LONG-TERM CONSOLIDATION CHARACTERISTIC OF DILUVIAL CLAY IN OSAKA BAY

抄録

On large-scale reclamation works, the consolidation settlement of diluvial clays which lie deep underground should be discussed. The diluvial clay in Osaka Bay is in a quasi-overconsolidated state by cementation bonding. The values of the compression index and the void ratio are very large in spite of the large overburden pressure. Therefore, its consolidation characteristic is considered to be different from that of the alluvial clay. In this paper, a series of long-term consolidation tests is carried out, and it is revealed that the value of coefficient of secondary compression (Cα) under a load in the quasi-overconsolidated region becomes to be that in the normally consolidated region as time elapses. Considering the effect of strain rate, this result shows that the yield stress is dependent on the strain rate. This also means that even if a clay behaves as an overconsolidated clay in the test, it might behave as a normally consolidated clay in the site. Therefore, it should be considered that the in-situ secondary compression settlement was underestimated if it was calculated by using C_α of the laboratory test. In addition, the settlements on two reclamation works in Osaka Bay are calculated by a proposed long-term settlement analyzing method using strain rate and time relationship, and the results are in good agreement with the observed settlement data at sites.