脆塑性迭代逼近算法的改进

Improvement of multi-step brittle-plastic approach

针对应力跌落计算中脆塑性迭代逼近算法存在的问题,在主应力空间,结合特征点变形和破坏特征,通过理论推导,系统分析偏应力等比例跌落方法、最小主应力不变跌落方法、塑性位势跌落方法及应力球量不变跌落方法的缺陷.考虑脆塑性变形和破坏过程中的泊松效应,提出改进的塑性位势跌落方法;推导应力跌落计算更新过程,编写UMAT子程序将该更新过程嵌入软件Abaqus,实现岩石弹塑性应变软化过程数值求解.采用所提改进方法替换原有的应力跌落计算方法,实现弹塑性应变软化过程的数值模拟.引入塑性强化算法,实现岩石弹塑性变形破坏全过程的数值计算,并进行多算例验证.对不同地质条件的Mine-by试验洞及某水电站引水隧洞辅助洞进行开挖模拟,结果表明所提改进方法能够合理模拟工程中围岩弹塑性变形破坏现象.

Aiming at the problem of multi-step brittle-plastic approach in stress-drop calculation,the defects of existing stress-drop calculation method based on the deviator stress dropping,the method based on the constant minor principal stress in the brittle-plastic process,the method based on the plastic potential theory and the method based on the invariant spherical stress were systematically analyzed in the principal stress space,combined with the deformation and the failure characteristics of feature points.Considering the Poisson’s effect in the brittle-plastic deformation and failure process,the method based on the plastic potential theory was improved.The corresponding stress update process was derived and embedded in the program Abaqus through the UMAT subroutine.The original stress-drop calculation method was replaced by the improved method,realizing the numerical simulation of elastic-plastic strain softening process.The calculation of full elastic-plastic deformation and failure process was further realized by introducing the plastic-strengthening algorithm,which is verified by several examples.The excavation simulation of Mine-by tunnel and auxiliary tunnels of a hydropower station diversion tunnel shows that the improved method can reasonably simulate the elastic-plastic deformation and failure phenomenon of surrounding rock.