(General session) Rock Engineering / Mining technologies

[2K0101-07-05] [Student presentation: Doctoral course] 3-D quasi-static modeling of mining-induced earthquakes in reverse or normal fault environment

○YATAO LI¹, Eiichi FUKUYAMA¹, Nana YOSHIMITSU¹ (1. Kyoto University)

Chairperson : Akihiro Hamanaka (Kyushu University)

Keywords:Induced earthquake, faulting process, Coulomb fracture criterion, quasi-static model

Mining-induced earthquakes that occur during longwall mining may cause damage not only to underground mining activities but also to the surroundings. This study simulates a 3-D mining-induced faulting process using the FEM software Code-Aster. We consider two typical faulting types, reverse and normal faults, and the working face passing through the fault plane from the hanging wall and footwall. In total, we considered four cases of fault reactivation in the initiation location of faulting during the mining process using the Coulomb fracture criterion. We investigate the difference among the four cases in the total amount of slip and the stress drop when the mining method and relative mining location are the same. The effect of working face geometry, as well as the intermediate stress, was also studied in detail. As the mining face approaches the fault, a large stress disturbance, including stress concentration, is expected on the fault close to the mining face. The fault stress ratio, defined as the ratio of shear stress to the normal stress on the fault, exceeds the coefficient of friction and may lead to fault slip. The maximum slip when the working face is located on the hanging wall side is larger than that in the footwall in both faulting types. If the faulting area becomes larger than the nucleation size defined in relation to the friction parameters, a dynamic rupture propagation will be triggered. Faulting type and mining face location are significantly related to fault instability. Since the orientation of tectonic stress and preexisting fault geometry can be investigated before mining, these issues should be considered in the mining plan. These considerations provide a theoretical view of tectonic and mining-induced stress to optimize the size of fault-protected coal pillars.