抛填土地层隧道侧穿施工对既有铁路桥墩的影响研究

The Influence of Tunnel Side Crossing Construction on Existing Railway Bridge Piers

针对某区间隧道近距离侧穿相距极近的2座特大桥期间的施工安全性问题,通过建立三维有限元模型研究了2座桥梁的桥墩位移。研究发现,隧道施工期间的桥墩位移满足控制标准,变形主要产生于掌子面距桥墩群桩前后约2D(D为隧道洞径)范围内,新建隧道左、右洞施工的纵向间距应控制在5D以上,建议采用较大外插角或全环增加长3.0m、直径25mm的中空注浆锚杆以加固围岩和封堵地下水,加固圈厚度宜≥3.0m;在确保单层初期支护能有效控制围岩变形的前提下,将双层初期支护调整为单层初期支护。

Aiming at the construction safety problem of a tunnel passing through two super large bridges which are very close to each other, a three-dimensional finite element model is established to study the pier displacement of the two bridges. It is found out that the deformation of bridge piers can meet the control requirements during tunnel construction. The deformation mainly occurs when the tunnel face is in the range of about 2D(D is the tunnel diameter) before and after the pier group piles. The longitudinal distance between the two newly built tunnels should be controlled above 5D. It is suggested to adopt larger external angle or increase hollow grouting anchor rod, which is 3.0 m in length and 25 mm in diameter to reinforce the surrounding rock and block groundwater. The thickness of reinforcement zone should not be less than 3.0 m. On the premise of ensuring that single layer primary support can effectively control the deformation of surrounding rock, the double-layer primary support can be adjusted into the single layer primary support.