Rock-burst simulations with 2D-DDA: Preliminary results

We investigate the mechanisms for rock-burst using the numerical Discontinuous Deformation Analysis (DDA) method. Using recently developed non reflective boundary and excavation sequence modeling capabilities we are now able to model dynamic deformation in high in-situ stress environments more accurately than before. First we perform verifications of P-wave propagation through a one-dimensional elastic bar and confirm DDA accuracy provided that the block length with respect to wave length is properly conditioned. We then test a newly developed radial P-wave propagation module to emulate an underground blast. We study two possible rock burst generation mechanisms: 1) due to strain relaxation as response to opening in high in situ stress environment, and 2) due to nearby blasting. A very strong relation between the initial stress and the velocity and acceleration of the ejected key blocks following the removal of the tunnel section is reported. We also find that the influence of blasting on rock burst phenomena is strongly related to the initial in situ stress level. We conclude that under relatively low in situ stress environments nearby blasting may indeed ejection of originally stable key blocks. However, under high in situ stress conditions strain relaxation poses a much greater rock-burst risk.