采用管棚预支护方法的盾构穿越既有地铁隧道变形特征及加固影响实测分析

Reinforcement effect and actual measurement analysis of new shield tunnel crossing existing metro tunnel with shed pre-supporting method

开展新建盾构隧道穿越既有地铁隧道影响机制的理论分析,收集并统计国内15个新建盾构隧道穿越既有地铁工程实例及相应实测数据,表明新建盾构近距离穿越易引起既有地铁隧道发生隆沉变形,最大竖向位移主要集中在±5 mm范围内,且既有地铁隧道变形与两隧道之间净距、加固情况和土质条件密切相关。基于杭州新建盾构地铁2号线近距离下穿地铁1号线工程,对盾构穿越全过程中既有地铁隧道变形规律进行深入探讨。同时,工程所采用的管棚结合水平旋喷加固既有地铁1号线下方土体,可有效减少既有地铁隧道的变形。穿越施工过程中应通过既有地铁实测变形数据对盾构施工参数进行实时调整,保证新建盾构安全穿越。

The theoretical analysis of the mechanism on the new shield tunnel crossing the existing subway tunnel was carried out,the 15 project instances and the corresponding measured data of new shield tunnels crossing the existing metro was collected and counted.The results showed that the uplift and settlement deformation of the existing subway tunnel were easily caused by new shield short-distance crossing,the maximum vertical displacement was mainly concentrated in the range of±5 mm,and the deformation of the existing subway tunnel was closely related to the clearance between the two tunnels,reinforcement and soil conditions.Based on the project of Hangzhou Metro Line 2 closely under-crossing Metro Line 1,the deformation of existing subway tunnel during the whole process of shield tunneling was deeply discussed.Meanwhile,the combination of pipe shed and rotary jet reinforcement below existing Metro Line 1 could effectively reduce the deformation of the existing subway tunnel.In the process of crossing construction,the shield construction parameters should be adjusted in real time through the measured deformation data of the existing subway tunnel,so as to ensure the safety of the new shield tunneling.