RELATION BETWEEN THE SHAKING AT THE EARTHQUAKE AND THE LEAKAGE OF WATER IN THE EMBANKMENT CONSTRUCTED BY THE COHESIVE SOIL OF FORMER RIVER COURSE

Abstract

At the Chuetsu earthquake, the leakage water was found in the embankment along the Uono-river in Niigata Prefecture. The embankment is immediately above the cohesive soil at the former river. After the earthquake, we investigated the ground and embankment condition by borings, trenchings, the density examination and the water permeability test. In the process of the survey, we found the slight leak of water from the crack which seems to be generated with the swelling of the embankment. We consider that the crack and/or the swelling of the embankment were caused by the two factors,i.e. the cohesive soil under the embankment and the earthquake­ induced vibration. The rainwater didn’t infiltrate the ground because of the cohesive soil under the embankment,and then the pore water pressure increased in the embankment. As the Chuetsu earthquake occurred at this condition, the excess pore water pressure deformed the embankment. We conclude that cohesive soil at the former river under the embankment is the important factor for the safety of the embankment at the earthquake.