基于M–C弹塑性本构模型的岩土体开挖回弹效应研究

Rebound effect of rock & soil excavation based on M–C elastic-plastic constitutive model

针对数值模拟开挖计算通常出现岩土体回弹现象,基于M–C弹塑性本构模型对基坑开挖过程中回弹效应进行了研究,分析了开挖回弹过程的力学机制和岩土体本构模型回弹力学参数的敏感性,并探讨了数值计算开挖回弹解决办法,研究结果表明:M–C本构模型参数中,岩土重度对一般岩土体开挖回弹的影响较为敏感,且坑底较地表影响更为显著;泊松比对岩土开挖回弹影响也较为明显;折减比例较小时,弹性模量和黏结力的敏感性较为突出,对地表回弹位移和基坑底部回弹位移影响较大;而内摩擦角对基坑底部回弹位移与地表回弹位移基本没有影响。研究结果可为岩土体基坑开挖的设计和回弹预测提供参考。

In view of the rebound phenomenon in numerical simulation calculation of rock & soil excavation, based on the M–C elastic-plastic constitutive model, the rebound effect is studied during the excavation process of a foundation pit. The mechanical mechanism and the sensitivity of the mechanical parameters for the rebound effect in rock mass constitutive model are analyzed. Besides, the solution to the rebound in numerical simulation of excavation is explored. The research results show that the effect of parameters in the M–C constitutive model on the rebound is as follows:(1) The impact of geotechnical gravity density on rebound of general rock mass excavation is relatively sensitive, and the effect on the bottom is far more significant than that on the surface.(2) The effect of Poisson's ratio on rebound displacement of excavating rock & soil is also obvious.(3) When the ratio of reduction is small, the sensitivity of elastic modulus and cohesive force is prominent. The effect on the bottom and the surface is significant on the whole.(4) However, the internal friction angle of rock and soil basically has no effect on the bound deformation. This study may provide reference for the design of excavation of foundation pits and rebound prediction.