Suggested methods for determining the strength of rock materials in triaxial compression: Revised version

Three different types of triaxial compression test are described. The tests are intended to measure strength of cylindrical rock specimens as a function of confining pressure. The three test types differ from each other in the manner by which the strength envelope is produced. With test type I (individual test), individual points on the failure (peak strength) envelope are obtained from several tests, while with test type II (multiple failure state test) and test type III (continuous failure state test) the envelope is produced with a single test employing a stepwise or continuous procedure. The information obtained from a single specimen increases thus from type I to type III; requirements on testing equipment are greater for test types II and III than for test type I. The suggested procedures do not contain provisions either for pore pressure measurements or for drainage of the specimen. If an effect of pore pressures is suspected, this should be tentatively investigated by running tests at different moisture contents; if this shows further evidence of pore pressure effects, appropriate modifications to the testing procedure will be required. The suggested methods described here supersede those published in an earlier document. (Author/TRRL)