The concept of “continuous failure state” triaxial tests

Summary

In a “continuous failure state” triaxial test the specimen is maintained in the state of failure while subjected to steady changes of its state of stress. First of all, the specimen is brought to a state of failure in the conventional manner at a chosen constant confining pressure. Then under monotonically increasing axial compression the confining pressure is continuously adjusted so that a straight line is produced in the stress-strain plane. Its slope is equal to that of the initially observed slope. It is shown that the stress path which the specimen is made to follow corresponds closely to ist failure envelope. Thus, it is possible, in principle, to determine the failure envelope of a rock with the aid of a single test specimen. Over 120 tests on four different rock types have been carried out, which have further established the empirical basis for this novel test concept.