Shear mechanical properties and frictional sliding responses of rough joint surfaces under dynamic normal displacement conditions

A comprehensive understanding of the dynamic frictional characteristics in rock joints under high normal load and strong confinement is essential for ensuring the safety of deep engineering construction and mitigating geological disasters. This study conducted shear experiments on rough rock joints under displacement-controlled dynamic normal loads, investigating the shear behaviors of joints across varying initial normal loads, normal loading frequencies, and normal loading amplitudes. Experimental results showed that the peak/valley shear force values increased with initial normal loads and normal loading frequencies but showed an initial increase followed by a decrease with normal loading amplitudes. Dynamic normal loading can either increase or decrease shear strength, while this study demonstrates that higher frequencies lead to enhanced friction. Increased initial normal loading and normal loading frequency result in a gradual decrease in joint roughness coefficient (JRC) values of joint surfaces after shearing. Positive correlations existed between frictional energy dissipation and peak shear forces, while post-shear joint surface roughness exhibited a negative correlation with peak shear forces through linear regression analysis. This study contributes to a better understanding of the sliding responses and shear mechanical characteristics of rock joints under dynamic disturbances.