Importance of the excavation level on the prediction of the settlement pattern from piled raft analyses

Abstract

This article analyses the effect of the excavation level on the settlement results from a standard analysis of a piled raft system. For that, a published case history that involved a house located in Gothenburg, Sweden by Hansbo (1993) was examined. This structure was founded over a soft, highly plastic marine clay of varying thickness, where the foundation was designed by using the concept of “creep piling”, i.e., piles in a state of full load mobilization. The analyses were carried out with the numerical tools DEFPIG and GARP, by considering a series of simplified assumptions for the load pattern, raft and pile characteristics and subsoil profile. The soil, pile and load characteristics have been considered, with analyses that allowed (or not) the effect of the excavation level. The exercise emphasizes the importance of such consideration for the assessment of the settlement pattern underneath the raft. This contribution concludes that it is not possible to precisely predict the behavior of piled rafts without a full understanding of its important input parameters, such as the excavation depth. It should be of considerable interest for those who design / simulate piled foundations and need to predict their performance in the presence of consolidating soft soils.