Successive cracking steps of a limestone highlighted by ultrasonic wave propagation

A number of laboratory tests (uniaxial, triaxial and hydrostatic) have been conducted on a dry porous limestone. A conceptual model is proposed to correlate deformation and damage fields (including acoustic emission activity) with the variation of ultrasonic velocities, quality factors and energies as measures of attenuation. This correlation is presented in a stress deviator versus confining pressure diagram. In this way, the successive steps occurring in the damage process of this rock are well described. In particular, the quality factor of S‐waves distinguishes clearly the onset of the initially stable cracking, while the velocity of S‐waves and strain measurements are sensitive to dilatancy which appears later in the damage process of the limestone studied.