HGS RESEARCH HIGHLIGHT – Numerical simulations of water flow and contaminants transport near mining wastes disposed in a fractured rock mass
Farouk, B.A., Aubertin, M., Simon, R., & Therrien, R. (2015). Numerical simulations of water flow and contaminants transport near mining wastes disposed in a fractured rock mass. In International Journal of Mining Science and Technology (Vol. 25, Issue 1, pp. 37–45). Elsevier BV. https://doi.org/10.1016/j.ijmst.2014.11.003
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This study uses HydroGeoSphere simulations to model unsaturated water flow and contaminant migration in a mining context, specifically the reclamation of open pits with mine waste products. Fractured rock masses are important to study as fractures present preferential flow paths that can promote contaminant transport. The mining industry generates considerable volumes of waste which must be disposed of responsibly. This waste can be an environmental hazard if not managed correctly.
Farouk, B.A. et al (2015)
In this research study, the HydroGeoSphere model was used to model advective solute transport and matrix diffusion of hypothetical aqueous contaminants (non-reactive). Several scenarios were modelled to see which factors impact water flow and solute transport surrounding a hypothetical open pit which has been backfilled with different mine waste products. The effects of hydrogeological properties of the filling material, fracture network characteristics and conductivity host rock are all investigated. There were six different cases simulated, each representing a different fracture pattern, some with coarse-grained waste rocks and some with fine-grained tailings. Solute plumes were compared at 10 days, 1,000 days, 10 years, and 20 years to estimate the sensitivity of the system to each parameter.
The results showed that the open pit filling materials affect unsaturated water flow and contamination transport. When the surrounding rock mass is non-fractured, water accumulates in the bottom of the open pit due to recharge, leading to high saturation. Furthermore, the regional gradient has a larger effect on contaminant transport when the surrounding rock mass has orthogonal fractures. Waste rock was found to have higher solute concentrations than the fine-grained tailings which pose a lower environmental risk in the context of disposal within the open pit.
“Hydro-Geosphere is a powerful numerical tool which has the advantage of rapid convergence and complex problems resolution.”
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Abstract:
A numerical tool, called Hydro-Geosphere, was used to simulate unsaturated water flow and contaminants migration around an open pit filled with mining wastes. Numerical simulations had been carried out to assess the influence of various factors on water flow and solute transport in and around the surface openings including recharge, properties of the waste material and presence of fractures in the surrounding rock mass. The effect of the regional hydraulic gradient was also investigated. The analyses were conducted by simulating various 2D cases using experimentally obtained material properties and controlled boundary conditions. The effects of the hydrogeological properties of the filling material (i.e., water retention curve and hydraulic conductivity function), fracture network characteristics and conductivity of the joints were assessed. The results illustrate that fractures control water flow and contaminants transport around the waste disposal area. A fracture network can desaturate the system and improve the regional gradient effect.