EVALUATION OF MECHANICAL BEHAVIOR OF A LARGE RIVER LEVEE DURING SEEPAGE AND DURING/AFTER EARTHQUAKE BASED ON SOIL-WATER-AIR COUPLED FINITE DEFORMATION ANALYSIS

Abstract

In this study, seepage/seismic behavior of a large river levee on alternately layered ground of sandy and clayey soil was evaluated by a soil-water-air coupled finite deformation analysis code. The main findings are as follows: 1) Focusing on the river level, the analysis during seepage and during/after an earthquake was performed. The higher the river level, the larger the deformation in a direction toward the landside. 2) If the water permeability of the sandy soil layer is as high as “gravel”, 8 hours after the river level rose, ground heaving which will lead to piping occurred near the landside toe. This is because the permeability of covering clayey soil layer is low and much water was supplied from the river to the sandy soil layer. 3) In the case of high permeability in the sandy soil layer as 2), during an earthquake, even when the river level is low, pore water is able to migrate in the sandy soil layer underlying clayey soil layer with low permeability. This results in liquefaction of the top of the sandy soil layer though the permeability is as high as gravel.