Numerical Modeling of Mining-Induced Seismicity - Review and Case Study Example from the Malmberget Mine

摘要

Mining-induced seismicity is an important issue for safe and reliable future mining. This paperrnpresents a brief review of different approaches for numerical modeling of mining-induced seismicity,rnwith some examples from mines in Sweden. There are numerous examples of predictions of strainrnburst seismic events, but calibration and prediction of fault slip events has proven to be more difficult.rnTwo different approaches for modeling fault slip can be identified: (ⅰ) using ESS (Excess Shear Stress)rnand continuum modeling, and (ⅱ) using discontinuum modeling and simulating shear slip onrngeological structures explicitly. Some examples of the use of each of these two approaches arernreferenced in the paper. A general discussion on the use of modeling and an outlook for the future inrnterms of our ability to numerically model and predict seismic events in mining concludes the paper.rnA detailed case study of modeling and using the ESS-concept in a slightly novel way is alsornpresented. A detailed three-dimensional numerical model, using the FLAC3D finite difference code,rnwas constructed for the LKAB Malmberget mine. The mining sequence in the model simulatedrnmining in each orebody, in 21 mining steps, from year 2008 to year 2030. A differential stressrncriterion, based on Diederichs (1999) was used as an indicator of potential seismic events. Moreover,rnthe nineteen largest recorded seismic events from the mine to date were analyzed. The maximumrnpossible seismic moment and the major probable shear plane orientation were calculated for eachrnlocation. ESS was calculated for disks (planes) with varying orientations and radius with 90% arearnwith positive ESS. The resulting maximum radius of the disk and the mean ESS value were used torncalculate the seismic moment. The results were compared with actual recorded seismic magnitudes,rnand predicted magnitudes for seismic events for future mining were evaluated.