An empirical relation for estimating mode I fracture toughness of rock

Rock failure results from the propagation of one or more cracks and thus can be considered as a fracture mechanics problem. It follows that the fracture toughness of rock is important in theoretical studies and engineering applications related to rock failure. Cracks can initiate and propagate in three ways in a material. These are mode I (tensile mode), mode II (shear mode) and mode III ( mixed mode). Some application areas of rock fracture mechanics can be listed as hydraulic fracturing, rock blasting, rock cutting, underground coal mine dust control, underground opening design, and comminution in mineral processing. In brittle materials, mode I is the essential failure mode since brittle materials are weak in tension. Three methods for measuring mode I rock fracture toughness of rock have been suggested by the ISRM. 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 tuff rock. This research aims to provide an empirical relation for determining fracture toughness of tuff rock. The results show that mode I fracture toughness of 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.

کلیدواژه ها:

tensile strength ، three point bending ، mode I fracture toughness