Behavior of granular column-improved clay under cyclic shear loading

Abstract

To investigate the influence of granular column on cyclic shear characteristics of treated clay, a total number of 42 large-scale cyclic direct shear test was performed. Clay undrained shear strength, granular column diameter, relative density of aggregates, shear displacement half-amplitude and numbers of loading cycles were all varied so that the behavior of the treated clay could be evaluated. The results of the experiments showed that the use of granular column improved up to 30% the maximum cyclic shear resistance compared to the untreated clay, particularly in the initial loading cycles. This improvement was much more considerable as column diameter and relative density of the aggregates increased. As well, increasing the number of loading cycles was found to decrease the magnitude of damping ratio. However, increasing both the column diameter and aggregates relative density has shown to reduce the corresponding value. In addition, the magnitude of secant shear stiffness was observed to reduce by progressing the number of loading cycles. Whereas, this downward trend became flatter as aggregates relative density increased; hence, bearing witness to the positive influence of granular column compaction on mitigation of the shear stiffness degradation with the progress of cycles.