Liquefaction of sand under bi-directional cyclic loading

A set of stress controlled bi-directional cyclic loading tests under isotropic consolidated condition was conducted for simulating the cyclic stress induced by wave loading.The stress path followed during the test in terms of σ d /2 and τ was controlled in shape of ellipse.The area bounded by the elliptical stress path was kept unchanged while the amplitude of the axial and torsional shear stresses were varied to study the effect of two components on the strength and deformation behavior of saturated loose sand.It was shown that the resistance to liquefaction of saturated sand was considerably related with both the area of elliptical stress path and the ratio of the two stress components.For the same ratio of two stress components,the resistance to liquefaction of saturated sand decreased with the increasing area of the elliptical stress path.However,for the same area of elliptical stress path,the sand might exhibit the highest resistance to liquefaction at a critical ratio of axial and torsional shear stresses,0.6⁰.75.The resistance to liquefaction increased with the increasing ratio of σ d /2 and τ when the ratio was less than the critical value,and decreased with the increasing ratio of σ d /2 and τ when the ratio was larger than the critical value.Moreover,the pore water pressure developed gradually to the initial effective confining pressure with transient fluctuation and phase matching axial load.