Development of a dewatering control strategy to prevent flooding within deep-level mines

Abstract

Deep-level mines are faced with continually increasing challenges regarding heat. New mining depths are constantly reached, and working conditions are becoming intolerable and unsafe. Underground conditions must be controlled effectively to safeguard the health of the mining personnel. Mine service water is used to control the temperature of the occupational environment. In essence, a certain portion of the overall heat is transported out of the mine via dewatering systems. Dewatering systems play an important part in mitigating heat loads underground. Refrigeration plants integrated with dewatering systems are responsible for providing chilled water to key working areas. The hot water needs to be extracted from the working areas and removed from the mine to prevent flooding. Some hot water may also be reintroduced to the refrigeration plants to be cooled again depending on the water reticulation system design. Unexpected failures within dewatering systems pose a major risk of flooding and mine down-time. Therefore, it is of utmost importance to maintain redundancy within dewatering systems. This can be achieved by identifying the general root cause of failures and developing an alternative dewatering control philosophy that reduces the risk of flooding within the mine. This study focused on increasing the reliability of current mine dewatering systems using simulation software to develop and test possible solutions to identified risks. The proposed methodology was applied to a case study mine situated in South Africa. The case study mine formed part of an integrated mining complex consisting of three different shafts. Upon case study inspection it was found that the case study mine had to stop production for a total of eight days due to dewatering column failure. The loss in production amounted to an estimated loss of R30 million for the 2019 financial year.

A calibrated digital twin model of the case study’s dewatering system was constructed and used to develop alternative dewatering strategies to prevent further failure of dewatering components. All critical dewatering components and additional infrastructure were investigated and integrated into the simulation model to develop a redundant and sophisticated dewatering strategy. Critical system control parameters were also developed to ensure all dewatering components operate within the design specifications. Two additional dewatering solutions were integrated into the current dewatering strategy to achieve redundancy, which was the main objective of this study. The developed control philosophy also introduced a buffer dam from where centralised dewatering control was possible between all neighbouring shafts. A mass balance within the case study mine was maintained and the simulation model predicted the outcome of the system changes with an average simulation error of 4.2%. Flooding within the case study mine was prevented resulting in no loss in production due to flooding for the 2020 financial year.