Effect of Rock Fracture Filling on Mode I and II Fracture Toughness

This paper focuses on some fracture toughness tests performed on the pre-cracked Brazilian specimens of rock-like materials. Also the effect of rock fracture filling on the fracture toughness was considered experimentally.  Fracture toughness is a key parameter for studying the crack propagation and fragmentation processes in rock structures. Fracture mechanics is an applicable tool to improve the mechanical performance of materials and components. It is a comparatively general phenomenon that rock fractures are naturally filled with gouging material, but the impact of fillings on rock fracture toughness has not yet been considered precisely. In the present study, an experimental investigation was made to evaluate the effect of rock fracture fillings on the crack propagation mechanism and fracture toughness of some rock like specimens. For this purpose, several molds are used for preparation of Brazilian disks with straight central crack. In the next stage, three different ratios of ingredients have been used for preparation of three model materials to fill the central pre-crack of the specimen. Diametrical compression load with a rate of 0.3 mm/min in different directions respect to the central crack orientation is applied to the Brazilian disk specimens and the failure loads corresponding to the each test are recorded. Result of laboratory tests indicates that fracture fillers strongly affect the value of rock fracture toughness while fracture filler has no influence on the failure mode of CSCBD specimens. Also the impact of filler cohesion on mode II fracture toughness is more than its impact on mode I fracture toughness.