Geotech

In the interests of re-mining and consolidating tailings on the West Rand for environmental and economic benefits, the concept of the Far West Gold Recoveries (FWGR) Regional Tailings Facility (RTF) was developed. The conceptual design of the RTF presents a 4th Generation upstream on-wall cyclone ring dyke dam with a pumped decant and expected Rate of Rise (RoR) of 4-6m per year.

If the RTF is implemented as designed, it should be possible over the next 3 to 4 decades, to re-move and re-locate virtually every existing gold tailings dam on the Far West Rand to the RTF – a total of 1,3Bt, thereby generating beneficial economic activity for the period and substantially reducing the current impact footprint.  The final RTF will have an ovoid footprint covering 960Ha, a top surface area of 550Ha, a height of 135m and side slopes of 1:4.

Geotechnical profiles and material parameters were obtained for the foundation through geotechnical investigations at the site of the proposed RTF. Tailings material parameters were derived via lab and insitu testing conducted on tailings at the Brakpan TSF – which is deemed representative of the proposed RTF.  Limit Equilibrium, 2D and 3D Finite Element modelling was undertaken to examine the stability of the proposed facility under predefined Mohr Coulomb strength conditions, as well as by employing the NorSand constitutive model.  Stability was found to be satisfactory for drained and peak-undrained conditions, but marginal when residual undrained conditions are assumed. A 2D and more detailed 3D dynamic analysis, where representative seismic time histories were developed and simulated indicate that meaningful liquefaction is not expected for a 1 in 5 000-year seismic event.

Project details