Experimental and numerical investigation on mechanical and fracture characteristics of jointed rock with varying roughness

Commonly existing joints in the surrounding rock of deep underground excavation significantly impact the stability and support of surrounding rock. In this study, the roughness of rock fracture surfaces at different unloading points was determined, and then jointed rock masses with varying joint roughness coefficients were prepared by 3D printing. The uniaxial compression tests and the discrete element particle flow code in 2 demension (PFC2D) numerical simulations were used to evaluate the strength characteristics and crack propagation with varying joint roughness. The results show that the peak strength, peak strain, elastic modulus and secant modulus increased with the joint roughness coefficient under uniaxial compression. Peak strength and elastic modulus were more sensitive to joint roughness. With the increased joint roughness coefficient, the failure mode of the rock sample transformed from shear failure to tensile-shear mixed failure and splitting failure. In addition, the strain with tensile and shear cracks increased, and the number of tensile cracks increased with the increasing joint roughness coefficients, whereas the shear cracks decreased. The initiation and propagation of microcracks are the fundamental reasons for the ultimate failure of jointed rock masses.