高地应力环境下跨活断层隧道抗错断铰接设计试验研究

Hinged design for resisting shear displacement of a deep-buried tunnel crossing an active fault under high in-situ stress conditions

当活动断层发生错动时,穿越活动断层的隧道会发生不同程度的破坏。以往的研究大多未考虑隧道埋深、高应力对跨活断层隧道的影响,结果不太能贴切实际。充分讨论了解决深埋隧道抗错断问题的必要性,通过跨活断层隧道模型试验,对比深埋隧道与浅埋隧道的破坏差异,并通过深埋铰接隧道错断试验,分析了隧道外部应力变化、衬砌应变与破坏形态。结果表明:(1)在深埋与浅埋环境下隧道整体变形皆呈“S”型变形,破坏较严重的区域都集中在断层带位置,其中深埋隧道的破坏模式主要以剪切拉伸破坏为主,产生了较大的挤压变形,破坏区域较大,而浅埋隧道主要以剪切破坏为主,在跨断层位置隧道被剪断。(2)在对深埋隧道进行铰接设计后,隧道由“S”型变形转化成“阶梯”型,隧道应变与外部岩体应力峰值得到降低,破坏程度显著减小。(3)通过对隧道衬砌裂纹分布分析,发现无铰接隧道为贯穿型破坏,裂纹影响至整个衬砌,铰接隧道裂纹影响范围约占隧道总长的66.6%,短铰接节段隧道裂纹影响范围约占隧道总长的33.3%,故深埋环境下采用更短的铰接节段对隧道的抗错断效果更佳。(4)通过对比前人研究的浅埋铰接隧道得出,浅埋铰接隧道在断层带外也会发生变形,而深埋铰接隧道破坏主要集中在断层带内位置,因此对于深埋隧道抗错断保护措施应当多集中在断层带位置。

When movement occurs in active faults,tunnels crossing these faults may sustain varying degrees of damage.Most previous studies failed to consider the impact of tunnel depth and high in-situ stress on tunnels crossing active faults,resulting in findings that are not entirely practical.In this paper,the necessity of solving the anti-dislocation problem of deeply buried tunnels is systematically discussed.Through model tests of tunnels crossing active faults,the differences in failures between deeply buried and shallowly buried tunnels were compared.Additionally,a dislocation test of deeply buried segmented tunnels was conducted to analyze the external stress changes,lining strains,and failure modes of the tunnels.The results are as follows:(1)The overall deformation of both deeply and shallowly buried tunnels exhibits an S-shaped pattern.The most severe damage is concentrated in the fault zone.The failure mode of deeply buried tunnels is primarily characterized by shear and tensile failure,resulting in significant compressive deformation and a larger damaged area.In contrast,shallowly buried tunnels mainly experience shear failure,with the tunnel being sheared apart at the fault crossing.(2)After implementing the hinged design for the deeply buried tunnel,the S-shaped deformation pattern is transformed into a ladder pattern,reducing the strain on the tunnel and the peak stress of the external rock mass,thereby significantly mitigating damages.(3)Through the analysis of the distribution of cracks in the tunnel lining,it is found that the tunnel without a hinged design has suffered from penetrating failure,with cracks affecting the entire lining.The cracks in the hinged tunnel affect approximately 66.6%of the total tunnel length,while those in the tunnel with shorter hinged segments affect only about 33.3%of the total length.Therefore,a deeply buried tunnel with shorter hinged segments can yield a better anti-dislocation effect.(4)By comparing previous studies on shallowly buried hinged tunnels,it is concluded that shallowly buried hinged tunnels will also suffer from deformation outside the fault zone,while the damages to the deeply buried hinged tunnel are concentrated mainly in the fault zone.Therefore,the anti-dislocation protection measures for deeply buried tunnels should be concentrated mainly in the fault zone.These findings can provide theoretical guidance and technical support for the design and reinforcement of tunnels crossing active faults under high stress conditions.