Abstract: Although the Shanghai soil unified model can describe the influence of soil structure and over consolidation, it cannot simulate the highly nonlinear modulus in small strain range. In this paper, combined with the classical theory of small strain stiffness, a small strain constitutive model based on Shanghai soil unified model is developed. The small strain constitutive model can describe the change rule of soil stiffness in the small strain range. The capability of the model is checked by the triaxial compression test results on Shanghai shallow soil. The results show that small strain constitutive model can describe that soil stiffness in the small strain range has initial high modulus and the non-linear attenuation characteristics, and the influence of structure and over consolidation on soil can also be reproduce well by the model.

Key words: soft soil, constitutive model, small strain, nonlinearity, structure, over consolidation