A Case Study of Long Term Settlement of Sensitive Soft Clay Due to Embanking

Abstract

Four possible questions are newly prepared in order to solve "delayed compression/secondary consolidation" problems of natural clay. First question is on the mechanisms of the occurrence of delayed compression and/or secondary consolidation of natural clay. This difficult compression/consolidation of the clay will be shown to be quite similar to the "compaction" of loose sand, both of which proceeds with decay and/or collapse of soil skeleton structure without any significant increase in mean effective stresses. Second question is the applicability of the Asaoka's method for predicting residual settlement. In usual cases the method works, but it tends to give significantly small prediction in case of delayed compression/secondary consolidation when the method is applied at very early stages of consolidation. What sort of natural clay does exhibit difficult delayed compression/secondary consolidation? This third question will be newly solved by introducing the new "two soil indices." The fourth question is on the counter-measures against delayed compression and/or secondary consolidation. We, Japanese soil engineers, have accumulated very many bitter experiences of delayed compression/secondary consolidation for years. All the questions mentioned above will be discussed together with those severe experiences.