基坑开挖引起复合地基下卧双线地铁隧道附加荷载的计算研究

为研究基坑开挖时复合地基及竖向、横向"双洞效应"对下卧双线地铁隧道竖向、横向附加荷载的影响,基于Mindlin应力解,得到在复合地基侧摩阻力作用下隧道轴线上的竖向、横向附加荷载,通过迭代法计算得到"双洞效应"引起隧道轴线上的竖向、横向附加荷载,借助竖向、横向总附加荷载引起的隧道位移对比验证,并分析隧道位置改变对侧摩阻力和"双洞效应"引起隧道竖向、横向附加荷载的影响。研究结果表明:侧摩阻力和"双洞效应"对隧道竖向、横向附加荷载的影响是不可忽略的,其影响主要表现为减小隧道的竖向、横向总附加荷载,且影响范围不变;在施工条件和规范容许范围内,应尽量减小双线隧道之间的距离,以及增大隧道与基坑中点的距离;当需要严谨精确地计算小净距地铁隧道"双洞效应"引起的附加荷载时,必须选用迭代法计算。

Calculation Study of Additional Load of Double-tube Metro Tunnels Under Composite Foundation due to Foundation Pit Excavation

In order to study the influence of composite foundation and vertical and lateral "double-hole effects" on the vertical and lateral additional load of underlying double-tube metro tunnels during foundation pit excavation, based on Mindlin stress solution, the vertical and lateral additional load on the tunnel axis under the side resistance of composite foundation is derived, and the vertical and lateral additional load on the tunnel axis caused by "double-hole effects" is calculated by iterative method. With the help of tunnel displacement caused by the total vertical and lateral additional load, the theoretical calculation of the additional load is compared and verified, and the influence of tunnel position change on the vertical and lateral additional load due to side resistance and "double-hole effects". The results show that the influence of side resistance and "double-hole effects" on additional vertical and lateral load can not be neglected, and the main influence is to reduce the total vertical and lateral additional loads of the tunnels, and the influence range remains unchanged; within the permissible range of construction conditions and codes, the distance between the double-tube tunnels should be decreased as far as possible, and the distance between the tunnel and the midpoint of the foundation pit should be increased; when it is necessary to accurately calculate the additional load caused by the "double-hole effects" of metro tunnels with small interval, the iterative method must be used.