Non-contact detection of acoustic emission signals from rock surfaces.
43rd U.S. Rock Mechanics Symposium/4th U.S.-Canada Rock Mechanics Symposium, June 28 - July 1, 2009, Ashland, North Carolina, paper no. ARMA 09-141. Alexandria, VA: American Rock Mechanics Association, 2009 Jun; :1-11
The purpose of the research was to investigate the feasibility of developing advanced acoustic emission (AE) monitoring for rock structure stability assessment. The equipment involves a laser interferometer based non-contact detection system to perform monitoring of AE activity in the process of rock deterioration. Two laser based sensing units were tested in this effort, namely, the unit using photo-induced electromotive force (PI -EMF) and the one using two-wave mixing (TWM) technique. In the initial experiments, TWM technique showed superior performance and technical maturity for AE signal detection on rock surface, while Ihe PI-EMF technique needs further developmenl. The TWM sensing unit was also compared with conventional piezoelectric transducer in AE monitoring test on rock specimens, In these laboratory tests, TWM sensing unit showed excellent performance. The frequency band, fidelity and signal-to-noise ratio are competent for the projected use. The significance of these tests is that it demonstrated that the TWM sensing unit could detect AE signals with similar sensitivity and accuracy to that of the conventional piezoelectric transducers. Therefore, the laser-based sensing unit (TWM) can be incorporated for development of AE based rock stabilily monitoring system. A series of acoustic emission tests were then conducted on specimens of rock, including weathered sandstone, shale and coal. The AE data were used for failure criteria development. The instrumentation for AE data collection has two channels: one is used for the laserbased TWM sensing unit; the other is used for conventional piezoelectric system as reference. Thirteen rock specimens (3 sandstone, 5 shale, and 5 coal) were tested under Uniaxial compression for the purpose of collecting AE data for parametric analysis and pallern recognition sludy. Finally criteria were established for prediction of instability development in the rock specimens.
Rock-mechanics; Ground-control; Ground-stability; Geology; Engineering-controls; Models; Computer-models; Mining-industry; Underground-mining; Monitors
43rd U.S. Rock Mechanics Symposium/4th U.S.-Canada Rock Mechanics Symposium, June 28 - July 1, 2009, Ashland, North Carolina, paper no. ARMA 09-141