Effects of Installation Method on Sand Compaction Piles in Clay in the Centrifuge

The effects of the method of installation of centrifuge model sand compaction piles (SCPs) in soft clay are studied. The comparative study involves the frozen pile method, a 1-g displacement method, and a high-g displacement method. The results show that, although all the SCP-improved models exhibit higher strength compared to the unimproved models, both displacement methods confer additional enhancement in strength to ground improvement, which was not present in the frozen pile models. In addition, wavy settlement patterns were also observed in the frozen pile models, but not in the displacement models. The observed differences were explained by the postulated differences in stress states of the improved models For the frozen pile models, thawing during reconsolidation was postulated to lead to a reduction in effective lateral stress, resulting in further softening of the clay. On the other hand, the cavity expansion effect caused by the displacement methods was postulated to lead to a set-up in the strength of the clay, thereby resulting in better integrity in the response of the improved ground to loading.