Hydrogeological Modeling of an Underground Gold Mine
CLIENT
AngloGold Ashanti
LOCATION
Sabará, Minas Gerais State, Brazil
TIMEFRAME
2023-2024
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Challenges
The underground mine is located in the city of Sabará, in the state of Minas Gerais, Brazil. Situated in the Quadrilátero Ferrífero region, the mine is a world-class gold deposit.
Understanding the flow dynamics within the underground mine and the water inflows at the lower mining levels, as well as providing support for future mine developments.
Solution
A critical analysis of groundwater level monitoring data from piezometers and flow measurements in watercourses within the mine’s area was conducted. This initial phase supported the development of a conceptual hydrogeological model. A numerical model was then developed to support the understanding of groundwater flow dynamics within the mine’s context and its relationship with adjacent areas. The numerical code selected for the study was FEFLOW software, chosen for its great flexibility in defining the numerical mesh, allowing for better representation of the geometry of the underground mine galleries.
Results
The monitoring data analysis revealed the need for daily evaporation monitoring, not just rainfall measurements. Additionally, the installation of new piezometers at lower mine levels and the expansion of the surface monitoring network were recommended in light of the projected mining advancement. There was no evidence of a depression cone, which is expected since the mine does not carry out groundwater dewatering.
The numerical model successfully simulated the variation in water levels within the piezometers. It was able to represent water inflows into the underground galleries up until the final stage of underground mining advancement in 2042. Model estimates showed no impact on the flow rates of the Sabará River segment between upstream and downstream points.