Mechanical Properties of Rocks Related to Drilling Technology. Ninth Quarterly and Summary Progress Report, 30 June 1976-30 September 1976.

摘要

Room-temperature, compression tests at strain rates from 10 exp -2 to 10 s exp -1 are run on Charcoal Granodiorite to 0.45 GPa confining pressure and on Berea Sandstone and Indiana Limestone to 0.25 GPa confining pressure. For each rock at each confining pressure, the differential stress at failure is relatively constant up to a strain rate of 1 s exp -1 and apparently increases abruptly above this strain rate. Dynamic analysis of the testing apparatus indicates that the apparent sudden increase in strength is due to machine inertia and does not reflect a real increase in the strength of the rocks. The actual failure stresses of the three rocks are relatively independent of strain rate betweenn 10 exp -2 and 10 s exp -1 . In the same interval, the strains at which the rocks begin to fragment tends to be lower at higher strain rates.