Hydrogeological Behaviour of Covers with Capillary Barrier Effects Made of Mining Materials

Abstract

A laboratory study and numerical predictions were conducted to evaluate the effectiveness of a cover with capillary barrier effects (CCBE) made of mining materials in limiting the generation of acid mine drainage. The present study included the installation of three experimental laboratory columns as physical models of CCBEs. Each column was instrumented to monitor the hydrogeological behaviour of the different layers of the cover. In the moisture-retaining layer, which is made of desulphurized tailings, the degree of saturation (Sr) is usually maintained above 85%, while Sr in the two waste rock layers placed above and below the moisture-retaining layer (MRL) is typically between 5 and 15%. Suctions were usually lower than the air entry value for the desuphurized tailings layers, while suctions largely exceeded the water entry value of the mine waste rock in the two capillary break layers (CBLs). The oxygen flux was calculated using numerical modeling at the bottom of the MRL. Results confirm that the oxygen flux is low (between 0.34 and 3 g/m2/year). This study also confirms the potential of mine waste rocks to act as a substitute for natural granular soils in the CBL of a CCBE.