双线盾构隧道下穿对邻近高铁桥梁群桩基础影响研究

Influence of buried depth and diameter of shield tunnel on pile foundation of existing bridge

高铁时代立体交通飞速发展,盾构隧道下穿高铁桥梁不可避免。结合苏州桐泾路北延工程实践,采用Ansys软件建立了双线盾构下穿高铁桥梁施工全过程的有限元分析模型,开展了直径13.67 m盾构下穿沪宁高铁32 m简支箱梁时群桩受力和变形分析。通过现场实测数据与数值计算结果对比,初步验证了有限元模型的有效性;再探讨了盾构隧道直径及埋深等关键参数对邻近高铁桥梁桩群受力和地表变形的影响。计算结果表明:随着隧道埋深与隧道直径的增大,地表整体沉降和邻近桥墩顶部沉降一般都在增大,且随着隧道埋深的增大,地表变形呈现由W型向V型变化。桥桩横向变形一般随着隧道埋深与隧道直径的增加而增大;桥桩竖向变形沿桩身从上至下基本相同,呈现刚体变形特征,仅当隧道埋深较大时,桥桩的竖向变形随隧道直径增大而一直增大。桥桩轴力沿桩身从上至下呈现先增加后减小特征,对于相同直径隧道,随着隧道埋深增加,桩身最大轴力先迅速增大,最后又陡然下降;对于相同埋深工况,随着隧道直径增大,桩身轴力均会明显增大。当隧道埋深较小时,桥桩桩身最大弯矩出现在与隧道中心相同深度处;当隧道埋深较大时,桩身最大弯矩出现在靠近桩顶处,随着隧道直径增大,桩身最大弯矩亦明显增大。

The rapid development of three-dimensional transportation in the era of high-speed rail makes it inevitable for shield tunnels to pass through high-speed railway bridges.Based on the practice of the North Extension Project of Tongjing Road in Suzhou,a finite element analysis model for the en⁃tire construction process of a double-tube shield tunneling through a high-speed railway bridge is estab⁃lished using Ansys software.The stress and deformation analysis of the group piles during the 13.67m diameter shield tunneling through a 32m simply supported box beam on the Shanghai-Nanjing highspeed railway is carried out.The effectiveness of the finite element model is preliminarily verified by comparing the field measured data with the numerical calculation results.The influence of key param⁃eters such as shield tunnel diameter and burial depth on the stress and ground deformation of adjacent high-speed railway bridge pile groups is further explored.The calculation results indicate that with the increase of tunnel burial depth and tunnel diameter,the overall surface settlement and the settlement at the top of adjacent bridge piers generally increase,and with the increase of tunnel burial depth,the ground deformation changes from a W-shaped to a V-shaped.The lateral deformation of bridge piles generally increases with the increase of tunnel burial depth and tunnel diameter.The vertical deforma⁃tion of bridge piles is basically the same from top to bottom along the pile body,showing a rigid defor⁃mation feature.Only when the tunnel is buried deeply,the vertical deformation of bridge piles in⁃creases continuously with the increase of tunnel diameter.The axial force of bridge piles generally in⁃creases first and then decreases from top to bottom along the pile body.For tunnels with the same di⁃ameter,as the tunnel burial depth increases,the maximum axial force of the pile body first increases rapidly,and then suddenly decreases.For the same burial depth condition,as the tunnel diameter in⁃creases,the axial force of the pile body will significantly increase.When the depth of the tunnel is small,the maximum bending moment of the bridge pile body occurs at the same depth as the center of the tunnel.When the tunnel is deeply buried,the maximum bending moment of the pile body occurs near the top of the pile.As the tunnel diameter increases,the maximum bending moment of the pile body also increases significantly.