考虑弹性模量劣化的洞室围岩弹塑性分析

Elastoplastic Analysis on Cave Surrounding Rock Considering Deterioration of Elastic Modulus

洞室开挖伴随岩体参数的劣化,描述参数的劣化对指导工程实践具有重要意义。为描述变形参数的劣化,基于霍克-布朗准则,利用损伤门槛值表征弹性模量劣化程度,通过泰勒级数简化求解含损伤门槛值的平衡方程得到塑性区半径解析解并给出损伤门槛值的取值方式,结合有限差分软件FLAC^(3D)对比验证了公式合理性。基于常弹性应变和变弹性应变2种假设,联合非关联流动准则获得了含损伤门槛值的塑性区位移表达式。最后,通过算例分析了不同参数下塑性区半径及洞壁位移变化规律。结果表明:劣化越严重,洞室越容易失稳;随着损伤门槛值增大,2种假设下的位移差值和塑性区半径逐渐增加,常弹性应变假设得到的位移偏小。为避免洞室失稳破坏,要重视支护的施作。

The excavation of the cavern is accompanied by the deterioration of the parameters of the rock mass,and it is of great significance to describe the deterioration of the parameters to guide the engineering practice.In order to describe the deterioration of the deformation parameters,based on the Hoek-Brown criterion,the damage threshold is used to characterize the degree of deterioration of the elastic modulus,and the equilibrium equation with the damage threshold is simplified by the Taylor series to obtain the analytical solution of the radius of the plastic zone and the damage threshold is given.The value method,combined with the finite difference software FLAC^(3D),verifies the rationality of the formula.Based on the two assumptions of constant elastic strain and variable elastic strain,the plastic zone displacement expression including the damage threshold is obtained by combining the uncorrelated flow criterion.Finally,the variation law of the radius of plastic zone and the displacement of the cave wall under different parameters is analyzed by an example.The results show that the more serious the deterioration is,the easier the cavern is to be unstable.As the damage threshold increases,the displacement difference and plastic zone radius under the two assumptions gradually increase,and the displacement obtained by the constant elastic strain assumption is smaller.In order to avoid instability and damage of the cavern,support should be provided in time.