Abstract: In this study, cyclic shear test were conducted on the crusted structural surface replicated with similar material under normal stress. The shear strength, deformation and morphology evolution characteristics of joints under cyclic shearing were studied without filling, with 3 mm yellow mud infilling, 3 mm plaster infilling and 3 mm detritus infilling, respectively. It was found that the failure mode of joints developed under cyclic shearing. Joints without filling changed from shear failure to wear-out failure, while joints with yellow mud mainly showed slip failure. Joints with plaster changed from shear failure to slip failure and then to wear-out failure, while joints with detritus changed from shear failure to wear-out failure. With the increase of cyclic shear times, the peak shear stress of joints without filling and with yellow mud infilling decreased in deceleration rate, while those with plaster and detritus infilling decreased firstly and then increased in deceleration rate. These results indicate that filling material can weaken the shear strength of joints under cyclic shearing, especially for those with yellow mud filling. Under different filling conditions, the average dilation angles all reduce in deceleration rate under cyclic shearing. The shearing shrinkage is more obvious in filled joints, in which the shearing shrinkage is the smallest with yellow mud infilling and the largest with plaster infilling. The wear degree of filled joints after cyclic shear is lighter than that of unfilled joints, while the wear degree is the smallest when filling yellow mud, the wear degree is relatively biggest when filling plaster.

Key words: joints, cyclic shearing, filling material, failure mode, shear behavior