The temperature-dependent shear strength of ice-filled joints in rock mass considering the effect of joint roughness, opening and shear rates

Abstract

Global warming causes many rockfall activities in alpine mountains, especially when ice-filled joints in the rock mass become thawed. The warming and thawing of frozen soils and intact rocks have been widely studied in the past several decades; however, the variation of shear strengths of ice-filled joints is not fully understood. In this study, a series of compression-shear experiments were conducted to investigate the shear strength of ice-filled rock joints by considering the effects of joint roughness, temperature, opening, shear rates and normal stress. The joint roughness can improve the shear strength of ice-filled joints. However, the contribution of joint roughness is controlled by some noticeable bulges instead of the joint roughness coefficient (JRC) index. The peak shear strength of the ice-filled joint linearly increases with the increasing aggregation of rupture ice area before these noticeable bulges. As the joint opening increases, the effect of joint roughness decreases, and the shear strength of ice-filled joints tends to be equal to the shear strength of pure ice. In addition, the shear strength quickly reduces with increasing temperature from -15 to -0.5 °C. The shear failure mode changes from shear cracking of joint ice to the shear debonding of the ice-rock interface above -1 °C. Increasing shear rate decreases the shear strength of ice-filled joints because the joint ice displays the brittle failure phenomenon at a high shear rate. The peak shear strength of the ice-filled joint linearly increases with the increase in normal stress. Moreover, it is also proved that the Mohr-Coulomb criterion can be used to characterize the shear strength of ice-filled joints under different normal stresses. This research can provide a better understanding of the warming degradation mechanism of ice-filled joints by considering the abovementioned important influencing factors.