叠线盾构掘进对既有建筑物桩基的位移分析

Displacement analysis of existing building pile foundation caused by excavation of stacked shield tunnel

为有效减少与深入分析叠线盾构隧道掘进对既有邻近建筑物桩基变形的影响,以广东省佛山市地铁3号线南海广场—叠滘区间叠线隧道穿越邻近建筑物桩基为工程背景,采用MidasGTSNX有限元软件,建立了不同桩长h与隧道半径r比值的三维有限元模型,分析叠线盾构隧道施工对既有邻近建筑物桩基的位移影响。通过对比现场监测数据与模型数据,得到在不同几何位置关系下,叠线隧道开挖对既有邻近建筑物桩基的影响规律。研究结果表明:当7<h/r<10时,桩基水平和纵向位移量最小;当h/r<7时,桩基水平和纵向位移量最大。上、下叠线隧道在穿越既有建筑物桩基时,工程设计应尽可能将下方隧道轴线置于桩底标高线以上,避免隧道在桩底标高线以下开挖导致桩基出现的承载力损失。该研究结果可为类似叠线隧道工程设计提供参考。

In order to effectively reduce the impact of underground tunnel boring on existing building pile foundations,in-depth analysis of the impact of stacked-line shield tunnel boring caused by deformation of adjacent building pile foundations,Foshan Metro Line 3 Nanhai Plaza-stacked Kau interval stacked-line tunnel through the pile foundations of adjacent buildings as the background of the project,the use of Midas GTS NX finite element software,the establishment of a three-dimensional finite element model of the ratio of the length of different piles h to the radius of the tunnel r The three-dimensional finite element model with different pile lengths h and tunnel radius r is used to analyse the displacement impact of the stacked-line shield tunnel construction on the pile foundations of the existing adjacent buildings.By comparing the on-site monitoring data with the model data,the impact of the stacked-line tunnel excavation on the pile foundations of existing neighbouring buildings is obtained under different geometric position relationships.The results of the study show that:when h/r is greater than 7 but less than 10,the total displacement of pile foundation is the smallest;when h/r is less than 7,the total displacement of pile foundation is the largest.When the upper and lower stacked-line tunnels cross the pile foundations of existing buildings,the engineering design should place the axes of the tunnels underneath above the pile base elevation line as far as possible,so as to avoid the loss of bearing capacity at the pile ends due to excavation of the tunnels below the pile base elevation line.The results of this study can provide a reference for the design of similar stacked-line tunnels.