Liquefaction Analysis of Reclamation Dike during Earthquake

中部、四国和九州地区有88个围垦堤坝，这些堤坝在第二次世界大战后完工。28个这样的堤坝和41个这样的地基是沙质土壤。利用建设部研究院建立的地震危险性衰减方程，对所有施工场地进行了地震危险性分析。根据这一分析，计算出了100年地震动值，其中3个区(宫崎市、三池县、德岛县)的地震动值超过100加仑，5个区(竹原、小岛、与奈米、国务、西国崎市)的震动值不超过100加仑但不低于80加仑，其他地区的震动值不超过80加仑。首先将该分析应用于具有不同氮值、地下水位、颗粒大小和比重的地面模型，然后将其应用于由砂土组成的每一个堤坝，并计算出安全系数。当土壤和地面条件变差时，很少有小于1.0的。但是，这些堤顶发生的深度超过6.0m，而且在实际问题中，这些堤防和地基必须考虑更多的细土，根据这些百年地震运动的液化分析结果，这些堤防将是安全的。最后，在这四十年中，没有一处堤坝被地震破坏。

There are eighty-eight reclamation dikes in the Chugoku,Shikoku and Kyushu region which have been completed after the Second World War. Twenty-eight of these dikes and forty-one of these foundation grounds consist of sandy soil. Seismic risk analysis were carried out for all construction sites by making use of the attenuation equations which were established by Research Institute,Ministry of Construction. From this analysis, the 100-year earthquake motion was calculated and three district(Miyazaki,Miike,Tokushima) had the value more than 100 gal, five districts (Takehara,Kojima,Yonago,Kokubu,Nishikunisaki) had the value no more than 100 gal but no less than 80 gal and the others had the value no more than 80 gal.Liquefaction analysis by Research Institute,Ministry of Construction's method were carried out by using the 100-year earthquake motion,stamdard penetration value(N-value), blueprins, soil explorations and groundwater level. First, this cnalysis was applied to ground models which have different N-vaiues, groundwater levels, grain sizes and specific gravities, then, to each dikes which consist of sandy soil and safty factors were calucated. When the condition of soil and ground become worse,few of them were less than 1.0. But, these happening depths from dike crests were deeper than 6.0m and,moreover,these dikes and foundation ground must consit of more fine soil in practical ploblems,accordingly from these results of liquefaction analysis for the 100-year earthquake motion, it was concluded that these dikes will be in safety. Finally,there was no dikes which was damaged by earthquake during these forty years.