Post-peak rock strain localization during monotonic and cyclic loading

Abstract

Post-peak characteristics of different rocks, having unconfined compressive strengths of 7 to 100 MPa were investigated in a series of monotonic and cyclic uniaxial compression tests. Lateral-strain rate feedback in a closed-loop system were implemented to control the applied axial load. The overall failure behaviour of rocks during either monotonic or cyclic loading was found to be independent of loading method and was a combination of class I (energy absorbing) and class II (energy releasing) behaviour. Strain patterns of the rocks were examined by applying three-dimensional digital image correlation (3D DIC). Strain localization mainly took place after peak stress around the future failure zone, whereas the areas of sample which w ere outside of the localized zone mainly experienced inelastic unloading. This behaviour was found to be more significant if localization is investigated by lateral strain. = Le caracteristiques de stress apres de pointe des differentes roches, ayant des resistances a la compression uniaxiale de 7-100 MPa ont ete etudiees dans une serie d'essais de compression uniaxiale monotones et cycliques. Lateral-deformation de vitesse dans un systeme circuit ferme ont ete prises pour controler la force axiale appliquee. Le comportement d'echec global de roches cours du chargement monotone ou cyclique en soit a ete juge independante de la methode de chargement et etait une combinaison de classe I (absorption d'energie) et de la classe II (liberant de l'energie) comportement. Les modeles de deformation des roches furent examines par trois dimensions de correlation d'image numerique. La zone de deformation localisee a eu lieu surtout apres le stress de pointe et autour de la zone de localisee, d'autre part, les zones de la roche qui etaient en dehors de la zone localisee experimente principalement le dechargement inelastique. Ce comportement a ete juge significative si la localisation est etudiee par deformation laterale.