走滑断层黏滑作用下隧道纵向及横断面分区破坏机理

Longitudinal and cross-sectional partitioned failure mechanism of tunnels subjected to stick-slip action of strike-slip faults

黏滑作用下走滑断层将出现永久性的错动位移,当隧道与此类断层相交时将发生严重破坏,并且具有明显的分区特征。为了揭示隧道纵向和横断面的分区破坏机理,为穿越活动断裂带隧道抗震设计提供支撑,本文首先通过震害实例调研总结得到隧道的三种破坏模式,即环向裂缝、斜向裂缝和纵向裂缝。给出并讨论了断层类型、交角、错动量和隧道刚度等关键影响因素。结果表明:1)断层类型是影响隧道力学响应和安全性的最显著因素,而倾角影响很小;2)受左旋走滑断层黏滑作用的隧道沿纵向可分为弯曲-压缩-剪切(L-BCS)区和弯曲-压缩(L-BC)区,而受右旋走滑断层黏滑作用的隧道可分为弯曲-拉伸-剪切(L-BTS)区和弯曲-拉伸(L-BT)区;3)L-BCS区和L-BTS区的范围为1.4D~1.7D(D为隧道直径),而L-BC区和L-BT区范围随关键影响因素变化而变化;4)隧道横断面可分为偏心受压(C-EC)区和偏心受拉(C-ET)区,分别发生偏心受压破坏或偏心受拉破坏。C-EC区和C-ET区的范围约为距断层面5D;5)穿越左旋走滑断层隧道的C-EC区包括上盘左拱腰、下盘右拱腰、拱顶和仰拱,C-ET区包括下盘左拱腰和上盘右拱腰。穿越右旋走滑断层隧道的横断面分区分布与左旋对称。

Permanent displacement occurs in strike-slip faults due to stick-slip action,causing significant damage and distinct partitioning features in tunnels intersecting these faults.To elucidate the longitudinal and cross-sectional partitioned failure mechanism of tunnels and provide seismic design support for tunnels intersecting active faults,we investigated several seismic damage examples to summarize three tunnel failure modes:circumferential cracks,inclined cracks,and longitudinal cracks.The key influencing factors,such as fault type,intersection angle,fault dislocation,and tunnel stiffness,were identified and discussed.The results show the following.1)The mechanical response and safety of tunnels are primarily influenced by fault type,while dip angle has a minimal impact;2)Tunnels subject to left-lateral strike-slip faulting can be longitudinally divided into bending-compression-shear(L-BCS)and bending-compression(L-BC)zones,while those subject to right-lateral strike-slip faulting can be divided into bending-tension-shear(L-BTS)and bending-tension(L-BT)zones;3)The range of the L-BCS and L-BTS zones is 1.4D-1.7D(D is the tunnel diameter),whereas the range of the L-BC and L-BT zones varies with key influencing factors;4)The cross section of tunnels can be divided into eccentric-compression(C-EC)and eccentric-tension(C-ET)zones,which are susceptible to eccentric compression or eccentric tension failure.The C-EC and C-ET zones are approximately 5D away from the fault plane;5)The C-EC zone of tunnels that traverse left-lateral strike-slip faults includes the left hance of the hanging wall,right hance of the footwall,tunnel crown,and tunnel invert,while the C-ET zone includes the left hance of the hanging wall and right hance of the footwall.In addition,the cross-sectional partitioning of a tunnel crossing a right-lateral strikeslip fault is symmetrical to that of a left-lateral fault.