear,which depends on the predominant mechanism when failure happen. The maximal tensile strain criterion can predict rock failure in tension,but is difficult to explain the effect of crack angle. Rocks are generally anisotropic. The principal strain axes are usually different from the loading axes. Therefore,the strains in the directions of loading axes may not be suitable to describe rock strength. The strain-based strength criterion considering tensile strains in three axes can describe rock strength. And it can describe the crack angle and its transformation. The theoretical analyses and laboratory tests presented in this paper validate this conclusion. With the increasing of the intermediate principal stress,the transformation of the strain failure criterion is of the same pattern as the transformation of the compressive strength and the maximum tensile strain criterion.