The Impact of Surface Water Seepage on Seismicity and Rockbursting in Mines

Abstract

Retrospective analysis of data obtained from long-term monitoring of technogenic seismicity and rockbursts at the Apatitovy Tsirk and the Rasvumchorr Plateau deposits (Russia) showed that there is a significant (by 50% or more) increase in the number of geodynamic events during spring snowmelt periods. An upswing of seismic activity within this rock massif occurs when following conditions are true: water reserve in the snow cover on the deposit area is more than 3 × 108 m3; snowmelt period exceeds 40 days; increase in water ingress rates continues for over 5 days and total water inflow volume exceeds the previous daily measurements by at least a factor of 2. Seismic activity of the massif starts to intensify after the snowmelt develops momentum. Major induced earthquakes occurred in the years when these conditions were met (for example, in 2005 there was a magnitude 2.3 earthquake; in 2009, M = 1.6 earthquake), and more than 1000 seismic events were recorded during the snowmelt period. It has been established that when mining reaches the depths of more than 500 m, seismic events during infiltration of atmospheric precipitation begin to occur from a depth of 100–200 m and are recorded to depths of about 900 m. A possible controlling factor of the seismic activation is the reactivation of tectonic faults, which occurs under conditions of the critically stressed state of the massif, due to a decrease in their normal compression during infiltration. Retrospective analysis of the factors contributing to a strong rockburst (K = 10–11) in 1990 at a bauxite mine in the South Urals shows that prior to this disaster there was an inrush of the Ai River waters into the mine workings through a large tectonic disturbance, which has not been previously taken into account when analyzing the mechanism of this geodynamic event. The intrusion of water into the fault located in the field of regional stresses and subsequent partial relief of its fault plane from normal stresses could have triggered the rockburst with fault-slip mechanism. The study of the relationship between amount of precipitation and the degree of water encroachment into the field, on the one hand, and seismicity, on the other hand, is needed to draw up recommendations on improving geodynamic and environmental safety of mining regions in order to ensure their sustainable development.

Slow earthquakes as rockbursts: evidence from subsurface rock pressure-stress accumulation and release modeling and time-domain seismic wave decomposition

“…(ii) Spring snowmelt may induce large earthquakes through rockbursts, with a seasonal increase in more than 50% seismicity 38 all of these increase the incidence of rockbursts.…”

“…Therefore, in practice, pore pressure is usually modeled as the main rock fracture force, and a fracture criterion that considers the effect of pore pressure can be a good predictor of the fracture pressure of a rock 35 . However, weak external perturbations (such as shear stresses from tidal turbulence 253637 , or normal stresses from water intrusion on faults within a regional stress field 38 ) can also cause rock damage. Weak external perturbationscanleadtounevendistributionofstressesindifferent rock parts, with each part expanding to a different extent and deformation constraints varying between internal zones, resulting in internal rock stresses.…”

“…At the same station, the loading pulse began to increase significantly in the diurnal cycle pattern or amplitude 1 to 6 months before the Tohoku-Oki earthquake (Yamamoto, Namie, and Iwanuma in Fig.5b). It is unlikely that a diurnal cycle caused by human activities would change significantly over time.Tidal semidiurnal cycles 253637 and diurnal temperature differences38 may have contributed to the diurnal periodicity of the rockburst energy pulse. Take the 2011 Tohoku-Oki earthquake as an example.…”

Research on Fault Activation and Its Influencing Factors on the Barrier Effect of Rock Mass Movement Induced by Mining

“…During deep underground mine extraction, various influencing factors will lead to fault activation, resulting in mining disasters. For example, rock bursting, mine water gushing, and mining area collapse on the surface [6][7][8][9]. Thus, one of the key elements impacting underground safe mining has been fault activation [10][11][12].…”