Liquefaction of sand under bi-directional cyclic loading

To simulate the continuous rotation of principal stress axes,a set of stress controlled bi-directional cyclic loading tests were conducted.Tests were performed with two cyclic stress components involving the horizontal shear stress(torsional shear stress) and the vertical shear stress(stress difference between vertical normal stress and horizontal normal stress) to provide an approximate presentation of wave or seismic loading conditions.The stress path shown in the orthogonal coordinates of stress difference and shear stress had an elliptical shape.The ratio of the shear amplitude between the longer axis and shorter axis and the area enclosed by elliptical rotational loading path were controlled in a planned way.Test results showed that the stress-strain behavior was significantly affected by the ratio of amplitude of the two shear stress components.But it was nearly independent on the area enclosed by elliptical rotational loading path.The deformation behaviors were classified as two different types based on the ratio value.