Effect of roughness on the shear behavior of rock joints subjected to impact loading

Abstract

The shear behavior is regarded as the dominant property of rock joints and is dramatically affected by the joint surface roughness. To date, the effect of surface roughness on the shear behavior of rock joints under static or cyclic loading conditions has been extensively studied, but such effect under impact loading conditions keeps unclear. To address this issue, a series of impact shear tests was performed using a novel-designed dynamic experimental system combined with the digital image correlation (DIC) technique. The dynamic shear strength, deformability and failure mode of the jointed specimens with various joint roughness coefficients (JRC) are comprehensively analyzed. Results show that the shear strength and shear displacement characteristics of the rock joint under the impact loading keep consistent with those under static loading conditions. However, the temporal variations of shear stress, slip displacement and normal displacement under the impact loading conditions show obviously different behaviors. An elastic rebound of the slip displacement occurs during the impact shearing and its value increases with increasing joint roughness. Two identifiable stages (i.e. compression and dilation) are observed in the normal displacement curves for the rougher rock joints, whereas the joints with small roughness only manifest normal compression displacement. Besides, as the roughness increases, the maximum compression tends to decrease, while the maximum dilation gradually increases. Moreover, the microstructural analysis based on scanning electron microscope (SEM) suggests that the roughness significantly affects the characteristics of the shear fractured zone enclosing the joint surface.