Abstract: An experimental research of rock dynamic fracture parameter under the action of impact load with the rectangular granite specimen with pre-cracks of Type I has been conducted. The test material is loaded by self-developed adjustable speed drop hammer impact tester which can realize low & medium impact loading speed；the data is recorded by data collecting system set up by high-speed cameras, and the data of specimen surface speckles images in the dynamic fracture process of crack is analyzed by using digital speckle correlation method. The quantitative results of displacement field evolution, the dynamic fracture of crack tip opening displacement, the speed of the crack growth and stress intensity factor of the dynamic fracture have been obtained. The experimental results have shown that the crack tip stress intensity factor increases after drop hammer contacts with the rock specimen, and when the stress intensity factor reaches a certain value, the prefabricated crack initiation and subsequent stress intensity factor of crack initiation is greater than the initial crack stress intensity factor.

Key words: digital speckle correlation method, stress intensity factor, crack propagation speed, the rock fracture, impact load