活动断层下城市地铁隧道变形破坏与损伤

Deformation failure and damage evolution of urban metro tunnels under active faults

依托某跨断层隧道工程,建立断层-隧道-围岩的精细化三维数值模型,考虑实际盾构施工中的注浆压力、顶推力、注浆时效硬化和材料的非线性行为。通过数值模型分析盾构隧道穿越不同宽度、倾角、倾向的断层破碎带时的变形机制、力学特性及损伤演化,利用控制变量法分别改变断层的宽度、倾角和倾向来研究单一变量的影响。研究结果表明:隧道拱顶的变形和损伤面积与断层宽度的增加呈现正相关,随着断层宽度的增加拱顶挤压现象更加明显,但当断层宽度增加至一定限值时,衬砌拱顶将脱离围岩向洞内凹陷,拱顶的应力呈现先增大后减小的趋势;随着断层倾角的增加,衬砌拱顶向洞内收敛量先增后减小,初始损伤位置与断层倾角相关;断层倾向增加使隧道的损伤范围和程度不断减小,环向应力集中受断层倾向影响较明显,随断层倾向的增加,雷达应力图由“X”逐渐转变为“十”字形。在隧道选址阶段,应尽量让隧道正交穿越断层且在穿越较宽的断层时提前采取预加固措施来保证隧道的安全稳定性。

Based on a tunnel project across a fault,a refined three-dimensional numerical model of fault tunnel surrounding rock was established in this study.The grouting pressure,jacking force,grouting hardening and nonlinear behavior of materials in actual shield construction were considered in the models.Through a series of numerical models,the deformation mechanism,mechanical properties and damage evolution of shield tunnels crossing fault fracture zones with different widths,dip angles and included angle were analyzed.In numerical simulation,the control variable method was used to change the width,dip angle and included angle of the fault respectively to study the influence of a single variable.The results showed that the deformation and damage area of tunnel vault were positively correlated with the increase of fault width.With the increase of the fault width,the arch extrusion became more obvious.However,when the fault width increased to a certain limit,the lining arch would converge to the tunnel from the surround-ing rock,and the stress in the arch would increase first and then decrease.With the increase of fault dip angle,the inward conver-gence of lining arch crown first increased and then decreased,and the initial damage location was related to the fault dip angle.The damage scope and extent of the tunnel decreased continuously with the increase of fault included angle.The circumferential stress concentration was obviously affected by the fault included angle.With the increase of fault tendency,the radar stress gradually changed from"X"to"cross-shaped".Therefore,the tunnel should cross the fault orthogonally as far as possible in the stage of tun-nel location and pre-reinforcement measures should be taken in advance when crossing a wide fault to ensure the safety and stability of the tunnel.