Soil Characteristics of Damaged and Undamaged Embankment Dams for Irrigation in Northern Awaji Island due to the 1995 Hyogo-ken Nanbu Earthquake

Abstract

This study was performed to clarify the soil characteristics of 40 damaged and 45 undamaged small embankment dams for irrigation (tame-ike in Japanese) in Northern Awaji Island, due to the 1995 Hyogo-ken Nanbu earthquake. With reference to the results of multivariate statistical analyses, pairs of damaged and undamaged dams were selected so that the conditions such as distance to epicenter, embankment volume (=dam height)×(crest length)(m²) and distance to Nojima Fault might become almost the same. Soil properties of damaged dams such as D₅₀ (0.514mm), moisture content (9.4%) and the cone penetration resistance (223kPa) are smaller than those of undamaged dams by 45 point, 30 point and more 30 point, respectively. But both specific gravities are the same. The damage rate (DR) of sandy soil is almost twice of that of gravelly soil. DR decreases as the moisture content or the cone penetration resistance increases.