MINING AT DEPTH UNDER WEAK ROCKMASS

CIM MEMO 2008
Barnard Foo, Iouri Iakovlev,
Abstract The São Bento Mineração Gold Mine is located in the eastern portion of the Iron Quadrangle Mining District in Minas Gerais, Brazil. The mine is located approximately 100 km East of Belo Horizonte, in the municipality of Santa Bárbara, Minas Gerais.

The mine is currently mining in unfavorable weak rockmass and at depth excess of 1,000 m below surface. The mineralisation is deposited within a faulting system hosted by poor rockmass. The deterioration of underground excavations by the poor ground and the increase in-situ stresses provide challenges to the stability of underground openings and safety to personnel.

A rehabilitation program was formed during the months of March to May of 2005 to rehabilitate the affected areas of the mine for production. The mine had been able to deal with these conditions by strategically implementing appropriate ground support and has managed to continue mining activities.

This paper summarises the ground conditions, failure mechanics, and the innovative use of support techniques to improve ground stability and work area safety within the defined rock mass in order to continue production at São Bento Mineração. A comparison of numerical stress predictions was performed with Phase2 on established design criteria and underground observations.
Keywords: Weak Rockmass, Rock Reinforcement, Numerical Analysis, Deep Mining
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