Abstract: With central cracked circular disk-split Hopkinson pressure bar (CCCD-SHPB) test system, the pure type I loading tests on the marble center cracked specimens are taken under different loading rates. Relationship between loading rate and dynamic rock fracture toughness of materials is determined. The disc specimen in test has a nonideal crack with center incision. Combining with the actual processing of specimens, the paper presents the prefabricated crack with the notch tip shape of small arc and introduces the machining method for specimens. The feasibility of the nonideal crack test specimen is demonstrated with finite element analysis. The results show that it is feasible to use the nonideal crack disc specimens with circular arc crack tip and the crack width of 1 mm to replace the ideal crack disc specimens; the error does not exceed 2.13%. Under the condition of pure type I loading, the fracture toughness of nonideal crack specimen shows obvious correlation with loading rate, and it increases with the loading rate increasing.

Key words: dynamic fracture, nonideal crack, pure type I loading