Acoustic Emission Source Localization in Heterogeneous Rocks with Random Inclusions Using a PRM-Based Wave Velocity Model

In situ rock mass usually contains discontinuities in various forms, including fissures, joints and fractures, etc., and it becomes more heterogeneous when the discontinuities are backfilled with artificial grouting. It is incredibly challenging to obtain an accurate wave velocity model for those rocks with random inclusions, making the AE sources more difficult to locate. This study first proposed a projective reconstruction method (PRM) to obtain the wave velocity model for heterogeneous rock. An improved AE source localization algorithm was proposed using the arrival time-based governing equations. Flawed sandstone samples with various inclination angles were then prepared and subjected to unconfined compression until failure. The fragments were restored to generate post-grouted samples with random inclusions. The feasibility and validation of the PRM-based wave velocity model and the proposed AE source localization algorithm were verified by pencil lead break tests. The AE source localization results were compared using three wave velocity models, i.e., averaged wave velocity model, 1D approximated wave velocity model and PRM-based wave velocity model. The results indicate that the PRM-based AE source localization for the post-grouted samples is much more accurate than the other two models. Finally, the fracturing mechanisms of the post-grouted samples with random inclusions under uniaxial compression conditions were illuminated based on the results of the AE source localization and moment tensor inversion. It is confirmed that the PRM-based wave velocity model was promising for the AE source localization in heterogeneous rocks with random inclusions.