穿越地裂缝带地铁隧道结构分段长度优化研究

Optimal length for segmented structure of the metro tunnel obliquely crossing active ground fissure zone

目前西安地铁建设中过地裂缝带隧道均采取分段设缝的结构措施,而隧道结构分段长度的优化问题是地铁隧道穿越地裂缝带设防的关键。本文以西安地铁斜交穿越地裂缝带为工程背景,通过分段设缝的地铁隧道斜交跨地裂缝带的有限元数值模拟,研究了斜交跨地裂缝带地铁隧道分段设缝的合理模式及分段隧道的合理长度。计算结果表明:对缝设置模式下分段设缝隧道结构塑性区范围较小,集中在隧道拱底、拱脚;而悬臂设置模式下塑性区分布范围大且较为复杂,不利于进行衬砌加强。地铁隧道穿越地裂缝带衬砌结构宜采取分段设缝的对缝设置模式,跨地裂缝带的分段隧道合理长度为15 m,位于地裂缝主变形区内的分段隧道长度可按10～15 m考虑,而穿越地裂缝主变形区之外的地铁隧道分段长度可根据轨道调坡及隧道防水等其他要求适当增加。研究成果可为地裂缝发育的城市地铁隧道结构设计及其他地下空间开发提供重要的理论依据和技术参考。

Ground fissure is the most typical geo-hazard in the city of Xi’an.At present,the segmented metro tunnel in Xi’an metro engineering construction are adopted against the active ground fissures and the optimal length of the segmented tunnel structure is the key to the design of the metro tunnel obliquely crossing active ground fissure zone.Considering the Xi’an metro lines passing through active ground fissure zones,the reasonable mode and optimal length of a sectional tunnel with flexible joints are studied in this paper through finite element numerical simulation for the segmented structure of a metro tunnel.The calculation results show that the plastic zone of the tunnel lining is in a small range and mainly distributes in the arch bottom and skewback of the tunnel under the mode of opposite joint,while it is in a large range and relatively complicated in the mode of cantilever,which is comparatively against the reinforced lining.The better of the two modes is opposite joint and the optimal length of the sectional metro tunnel is 15 m.In addition,the main deformation zone of tunnel outside the scope of ground fissures can be segmented according to 10-15 m,the length of the fortified area of tunnel beyond the main deformation zone can be properly increased according to other requirements,such as the tunnel waterproof,adjustment of rail slope,etc.The conclusions can be presentedas the reference for structure design of urban metro construction and underground space development under the action of ground fissures.