Abstract
Abstract The behavior of the inelastic strain of rocks under the loading of compression reflects the history of stresses applied to the rocks. A number of methods based on this rock property of stress memory have been proposed for measuring in-situ stress. The magnitudes of in-situ stress can be determined from drilled core samples by deformation rate analysis (DRA); in other words, rocks do have the property of in-situ stress memory. In general, the inelastic strain of rocks increases with an increase in applied stress difference. The Keiser effect observed in laboratory experiments is explained as the behavior of the inelastic strain of this well-known mode. However, this effect cannot be the mechanism of the in-situ stress memory because the effect does not potentially allow us to determine the magnitudes of previously applied stress. Here, I theoretically show that rocks exhibit another mode of inelastic strain under axial loading of compression—if locally concentrated stresses in rocks relax to some extent under in-situ stress at depth. The magnitudes of in-situ stress can be determined from the behavior of this mode of inelastic strain under axial loading. The results of DRA suggest that this hypothesis is actually valid and that it is not only valid for the DRA, but also for the other rock core-based methods used for measuring in-situ stress.
Highlights
When uni-axial loading of compression is applied to a rock specimen in a laboratory, acoustic emission (AE) activity starts just at the point as which the applied stress exceeds the peak of stress previously applied to the specimen or the previous stress (e.g., Kurita and Fujii, 1979; Yoshikawa and Mogi, 1981)
The magnitudes of in-situ stress can be determined from drilled core samples by deformation rate analysis (DRA); in other words, rocks do have the property of in-situ stress memory
I have reviewed deformation rate analysis, which is a method developed for detecting in-situ stress memory in the inelastic deformation behavior of rock specimens under uni-axial loading of compression and demonstrated evidence for the existence of the rock property of in-situ stress memory
Summary
When uni-axial loading of compression is applied to a rock specimen in a laboratory, acoustic emission (AE) activity starts just at the point as which the applied stress exceeds the peak of stress previously applied to the specimen or the previous stress (e.g., Kurita and Fujii, 1979; Yoshikawa and Mogi, 1981). This phenomenon is known as the Kaiser effect. When the applied stress is increased again after unloading, new microfractures hardly occur at first, and the preexisting cracks
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