The effects of phase shift (delta) between compression and shear waves, and consolidation stress ratio (K-c) on the liquefaction resistance of sand under simultaneous compression and shear wave loading is investigated using a hollow cylinder torsional shear apparatus. The differences caused by prior stress history (assessed using drained versus undrained preshear) highlight the importance of test protocols in undertaking research to explore the effects of complex dynamic loading paths. The liquefaction resistance of sand was highly dependent on the loading path. However, it was not affected much by variations in delta, if the horizontal shear stress ratio (tau(z theta)/sigma(mc)') and the ratio between shear stress increment and normal stress increment (Delta S/Delta N) were held constant. In tests with constant cyclic stress ratio (CSR), an increase in delta decreases the cyclic resistance because the increase in delta causes a reduction in the rate of deviatoric stress increment per degree of principal stress rotation. At a given CSR, for delta not equal 0 cases, a change in Delta S/Delta N does not affect the liquefaction resistance of sand because the magnitude and pattern of rotation is not affected much by Delta S/Delta N (for the ratios explored in this research). Increasing K-c or static shear stress ratio (alpha(st)) increased the cyclic resistance of the tested sand for Delta S/Delta N<1. The rate of increase in cyclic resistance with increasing alpha(st) decreases with the increase in Delta S/Delta N and was essentially unchanged for Delta S/Delta N=1. This observation, that the rate of increase in cyclic resistance with alpha(st) decreases with increasing Delta S/Delta N, is consistent with the observation in the literature that the cyclic triaxial loading yields higher static shear stress correction factor (K-alpha) than cyclic simple shear in loose sand. (c) 2024 American Society of Civil Engineers.
来源平台：JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING
