Numerical modelling of piled retaining wall in unsaturated Adelaide clays

Abstract

Unsaturated clays found in the Plains of Adelaide, South Australia, are typically stiff-to-hard and can exhibit high shear strength due to very high suction. Such suction hardening behavior allows deep vertical cuttings to stand unsupported for significant periods of time. It is evident, from previous studies, that unsaturated soil mechanics is particularly relevant to the design of earth structures in South Australia because of its semi-arid climate. The South Australian Government is currently constructing a 4 km section of non-stop roadway, featuring 3 km of a depressed motorway to a maximum depth of 8 m below street level. In the early design and planning stages of the project, various retaining wall options were considered. Cantilever soldier piles were constructed adopting varying diameters and center-to-center spacings, as part of a full-scale field trial that was undertaken during the design phase. This study examines the use of numerical methods for stability analysis of deep cuttings, using the finite element method to model the performance of the piled retaining walls with different design configurations.