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 cor relate 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 devia tor versus confining pressure diagram. In this way, the successive steps oc curring in the damage process of this rock are well described. In particula r, the quality factor of S-waves distinguishes clearly the onset of the ini tially stable cracking, while the velocity of S-waves and strain measuremen ts are sensitive to dilatancy which appears later in the damage process of the limestone studied.