The 4th International Symposium on Mine Safety Science and Engineering (ISMSSE2018)

302 / 2018-05-02 17:02:05

Determination of a geometrical constant for a circular slip zone

seismicity,Dynamic Analysis,seismic efficiency,geometric constant

Mine Dynamics Disaster > Rock burst impact

Induced seismicity has been recognized as one of the most important phenomena in the field of mining engineering and other relevant fields, such as geothermal energy development. Importantly, the occurrence of seismic events cannot be predicted with only fault frictional behavior. The shear stiffness of the surrounding rockmass also plays a dominant role. The rockmass shear stiffness is generally believed to be calculated from G·η/L, where G, η, and L are shear modulus, geometrical constant, and slip size, respectively. The present study aims to estimate the geometrical constant for a circular slip zone. A 3D numerical model including an inclined fault is constructed, where a seismic event is induced in a circular region on the fault by decreasing effective normal stress in the region, which is followed by the dynamic decrease in the frictional resistance of the fault dictated by a slip-weakening law employing a non-linear exponential function. First, it was demonstrated that the surrounding rockmass stiffness has a significant effect on the amount of radiated energy, i.e. radiated energy is inversely correlated with the surrounding rockmass stiffness. Then, a model parametric study was undertaken with respect to the radius of the slipped zone and a constant in the slip-weakening model. The result implies that the geometric constant is dependent upon not only the geometrical shape of the slipped zone but also seismic efficiency. Then, further analyses were performed while changing the parameters but keeping seismic efficiency at 6 % for all the models. The analyses yielded the same geometrical constant of about 3 for all the models. It was thus concluded that the geometrical constant is around 3 for fault-slip having a circular slip zone when its seismic efficiency is 6 % and that the geometrical constant changes depending on the magnitude of seismic efficiency.