Deformational Characteristics of Rocks Containing a Single Discontinuity (TECHNICAL NOTE)

For the purpose of exploring deformation characteristics of jointed rock masses, influence of joint inclination and confining pressure on the mechanical behavior of discontinuous rock a series of compression tests were conducted under satisfactory testing conditions on three types of sandstone from various locations. Three groups of jointed specimens were used in this research, including specimens containing saw cut planar joint, shear-surface joint and split breakage joint. The specimens were tested triaxially up to 70 MPa confined pressure. A 5 MN servo-controlled stiff testing machine was employed and a monitoring system was set up using a microcomputer controlled logger. The deformation characteristics of jointed specimens with saw cut joints were different in low and high confinements, however, in split breakage joints sliding behavior was the same in low and high confinements. Mohr envelope for 60° inclination in split breakage joints was above that of 45° in both saw cut and split breakage joints, i. e. a higher coefficient of sliding friction or a higher shear strength across the joint for this orientation.