Micro–Macro Strength Criterion and Elastoplastic Constitutive Model for Frozen Mixed Soils

Frozen mixed soils are widely distributed in the strata and slopes of permafrost regions. This paper aims to study the strength criterion and elastoplastic constitutive model for frozen mixed soils from micro to macro scales. Based on the knowledge of mathematical set theory and limit analysis theory, the support function of frozen soils matrix is derived. The concept of local equivalent strain is proposed to solve the problem of nonuniform deformation caused by rigid inclusions in frozen mixed soils. According to the nonlinear homogenization theory and the Mori–Tanaka method in micromechanics, the strength criterion of frozen mixed soils is established, which can consider coarse particle contents. By introducing the concepts of equivalent yield stress and equivalent plastic deformation, the elastoplastic constitutive model is proposed by the associated flow rule, which can also consider the influence of coarse particle contents. Finally, using the data in the literature, the proposed strength criterion and elastoplastic constitutive model for frozen mixed soil are verified, respectively. The effects of coarse particle contents on the mechanical properties of frozen mixed soils are discussed.