An updated binary medium constitutive model of frozen rubber reinforced expansive soil under confining pressure

Abstract

Rubber reinforcement can effectively improve the swelling characteristics and shear strength of expansive soil. However, rubber-reinforced expansive soil has a more complex structure and mechanical properties, especially in a frozen state, and existing models have not been applied to fully characterize its shear deformation characteristics. In this paper, the updated binary medium model of rubber-reinforced expansive soil is proposed based on the theory of the binary medium model and the homogenization theory of heterogeneous material. The deformation and damage mechanism of frozen rubber-reinforced expansive soil is discussed by using the concept of the binary medium model at the microscopic level, and the updated binary medium model is verified by the triaxial tests of frozen rubber-reinforced expansive soil under confining pressure conditions. The main results obtained: (1) Based on the theoretical framework of rock and soil failure mechanics and the concept of updated binary medium model, saturated frozen rubber-reinforced expansive soil can be abstracted into cementing elements (ice-rubber-soil skeleton) with strong cementation properties, elastic friction elements (rubber) and elastic–plastic friction elements (ice-soil broken skeleton) without cementation properties. (2) The stress–strain curve of frozen rubber-reinforced expansive soil can be divided into three stages: linear elastic stage (ε < 1.33%), elastic–plastic stage (1.33 % < ε < 4.17%) and strain softening stage (ε > 4.17%), which can be interpreted by the conversion between the cementing elements and the friction elements in the updated binary medium model.(3) The measured values of stress and strain of rubber-reinforced expansive soil match the calculated values of the model (R2 = 0.92), and the peak point strain deviation and stress deviation of the model and test values are 9% and 3%, respectively, indicating that the updated binary medium model can better simulate the stress–strain relationship of rubber-reinforced expansive soil. (4) The fitting degrees of the unary medium model and the binary medium model are 0.74 and 0.36, respectively. Compared with the updated binary medium model, there are fewer parameters in the equations, the binary medium model species lacks rubber as an elastic material, and the unary medium model lacks elastoplastic and elastic materials, so it is not suitable for simulating the stress-strain relationship of frozen rubber-reinforced expansive soil.