Stone columns are used in practice for ground improvement of soft subsoil. Current design procedures of these columns are based on simple empirical calculations. This research project investigates the behavior of a base reinforced embankment constructed on a soft clay layer, which is improved with stone columns. Centrifuge tests were performed in order to gain a deeper understanding of the interaction problem within the structure. Stone columns were constructed in-flight using a newly developed installation tool. First analysis of test data shows a significant change in stress state due to column construction and the influence on the clay behavior.
The issue of settlement and the calculation of the thickness of the deformation zone are addressed in this paper. A short overview is given concerning the thickness of the deformation zone values used in general practice; the available soil models are also briefly introduced. A particular problem is used to compare the results of obtained depth of the influence zone calculated by available formulae and estimated by finite element analyses with different soil models, such as the “hardening soil”, the “Cam-Clay” and the “hardening soil with small strain” models. The deformation zone of a soft clay layer beneath a 10 m-high and 80 m-wide embankment is evaluated, and the results are compared. Special attention is given to the soil models and their capabilities and drawbacks for calculation of deformations due to large embankments.