Centrifuge Model Tests on Internal Stability of Group Column Type Improved Ground under Embankment
Masaki KITAZUME and Kenji MARUYAMA
Abstract:The Deep Mixing Method, an in-situ soil stabilization technique using cement and/or lime, is often applied to improve soft soils. The group column type improvement is extensively applied to stabilize foundations of embankment or lightweight structures. The improved ground design procedure in Japan assumes two failure patterns related to external and internal stabilities. External stability is evaluated for the possibility of sliding failure, in which DM columns and clay between show horizontal displacement on a stiff layer without any rearrangement of columns. For internal stability, the possibility of rupture breaking failure is evaluated by slip circle analysis, assuming the shear failure mode of DM columns. In this study, a series of centrifuge model tests was carried out to investigate the internal stability of improved ground under embankment loading. This paper describes the failure modes of DM columns and a proposed simple calculation that takes into account the bending failure mode. Key Words:Deep mixing method, Group column type improved ground, Internal stability, Failure mode, Centrifuge model test