地盤の液状化問題と地質学の課題

概要

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Knowledge of soil liquefaction raised over the past decade is reviewed and factors causing the liquefaction are classified into a three categories: (1) the primary cause, (2) the site conditions, and (3) the exciting cause (earthquake-induced stress). The primary cause is loose packing of sandy sediments, which can be described in terms of relative density, stress ratio causing liquefaction, and penetration resistance of the sandy sediments. The site conditions which lead to or magnify the liquefaction are closely related to topographical conditions including artificial modifications, the construction-ground response during earthquake, and dissipation conditions of the developed pore water pressure. The primary cause, "loose packing" of the sandy sediments with high liquefaction potential, appears to have anintimate relation with the sedmentary process of the sediments. Consequently detailed studies of the ground form sedimentological and geological aspects are indispensable for evaluating liquefaction sites. Importance of diagnosis of wet-interdune sand deposits or remoulded dunes and from the original eolian sediments is shown for example. An overall investigation of the site conditions from the geotechnical viewpoint is highly significant to check and foresee the liquefaction disaster.
日本地質学会の論文