Schmidt, ES & Eberhardt, E 2017, 'Numerical investigation of the use of hydraulic stimulation to mitigate fault slip risk in deep mines', in J Wesseloo (ed.), Deep Mining 2017: Proceedings of the Eighth International Conference on Deep and High Stress Mining
, Australian Centre for Geomechanics, Perth, pp. 79-88, https://doi.org/10.36487/ACG_rep/1704_03_Schmidt
Fault slip and associated seismicity present a significant risk to the safety of underground mines. This paper investigates whether hydraulic stimulation, defined as the injection of pressurised fluid into a rock mass in advance of mining, has the potential to mitigate such risks. Fluid injected in the proximity of a criticallystressed pre-existing fault plane decreases the effective normal stress acting on the fault, initiating slip. Based on this concept, hydraulic stimulation could be used to trigger the release of built-up strain energy in advance of mining.
Numerical investigations are carried out in a two-dimensional distinct element code to model the effect of injection on the slip of a pre-existing fault located adjacent to a conceptualised open stope mining operation. Injection is accompanied by slip and a significant decrease in shear stress acting on the fault. When no injection is performed, excavation triggers a series of slip events in response to the changing abutment stresses, generating a maximum Mw 1.3 event. Conversely, when hydraulic injection is performed prior to the mine excavation sequencing, the total number of slip events is reduced, and a lower maximum magnitude of Mw 1.1 is observed. Longer injection durations are observed to trigger larger areas of slip and greater total shear displacements. However, a consequence of injection activities is that stress becomes concentrated outside of the fluid propagation front, potentially triggering seismicity in areas where it was not originally anticipated.
Keywords: fault slip, induced seismicity, hydraulic injection, numerical modelling, rockbursts, shearing
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