Triaxial Deformation Rate Analysis (DRA)

Reliable and low-cost in situ stress measurement is important for design and operation of underground excavations. Deformation rate analysis (DRA) is a rock memory stress determination method based on carrying out cyclic, non-destructive uniaxial compression tests on rock cores in the laboratory. The DRA method may not be applicable to rock cores with low uniaxial compressive strength as fractures or failure may be induced during loading. A triaxial DRA test was proposed with the intention of increasing rock strength by confining stresses in the course of DRA testing. However, triaxial DRA tests overestimate the pre-stress (the maximum previous stress), with the error increasing as the confining stress increases. To solve this problem, we develop a simple DRA model and propose linear triaxial deformation rate analysis (LDRA) based on performing triaxial DRA tests with different confining stresses and reconstruction of the pre-stress using linear regression. The LDRA method is demonstrated to work well on determining the maximum previous stresses memorized in rocks.