Publications Details
Core based stress measurements: A guide to their application. Topical report, July 1991--June 1993
This report is a summary and a guide to core-based stress measurements. It covers anelastic strain recovery, circumferential velocity anistropy, differential strain curve analysis, differential wave velocity analysis, petrographic examination of microcracks, overcoring of archieved core, measurements of the Kaiser effect, strength anisotropy tests, and analysis of coring-induced fractures. The report begins with a discussion of the stored energy within rocks, its release during coring, and the subsequent formation of relaxation microcracks. The interogation or monitoring of these microcracks form the basis for most of the core-based techniques (except for the coring induced fractures). Problems that can arise due to coring or fabric are also presented, Coring induced fractures are discussed in some detail, with the emphasis placed on petal (and petal-centerline) fractures and scribe-knife fractures. For each technique, a short description of the physics and the analysis procedures is given. In addition, several example applications have also been selected (where available) to illustrate pertinent effects. This report is intended to be a guide to the proper application and diagnosis of core-based stress measurement procedures.