Experimental investigation and strength model of rough ice-filled joints under tensile and shear loading

Warming softening of ice-filled joints has caused many rockfall disasters in cold regions. A series tensile and shear strength tests were conducted to investigate the thawing softening mechanism of ice-filled joints by considering the effect of the joint opening, temperature and roughness. The joint opening has little influence on the tensile strength of ice-filled joints, but the temperature is a remarkable influencing factor. When the temperature increases from -15 degrees C to -0.5 degrees C, the average tensile strength of ice-filled joint reduces from 0.64 MPa to 0.22 MPa, which displays a constant logarithmic decay function against the freezing temperature and it is similar to the change rule of pure ice. The shear strength of the ice-filled joint decreases with increasing the infill thickness, and tends to be the shear strength of pure ice beyond the critical infilling thickness. In addition, all the tensile failures are inside the joint ice, however, the shear failure is mainly caused by the debonding of ice-rock interface when the temperature increases to -0.5 degrees C. It implies that the tensile bonding strength of ice-rock interface also is larger than that of the solid ice itself even at a high freezing temperature. Based on the experimental results, a new shear strength model of the ice-filled joint is proposed for Barton's joint profiles by considering the effect of temperature and infill thickness. It has been validated that this model is accurate to predict the shear strength of ice-filled joint, which may be used to estimate the stability of freezing joint rock slope in cold regions.

Automated summary

Warming softening of ice-filled joints in cold regions has caused rockfall disasters. This study conducts a series of tests to investigate the thawing softening mechanism of ice-filled joints, considering the effects of joint opening, temperature, and roughness. The results show that temperature is a significant factor impacting the tensile strength of the joints, while joint opening has little influence. The shear strength decreases with increasing infill thickness, and when the temperature reaches -0.5 degrees C, shear failure is mainly caused by debonding of the ice-rock interface. A new shear strength model is proposed based on the experimental results, which accurately predicts the shear strength of ice-filled joints and can be used for stability estimation in freezing joint rock slopes in cold regions.