The use of the Brazilian test for the rapid estimation of mode I fracture toughness of Karaj tuff rock

The mode I or opening mode fracture toughness (KIc) is an important parameter for characterizing the fracture behavior of rock and is a parameter used in many applications such as mining and tunnelling. Method for the determination of mode I fracture toughness are numerous. Despite the standardisation of the fracture toughness test, the use of the test for rock characterisation and indexing purposes is not widespread. Since the determination of mode I fracture toughness by testing is time-consuming and costly, therefore, a simple method for determining fracture toughness of rock would be helpful. In this research, Brazilian test and three point bending test are performed on some specimens of Karaj tuff rock collected from Chalus area located in Alborz province. This research aims to provide an empirical relation for determining fracture toughness of Karaj tuff rock.
The results show that mode I fracture toughness of Karaj tuff rock can be estimated with a high level of accuracy by using the proposed relations because the correlation coefficient of the relation is 0.89.