Development of Earthquake Resistant Evaluation Method for Decrepit Small Earth Dam using Non-Destructive Exploration

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The Japanese Government anticipates an occurrence of a Nankai earthquake in Shikoku Island in the near future. Takamatsu, the capital city of Kagawa Prefecture, has been serious damaged by Nankai Earthquakes at intervals from 90 to 150 years. Recent earthquakes have suggested that many irrigation pond embankments could be seriously damaged in the event of an earthquake. The seismic damage is closely related to the embankment condition. It is therefore very important to clarify the embankment conditions when an earthquake-resist design of a structure is considered.The objective of this study is to estimate the motion amplification of bank of irrigation ponds by surface wave exploration and microtremor measurement. In this study, four types of the irrigation ponds were classified. S-wave velocity of bank is small in the ponds situated in plain and large in the ponds situated in the foot of the mountain or mountain. However, with regard to S-wave velocity of alluvium, the difference in types of the ponds is small. The relation between S-wave velocity of bank and height of bank has positive correlation. Similarly, the relation between predominant period and height of bank has positive correlation. But, the relation between amplification and predominant period of bank has negative correlation. Motion amplification of bank is strongly affected by the vibration characteristics of the foundation and the bank.