基于统一强度的非轴对称荷载隧道围岩弹塑性分析

Elastoplastic analysis of tunnel surrounding rock under non-axisymmetric load based on unified strength

为了完善非轴对称荷载作用下隧道围岩的弹塑性分析方法,本文基于统一强度理论,推导了非轴对称荷载作用下隧道围岩应力及塑性区半径解析解。分析表明:隧道围岩弹塑性交界面上径向应力和切向应力均受屈服准则系数b的影响,呈现出随着b值的增大,弹塑性交界面上径向应力减小,切向应力增大的特点,以b为0时隧道顶板围岩径向应力作为参照,b为0.25、0.5、0.75和1时径向应力分别减小5.7%、9.8%、12.9%和15.4%;同时隧道围岩塑性区半径随着b值的增大而减小,以b为0时隧道顶板围岩塑性区半径作为参照,b为0.25、0.5、0.75和1时塑性区半径分别减小19.2%、29.8%、36.3%和40.8%。表明工程实践中基于Mohr-Coulomb强度理论往往偏于保守,若能不同程度地考虑中间主应力的影响具有重要意义。

In order to improve the elastoplastic analysis method of tunnel surrounding rock under non-axisymmetric load,the analytical solution of stress and plastic zone radius of tunnel surrounding rock under non-axisymmetric load is derived in this paper. The analysis shows that both the radial stress and the tangential stress on the elastoplastic interface of the tunnel surrounding rock are affected by the yield criterion coefficient b, and with the increase of b value, the radial stress decreases and the tangential stress increases on the elastic-plastic interface. When b is zero, the radial stress of tunnel roof surrounding rock is taken as a reference. When b is 0.25, 0.5, 0.75 and 1, the radial stress decreases by 5.7%,9.8%, 12.9% and 15.4%, respectively. Meanwhile, the plastic zone radius of surrounding rock decreases with the increase of b value. When b is zero, the plastic zone radius of tunnel roof surrounding rock is taken as reference. When b is 0.25,0.5, 0.75 and 1, the plastic zone radius decreases by 19.2%, 29.8%, 36.3% and 40.8%, respectively. It shows that the strength theory based on Mohr-Coulomb tends to be conservative in engineering practice. It is of great significance to consider the influence of intermediate principal stress in different degrees.