This study is aimed to investigate the regularities of the shear strength

shear deformation and other mechanical properties of joint rock mass with different roughnesses under compression-shear stress. Marble specimens were prepared with the dentate height of 0

1 and 3 mm

respectively. Then direct shear tests were conducted on the marble specimens under different normal stresses.Experiment results show that curves of shear stress and displacement can be divided into two types: sliding failure type and peak shear type. The climbing-gnawing process of joints goes through four stages: the compaction stage

the climbing stage

the saw-tooth cutting stage and the completely crushing stage. The curves of shear strength with the normal stress of the dentate joint present more obviously three-segment line feature

and a trilinear shear strength criterion is established. The curves of shear stiffness with normal stress present a convex type

and a shear stiffness model is put forward. The dilatancy curves of dentate joint present firstly shear contraction and then shear dilation

and an empirical formula for evaluating shear dilation is proposed.