基于断裂力学的隧道近接断层破碎带结构破坏分析

Structural Failure Analysis of Tunnel Approaching Fault Zone based on Fracture Mechanics

为减少裂隙发育地层隧道施工风险,以云南省某穿越断层破碎带隧道为依托,结合现场地应力测试及病害统计结果,基于断裂力学位移不连续边界元方法模拟了次生断裂的形成,分析了隧道在裂缝带影响下的破坏规律。结果表明:当不存在局部软弱区域时,次生断裂主要集中在主断层附近;由于纵向地质差异的存在,次生裂缝区域可能出现在离主断层较远的地方;当水平地应力较大时,裂缝带位于隧道侧部的危险最大;断裂带可能会导致隧道结构不均匀的变形和破坏;最危险的隧道部位为拱脚、边墙和仰拱;当地应力以水平方向为主时,侧部断裂带潜在风险最高,而竖向地应力的增大可能会加剧顶部、底部断裂带风险。结合现场衬砌病害情况,模拟结果较为合理,因此隧道洞身周围可能存在次生断裂。该研究有助于断裂带隧道安全建造,为类似工程提供参考。

To reduce the risk of tunnel construction in fractured strata,based on a tunnel crossing the fault fracture zone in Yunnan Province,combined with the in-situ stress test and defects statistical results,the formation of secondary fractures is simulated based on the displacement discontinuous boundary element method of fracture mechanics,and the failure law of the tunnel under the influence of the fracture zone is analyzed.The results show that when there is no partial weak area,the secondary faults are mainly concentrated near the main fault.Due to the existence of longitudinal geological differences,the secondary fracture area may appear far away from the main fault.When the horizontal in-situ stress is relatively large,the risk when the fracture zone located at the side of the tunnel is the greatest;the fracture zone may cause uneven deformation and damage of tunnel structure;the most dangerous areas of the tunnel are the arch foot,side wall and inverted arch.When the local stress is mainly horizontal,the potential risk of the lateral fault zone is the highest,while the increase of the vertical in-situ stress may aggravate the risk of the top and bottom fault zones.Combined with the in-situ lining defects,the simulation results are reasonable,therefore secondary fractures around the tunnel may exist.This study is helpful to the safe construction of tunnels in the fault zone,and provides some reference for similar projects.