岩石材料裂纹尖端起裂特性研究

The characteristics of crack initiation at the crack tip in rock material

通过综合考虑Williams展开式中奇异应力项和非奇异应力项(T应力),运用断裂力学方法深入探讨远场拉–压、压–压应力组合下裂纹尖端起裂特性。在最大周向应力准则中考虑T应力的影响作用,并将其作为拉伸破裂判据;在剪切破裂方面,提出考虑法向应力影响的最大剪应力准则。通过对拉伸和剪切破裂发生条件的探讨,进一步阐明剪切破坏与裂纹倾角、内摩擦角、抗拉强度、黏聚力等参数之间的关系。研究结果表明,Williams展开式中非奇异应力项对于裂纹起裂角有重要的影响,所提出理论比传统理论计算的起裂角与实验结果更加吻合。随着内摩擦角的增大,剪切破裂减弱而拉伸破裂增强。随着黏聚力增大或者抗拉强度降低,拉伸破裂增强而剪切破裂减弱。

The characteristics of crack initiation in rock under far-field tension-compression and biaxial compression loading were analyzed by considering both the singular and nonsingular stress（T-stress） terms at the crack tip. The modified maximum tangential and shear stress criterion was developed for evaluating tensile and shear cracking. The condition of tensile and shear fracture was discussed to further clarify the effect of inclination angle, friction angle, tensile strength and cohesion on fracture types in rock. The results indicate that the nonsingular stress terms have important influence on the near-tip stress field and the modified theory agrees well with experiment. Results with the increment of the friction angle, the shear failure is weakened while the tensile failure is strengthened. However, with the increment of the cohesion or decreases of the tensile strength, the shear failure is strengthened and the tensile failure is weakened.