To investigate the stress path dependent of rock joints, a comparative experimental study was conducted using cement mortar replicas of artificially split rock joints. In total, 32 replicas were casted and divided into four groups by joint roughness coefficient (JRC). The effects of morphologic characteristics, normal stress levels and stress paths on the shear strength of joints were investigated through tangential loading tests and normal unloading tests. The comparative analysis on the test

more »

... esults indicated that the shear resistance has a distinct unloading effect. The variation trend of shear/normal stress ratio against the normal stress and JRC of the two test conditions were identical. However, under low normal-stress condition, the stress ratio of the joints under normal unloading stress is the higher one; while under higher normal stress, the relationship becomes converse. Compared to that of the tangential loading condition, shear/normal stress ratio of the unloading stress path reduces rapidly as the increasing of normal stress, and the influence of the morphology is masked under lower normal stress. The comparative study revealed a previously unknown unloading effect on the mechanical behavior of rock joints and will aid the estimation of the rock joints' stability in a complex stress environment.