EXPERIMENTAL-STUDY OF FRACTURE SURFACE-ROUGHNESS ON ROCKS WITH CRACK VELOCITY

In this paper we address the question of the influence of crack veloci ty on the fractured surface roughness. We studied samples made of Bere a sandstone, chosen for their good macroscopic homogeneity and their g ranular microstructure. The samples were fractured in a double cantile ver geometry, which allowed for a controlled crack speed that was main tained constant for each sample using an imposed displacement quadrati c in time. The range of speed covered in the experiments was 5 x 10(-4 ) m s(-1) to 2 x 10(-1) m s(-1). Systematic profilometry measurements of the fractured surfaces revealed a self-affine geometry characterize d by a roughness exponent, which was found to be independent of the cr ack speed.