浅埋大跨度小净距连拱隧道施工监测及分析

Monitoring and analysis of shallow-buried double-arch tunnel with large section and small clear-distance

针对浅埋大跨度小净距双连拱隧道在施工过程中围岩变形及应力分布复杂的特点,基于苏州凤凰山隧道,根据监测结果,分析了双连拱隧道施工过程中拱顶沉降和水平收敛的变化情况及各洞开挖过程中的相互影响、围岩与初期支护、初期支护与二次衬砌的接触应力及锚杆轴力的变化规律。结果表明:1)在洞口处拱顶沉降较大,上台阶环向土的开挖对拱顶沉降影响最大。2)在各导洞及主洞进口处收敛值较大,各断面开挖时,初始收敛速率很快,最快达到1.2 mm/d,最后趋于平稳。3)中隔墙左侧接触压应力最大,支护体系受力小于设计值,围岩基本处于稳定状态。

In the construction process of small clear-distance shallow-buried double-arch tunnel with large section,the deformation and stress of surrounding rock were very complicated. A monitoring task of measuring the deformation of surrounding rock and stress of lining system were carried out in the Phoenix tunnel in Suzhou. According to the consequences of monitoring,the longitudinal crown settlements and horizontal convergence and the change rule under construction of them were analyzed; the contact stress between surrounding rock and initial support,the contact stress between initial support and second lining and the stress of bolt were studied. The longitudinal crown settlement and the horizontal convergence were bigger in the entrance of each tunnel. The construction of the upper stage in the left and right holes changed the longitudinal crown settlement greatly. The convergent velocity was fairly fast at each section,the maximum of convergent velocity was 1. 2 mm / d,and then tended to be stable finally. The contact stress was biggest in the left side of the middle wall of the double-arch tunnel. The stress of lining was far below the design value,which indicated that the construction scheme and lining system were feasible.