Effects of Strain Rate on Rock Joint Deformation

For the purpose of studying the effects of strain rate on deformational characteristics of rock specimens containing a single joint when subjected to gradually increasing compressive loading, a series of triaxial tests was conducted at constant strain rates of 2.08 x 10-6/s (slow rate), and 8.33 x 10-4/s (fast rate). Triaxial tests were performed under satisfactory end-specimen condition on two types of sandstone by a 5 MN servo-controlled stiff testing machine up to 30 MPa confining pressure. Increased strain rate decreased the reduction in volume or a slower strain rate resulted in a further closure of the joint. A faster strain rate led to a higher Poisson's ratio. Poisson's ratio decreased to a lower magnitude both at fast and slow rates due to an increase in confining pressure. Lateral strain increased as strain rate changed from fast to slow.