Strength deterioration mechanism and model of interface between frozen soil-rock mixtures and structures under ice water occurrence and evolution

The ice-water transitions in the pores of the interface layer between frozen soil-rock mixtures can easily induce strength degradation under temperature rise. However, there is a gap in the current researches on the mechanism and quantitative characterization of interface strength degradation. The degradation of interfacial strength under ice-water evolution in the melting process is therefore studied by the testing samples with rock contents of 0%, 15%, 30% and 45% using the nuclear magnetic resonance and direct shear tests. The strength degradation model considering the change rates of membrane water and capillary water is proposed for the first time combining with the Mohr-Coulomb criterion. The results indicate that the unfrozen capillary water increases with rock content due to the change of pore structures at the interface; the degradation degree of interfacial strength under temperature rise decreases with the increasing rock content. The attenuation of interfacial cohesion is greater than that of internal friction angle after melting. The relations between cohesion and internal friction angle with unfrozen water content are nonlinear and staged linear, respectively, because the interfacial cohesion and internal friction angle deteriorate differently with changing film water and capillary water. With the increasing rock content, the deterioration coefficients of film water and capillary water exhibit the trend of "one decreases and the other increases", and the deterioration coefficients of sliding and interlocking friction strengths show downward and upward trends respectively for both the particles and the particle-structure interface.