Experimental investigation on shear performance degradation of ice-rich debris under thawing

Abstract

The mechanical behaviors of ice-rich debris (IRD) under a certain freezing temperature have been widely studied. Comparatively, data on the mechanical properties of IRD under thawing conditions is still limited at present. However, the degradation of the IRD mechanical performance caused by thawing is generally considered one of the important causes of catastrophic rock-ice avalanches all around the world. In this paper, a new variable, the thawing ratio (Δv), was introduced to quantitatively evaluate the amount of ice melting during thawing treatment. Then, systematic direct shear tests on IRD specimens were carried out considering the effects of Δv (2, 4, 6, 8, and 10%), initial ice contents (40, 65, and 90%), and normal stresses (150, 350, 550 kPa). Experimental results, including the thawing law, shear stress-strain curve, shear stiffness, and shear strength of IRDs were presented and analyzed. The results indicate that the IRD with lower initial ice contents is more sensitive to temperature rise. The strength parameters, including the peak shear stress, cohesion, and inner friction angle are linearly decreased with increasing Δv. It was found that their values can be reduced by approximately half when Δv reaches 10%. In addition, results also indicate that the shear strength of IRDs is more vulnerable to thawing with the decrease in initial ice content. The analysis of the factors affecting the shear strength of IRDs suggests that the reduction in the contribution of cementitious force and friction on the ice-debris contacts can be responsible for the dramatic strength degeneration of thawing IRDs.