LIQUEFACTION-INDUCED LATERAL SPREADING OF MILDLY SLOPING GROUND

Dynamic centrifuge modeling was used to study the behavior of two mildly sloping ground models subjected to earthquake lending and liquefaction. The first model consisted of a uniform layer of saturated sand, and the second consisted of a layer of sand overlain by a relatively impermeable layer of nonplastic silt; both model slopes were constructed at an angle of 2.6 degrees. Time histories of acceleration. excess pore water pressure. and displacement are presented with photographs to illustrate the mechanisms of failure. In both tests approximately 0.8 m of prototype lateral displacement was measured at the surface. In the uniform sand model this lateral displacement was distributed throughout much of the layer: however, in the layered model displacement was concentrated along the interface between soil layers. The concentration of displacement is consistent with a reduction in the sliding resistance between the silt and the sand layers due to the redistribution of voids at the interface, This possibility of redistribution of voids indicates that care must be taken when using undrained strengths in the postliquefaction analysis of layered slopes.