Slope stability studies of dumps & stacks at Noamundi-Katamati iron ore mines, India – a case study

Dump slope stability is an important aspect of open cast mining. It has a direct impact on the safety of man and machinery as well as the mine economics. Noamundi and Katamati captive iron ore mines of Tata Steel Limited, India have been supplying iron ores to its own steel works since decades. The waste and reject material generated during excavation are placed in dumps and stacks respectively at designated places within the leasehold. In this paper, the factor of safety (FoS) for all the waste dumps and reject stacks have been calculated using FLAC 3D software. The waste dump material properties like density, cohesion, internal angle of friction, optimum moisture content, natural angle of repose have been determined in the geotechnical laboratories. Empirical equations are used to calibrate the values of cohesion and angle of internal friction to represent the original dump mix responsible for stability. 3D numerical modelling was carried out by averaging the results of the samples of each dump and reject stacks. Further, a few more analyses were also carried out along selected sections with low FoS values using parameters sampled from the vicinity of those corresponding lines. Finally, a risk matrix was prepared based on the FoS values obtained through this study & monitoring strategy framework was proposed accordingly to monitor dumps and stacks in an effective and sustainable manner.