A SITE SURVEY OF DAMAGED RIVER LEVEES FOCUSED ON THE HETEROGENEITY OF SOIL LAYERS

Abstract

Site survey to clarify the cause of river levee failures were conducted at the sites where water leakage or sand boil had been taken place. The dense sampling of foundation soil at the back-toes of the river levees were carried out to make the difference of soil layers clear. The difference is that a high permeable gravel soil layer at the shallow depth in the Naka-river or a low permeable silty soil layer at the surface in Yoshida-river, which considered as the main cause of the water leakage or the sand boils. The improved method of site survey for a river levee is proposed combined with the topographical survey.