Numerical analyses on the failure of deep mixing columns reinforced by a shallow mixing layer

Abstract

Soil cement mixing by deep mixing technique is used as a soft soil improvement method. Deep mixing columns are widely used to support embankment constructed on a soft ground area. In order to applying this improvement method, the failure pattern of group column type improvement should be analyzed. Researches on the failure pattern of columns are done by some authors when the columns individually fail. Due to individual failure of columns under loading, a layer of shallow mixing layer is proposed to reinforce individual columns working as a group in order to increase the stability as well as loading capacity of columned improved area. This research focuses on the failure pattern of group of columns which are fixed by the shallow mixing layer under embankment. By comparing to failure mechanism of individual columns, the effect of shallow mixing layer on failure pattern of deep mixing columns is also discussed. Finite element method is used for this analysis with Plaxis code under plain strain condition. The effect of thickness of shallow mixing layer on reducing horizontal displacement of embankment isvarious with different values of strength and stiffness of cement mixing area which is discussed in this research.