Method for Estimating Fully Coupled Response of Deep Excavations in Soft Clays

The influence of excavation rate, geometric layout, and hydraulic conductivity of basal and retained soils on the fully coupled solid-fluid behavior of braced excavations in cohesive soils is presented. Fully coupled excavation analyses were performed using the hypoplasticity clay model to reproduce the constitutive soil behavior combined with Biot's consolidation theory. A method aimed at predicting excavation-induced ground movements using excess pore-water pressure ratios as a function of site-specific groundwater considerations is presented for the determination of the recommended type of excavation analysis (i.e., drained, partially drained, or undrained). Results obtained from the numerical simulations indicated that excavation rate to hydraulic conductivity ratios, ER/k, smaller than 0.1 and larger than 10,000 can be analyzed under drained and undrained conditions, respectively. The proposed method was validated with published case histories, and its ability to estimate excavation performance in terms of excess pore-water pressures and excavation rates is presented in this paper.