基于FDEM数值模拟的软岩隧洞大变形预测

Large Deformation Prediction of Soft Rock Tunnel based on FDEM Numerical Simulation

软岩隧洞收敛变形量预测对隧洞施工方法、设备选型和支护设计具有重要意义。采用有限元-离散元耦合数值模拟方法(FDEM)对软岩隧洞掘进过程开展了模拟研究,并调研了地应力量值对隧洞收敛变形量的影响。结果表明:隧洞大变形机理为开挖卸荷引起径向应力降低、切向应力升高,升高的切向应力造成围岩发生共轭剪切破坏,并持续向深处完整围岩扩展,深部破裂块体对浅部碎裂岩块的接触挤压产生宏观空隙,造成体积增大,发生具有碎胀效应的挤压大变形;随着围岩强度应力比的降低,围岩收敛变形量呈指数函数增大,相关系数高达0.996,为软岩隧洞收敛变形量预测提供了经验公式。

The prediction of convergence deformation of soft rock tunnel is of great significance for tunnel construction method,equipment selection and support design.The combined finite-discrete element method(FDEM)is used to simulate the tunneling process in soft rock,and the influence of in-situ stress on the convergence deformation is investigated.The results show that:the large deformation mechanism of the tunnel is that the excavation unloading causes the radial stress to decrease and the tangential stress to increase.The increased tangential stress causes the conjugate shear failure of the surrounding rock,and continues to propagate into the deep intact surrounding rock.The contact and squeezing of the deep fractured rock to the shallow fractured rock produces macro voids,which causes the volume to increase,and the large deformation with fracture-swelling effect occurs;with the decrease of the strength-stress ratio of surrounding rock,the convergence deformation increases exponentially,and the correlation coefficient is as high as 0.996,which provides an empirical fitting equation for predicting the convergence deformation of soft rock tunnels.