Residual stress features in drill cores

Abstract

S U M M A R Y The features caused by residual stresses in carboniferous sandstone drill cores from 5300 m depth were investigated by various methods: strain redistribution after secondary overcoring, anisotropy of ultrasonic wave velocity and its pressure dependence, as well as fracture tests. This was complemented by microscopic inspection of thin sections. Comparison of the different methods applied revealed a remarkably good correlation between principal stress directions. All effects observed can be explained by one common feature of stress redistribution-the formation of microcracks. The crack-closing pressure derived from acoustic velocity measurements, as well as the tensile strength resulting from the Brazilian test, gave an estimate of the magnitude of residual stresses.

Constraining Internal States in Progressive Rock Failure of Carrara Marble by Measuring Residual Strains With Neutron Diffraction

“…In geological studies, most residual strain data of rocks is considered as strain memory and interpreted regarding the potential paleo‐stress field (Engelder & Sbar, 1977; Sekine & Hayashi, 2009; Zang & Berckhemer, 1989). A scenario of how the residual strains are locked‐in, the Carrara marble would either be by the external tectonic forcing or internally organized by material properties during the formation of the Apuan Alps.…”

“…The spatial variable introduction and relaxation of residual strains during the pretesting produced a spatial anisotropy within the initially spatially isotropic residual strain state in Carrara marble (Figures 3–6). It has been observed that spatial persistence of residual strains would be aligned with preferred orientations of fractures in rocks (Friedman & Logan, 1970; Weinberger et al, 2010; Zang & Berckhemer, 1989). If the residual strain is spatially inhomogeneous, it is expected that the local strain may lead to a change in direction of fracture propagation that is not necessarily aligned with the global stress direction (Friedman & Logan, 1970; Lee et al, 2011).…”

“…Journal of Geophysical Research: Solid Earth Initially, so-called "residual stresses" (measured as residual strains) have been examined using strain relief methods including overcoring, microcrack orientation, and density maps (Hoskins & Russell, 1981;Zang & Berckhemer, 1989). Likewise, in conceptual approaches, residual stresses have been linked to rock failure, exfoliation and spalling (Emery, 1964;Kieslinger, 1958;Müller, 1969).…”

“…In geological materials, unlike for engineered materials, stress conditions and magnitudes of external forces which were necessary to produce the observed residual strains are unknown. The residual strain state has, therefore, itself been widely used to infer the stress magnitude and spatial direction of former geological stress fields (Engelder & Sbar, 1977; Sekine & Hayashi, 2009; Zang & Berckhemer, 1989).…”

Numerical study on crack evolution in diagenetically consolidated sandstones

“…0148-0227/91/91JB-00358505.00 responsible for microcrack formation, that is, when other effects like thermal cracks are of minor importance, the influence of cracks on physical properties may be interpreted with respect to the in situ state of stress [e.g., Ren and Roegiers, 1983;Carlson and Wang, 1986;Charlez et al, 1986;Vernik and Zoback, 1989]. A preferentially oriented crack distribution reflects the direction, and the crackclosing pressure, the magnitude of in situ stress for micromorphically isotropic but heterogeneous materials [e.g., Plumb et al, 1984;Charlez et al, 1986;Zang and Berckhemer, 1989].…”