Physical properties of flake-shaped sand soils are remarkably different from those of the common standard quartz sand soils composed of circular-shaped particles.The rising of pore-water pressure under cyclic loading will lead to stiffness degradation of fully-saturated sand soils.And liquefaction of the soil will be triggered when its pore-water pressure reaches to a threshold

breaking down the soil mass.Considering different values of static deviatoric stress

ratios of alternating stresses and the number of cycles

a series of tests were performed with the WFI cyclic tri-axial apparatus to study the dynamic stress-strain relationship of Nanjing flake-shaped sands.It has been observed that initial static deviatoric stress ratio

axial cyclic stress ratio and the number of cycles have remarkable effect on the stress-strain relationship of Nanjing flake-shaped sands.An empirical equation on degradation of secant shear modulus has been formulated on the properties of secant shear modulus in each unload-reload loop of dynamic stress-strain relationship. The static deviatoric stress ratio has remarkable influence on the degradation of shear modulus. With the numbers of cycles increasing

the stress-strain hysteretic loops separate from each other gradually and the stress-strain hysteretic loops are leaning gradually towards the coordinate axis of strain.In addition

the empirical equation of shear modulus degradation has been based to describe the dynamic stressstrain relationship of Nanjing flake-shaped sands with the modified Masing’s criteria.