Using the local degradation approach to assess and overcome errors owing to damage in multistage triaxial testing of rock

摘要

Multistage (i.e. multiple confining pressure) triaxial testing on one pressure)triaxialtestingononerock specimen aims to produce a peak strength criterion for the material whilst avoiding the need to perform several single-stage tests on separate samples. Notwithstanding the economy this brings, there is the question whether the damage that is progressively induced as the specimen is loaded to a critical stress at each stage could result in the multistage test underestimating the strength of the material. To explore this, we use the local degradation approach (Fang & Harrison, 2002) to firstly repllocaldegradationapproach(Fang&Harrison,2002)tofirstlyreplicate single-stage and customary multistage triaxial testing, and then perform a hypothetical test in which the confining pressure is increased before damage occurs. This modelling confirms that the established multistage test does underestimate the strength of rock, and suggests how significant improvements may be made by developing and adopting a new testing procedure.