VERIFICATION OF THE ELASTO-VISCOPLASTIC APPROACH ASSESSING THE LONG-TERM DEFORMATION OF THE QUASI-OVERCONSOLIDATED PLEISTOCENE CLAY DEPOSITS

摘要

A series of elasto-viscoplastic finite element analyses is performed to describe the long-term settlement measured at the reclaimed islands in Osaka Port. The compression modeling for the quasi-overconsolidated Pleistocene clays proposed by the authors has been incorporated to the procedure in which an elasto-viscoplastic deformation is assumed to occur even in the quasi-overconsolidated region (p_0 ≤ p ≤ p_c). One-dimensional analysis is adopted for assessing the settlement of Sakishima and Yumeshima Reclaimed islands, whereas the plane-strain finite element analysis is carried out for investigating the deformation of the Pleistocene deposit beneath the sheet-pile composite revetment at Maishima Reclaimed Island. The proposed procedure is found to provide larger settlement for all cases compared to the conventional approach because of the consideration of viscoplastic deformation in the quasi-overconsolidated region. As for the case of the sheet-pile composite revetment, the effect of stress concentration due to ground improvement with SCP for the Holocene clay layer is remarkable on the underlying Pleistocene deposit. The measured settlement of the individual Pleistocene clay layers as well as the total settlement of the Pleistocene deposits are precisely described by the proposed procedure, whereas the conventional approach in which the instantaneous elastic deformation is assumed to occur in the quasi-overconsolidated region exhibits serious underestimation. From these results, the predictive accuracy of the proposed procedure is verified for assessing the long-term settlement at the reclaimed islands in Osaka Port.