双线大直径输水隧道建设对既有桥梁及桩基的影响分析

Construction of large diameter twin water conveyance tunnels affects existing bridge and pile foundation structure

为准确分析双线大直径输水隧道下穿对既有桥梁结构的影响,构建桥梁-地层-桩基-盾构隧道高精度数值仿真模型,对桥梁桩基结构及盾构过程进行精细化模拟,结合基于智能算法的土层参数反演模型,获取更接近真实情况的土层参数,以提高数值模拟精度。结果表明:输水隧道盾构开挖引起的地表最大沉降量为15.01 mm,基于反演的地表变形计算结果与实际监测值的误差减少约70%;盾构隧道双线开挖会引起地表二次沉降变形,两条盾构隧道中间区域的地表二次沉降量最大,约占总沉降量的60%,最大二次沉降量为5.06 mm;隧道两侧的桩基受到影响较大,最大位移为10.03 mm,位于桩基顶部,而隧道开挖对桩基内应力分布影响较小,可以认为无影响。

Underground large diameter twin water conveyance tunnels which underpass the existing bridges will affect the stability of the bridge foundation and structure.To clarify the impact,a high-precision numerical model of bridge-stratum-pile foundation-shield tunnel is constructed for the fine simulation of bridge pile foundation structure and shield tunneling process.Then the simulation results are combined with an intelligent algorithm-based stratum parameter inversion model to obtain more realistic soil stratum parameters.The results show that the maximum surface settlement caused by shield tunneling is 15.01 mm,and the error of the calculated surface deformation based on inversion is reduced by about 70%,compared with that of the actual monitoring value;the excavation of the twin tunnels will cause secondary settlement deformation on the surface,with the largest secondary settlement found in the area between the two shield tunnels,which accounts for about 60%of the total settlement,and the maximum secondary settlement is 5.06 mm.Moreover,the pile foundations on both sides of the tunnels are greatly affected,with a maximum displacement of 10.03 mm,located at the top of the pile foundation.However,tunnel excavation has a relatively small impact on the stress distribution inside the pile foundation,which is negligible.