Abstract: Geometry and mechanical characteristics of joints are key factors affecting the shear behaviors and fracture patterns of jointed rock mass. Using 3D printing technique, experimental jointed rock specimens containing rough joints with varied joint roughness coefficient (JRC), different types of geometrical joints, and fractrues network were established respectively. Then direct shear tests were conducted on the jointed rock models to study the shear strength and failure patterns. The results show that the values of shear strength of jointed rock models fluctuate greatly with varied JRC curves. The peak shear displacement decreases with increasing amplitude of fluctuation. The lowest and highest values of shear strength are found in plane and rectangular joints, respectively. Moreover, the value of shear strength of sinusoidal type is found similar to that of triangular type. The shear strength of the 3D-printed fractured rock specimens are apparently lower than that of the intact rock specimens. When considering joint roughness, the peak shear stresses of rough discrete fractures network (RDFN) models are higher than those of the discrete fractures network (DFN) models. The solid rock specimens exhibit typical brittle shear failure. The fracture patterns of DFN model and RDFN model are relatively complex and the main shear fractures are found along the shear direction. Meanwhile, certain intersection points between joints and certain surfaces have significant influence over the shear failures. The present work provides references for the application of 3D printing technique in studying the shear behaviors of fractured rock masses.

Key words: jointed rock mass, 3D printing, direct shear test, fractures patterns, experimental study