Numerical investigation of the influence of waste rock inclusions on tailings consolidation

The construction of waste rock inclusions (WRIs) in a tailings impoundment constitutes an alternative disposal technique that aims at improving the management of mine wastes. This technique consists in strategically placing the WRIs inside the impoundment, at the beginning and during its operation, to form compartments (or cells) in which the tailings are stored. Such inclusions can serve various purposes. In this paper, the authors investigate the effects of drainage from WRIs on tailings consolidation during filling of the impoundment, using experimental data from hard rock mines that provide the hydrogeological and geotechnical properties introduced in the numerical analyses. The model used for the simulations represents a cross section of a portion of a tailings impoundment containing a WRI. The numerical calculations results illustrate how the WRI affects the dissipation of the excess pore water pressures (PWPs) during filling of the impoundment, and help quantify the extent of the zone of influence of the inclusion. The results from the parametric analysis show that the saturated hydraulic conductivity k(sat), compression index C-c, thickness, and deposition rate of the tailings are the main factors that affect the efficiency of WRIs to accelerate dissipation of excess PWPs. The discussion that follows recalls the main limitations of this investigation and addresses practical aspects related to the WRIs technique.