Prediction of Subsidence Parameters & 3-D Analysis at Balaghat Underground Manganese Mine of MOIL Limited, India

Abstract

Subsidence is a time-dependent process and controlled by various factors including methods of mining, depth of extraction, thickness of deposit, and topography, as well as the in-situ properties of the rock mass. Subsurface deformation leading to surface subsidence includes the local lateral and upward displacements of rock above un-mined areas [1]. In this context, MOIL has conducted in-house research investigations of the subsidence phenomenon related to the underground mining of manganese ore at Balaghat mine. The mine has the manganese ore body at an average thickness of 10 m in north and 5 m in south, dipping at an average gradient of 40°-65° in north and 50°-80° in south. The ore body has fairly long strike length 2500 m at the deeper levels around 550 m below the surface. Considering the ore body and the hanging wall characteristics the subsidence phenomenon would be very much comparable to a coal mine situation. Taking this factor into consideration, the prediction of subsidence parameters has been carried out by adopting the well accepted and conventional coal mining subsidence prediction methods that have been developed in the country and are suitable for Indian mining conditions. The computations showed that the parameters of importance are well within the limit for permissible subsidence. The monitoring is done on a continuous basis at quarterly intervals, at two sites above the mine workings at Balaghat Mine. The quarterly monitoring data from Jan 2014 to Dec 2016 clearly suggests that no noticeable movement took place in any of the three orthogonal directions at these places. This is evidence enough that the subsidence at the Balaghat mine surface land is not of any measurable significance. The paper presents the scientific investigations carried out by the MOIL for prediction of subsidence parameters and successful 3-D analysis of subsidence monitoring at Balaghat Mine.