Study of Earthquake Disaster Prevention of Waterfront

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The summary of the results of the present research is as follows ;(i) It was pointed out based on the state of the art on lifeline performance in reclaimed ground during past earthquakes that specific research subjects such as earthquake motion in the neighborhood of fault, dynamic response of soft ground, liquefaction-induced ground displacement and its effect on buried lifeline facilities should be proceeded to create earthquake-proof urban societies in waterfronts in Japan.(ii) Liquefaction can cause several kinds of damage to lifeline structures ; settlement and tilting of structures due to reduction of bearing capacity of ground, floating of buried structures due to the buoyancy of the liquefied soil, collapse of quay walls and retaining walls due to earth pressure increase, failure of earth structures like embankment, and damage to liquefaction-induced large ground displacement.(iii) The liquefaction-induced ground displacements were found during ten past earthquakes in Japan as … More well as in United States. The ground displacements were oriented from sand dunes and natural levees with a little higher elevation towards old streams of big rivers with a lower elevation. The maximum ground displacement reached over 12 m during the 1964 Niigata earthquake.(iv) The magnitude of the ground displacement has a close correlation with the thickness of the liquefied layer, but not with the gradient of the ground surface. The mechanism of the occurrence of the liquefaction-related large ground displacement has not been clarified. Therefore, more studies on case histories of ground displacement, numerical analyses, experimental studies are required.(v) The liquefaction-induced ground displacement caused severe damage to buried structures such as foundation piles and pipelines. It was conjectured from examination of damaged structures and experimental studies that a drag force of liquefied soil was applied to the buried structures.(vi) A method to prevent liquefaction-induced ground displacement, where flexible inground walls are constructed in liquefiable soil, was proposed and its effectiveness was verified by shaking table tests. Less