Abstract
Mining of sulfidic ore generates acidic waste which often leads to the generation of acid rock drainage (ARD) having an adverse impact on aquatic flora and fauna. Engineered multilayer cover is one of the commonly used methods to prevent oxygen from being transported to mine waste. The sealing layer has a key function in the cover, thanks to its high water retention capacity and a low hydraulic conductivity, which enable the layer to remain near water saturation, effectively hindering oxygen diffusion. When adequate material is not available improvement of local soil material with a sealing agent is principally the only option to produce sealing layer material. Apart from bentonite clay, Green Liquor Dregs (GLD), a waste from the pulp and paper industry, have the ability to reduce the oxygen diffusion when mixed to granular soil, improving the water retention capacity of the blend. Experience from the development of Till/GLD-blends for the construction of sealing layers is compiled to address issue related to soil amelioration using waste with focus on material variation and quality control. The presentation focuses on the opportunities and challenges for the establishment of a circular system based on reutilization of a waste, herein GLD for improvement of soil’s geotechnical property.
Highlights
The global annual generation of mine wastes has been estimated to 15.000 – 20.000 million tons of solid waste [1], the majority of which containing residual sulfidic minerals
In contact with air and water, sulfide containing waste often leads to the generation of acid rock drainage (ARD), an acidic leachate with high concentrations of metals and metalloids [2], which is a threat to environment [3,4]
The sealing material should have a high water retention capacity (WRC) to avoid dehydration and a low hydraulic conductivity (HC), to maintain the sealing layer to remain near water saturation, effectively hindering oxygen diffusion
Summary
The global annual generation of mine wastes has been estimated to 15.000 – 20.000 million tons of solid waste [1], the majority of which containing residual sulfidic minerals (primarily pyrite, FeS2). Engineered covers are typically multi-layer constructions which design depends on waste properties, cover material availability, water table position and climatic conditions [6,7]. Mixed in a limited amount with granular soil such as till, an increasing addition of GLDs have the capacity to improve the WRC of the mixture, while keeping relatively good geotechnical properties. The success of the methods relies on an efficient mixing of the GLD in the matrix and a sufficient degree of compaction of the blend. Both mixing and packing are essential to obtain a functioning barrier at full scale. - Compaction degree that can be achieved in slopes and flat areas
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