The hydrate-bearing muddy silty sand formations in the Shenhu area of the South China Sea display significant strain softening and volumetric dilation during the mid-to-late stages of loading, particularly under conditions of low initial porosity, low effective confining pressure, and high hydrate saturation. To accurately characterize these complex mechanical behaviors, a state-dependent elastoplastic constitutive model tailored to hydrate-bearing reservoirs has been developed. This model refines the yield surface equation of the Modified Cam-Clay (MCC) model by incorporating the effects of hydrate-induced cementation and the initial consolidation of the soil skeleton. By introducing dilatancy coefficients and plastic moduli as functions of hydrate saturation, effective porosity, and stress state, the model provides a precise representation of the flow direction and hardening behavior of the soil, forming a comprehensive elastoplastic model. With clearly defined parameters, the model achieves a high accuracy of 92.7%, meeting the precision requirements of engineering applications. This model offers a strong theoretical basis for numerical modeling and the analysis of hydrate-bearing formations.
Song et al. (Tue,) studied this question.