Stability analysis
of a closed underground hard rock metal mine using Finite Element Method
Praveena Das Jennifer and Porchelvan P.
Disaster Advances; Vol. 15(6); 11-22;
doi: https://doi.org/10.25303/1506da11022; (2022)
Abstract
Active deep hard rock metal mines with long mining history come with inherent problems
of stability and mining induced issues. These hard rock mines once closed, still
pose even greater environmental risks and stability concerns. The issues of post-mining
impact on environment are usually undervalued and disregarded. It is very essential
to give utmost importance to these mines by following standard mine closure methods
and remediations using post-mining management plans for long-term monitoring and
risk assessments associated with the mine for the safety of life and structures
above. The area identified for the study is Kolar Gold Fields mine located in Karnataka,
India. The mine was completely closed in 2000. The underground mine has been posing
post-mining induced seismicity even today. Due to the complexity of the underground
mine and the inaccessibility to the mine post closure, the Finite Element Method
of approach has been used. The approach is developed to simulate a model similar
to actual field conditions, subjecting them to the seismic loads, varying the parameters
which play a significant role, assessing the entire Kolar Gold Fields mines for
vulnerable zones subjected to post-mining induced effects and finally making it
possible to evaluate the stability conditions of the deep hard rock underground
metal mine.
The simulations were carried out for the three cases with varying the peak ground
acceleration (PGA) for a low PGA of 0.06g, for an intermediate PGA of 0.1g and high
value of 0.2g. It can be inferred that as the acceleration is increased from 0.06g
to 0.22g, there is a corresponding increase in ground acceleration observed at the
ground surface for each case. The maximum acceleration for PGA of 0.06g is 0.071g,
for PGA of 0.10g, it is 0.170g and for PGA of 0.22g it is 0.266g. The results were
validated with the field observations (data of seismicity from installed seismic
monitoring systems). The Finite Element Method of approach has aided in quick assessment
of stability of the underground closed mine.