At the Hyogo-ken Nanbu Earthquake on January 17, 1995, on the artificially reclaimed island, a very large bulk of mud was ejected and the ground subsidence of 30-50cm or more was observed. In this paper, to clarify the effect of earthquake-induced settlement of clay layer on the ground subsidence, firstly the settlement-time relations for the separate layers in the ground which measurement was started from one year before the earthquake are shown and the effects of the earthquake on the settlement of clay layer are investigated. Secondly, the earthquake-induced settlement of the alluvial clay layer in the Port Island was predicted. Thirdly, multi-directional simple shear tests were carried out and the direction of cyclic shear on the settlement of clay layer was observed. In conclusion, following results were obtained. 1) The earthquake-induced settlement of alluvial clay layer of 16m thick reaches over 4cm. 2) When a clay is subjected to the multi-directional shear strain, the larger the phase difference in the sinusoidal shear strains applied from two directions, the smaller the effective stress and therefore the settlement in the reconsolidation stage is affected by the phase difference.
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