全方位高压喷射工法桩施工引起下卧地铁隧道变形实测分析

Analysis on Measured Deformations of Underlying Subway Tunnel Caused by Omni-directional High Pressure Jet Method Pile

为进一步研究全方位高压喷射(Metro Jet System,MJS)工法的施工影响,结合苏州某基坑工程,采用现场实测的方法分析MJS工法桩加固坑内土体施工引起下卧地铁隧道变形及其规律。结果表明:在MJS工法桩施工期间,①MJS工法桩施工范围内的地铁隧道拱顶、道床和拱腰位移总体为上抬,净空收敛总体为压缩,MJS工法桩施工范围外的相应值总体为下沉和拉伸;②地铁隧道各监测断面的拱顶、道床、拱腰位移及净空收敛最大值均满足设计要求;③地铁隧道沿其纵向变形呈“弓形”变化。研究得出采取MJS工法群桩跳打施工,有益于减少坑内土体加固对下卧地铁隧道变形的影响。

In order to further study the construction impact of the omni-directional high-pressure jet(Metro Jet System)construction method,based on an excavation project in Suzhou,the deformations of the underlying subway tunnel caused by the construction of MJS soil reinforcement method are measured and analyzed.The results show that:during the construction of MJS method piles,①generally,the displacements of the vault,bed and haunch of the subway tunnel within the construction scope of MJS pile are upward,and the clearance is compression,whereas the corresponding values outside the construction scope of MJS pile are subsidence and stretching.②The maximum displacement and clearance convergence of vault,track bed and haunch of each monitoring section of subway tunnel meet the design requirements.③The longitudinal deformation of subway tunnel changes in a“bow”shape.The study concludes that the adoption of the MJS construction method for group pile jumping construction is beneficial to reduce the influence of soil reinforcement in the pit on the deformation of the underlying subway tunnel.