Effect of freeze–thaw cycles on deformation properties of deep foundation pit supported by pile-anchor in Harbin

Abstract

Abstract In the course of the construction of deep foundation pits during the winter in seasonally frozen areas, the pit wall soil is often unstable due to frost heave and thawing settlement, which leads to hidden safety hazards in engineering construction. Based on the analysis of the deformation data of a pile-anchor supporting a deep foundation pit in Harbin obtained from monitoring during the winter, the influence of freezing and thawing cycles was investigated. The results show that the horizontal displacement in the middle of the shallow layer of the foundation pit is significantly larger than that on both sides during the freeze–thaw cycles, and the spatial effect becomes noticeable. The stress concentration at the external corner of the foundation pit, coupled with the effects of atmospheric precipitation and freeze–thaw cycles, led to the maximum growth rate of horizontal displacement up to 1.40 mm·day−1. The external corner effect is evident from 1 m in the shallow layer of the pit to the depth H/2 of the foundation pit. The support scheme is generally feasible, and we can appropriately enhance the support of the shallow layer of the foundation pit during the freeze–thaw cycles. For similar projects experiencing freeze–thaw cycles, the safety reserve can be appropriately enhanced when carrying out support design.