上覆路堑开挖对既有下卧大断面隧道影响研究

Study on the Influence of Overlying Cutting Excavation on Existing Underlying Large Section Highway Tunnel

为研究上覆路堑开挖对下卧大断面隧道的影响,以厦门翔安机场高速内厝互通新建匝道路堑上跨既有下沙溪隧道工程为依托,构建三维数值分析模型,动态模拟山体开挖及道路建设过程,研究开挖卸荷对隧道结构受力及变形的影响,并通过实测监控隧道安全。研究表明:下卧隧道与道路开挖地表最大位移的位置距离越近,隧道变形越大;开挖过程中,边坡地表和隧道最大位移位置动态变化,隧道变形最大位置总是指向地表最大位移位置;上方匝道边坡开挖引起左洞隧道侧壁内侧受拉,易导致隧道二次衬砌的内侧开裂等病害;现场实测表明,隧道隆起最大值为6.2 mm,下卧隧道处于安全状态。

In order to study the impact of the excavation of the overlying cutting on the underlying large section tunnel,based on the existing xiashaxi tunnel project on the upper span of the new turn road cutting of neicuo interchange of Xiamen Xiang’an Airport Expressway,Build a three-dimensional numerical analysis model to dynamically simulate the process of mountain excavation and road construction,study the influence of excavation unloading on the stress and deformation of tunnel structure,and monitor the tunnel safety through actual measurement.The results show that:The closer the distance between the underground tunnel and the maximum displacement of the road excavation surface,the greater the tunnel deformation;In the process of excavation,the maximum displacement position of slope surface and tunnel changes dynamically.The maximum deformation position of tunnel always points to the maximum displacement position of surface and deflects accordingly;The excavation process of the upper ramp slope causes the tension on the inner side of the side wall of the left tunnel,which is easy to cause the inner side cracking of the tunnel secondary lining and other diseases;The field measurement shows that the maximum uplift of the tunnel is 6.2 mm,and the underlying tunnel is in a safe state.