大断面海底隧道异常变形控制措施研究

STUDY ON ABNORMAL DEFORMATION CONTROLLING MEASURES FOR LARGE CROSS-SECTION SUBSEA TUNNEL

厦门海底隧道是我国第一条海底隧道,其地质条件差,地下水丰富,施工过程中,支护结构常发生较大的变形,为了保证施工安全,应寻求一套合理的控制措施用以抑制异常变形。基于厦门东通道海底隧道的现场实测数据,并结合数值模拟,对设置锁脚锚杆、加强临时支护刚度、仰拱注浆、井点降水、改变工法以及各种措施组合等控制措施进行了研究,制定了抑制异常变形的工程对策。研究结果表明,所列举的各工程措施都可以在一定程度上减小隧道支护结构的变形,而且这些措施也会在一定程度上降低围岩的塑性区范围。例如,在采用锁脚锚管后,隧道的拱顶下沉可减小约17%,减小水平收敛约12%;仰拱注浆适用于控制初期支护封闭后隧道发生的整体下沉,可减小拱顶下沉约18%。这些措施可为厦门海底隧道后续施工及类似工程提供一定的参考。

Xiamen East Passage 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. It is important to seek for a reasonable countermeasure to restrict the large deformation to ensure safety construction. Focused on Xiamen East Passage subsea tunnel, field monitoring data are analyzed and numerical calculation is employed. Some measures against abnormal deformation, including setting locking anchor bar, enhancing stiffness and intensity of temporary support, grouting in inverted arch, constructing continuous wall for groundwater proof, changing construction method, are taken. Finally, the countermeasure for abnormal deformation is offered. The analytical results indicate that, to some extent, each countermeasure can decrease the displacements of the tunnel support and all these countermeasures will also reduce plastic area in surrounding rock and increase structure safety to a certain extent. For example, after setting locking anchor bars, arch crown settlement will be reduced about 17%; and level convergence will be reduced 12% and after grouting in inverted arch; arch crown settlement will be reduced about 18%. The analytical method and result can provide references to the latter construction of Xiamen subsea tunnel and the other similar engineering cases.