Scenario Simulations for Underground Mine Dewatering, Itabira Complex
CLIENT
Vale
LOCATION
Itabira, Minas Gerais State, Brazil
TIMEFRAME
2021
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Challenges
The Itabira Complex, the birthplace of Vale’s iron mining operations, is located in the municipality of Itabira, Minas Gerais. As the feasibility of ore extraction through underground mining was studied, it became essential to understand the viability of lowering the groundwater level below the planned mining galleries.
The goal was to simulate the lowering of the water table to dewater the gallery and mining chamber areas, ensuring that the water level reached an elevation at least 20 meters below the lowest planned excavation level.
Solution
A numerical model was developed to simulate the lowering of the water table using the Multilayer Well boundary condition for each of the proposed mines.
The primary methodology for this simulation was the introduction of the Multilayer Well boundary condition, which simulates water extraction through deep tubular wells. In this boundary condition, the daily pumping rate is an input parameter, and the distribution of pumped volumes across the different layers of the model is a simulation output.
To plan the dewatering, it was assumed that the development of the iron ore mining galleries would begin in 2026, with mining operations concluding in 2030. For dewatering planning, in the proposed simulation scenario, pumping started in 2022 to drain the aquifer by 2026, over a period of 1825 days.
A conceptual design for the groundwater dewatering system was presented, detailing the number of wells, depths, and quantities to support the project, along with a hydrogeological instrumentation plan.
Results
The water level simulations for the mines were conducted in parallel with the water level lowering in the open pits, considering a 5-year horizon to achieve the necessary drawdown, indicating synergy between the two dewatering processes.
The results defined the required pumping rates, the time needed for dewatering, the number and location of wells, and the estimated cost to implement the dewatering system.