Effect Analysis of Excavation and Unloading of Deep Foundation Pit in Soft Soil Stratum on Pile Foundation of Underground Station

Abstract

Objective In the excavation process of deep foundation pit of underground station in deep soft soil stratum, excavation and unloading of the overlying soil in the pit will obviously impact the previously constructed superlong pile foundation in the pit, threatening the structure stability and engineering safety. In order to explore the effects of large-scale deep foundation pit excavation and unloading on the pile group at the station foundation pit bottom, it is necessary to analyze the deformation law of the superlong pile under pressure. Method A numerical analysis software Midas GTS NX is used to establish a finite element numerical calculation model for the underground station S2 east end well and make the excavation simulation analysis. Based on a comparison of the on-site actual monitored data and the numerical calculation results, the deformation law of the pile group at the pit bottom affected by the foundation pit excavation is discussed. Result & Conclusion The results show that the pile area under tension increases with the deepening of excavation，both the maximum tension and the maximum pressure of the end well pile foundation are greater than the standard range. The vertical displacement of the pile foundation at the pit bottom continuously increases in the process of excavation. The largest pile displacement occurs at the farthest distance from the edge of the end well. In the later stage of excavation, as the incremental uplift of the pile foundation increases significantly, the vertical displacement of the pile top needs to be monitored in real time to prevent engineering accidents.

Keywords

• surburban railway station
• deep foundation pit excavation
• pile foundation
• finite element analysis