NUMERICAL ASSESSMENT FOR THE BEHAVIOR OF THE PLEISTOCENE MARINE FOUNDATIONS DUE TO CONSTRUCTION OF THE 1ST PHASE ISLAND OF KANSAI INTERNATIONAL AIRPORT

摘要

A series of elasto-viscoplastic finite element analyses is performed to assess the stress and deformation of the Pleistocene marine foundation due to construction of the 1st phase island of Kansai International Airport in Osaka Bay. Attention is paid to the modeling of permeability for Pleistocene sand gravel layers considering the sedimentation environment because the performance of excess pore water pressure is strongly dependent on the extent of distribution as well as the change of thickness of those permeable sand gravel layers. The concept of "mass permeability" is introduced to model the actual process of dissipation of excess pore water pressure in the field. The mechanism for the propagation of excess pore water pressure is also discussed. Special attention is given to the modeling of the compressibility of the highly structured Pleistocene clay layers, exhibiting already significant visco-plastic deformations even in the quasi-overconsolidated effective stress range. The present numerical analyses are found to describe the large and long-term settlement together with the slow dissipation of excess pore water pressure in the Pleistocene clay and sand gravel layers that actually has taken place in the field. A detailed comparison of the distribution of excess pore water pressure and the differential compression for the individual Pleistocene clay layers shows that the calculated performance can well describe the actual behavior of the Pleistocene deposits due to the construction of the 1st phase island of Kansai International Airport.