Protection of river levees from earthquake induced lateral flow by cement mixing

Abstract

Loose sandy soil layers are prone to liquefaction under strong earthquake motions, causing damages to civil engineering structures. Where liquefiable soil surfaces are sloped, liquefaction-induced lateral flow tends to increase the extent of damage. Previous studies have shown that such damage can be adequately prevented by deep mixing with cement. However, reinforcing the entire depth of liquefiable ground is costly for river levees. The cost and construction period can be reduced by improving only shallower parts immediately beneath river embankments. In order to rationalize the design approach, the present study aims to evaluate the effect of shallower mixing with cement on the deformation characteristics of river embankments located on liquefiable ground taking into account the effect of sloping ground. A series of shaking table model experiments were carried out with a centrifugal acceleration of 50g. The experimental results revealed that cement mixing for shallower parts can mitigate the settlement of embankments regardless of the occurrence of lateral flow. Furthermore, the embankment body located above the cement-treated soil block was found to withstand strong earthquake motions and retains its shape safely. This would contribute to rapid repair of river embankments immediately after a strong earthquake.