Publications

True triaxial testing of castlegate sandstone

Ingraham, M.D.; Issen, K.A.; Holcomb, David J.

Deformation bands in high porosity sandstone are an important geological feature for geologists and petroleum engineers; however, formation of these bands is not fully understood. The theoretical framework for deformation band formation in high porosity geomaterials is well established. It suggests that the intermediate principal stress influences the predicted deformation band type; however, these predictions have yet to be fully validated through experiments. Therefore, this study investigates the influence of the intermediate principal stress on failure and the formation of deformation bands in Castlegate sandstone. Mean stresses for these tests range from 30 to 150 MPa, covering brittle to ductile behavior. Deformation band orientations are measured with external observation as well as through acoustic emission locations. Results of experiments conducted at Lode angles of 30 and 14.5 degrees show trends that qualitatively agree with localization theory. The band angle (between the band normal and maximum compression) decreases with increasing mean stress. For tests at the same mean stress, band angle decreases with increasing Lode angle. Copyright 2010 ARMA, American Rock Mechanics Association.