PROGRESSIVE FAILURE OF UNSATURATED FILL SLOPECAUSED BY CUMULATIVE DAMAGE UNDER SEEPAGE SURFACE

Abstract

Seepage surface positionof fill slope canfluctuate owing to rainfall and groundwater supply from behind theslope. Therefore,in this study, shaking-table tests of an unsaturated fill slope were conducted to examine the influence of the seepage surface position on the fill slope stability bycomparingwith previous results in the fully saturated condition. An acceleration amplification factor was used to evaluate the stability. Ifthe embankment wasin an unsaturated condition, a slip plane was formed along the seepage surface. With ongoing increase of input acceleration, the slip progressedto behind the slope. Comparison of the unsaturated and saturated results showed that although the failure mechanism in which the slip surface was formed by the reduction in rigidity was common, the input acceleration at failure and deformation mode were different. When the slip surface was formed and failure occurred, the input acceleration in the unsaturated fill slope wasmore massive, and the deformation at the same excitation stage was small. These results imply that the unsaturated fill slope has a higher earthquake resistance than the saturated fill slope. Moreover, it is shown that the progress of plastic deformation inside the embankment and the formation process of the slip plane can be estimated from the change in the acceleration amplification factor regardless of seepage surface position.