A new method for measuring the dynamic fracture toughness under blast loads using arc-edge rectangle with edge notches

Abstract Drilling and blasting method is a common method of rock fragmentation in engineering. Meanwhile, the dynamic behaviours of rocks under blasting loads are different from those under impact loads. In this paper, a large-size arc-edge rectangle with edge notches (LAREN) specimen was posed to investigate the dynamic fracture parameters of brittle rock materials under blasting load. Three types of radial pre-cracks with different lengths were used, combining with the crack propagation gauge velocity test system, and the crack initiation time and propagation time were obtained, so as to obtain the crack propagation speed which is to be modified by the fractal theory. Also, the specimen rationality was analyzed by AUTODYN code in depth. At last, the dynamic stress intensity factors were estimated by using nonlinear finite element software ABAQUS and experimental results. It is concluded that the LAREN specimens can effectively lower the influence of the reflected tensile stress wave (by 54.18%) on the dynamic crack initiation and propagation, and have good applicability in the measurement of dynamic fracture parameters under blasting. With the development of pre-crack length, the crack time becomes longer, the average propagation speed becomes smaller, and the fluctuation of speed becomes smaller and tends to be stable. The increase of the pre-crack length also leads to the gradual decrease in the test value of the crack initiation toughness, while the test value of the propagation toughness is not constant.