A case study of the effect of dynamic compaction on liquefaction of reclaimed ground

This paper presents findings of a case study on the effect of dynamic compaction (DC) on liquefaction potential. The effect of DC is observed in two aspects: the increase in soil strength and the reduction in the variation of soil strength. The effect on the reduction of liquefaction potential through the increase in soil strength is well recognized but the benefit of DC through the reduction in the variation of soil strength is seldom reported. To recognize this benefit, the liquefaction potential is expressed herein in terms of liquefaction probability, as the analysis of the liquefaction probability necessitates the consideration of the coefficient of variation of key soil parameters, which can be captured in a DC project. The above concept is illustrated through a case study of a site where CPTs were conducted before and after DC and where liquefaction manifestation was observed in the 1999 Chi-Chi earthquake. The results of the analysis of these CPTs for liquefaction potential at the site before and after DC are reported. The implication of this study is significant in engineering practice; for example, it provides a basis for risk-based or performance-based design of ground improvement to mitigate the liquefaction hazards. The effect and benefit of ground improvement through the reduction in the variation of soil strength is a topic that is worthy of further studies.