Centrifuge model tests on suffusion-induced deterioration and its consequences in seismic response of levees

Abstract

Shake table tests on a levee deteriorated by seepage-induced internal erosion are performed in a geotechnical centrifuge to investigate the effects of erosion-induced heterogeneity and mechanical characteristics change on the seismic response of the levee. Among the several forms of internal erosion, suffusion, in which the seepage-induced loss of soil integrity occurs with the migration and loss of finer particles, is the focus of this study, since it progresses and puts structures in danger, while going unnoticed. In the tests, the model levee made of gap-graded soil is firstly subjected to repeated seepage flow by changing the water level in the flood channel. After lowering the water level and making the levee dry, earthquake motions are applied to the model deteriorated by suffusion. The progression of suffusion in the levee is confirmed by comparing the results of tests having the same initial condition, but subjected to a different number of seepage cycles. The shake table tests reveal that the natural frequency of the levee and the equivalent shear wave velocity in the levee significantly decrease with suffusion, suggesting that a reduction in soil stiffness occurs due to suffusion. However, no significant difference can be confirmed in the earthquake-induced crest settlement depending on the seepage cycles, suggesting that no marked change in strength or cyclic-shearing-induced compression occurs with suffusion within the scope of this study.