One-Dimensional Reverse Consolidation Model for Basal Soil from Deep Excavation Based on the Continuous Drainage Boundary

Abstract

Excavation-induced unloading effects and dewatering-induced groundwater seepage inevitably result in basal soil reverse consolidation in deep excavation. However, this reverse consolidation process is rarely considered because most previous analytical methods were developed based on total stress analyses. This study proposes a one-dimensional reverse consolidation model for basal soil of deep excavation. Based on the consolidation theory proposed by Terzaghi, governing equations of soil reverse consolidation caused by excavation and dewatering were separately established. The continuous drainage boundary was introduced to describe the construction processes. The reverse consolidation responses of basal soil were obtained by superimposing analytical solutions of the excess pore-water pressures that resulted from excavation and dewatering. The proposed model was verified by existing solutions and a well-documented excavation case history. Moreover, the reverse consolidation characteristics of basal soil were investigated by parametric analyses. Results indicate that the excavation-induced variations in pore-water pressure decreased with increasing excavation depth. The final pore-water pressure and effective stress were predominantly affected by excavation duration rather than interval distribution. In addition, a smaller coefficient of consolidation led to lower pore-water pressure and greater effective stress at a given excavation depth.