Deformation Behavior of a Large-Scale Excavation and the Effect of an Adjacent Foundation Pit on the Excavation

Abstract

A large-scale foundation pit with an area of 39,677 m² (B2) was excavated to the south of an existing 25,720 m² Chengdu Universal Trade Plaza (CDUTP) foundation pit (B1) in Chengdu, China. The purpose of this manuscript was to investigate the deformation characteristics of B2 and compare the difference of deformation characteristics between foundation pits B1 and B2. Direct monitoring results of foundation pit B2 were comprehensively investigated and compared with that observed in B1, which include lateral movement, column movement, stress in the columns, and axis force in the anchor cable. Additionally, a strategic approach to mitigate potential extensive lateral deformation was introduced. The monitored results for B2 revealed that the deflection and vertical movement of the columns were comparatively smaller than the reported lower boundaries. The maximum excavation-induced lateral column deflection exhibited a notable 35% reduction in comparison to the lateral deflection observed in the new excavation. However, vertical column movements were approximately twice as pronounced as those in B1. Furthermore, the installation of temporary columns with anchor cables in front of permanent columns proved effective in limiting the vertical deformation during excavation in close proximity to the permanent columns. This research provides valuable insights into the documentation of large-size excavations in soft soil, along with corresponding mitigation approaches.