Stability analysis of an abandoned deep metal mine using numerical analysis tool: A case study

Abstract

In the recent years due to rapid urbanisation, the key focus has been shifted to development of rural and remote areas. Abandoned mine sites are being evaluated for land reclamation with remediation measures as part of the development program. The abandoned mines come with inherent risk like unpredictable potential future subsidence and sinkhole formations on the surface. The identification of these potential risk areas stands as a major challenge for remediation. The inaccessibility to site makes it even more difficult to study the current geo-mechanical stress conditions for stability evaluation. Despite these limitations, it is essential that abandoned mine sites could be evaluated to atleast give an indicative understanding of current scenarios with regard to safety.Using numerical analysis tool, it is possible to simulate a model similar to that of the abandoned mine, to identify the potentially stressed zones and assess the stability of the underground excavation. The finite element method is used to develop a numerical model using GTS NX software. The software aided in evaluation of stress distributions and stability of the closed mine since the mine presents a hydro geological problem. The model analysis has proved to be very helpful in observing the mechanical behaviour of materials, modelling of rock systems and understanding the deformations in the rockmass.Three case conditions of varying the input parameter of peak ground acceleration (PGA) with a minimum PGA value of 0.06g to a maximum PGA value of 0.22g was used in the model studies of Champion Reef mine (3.2km deep gold mine). The vulnerable zones of seismicity were identified to be concentrated at a depth below 1500m from the surface and the maximum peak ground accelerations observed at the surface was found to be 0.1g to 0.22g. The model developed and approach used in this study is an attempt to present the overall view of the probable stability condition for a rough risk assessment study of the deepest Champion Reef metal mine in Kolar Gold Fields.