The application of more confining pressure (s3 2.5 MPa) limited the growth of tensile fractures parallel to the major principal stress direction (parallel to y-axis), thus resulting in a more shear-dominated fracturing process. Unlike the models at low confinement (s3 ¼0e1 MPa), in which one or two major macroscopic
fractures developed, the fractures in triaxial models with s3 2.5 MPa formed shear bands or faults (Figs. 10 and 11). As the confining pressure exceeded 5 MPa, for instance, in the case of s3 ¼12.5 MPa in Figs. 12 and 13, shear failures formed a network of small fractures that continued to deform plastically. As a result, no
noticeable plane of failure was formed and a more ductile postyield stress response was captured (see Section 5.2.2).