Through model tests under direct shear condition

the shear deformation of rock containing coplanar close joints with the same continuity and different undulating angles are studied under different normal stresses. Direct shear tests show that before peak shear strength

the shear stress-displacement curve of intermittent joint has linear and nonlinear segments; the rock bridge produces some degree of weakening under normal and shear loads; and shows macroscopic shear stress softening when accumulated to some degree. The four stages of crack development and characteristics of shear stress-deformation curve are described in detail; and an empirical constitutive model is suggested which can fit the whole process of shear stress-shear deformation curve. Piecewise function is used to describe curve characteristic. Data analyses show that the model can fit the shear stress-shear deformation trends and has a high fitting accuracy which verifies the correctness of this new model; finally

its inadequacy is also given briefly.