Cyclic strength of saturated sand under bi-directional cyclic loading

Abstract

Subject to cyclic loading due to ocean waves and earthquakes, both the shear stress and axial cyclic stress need to be accounted for in the analyses of stress state and cyclic strength. For laboratory soil test, the loading condition can be simulated by performing hollow cylindrical apparatus test, and also the effects of ratios and phase angles between dynamic axial and horizontal shear stress can be considered. In the present study, the maximum shear stress amplitude of soil element is defined as a measure of cyclic strength. Based on the theoretical analysis and experimental tests, this study investigates the influence from the ratios and phase angles on the number of load cycles leading to liquefaction failures. In addition, the characteristics of pore water pressure development are also studied. The theoretical and experimental results indicate that the ratios and phases between the axial dynamic load and torsional dynamic load significantly affect the dynamic strength of sands. Moreover, ratios and phases between the axial dynamic load and torsional dynamic load influence the accumulation speed of pore water pressure significantly. Nevertheless, when the pore water pressure is normalized, the sensitivity of their influences on the pore water pressure development cannot be identified.