Research on reliability design method of agricultural infrastructures for earthquakes.

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This research is divided into following two parts.1. Reliability design of embankment constructed by sandy material for prevention of liquefaction.In this research, the calculation method for the probability of liquefaction in a sandy ground and the reliability design method for liquefaciton are discussed.Usually, the liquefaction resistance is simply determined from the effective vertical stree sigma_v', theSPT blow count N,the median grain size D_<50> and the fines content F_c with the empirical equation. The last three parameters generally have large spatial variability and the statistical models of these parameters are required for the liquefaction analysis. These statistical models were determined by minimizing AIC here.The dynamic load by the earthquake was determined based on 1) the deterministic design maximum acceleration, or 2) the statistical model of the annual maximum acceleration. The statistical model was decided from the historical earthquake data records. The maximum acceleration is probabilistic parameter in the latter case.The Monte Carlo method was applied for all probabilitic parameters and probability of liquefaction in a sandy ground was evaluated. Finally, the optimum ground improvement method and the optimum probabiity of liquefaction are discussed, particularly the sand compaction pile method (SCP) was picked up as a ground improvement method.2. Investigation for disaster of farm ponds caused by Hyogoken-Nanbu Earthquake in Awaji Island.We research group investigated the disaster of farm ponds. Based on the investigation results, the multiple regression analysis was conducted. As a result, the relationship of the failure rate of the ponds with the distance from the earthquake source, longitudinal directions of the embankments, construction period, characteristics of the material, and geology in construction sites, was clarified. Particularly, the quantification theory II was used in the analysis here.