SHAKING TABLE TESTS OF EMBANKMENTS RESTING ON LIQUEFIABLE SANDY GROUND

A series of shaking table tests of earthen embankment founded on saturated sand ground was perfomed. Six reduced scale models were subjected to different input accelerations. The results of this experimental study show the followings : (1) when the model is subjected to shaking, the ground beneath the embankment does not liquefy, whereas the ground in the free ground easily liquefies, (2) the soil that has liquefied exhibits sharp response acceleration, (3) embankment slumps and cracks as a result of softening of the underlying ground associated with porewater pressure generation. The extent of such damage is more extensive when subjected to an earthquake input motion of vibrational type with longer duration and lower frequency. Further, the experimental response of the models and especially the spiky accelerations are explained by using an inverse technique to reconstruct the local response of soil from measured data. This inverse technique shows that the spiky accelerations were caused by cyclic mobility effect and that the liquefaction largely depends on the spatial variation in stress condition.