软土地层并行曲线隧道施工顺序对既有隧道的影响

为了研究并行曲线隧道施工顺序对既有隧道的影响,以横琴杧洲隧道工程为依托,建立了并行曲线隧道三维有限元数值模型。在此基础上,研究了不同施工顺序和曲率半径r(r=500,800 m)下新建曲线盾构隧道开挖对既有隧道变形的影响。结果表明:施工顺序对既有隧道位移影响较小,曲率半径对既有隧道位移影响相对较大; 随着曲率半径(r=500～800 m)的增加,既有隧道位移增加约15%; 既有隧道的位移主要在盾构开挖面前方2D(D为隧道外径)、后方1D范围内产生; 施工顺序对既有隧道内力的影响与曲率半径有关; 隧道曲率半径为500 m时,施工顺序对既有隧道内力变化影响规律相似,即离盾构开挖面最近的既有隧道剖面产生的弯矩最大,且最大弯矩和最小弯矩均出现在靠近新隧道一侧; 内侧隧道先开挖时,既有隧道的弯矩(绝对值)更小,此时对于并行曲线隧道施工,内侧隧道先开挖更安全; 在盾构开挖面前方一定距离内既有隧道产生的轴力最大; 隧道曲率半径为800 m时,双线隧道近似于平行隧道,施工顺序对既有隧道内力变化和大小影响较小。

Influence of Construction Sequence of Parallel Curved Tunnels on Existing Tunnels in Soft Soil Stratum

To study the influence of the construction sequence of parallel curved tunnels, a three-dimensional finite element numerical model was established according to the Mangzhou tunnel project in Hengqin. On the basis, the deformation of existing tunnel induced by the new curved shield tunnelling was investigated under different construction sequences and radii of curvature r(r=500, 800 m). The results show that the construction sequence has a small effect on the existing tunnel displacement, while the radius of curvature has a relatively large effect on the existing tunnel displacement, which increases by about 15% with the increasing of the radius of curvature(r=500-800 m). The existing tunnel displacements mainly occur within 2D(D is the tunnel outer diameter)in front of the shield excavation face and 1D behind it. The effect of the construction sequence on the internal forces of the existing tunnel is related to the radius of curvature. For a radius of curvature of 500 m, the construction sequence has a similar effect on the internal forces of the existing tunnel as the existing tunnel profile closest to the shield excavation produces the largest bending moment, and both the maximum and minimum bending moments occur close to the new tunnel side. The bending moment(absolute value)in the existing tunnel is smaller when the inner tunnel is excavated firstly, making it safer to excavate the inner tunnel firstly for parallel curved tunnel construction. The greatest axial forces are generated in the existing tunnel at a certain distance in front of the shield excavation face. The double-line tunnel with radius of curvature of 800 m is approximately similar to parallel tunnel and the construction sequence has a small effect on the variation and magnitude of the internal forces of the existing tunnel.