Relaxation and the Behavior of Failed Rock.
Internat J Rock Mechanics & Min Sci 1972 Nov; 9(6):699-712
A servocontrolled hydraulic testing machine was used to conduct uniaxial compression tests which demonstrate the time-dependent behavior of a brittle porous rock such as tuff. The applied strain rate ranged from 10-2 to 10-7/sec. The strength increased as applied strain rate was increased, and strength variation was confined to the range between elastic limit and ultimate stress. Load-deformation behavior for all test specimens was essentially the same for the load range below elastic limit regardless of applied strain rate. Stress relaxation curves were obtained by holding applied deformation constant as soon as a macrocrack initiation was observed in the specimen. From the behavior of stress relaxation, a theory of time-dependent rock strength was presented.
Internat. J. Rock Mechanics & Min. Sci. V. 9, No. 6, November 1972, PP. 699-712