Physical modeling tests on the slope destabilization induced by internal erosion

摘要

In recent earthquakes which occurred in the mountain area, such as the 2007 Noto Hanto Earthquake, most of therndamages of houses, roads and railways were associated with the failure of fills built on catchment topography. Fillsrnbuilt on catchment topography such as valley and swamp are vulnerable to earthquakes. Internal erosion prior tornearthquake potentially makes earthquake-induced damage of geotechnical structure larger. In this paper, physical modelrntests on seepage-induced internal erosion in levee are presented. Target erosion mode is suffusion and effects of amountrnof fine fraction and boundary condition on soil erodibility are discussed. Extent of erosion-induced deterioration ofrnshearing resistance of levee against external load is also discussed through comparisons of bearing capacity on top ofrnthe slope before and after the seepage test. Suffusion in levee can be produced in the small scale model tests. After arncertain elapsed time, decrease of the fine fraction due to suffusion widens the flow channel and the internal erosion raternincreases. This result in increase of flow velocity and tractive force and suffusion is progressively broadened from therntoe to middle of the embankment as in the backward erosion. Deterioration of shearing resistance of levee is confirmedrnby the bearing capacity tests at top of the slope before and after suffusion.