三线并行小净距隧道施工诱发邻近桩基变形响应研究

Research on Deformation Response of Adjacent Pile Foundations Induced by Construction of Three⁃Lane Parallel Small Clear Distance Tunnels

依托南通轨道交通1号线孩环区间(孩儿巷站—环城东路站)三线并行小净距盾构隧道工程,采用离散元法(Discrete Element Method,DEM)—有限差分法(Finite Difference Method,FDM)耦合的数值仿真,分析桩基础长度、桩隧距对桩基础变形的影响。结果表明:三线小净距隧道施工会引起邻近桩基沉降;桩底和隧道顶部位于同一深度时,桩基水平位移最大值出现在桩底,桩基变形以倾斜为主;桩底与隧道底部位于同一深度和桩底位于隧道底部以下时桩基水平位移最大值出现在隧道轴线位置,桩基变形以弯曲为主,但桩底位于隧道底部以下时桩基对隧道施工表现出更强的敏感性;三种长度的桩基最大拉应力所在截面靠近隧道一侧和远离隧道一侧拉压应力状态均完全相反;桩长一定时,随桩隧距增大,桩基的沉降、最大水平位移、最大轴向拉应力均减小。

Based on the three-lane parallel small clear distance shield tunneling project of the Haihuan section(Haierxiang Station-Huancheng East Road Station)of Nantong rail transit line 1,the numerical simulation coupled with Discrete Element Method(DEM)and Finite Difference Method(FDM)was used to analyze the influence of pile length,the distance between pile and tunnel on pile foundation deformation.The results show that the construction of a three-lane small clearance tunnel causes settlement of adjacent pile foundations.When the bottom of the pile and the top of the tunnel are at the same depth,the maximum horizontal displacement of the pile foundation occurs at the bottom of the pile,and the deformation of the pile foundation is mainly inclined.When the pile bottom is at the same depth as the tunnel bottom and the pile bottom is below the tunnel bottom,the maximum horizontal displacement of the pile foundation occurs at the tunnel axis position.The deformation of the pile foundation is mainly bending,but when the pile bottom is below the tunnel bottom,the pile foundation shows stronger sensitivity to tunnel construction.Tension and compression state of the cross-section where the maximum tensile stress of three different lengths of pile is located near the tunnel are completely opposite to that away from the tunnel.When the length of the pile is constant,as the distance between pile and tunnel increases,the settlement,maximum horizontal displacement,and maximum axial tensile stress of the pile foundation all decrease.