The characteristics of dynamic fracture toughness and energy release rate of rock under impact

Abstract

To investigate the characteristics of rock fracture toughness and dynamic energy release rate, impact experiments were conducted in large single cleavage semicircle compression (LSCSC) specimens. Fracture toughness and energy release rate of three sandstones were investigated and a drop-weight device was applied. Crack length and crack propagation velocity were corrected by fractal method, and fracture surface morphology was obtained by scanning electron microscope. The dynamic stress intensity factor (DSIF) was acquired from the finite element model established in the ABAQUS. The DSIF history was acquired, and the initiation and propagation toughness were determined according to the measuring result of fracture time. It shows that, for a material, propagation toughness is related to its Young’s modulus, and the higher the Young’s modulus or wave impedance is, the larger the propagation toughness is. For black sandstone, the energy release rate increases rapidly with crack length, whereas for green and red sandstones, it increases slightly under a same speed impact.