盾构斜交下穿既有框架隧道数值模拟分析

在城市地铁建设中,经常出现新建隧道下穿既有隧道的情况,为研究新建盾构隧道施工对既有公路框架隧道的影响,以宁波地铁1号线世纪大道站—海晏北路站区间隧道斜交下穿浅覆土市政公路框架隧道工程为依托,采用三维有限元数值分析方法,研究盾构隧道在下穿框架隧道3个阶段(盾构到达既有隧道正下方前、穿越既有隧道正下方及穿出既有隧道后)施工过程中盾构机顶进力、壁后注浆压力对于上部框架隧道沉降、侧移及扭转影响的规律,计算结果表明,在盾构到达既有隧道正下方前及穿出既有隧道后,沉降量和扭转幅度在一定范围内随顶进力和注浆压力的增大而增大;盾构下穿既有隧道正下方阶段,沉降量和扭转幅度在一定范围内随顶进力和注浆压力的增大而减小。施工过程中宜随着盾构与既有隧道位置关系的改变,及时调整各项施工技术参数,减小对上部隧道的影响,保证盾构顺利掘进。

Numerical Simulation of Oblique Subway Shield Tunneling Undercrossing Existing Frame Tunnel

New shield tunnels are often undercrossing existing tunnels. To study the influence of new shield tunnel construction on existing frame tunnel with reference to Ningbo Metro Line 1 Century Avenue Station-Haiyan North Road Station tunnel undercrossing shallow municipal highway tunnel,this paper applies three-dimensional finite element numerical analysis to study the effects of jacking force,grouting pressure on the upper frame tunnel settlement,lateral displacement and torsion in three undercrossing stages( to reach the existing tunnel,to pass through the existing tunnel and to come out of the existing tunnel). The results show that: both before and after the shield piercing below the existing tunnel,the magnitude of settlement and the reverse within a certain range increases with the increase in jacking force and grouting pressure; when shield just piercing below the existing tunnel,the magnitude of settlement and reverse within a certain range decreases with the increase in jacking force and grouting pressure.Thus,it is recommended to timely adjust the technical parameters of shield with the change of shield positional relationship with the existing tunnel,and to reduce the impact on the upper tunnel for a smooth shield construction.