Fracture analysis of rock specimens weakened by rounded-V and U-shaped notches under pure mode I loading

Abstract

In this paper, the mode I fracture resistance of rock specimens weakened by rounded V (RV) and U-shaped notches is investigated experimentally and theoretically. For this purpose, several experiments were conducted on the Brazilian disks with central RV and U-shaped notches under pure mode I loading. Then, the fracture resistances of tested specimens were justified by a modified form of the border stress criterion. The border stress criterion states that the onset of fracture takes place when the tangential stress at a critical distance from notch border attains to a critical value. In the conventional border stress criterion, only the first term of stress series expansion around the notch border is used. The critical distance in the rock materials is relatively large and the first term cannot provide accurate description for stress field at the critical distance. Thus, the more accurate stress field is obtained from finite element analysis. It is shown that the modified border stress criterion can predict the fracture resistance of notched specimens in good agreement with experimental results.