Numerical study of the settlement of rafts on soft soils improved by small groups of stone columns

Document Type : Research Article

Authors

Department of Civil and Environmental Engineering, Amirkabir University of Technology, Tehran. Iran

Abstract

Stone column installation is used as an economical, simple and efficient technique for soft ground improvement in order to reduce settlements, increase bearing capacity and accelerate drainage of the foundation soil. While design approaches and analytical methods usually consider the condition of very large loaded area by using unit-cell models, many practical stone column improvement projects deal with finite or semi-infinite loading areas (e.g. storage tank foundations and road embankments, respectively). In recent years, some recommendations have been presented in the literature for the prediction of settlements of small groups of stone columns (Sgroup) based on results of unit-cell models (Suc). However, these methods have been developed for specific soft soils or loading condition. This paper presents results of a comprehensive study on the settlement of small groups of stone columns and provides a relationship for the estimation of the ratio of settlement of a finite sized stone column supported foundation (SCSF) to the settlement of an infinite group as obtained from a unit-cell model (Sgroup/Suc). The sub-soil and loading conditions are conveniently taken into account in the proposed relationship. For this purpose, settlement of a large number of SCSFs having various geometrical and mechanical conditions are investigated using numerical FEM modeling.

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