The measurement of the in-situ stress state by acoustic emission method (AEM) in weak rocks

The overcoring and hydraulic-fracturing methods are widely used for in-situ stress measurements. However, their use is restricted to the construction of civil engineering structures of great significance due to their high cost. Furthermore, it becomes quite difficult to apply these techniques to rocks, which yield. In addition, the stress measurements in weak rock are-also extremely difficult due to problems in attaching the strain gauges to the borehole wall. The authors have been recently performing stress measurements using the acoustic emission method (AEM) in Turkey as well as in Japan. The applications generally involve weak sedimentary rocks such as mart, shale, tuff and limestone and samples are gathered at depths less than 150 m. The samples gathered at Cappadocia region, Orhaneli and Demirbilek open-pit mines in Turkey and Oya tuff underground quarry in Japan are used to infer the crustal stresses and they are compared with those obtained from other methods such as focal plane solution method and fault striation method. The results indicated that the results obtained from the AEM are reliable and consistent with those inferred from other methods even in weak rocks. The authors report the results of measurements and discuss the suitability of the AEM for inferring in-situ stresses in weak rock in this article.