Dynamic Stress-Strain Relationship of Nanjing Flake-Shaped Sand under Cyclic Loading

Abstract eng:
Comparing with the common quartz sand soils composed of the circular-shaped particle, the flake-shaped sand soils have remarkable differences in physical mechanics properties. With the dynamic pore-water pressure rising, the stiffness degradation of saturated sand soils is caused under cyclic loading. And liquidation of saturated sand soils is triggered when the dynamic pore-water pressure accumulates to some level, so that soil structure is broken down. Considering different static deviator stress levels, axial cyclic stress ratio levels and the number of cycles, a series of dynamic stress-strain relationship tests of Nanjing flake-shaped sand were performed by using the WFI cyclic triaxial apparatus made in England. It is observed that initial static deviator stress levels, axial cyclic stress ratio levels and the number of cycles have marked effect on stress-strain relationship of Nanjing flake-shaped sand. By considering the properties of secant shear modulus in each unload-reload loop of dynamic stress-strain relationship, an empirical equation on degradation of secant shear modulus is established based on series of test results. The static deviator stress level has remarkable effect on the degradation of shear modulus. With the numbers of cycles increasing, the stress-strain hysterisis loops separate each other gradually and the stress-strain hysterisis loops are leaning gradually towards the coordinate axis of strain. In addition, based on the empirical equation of shear modulus degradation, the dynamic stress-strain relationship of Najing flake-shaped sand was described by using modified Masing’s rule.

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