翔安海底公路隧道陆域段变形控制措施研究

Study of deformation controlling measures for large-span shallow tunnel

翔安隧道是我国第一条大跨公路海底隧道,其两端陆域段位于富水的强风化岩层中,地质条件极为复杂。隧道施工期间,部分断面发生了较大变形,超过了预留变形量,给二次衬砌的施工造成了影响,而且过大的变形有时还会导致隧道围岩失稳,应寻求一套合理的变形控制措施。基于现场监测数据和施工记录,并结合数值方法,对隧道施工过程中所采取的工程措施的作用效果进行了研究。结果表明,增设锁脚锚管、加强临时支护及管井降水等工程措施都可以在一定程度上减小隧道支护结构的变形,但在地质条件较差的富水强风化岩层中修建大跨公路隧道时,将两种或多种工程措施的组合起来使用效果更佳。例如,在采用降水(连续墙)+加强临时支护+锁脚锚管的组合方案后,隧道的拱顶下沉减小了46%～60%,水平收敛也减小了约30%。这些措施可为今后类似工程提供一定的参考。

Xiang＇an subsea tunnel is the first subsea tunnel in China; and its geological conditions are complex and unfavorable with enriched groundwater. During the tunnel construction, the deformation of tunnel support is great; and it has brought the bad-effect on the construction of quadric lining; moreover, the large deformation maybe bring on the surrounding rock collapse. It is important to seek for a reasonable countermeasure to restrict the large deformation to ensure safety construction. Focused on Xiang＇an subsea tunnel, field monitoring data and construction annel are analyzed and numerical calculation is employed. Some measures and its combination against abnormal deformation during the tunnel construction are taken. The analytical results indicate that, to some extent, the countermeasure including setting locking anchor pipe, enhancing stiffness and intensity of temporary support, constructing continuous wall for groundwater proof, can decrease the displacements of the tunnel support. But the effection of using the combination project is better during constructing the large-span tunnel in the complex geological conditions. For example, after adopting the seventh combination project, arch crown settlement will be reduced 46-60%; and horizontal convergence will be reduced about 30%. The analytical method and result can provide references to the other similar engineering cases.