Study on the influence of reverse faulting on deformation of foundation pit retaining piles

Abstract

The mechanical properties of soil in fault-fracture zone areas are diverse and complex. Deep excavation projects often encounter adverse geological conditions such as reverse faulting, which can lead to surface subsidence and collapses, posing significant challenges to excavation safety. Currently, there is limited research in the field of deep excavation engineering that analyzes the influence of reverse faulting on the deformation of retaining piles, and the existing research methods are not systematic enough. Therefore, this study aims to investigate the characteristics of how reverse faulting affects the deformation of retaining piles in deep excavation projects. Various research methods were employed, including numerical simulation, on-site monitoring, and orthogonal experiments, using a deep excavation project in Shenzhen as a case study. The results of the study indicate that reverse faulting exacerbates the deformation of retaining piles, causing the trend of increased deformation to shift upward. The upper part of the pile is significantly more affected than the lower part, and the overall deformation of the pile exhibits an approximate spoon-shaped curve distribution, with the maximum deformation occurring in the upper-middle section of the excavation. Under the influence of reverse faulting, the deformation of retaining piles is positively correlated with fault slip distance and fault dip angle, while it is negatively correlated with fault position. The growth rate of the maximum deformation of retaining piles, denoted as r(ΔZmax/Δ), increases approximately logarithmically with increasing fault slip distance and exponentially with increasing fault dip angle, but decreases approximately logarithmically with increasing distance from the fault to the excavation. An analysis of the sensitivity of fault slip distance, fault dip angle, and fault position to the maximum deformation of retaining piles was conducted. It was determined that the fault dip angle has the highest sensitivity, followed by fault slip distance, while fault position has the lowest sensitivity. Based on the fitting of 64 sets of orthogonal experimental data, a good linear relationship was established between the maximum deformation of retaining piles (Uhm) and the indicator η($$\theta \pi T/180^{^\circ } S$$ θ π T / 180 ∘ S ), leading to the development of a predictive model for the maximum deformation of retaining piles under the influence of reverse faulting. These research findings provide valuable insights and references for similar engineering projects.