Centrifuge Model Tests on Failure Pattern of Deep Mixing Columns on Inclined Foundation-Paper

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The study investigates the internal stability and failure behavior of group-column deep-mixing (DM) ground constructed on inclined foundations. Existing design methods largely assume a horizontal foundation, so the authors used centrifuge model tests to assess how foundation slope affects column failure and ground deformation.<br /><br />Cement-stabilized model columns were installed in uniform kaolin clay above either a horizontal base or one inclined at 30°. The improved ground was loaded with backfill, with tests examining both caisson-supported and embankment-type structures. Column failure, earth pressures, and ground and structure displacements were monitored.<br /><br />The DM columns generally failed in bending, triggering rapid increases in ground deformation. Failure occurred progressively rather than simultaneously. For caisson-type tests, the rearmost column failed first on a horizontal foundation, while a foremost column failed first on the inclined foundation. In embankment-type tests, the failure sequence differed, and the authors note that further research is needed to explain the difference.<br /><br />In both structural configurations, failure pressure decreased approximately linearly as foundation inclination increased. At a 30° inclination, failure pressure was about 70% of that on a horizontal foundation. Inclination had a greater effect on internal stability than on external stability. Greater column strength increased failure pressure, although sufficiently strong columns may shift the governing mode from internal column failure to external failure.<br /><br />The results show that foundation slope affects both the sequence of column failure and the capacity of DM-improved ground. They suggest that design approaches based on horizontal foundations may not adequately represent internal stability on inclined foundations.

Keywords

deep-mixing ground

internal stability

inclined foundation

centrifuge model test

column failure

cement-stabilized columns

kaolin clay

earth pressure

ground deformation

failure pressure