where [[gamma].sub.a] is the shear strain amplitude of the "n" times of stress cycle, a' is the initial effective normal stress, whose value will be the octahedral shear strain amplitude [[gamma].sub.oct] and the initial octahedral
aoct in the two-dimensional and three-dimensional conditions respectively, u is the ultrastatic pore water pressure, and [C.sub.1], [C.sub.2], m, n, k are the soil-related parameters.