基于强度理论的岩石损伤弹塑性模型

Elastoplastic model of damaged rock based on the strength theory

根据单轴受力特性曲线唯象地考察岩石材料损伤演化,定义弹性应变表示的一维损伤变量及其本构模型,利用双剪强度理论将其推广至三维模型.塑性是潜在破坏面的摩擦滑移,在传统塑性理论的框架中,建立了基于摩尔-库仑强度理论与潜在滑移面摩擦软-硬化特性的各向异性损伤弹塑性本构关系.结果表明,计算的损伤演化与CT观测结果符合很好,用本文的弹塑性模型反映损伤材料的力学特性是可行的.

The one-dimensional damage variable was defined based on the elasto-brittle behavior of rock under uniaxial loading. To define the damage and its evolution in three-dimensional loading, the twln-shear theory was introduced to generalize the one-dimensional damage model into the three-dimensional model. The elastic behavior of the damaged material under loading can be expressed by reducing the elastic module, and the plastic flow can be represented by the slide on the plane between the two parts of the fractured rock. To establish the elastoplastic model of the damaged material, the concept of effective stress was used to contain the effects of damage in the yielding equation as well as in the function of plastic potential. The model was established in the frame of the classical plasticity theory in which the Mohr-Coulomb criterion was employed as the yielding criterion, and the friction law on the pre- sliding plane was taken as the hardening-softening rule to describe the change of the yielding surface with the progressive yielding. The comparison of the calculated results with tested results by a CT machine shows that the damage model presented in the paper can accurately describe the damage evolution of rock in Nanqiao Sandstone, and that the damage-elasto-plastic model is indeed feasible in describing the mechanical properties of the damaged material.