埋立地盤の形成史と液状化現象について  [in Japanese] Geohistory of Reclaimed Land and Soil Liquefaction  [in Japanese]

As is evident from many reports of past earthquake disaster, liquefaction during earthquake occurs generally in loose sandy deposits. Especially, disastars caused by liquefaction are localized on alluvial sandy deposits, reclaimed old-riverbed, artificial fill ground and so on. The large-scaled reclaimed-land, created on the shallower sea bed in a bay was hurriedly constructed in the age of high level of Japanese economic growth after War. Therefore, the reclaimed soil has not yet settled sufficiently, and are in dangerous condition to disastarduetoseismicliquefaction. However, fortunately the land, reclaimed close together in the coast of Tokyo Bay, Ise Bay, Osaka Bay and the Inland Sea of Japan, has not yet undergone a destructive earthquake since reclaiming. In this paper, the ground of reclaimed land, which consists of sandy soils, that is, the commonest reclamation type, is discussed from the viewpoint of seismic liquefaction. As a result of discussion can be summarized as follows :1) Some of liquefaction factors must be researched by sedimentology and stratigraphy in the field of geology. 2) Each of many geotechnical properties of reclaimed land, i.e. "formation of soft ground", "lower density″and "higher groundwater-table", and so on, is closely related to factors of liquefaction, combined with other subjects of construction engineering. 3) Judging various factors of seismic liquefaction from geological diagenesis, reclaimed land has a weak point for liquefaction because of its youth.