基于应变的岩石类脆性材料损伤研究

STUDY ON BRITTLE ROCK FAILURE CRITERION BASED ON STRAINS

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两种类型。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。理论分析和实验室试验证实了这一结论。并且随中间主应力的升高,岩石应变破坏准则的变化与抗压强度准则、最大拉应变准则的变化具有相同的规律。

When rocklike materials are tested in triaxial compression, two kinds of failure, ductile failure and brittle failure, may happen. Rock failure essentially results from the relative displacement among mineral particles. Generally, rock failure can be either tensile or shear, depending on which mechanism is predominant during the failure process. The maximum tensile strain criterion can predict rock failure in tension, but cannot explain the crack angle. Rocks are generally anisotropic. The principal strain axes are usually different from the loading axes. Therefore, strains in the directions of the 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. Theoretical analyses and laboratory tests have validated this conclusion. With the increase of the intermediate principal stress, the transformation of the strain failure criterion is of the same pattern as the transformation of the compressive strength criterion and the maximum tensile strain criterion.