Liquefaction of Sand Due to Multidirectional Cyclic Shear

ABSTRACT

A rational method is presented for estimating the effect of multidirectional shaking on the basis of two parameters which can readily be determined from unidirectional cyclic shear tests on saturated sand under undrained conditions. The method is based on the assumptions that the generation of excess pore water pressure due to cyclic shear in one direction is independent of that in the transverse direction, and that the relationship between the shear stress amplitude and the number of cycles to liquefaction is linear in a log–log plot. The effect of multidirectional shaking estimated by the proposed method is in good agreement with that observed in the laboratory by other investigators. It is indicated that reduction of liquefaction resistance due to transverse shear becomes more pronounced when the excess pore water pressure starts building up earlier or the shear stress amplitude vs. number of cycles curve becomes steeper.