盾构双隧道小净距下穿既有车站掘进方案影响研究

Effect Research of Excavation Scheme in the Close Distance Undercrossing Construction of Shield Double Tunnels Beneath Existing Stations

由于地铁运营方式的网络化,使得新建隧道工程穿越既有地铁设施问题应运而生,给新建地铁施工带来更严格要求。因受到施工环境等诸多因素制约,双隧道地铁盾构施工常采用对向或同向开挖的方式。以北京地铁8号线某区间隧道为例,采用有限元软件对隧道施工过程进行数值分析,并与现场监控量测数据相结合,比较不同开挖间距、不同开挖掘进次序对既有车站结构变形的影响。结果表明:(1)近距离下穿既有车站,对向掘进、同向掘进两种开挖方式下,既有车站沉降变形值差距不大,可按实际环境、条件选取掘进次序;(2)左右线距离间隔越小,同向掘进双隧道时,后方盾构施工对既有车站结构沉降影响越明显;(3)若因工期紧张,掘进开挖作业需双线进行,后行隧道、先行隧道二者开挖面距离不低于30环,并加强后行隧道的沉降控制。

Due to the networked operation of the subway,the problem of new tunnel projects crossing existing subway facilities has emerged,which has brought stricter requirements for the construction of new subways.Because of various factors such as construction environment constraints,shield tunneling construction in double tunnel subways often adopts opposite or same direction excavation methods.In this study,numerical analysis of tunnel construction operations in a certain section of Beijing Metro Line 8 was carried out using finite element software,and on-site monitoring and measurement data was combined to compare the effects of different excavation spacing and excavation sequence on the structural deformation of existing stations.The results show that:(1)when crossing beneath the existing station at a close distance,there is not much difference in the settlement deformation values of the existing station under the methods of excavating in opposite directions and excavating in the same direction.The excavation order can be selected according to the actual environment and conditions.(2)The smaller the distance between the left and right lines,the more significant the impact of shield tunneling on the settlement of the existing station structure when excavating double tunnels in the same direction;(3)If the construction period is tight and the excavation work needs to be carried out for both tunnels simultaneously,it should maintain an interval of no less than 30 rings between the later tunnel and the prior tunnel.Additionally,settlement control measures should be implemented for the tunnel excavated later.