Abstract: In order to study the influence of fissures on the macroscopic fracture morphology of rocks,the Brazilian splitting tests of sandstone under three fissure types,single fissure,collinear double fissures and parallel double fissures,were carried out. The fracture morphology of sandstone samples under the three fissure types with different inclination angles was analyzed and classified,and the changes of tensile strength of the three fissure types under different fissure inclination angles were analyzed. Test results showed that the existence of fissures weakened the tensile strength of the rock,and the number of fissures, the inclination angle of the fissures and the geometric arrangement between the fissures affected the fracture morphology and tensile strength of the specimen. There were five types of fracture forms in single-fissure sandstone samples,four fracture forms in collinear double fissures,and three types of fracture forms in parallel double fissures,and the heterogeneity of the rock led to different fracture morphologies of samples under the same fissure inclination. The tensile strength of single fissure and collinear double fissures sandstone is the largest at 0° fissure inclination,with the increase of fissure inclination,the tensile strength of single fissure sandstone first decreases and then rises and then decreases,the tensile strength of collinear double fissures sandstone shows a downward trend,while the tensile strength of parallel double fissures sandstone is the greatest at 45° fissure inclination.

Key words: Brazilian splitting test,prefabricated fissures,fracture morphology,tensile strength