Experimental study on dynamic notch fracture toughness of V-notched rock specimens under impact loads

In this study, the dynamic notch fracture toughness of V-notched rock specimens was investi-gated. V-notched semicircular bend specimens made of a medium-grained granitic rock called Fangshan granite were subjected to tests using a split Hopkinson pressure bar (SHPB) system combined with an ultrahigh-speed camera. First, an empirical formula was derived using dimensional analysis to calculate the fracture parameters of sharp V-notches, and the dynamic notch fracture toughness was calculated using dynamic forces obtained from the SHPB tests and the empirical formula. Second, full-field displacement fields generated during the dynamic fracture process were measured using the digital image correlation (DIC) method, and the notch fracture toughness was extracted using the displacement fields at the V-notch tip. Third, the experimental results obtained using the empirical formula were compared with the DIC results and subsequently validated using a modified mean stress criterion. The proposed methods have significant applications in the fracture assessment of rock structures weakened by notches.