Centrifuge tests on column type mixing improved ground with surface improvement

A group column type Deep Mixing improved ground is extensively applied to stabilize foundations of embankment or lightweight structures. A design procedure in Japan assumes two failure patterns related to external and internal stabilities. The authors conducted research projects on the failure mechanism and stability of the improved ground subjected to embankment loading. The projects involved investigation of the failure pattern and criteria of two stability analyses. A series of model tests was conducted to investigate the effect of a surface improvement layer connecting DM columns on embankment stability. This paper describes the failure mode of the DM columns and a proposed simple calculation that incorporates the effect of the surface improvement layer.