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The Effect of Fluids and Cyclic Loading on the Elastic Constants of Rocks
Semiannual rept. 18 Dec 1970-18 Jun 1971
BATTELLE MEMORIAL INST COLUMBUS OH COLUMBUS LABS
Pagination or Media Count:
Simultaneous measurements of acoustic velocity and linear strain have been made on samples of Salem limestone and Berea sandstone. Cyclic loading conditions of 0-1-0-5-0-8-0 Kb were made on these samples. The results show that thin cracks have a large effect on acoustically measured properties and little effect on linear strain. Both rock samples are quite porous and exhibit the crushing mode of failure at 1.5 Kb for the limestone, 5 Kb for the sandstone. This crushing greatly decreases the static modulus but changes the acoustic modulus only slightly. A peculiar knee develops in the velocity curve near the pressure of the crush-up and appears to be an indicator of it. The results suggest that volume measurements of elastic constants are to be preferred to acoustic measurements for evaluating excavation of rock.
APPROVED FOR PUBLIC RELEASE