捷运潜盾隧道位移修复工程实例

A case of rehabilitation for tunnel displacement in shield-driven tunnels

台北捷运板桥线中之一段潜盾隧道于掘进作业完成后,因受邻近工程施工之影响导致隧道产生位移及变形。位移发生后,隧道之仰拱混凝土与环片产生分离并于隧道顶部发现裂缝。明显地,隧道之位移已经对隧道环片造成损害并改变原有环片的受力行为。由于潜盾隧道外土壤之扰动及隧道之损害情形难以清楚得知,为避免对隧道产生进一步的影响并确保潜盾隧道符合未来捷运通车后之结构安全标准,故于1999年11月开始在潜盾隧道内进行修复工作。 由监测仪器的资料显示,潜盾隧道于位移变形后已经逐渐趋于稳定,如果对隧道外之土壤进行改良,可能对已受损之隧道造成进一步的沉陷。如何使隧道能够不再位移并恢复应有的强度便成为修复工作必须考虑的因素之一。本工程隧道之修复方式经评估后,决定于隧道内增设钢环片,以钢环片之结构强度取代受损的环片。文章将对隧道之损害情形、修复方式选择之考量因素及钢环片组立之施作过程加以叙述,期望能提供尔后工程界施工参考。对于隧道损害之原因则将于另文中加以讨论。

Displacement and deformation have occurred in one of shield - driven tunnels, after it is completed, on Banqiao line Taibei metro system due to adjacent construction, resulting in the separation of concrete at invert from segment and cracks on the roof. Obviously, the segment is damaged and the force behavior of segment is changed due to the displacement of tunnel. Since it is difficult to determine the surrounding disturbance outside of tunnel and the damage in tunnel, rehabilitation work in the shield-driven tunnel begun in Nov. 1999 to ensure the tunnel, when it is put into operation, comply with the safety standard for structure. Data obtained from monitoring instrument shows that the displacement in the shield -driven tunnel trends to be stable gradually and further settlement will probably occur in the damaged tunnel if ground improvement is taken outside the tunnel. Therefore how to avoid further displacement and obtain the strength of the tunnel is the key of rehabilitation. After evaluation of the rehabilitation methods, it is decided to replace the damaged segments with steel ones. In this paper, the damage extent, factors for the selection of rehabilitation methods and steel segment installation are introduced, which can be taken as a reference for the future.