Elasto-plastic consolidation analysis for strutted excavation in clay

Abstract

Ground movements and strut loads in strutted excavations in clay have been observed to change with time. In this paper, the time-dependent behaviour of excavation support system is studied by comparing the results of undrained and consolidation analyses with data from an instrumented excavation project. Dissipation of excess pore pressure is modelled using a fully coupled consolidation analysis while the soil is assumed to be an elastic-perfectly plastic material obeying the Mohr-Coulomb yield criterion. The results of the study show that the undrained analysis underestimates the sheet pile wall movement and fail to reflect the progressive movement of the sheet pile. In contrast, these effects are well-predicted by the consolidation analysis, thereby indicating that dissipation of excess negative pore pressure can indeed account for much of the observed progressive ground movement and build-up of strut loads with time. The elasto-plastic consolidation model can also simulate excavation sequence including uneven excavation and time delays in excavation and strutting.