上长坪连拱隧道无中导洞施工方法比选研究

Comparison and Selection of Construction Methods for Multi-arch Tunnel of Shangchangping without Middle Drifts

目前国内外连拱隧道大多采用中导洞法施工,而对无中导洞施工研究相对较少,缺少相关工程经验,且未对无导洞法施工技术优缺点和适用范围做深入而系统的研究。本文研究的上长坪隧道为分离式隧道过渡到连拱隧道,因其与大桥衔接过渡,设计的中隔墙厚度不等厚,采用复合式薄直中墙,其结构设计新颖,在设计无法做变更及4个月完成504m的工期要求下,为实施高难度操作的设计方案,采用竖直型钢喷射混凝土结构及斜向支撑成功解决了中墙二次衬砌浇筑的难题,其竖直型钢喷混结构浇筑在左右洞二次衬砌之间作为中隔墙的结构部分,成功开创了复合式薄中墙设计施工新工艺。同时,此工法有效解决了防水漏水问题及成本控制问题,为无中导洞施工方法增加了新的工艺类型,提供了Ⅳ级围岩隧道无中导洞施工新型案例。

At present,most multi-arch tunnels at home and abroad adopt the construction method of middle guiding tunnel,but the research on the construction without middle drift is relatively few.As for no drift construction,few actual engineering experience and nearly no deep and systematic research on the advantages,disadvantages and application can be found.Shangchangping tunnel is a separated tunnel transiting to multi-arch tunnel.Due to its connection and transition with the bridge,the design of the middle partition wall varies in thickness,which adopts the composite thin straight middle wall with novel structural design.With the requirement of no change in design and finish 504 m within 4 months,in order to implement the challenging design scheme,the problem of pouring the second lining of the middle wall is successfully solved by using vertical steel shotcrete structure which is poured between the left and right holes as the structural part of the middle partition wall.At the same time,the problems of leakage prevention and cost control are also resolved,and the unprecedented construction technology is introduced to increase the new process type,providing the new case of no middle guide tunnel construction for Ⅳ surrounding rock tunnel projects.