Predicting Excavation-Induced Settlement for Embedded Footing: Case Study

Abstract

Analytical solutions are proposed to evaluate the average settlement under an embedded footing in an elastic soil. The rigid foundation was simplified as a uniformly loaded area. Four factors, the Gibson, trench, sidewall friction, and retaining wall effects, were considered to reduce the settlement of the footing due to embedment. Immediate settlement of a footing can be calculated using either conventional influence factors or by a finite-layer-based consolidation analysis with a short time interval. The effectiveness of the proposed techniques was evaluated by comparing results obtained from different approaches, and a maximum difference of 1% was observed. The method was also used to analyze the settlements of the base slab of an excavation, which were compared with field measurements of the West Extension Line of the Nanjing Metro Line 1. On the basis of the analysis, the reason why a compensated foundation could experience excessive settlement is discussed. Overexcavation induced by basal heave results in a very loose state of the soil underneath the footing where swelling could occur. Reloading after backfilling easily causes large settlements. Therefore, an arched beam foundation is proposed to reduce the magnitude of further settlement of the footing.