Acoustic Emission Technique to Detect Micro Cracking During Uniaxial Compression of Brittle Rocks

Excavation of deep underground openings causes redistribution of primary stresses and induces initiation and propagation of micro cracks. Changes in rock properties ahead of an advancing tunnel face may influence stability and penetration rates in TBM tunneling. This study is part of a PhD project where the focus is on stress-induced micro cracking and its influence on rock strength reduction. We demonstrate results from acoustic emission (AE) measurements on two homogeneous diorite samples tested under uniaxial compression. The aim was to gain information about the influence of experimental setup and settings on AE events in brittle rock. From the stress strain curve and the number of acoustic signals, main deformation stages could be determined. A three-dimensional localization of acoustic events showed a typical conjugate shear system. Future work will include tests on different rock types after inducing controlled damage by uniaxial loading. Lateral strain measurements combined with AE analysis will be applied in order to quantify rock damage and its influence on rock strength.