: In-situ stress measurement using AE (Acoustic Emission) and DRA (Deformation Rate Analysis) was adapted to investigate the underground stress conditions. These methods are usually carried out under uniaxial loading in the laboratory and they consume delay time from drilling to testing. Therefore, it should be considered how the lateral stress and delay time influence on the test results for the in-situ stress determination. As the delay time increased, the accuracy of estimating the pre-stress decreased. The pre-stress of the specimen loaded axially was determined within an error of less than 9% (using AE) and 4% (using DRA). And the specimen on which axial pre-stress and the confining pressure were loaded had an error of less than 17% (using AE) and 14% (using DRA). The results of AE and DRA for field specimens were very similar with each other but smaller than those of hydraulic fracturing method.


The stress concentration around an underground excavation depends on the magnitude of in-situ stress and the geometry of excavation. So in-situ stress is one of the most important factors in the process of designing the underground excavation or estimating its stability. In-situ stress measurement can be done through several methods. Jacking method, stress relief method, and hydraulic method are carried out to determine the in-situ stress in the field. On the other hand, methods using AE (Acoustic Emission), DRA (Deformation Rate Analysis), DSCA (Differential Strain Curve Analysis) or ASR (Anelastic Strain Recovery) are done in the laboratory (Amadei & Stephansson, 1997).

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