A systematic study was undertaken to assess the effects of the magnitude and nature of principal stress rotation on the cyclic resistance of sands. Test results over a range of α_σc and 〖∆α〗_σ indicate that that the weakest cyclic resistance at a given initial α_σc always correspond to 45° stress rotation, and for a given magnitude of stress rotation (fixed ∆α_σ) the liquefaction resistance generally depends on the magnitude of the torsional shear stress applied on the horizontal plane. A limited number of experiments were carried out to investigate the applicability of the Skempton & Henkel pore pressure formulations for generalized 3D initial stress states. Skempton’s pore pressure parameter formulations for isotropic material have been extended to cross anisotropic materials, and it was shown that the principles are applicable even for cross anisotropic materials under generalized initial loading conditions.