A new approach for studying the load–displacement characteristics of rammed aggregate piers

This paper investigates the load–displacement characteristics of rammed aggregate piers (RAPs) by applying the innovative idea of simulating the ramming procedure of the aggregates as a fully dynamic process. High radial stresses, induced by ramming, play an important role in the load–settlement behaviour of RAPs. Previously, two simplifying assumptions have been used for considering the effects of ramming in the numerical simulations of RAPs by researchers: (a) prescribed displacement of the cavity wall, and (b) prescribed volumetric strain of the cavity. The dynamic method in this paper, which simulates the cavity expansion in separate lifts, offers a useful option for the analysis of the cases in which the exact amount of the increase of the cavity diameter is not known earlier such as for RAP design purposes or evaluation of a completed project installed on RAPs. A parametric study is conducted using this method to investigate the effects of various parameters such as embedment depth, decreased compaction energy and soil friction angle on the behaviour of RAPs. A simple design method is then provided along with the design charts based on the results of the parametric study.