Effects of Strong Ground Motion Duration on Liquefaction Behavior of River Levee

In the Chubu region,central Japan,two kinds of earthquakes are likely to occur with different duration characteristics:① the Tonankai-Tokai coupled earthquake,with duration longer than 100 s at a maximum acceleration of about 2.4 m·s-2;② an inland earthquakes due to active faults,with duration shorter than 20 s at a maximum acceleration of about 6.0 m·s-2.Saturated loose sand deposits are widely distributed over the low alluvial plain in this region which,therefore,have a high liquefaction potential.Based on the Biot theory for simulating coupled hydro-dynamic behavior in saturated porous media,this study presents a numerical assessment of the seismic behavior of a river levee founded on liquefiable foundation soils under earthquake loading.Analysis is carried out by using an effective stress-based,fully coupled,finite element method,in which the behavior of the liquefiable sand is described by a cyclic elastoplastic constitutive model.The liquefaction responses of the river levee are compared between two different earthquakes.Numerical results show that the strong motion duration has a significant effect on the liquefaction behavior of the levee including excess pore water pressures,accelerations,and deformations.The longer ground motion may lead to much larger settlement of the river levee.