小净距立体隧道交叉段现场监测分析

On-site Monitoring and Analysis of the Surrounding Rock of the Small Spacing Overlapped Tunnel

为保证小净距立体隧道开挖过程中围岩之间的稳定性及支护体系的安全性,本文以新建隧道上跨既有隧道为工程背景,对隧道交叉段洞内外状态、拱顶下沉以及净空变形等观察及量测,分析新建隧道上跨施工时对下部既有隧道围岩力学动态响应及支护结构稳定性的影响。得到以下结论:①隧道上跨施工时,拱顶沉降累计最大值出现在靠近底板处,交叉中心点累计沉降值最小;②最大净空收敛出现在拱肩位置,拱腰和边墙位置水平收敛依次减小;③在交叉隧道施工及设计中,应对隧道底板及拱肩部分加强支护,并加强监控量测;④合理的开挖及支护方案能够有效地控制隧道交叉段围岩的拱顶下沉及水平收敛,能够降低新建隧道上跨开挖时对原有隧道的影响。

In order to ensure the stability between the surrounding rock during the excavation process of the small clear distance tunnel and the safety of the supporting system,this paper takes the newly built tunnel over the existing tunnel as the engineering background,through the inner and outer state of the tunnel crossing section,the paper observes and measures the sinking and clearance deformation,and analyzes the influence of the construction of the new tunnel on the dynamic response of the surrounding rock and the stability of the supporting structure.The following conclusions are obtained:①When the tunnel is over-span,the cumulative maximum value of the vault settlement appears near the bottom plate,and the cumulative settlement value of the intersection center point is the smallest;②The maximum clearance convergence occurs at the shoulder position,the horizontal convergence of the the arch waist and the side wall position is reduced in turn;③In the construction and design of the cross-over tunnel,the support of the tunnel floor and the shoulder portion should be strengthened and the monitoring and measurement should be strengthened;④Reasonable excavation and support scheme can effectively control the collapse of the dome of the surrounding rock of the tunnel and the horizontal convergence and can reduce the impact of the new tunnel on the existing tunnel.