Abstract: To investigate the effect of loading rate on tensile strength of rock materials and morphologies of fracture joint surfaces, Brazilian disc tests were conducted on three rock samples (i.e., granite, basalt and limestone) under different loading rates. The tensile strength was determined and the effect of loading rate on tensile strength was presented in detail. Three-dimensional (3D) scanning technique was employed to establish the digital terrain of fracture joint surface, and the effect of loading rate on fracture morphology of fracture surface was studied qualitatively. The relationships between surface roughness and loading rate and tensile strength were further analyzed by calculating the roughness index of fracture joint surface of three kinds of rock. The results show that tensile strength increases with the increase of loading rate, and under the double logarithmic coordinate system, it shows a good linear correlation between the parameters. According to the morphology of the fracture joint surface of rock materials, and from the perspective of the roughness of combination of qualitative and quantitative evaluation, it is found that the loading rate and tensile strength have a significant influence on the roughness of the fracture joint surface. The higher the loading rate is, the greater the tensile strength is, and the roughness of the fracture joint surface is. This study provides some reference for a better understanding of the relationship between the morphology index and mechanical parameters of the joint surface.

Key words: Brazilian disc test, loading rate, tensile strength, morphology of joint surface