Consolidation and deformation around stone columns: Comparison of theoretical and laboratory results

A unit cell, i.e. only one stone column and its corresponding surrounding soil, is used to study the consolidation and deformation around end-bearing columns under distributed loads. The results of laboratory measurements are compared with analytical solutions and numerical simulations. The large amount of data available from the laboratory allows for a detailed comparison. The main soil responses, such as the equivalent coefficient of consolidation, the stress concentration factor and the settlement reduction are analysed using the different approaches. The soil improvement directly depends on the stress distribution between soil and column. Column yielding, and consequently the friction and dilatancy angles of the gravel control the final improvement. Therefore, only the analytical solutions that properly consider plastic strains in the column accurately predict the soil improvement. An issue that influences the stress distribution with time and as a result the consolidation process is the high small-strain stiffness of the column, which is not considered in the analytical solutions but has a small influence for high degrees of consolidation, and hence, for practical purposes. (C) 2012 Elsevier Ltd. All rights reserved.