Clean Energy Systems in the Subsurface: Production, Storage and Conversion

Abstract

In this paper, the study on the spatial distribution of acoustic emission (AE) events in rock salt under different stress conditions was reported. The study showed that under indirect tensile stress condition, the AE events were mainly induced by the stress concentration near the loading surface and by intergranular deformation before rock failure, while during failure and the post-failure process the AE events were essentially related to the damage development, especially near the tensile failure surface. Under uniaxial compressive stress condition, the closure of initial micro-cracks including those artificially produced during coring and sample preparation and intergranular deformation were the main mechanisms responsible for the occurrence of AE events at the initial deformation stage, and then transferred to damage development until the post-failure stage was met. In triaxial compression tests, the influence of the closure of initial micro-cracks and intergranular deformation was still the main cause for AE events at the confining pressure loading stage and the initial axial loading stage. However, the influence of plastic deformation becomes more pronounced at the plastic yield stage and the post-peak stage. Intensive occurrence and accumulation of AE events before rock failure was noticed under different stress conditions. In indirect tensile tests, the recorded AE events were mainly accumulated along the failure surface. However, this reasonable phenomenon was not evident in uniand triaxial compression tests, where the spatial distribution is generally homogeneous. © Springer-Verlag Berlin Heidelberg 2013.