Settlement of Sands under Multidirectional Shaking

Tests on samples of dry sand subjected to shaking in one, two, and three dimensions show that the settlements caused by multidirectional shaking may be significantly greater than the settlements caused by shaking in one direction only. The settlements caused by combined horizontal motions are about equal to the sum of the settlements caused by the components if they act separately. Vertical motion superimposed on horizontal motion causes an increase in settlements. By using a simple correction factor based on these findings it is shown that the settlement computed from the results of cyclic simple shear tests and a one-dimensional response analysis agrees well with the observed settlement of a clayey sand fill in the San Fernando earthquake.