Due to the possibility of pumping operations ceasing at a deep level gold mine in South Africa, which would result in the possible re-watering of the mine, underground plugs were required to prevent flooding of the neighboring mine. Three 25 meter long parallel-sided haulage plugs have been designed to safely resist hydrostatic heads of 1 100 m (45 level and 140 level plugs) and 1 181 m (43 level plug) respectively. This paper details the design of the plugs which considered shear failure along the rock-concrete interface, excessive seepage around the plugs, and long-term disintegration of the concrete. Site investigations comprising geological mapping and Lugeon testing, and site preparation consisting of pre-grouting of the surrounding rock mass are discussed. The plug design addresses the constituent materials and components of the plugs, the inclusion of a lime deposit to neutralize acidic mine water in the immediate vicinity of the plugs, and a bentonite geotextile to serve as a buffer to resist chemically aggressive mine water. A Monte Carlo simulation has been carried out in order to predict the probability of failure of the plugs.
