Geotextiles and geosynthetic solutions provider Kaytech recently supplied its drainage products to chrome-ore mining and smelting group Samancor Chrome’s Millsell operation, near Rustenburg, in the North West, to ensure proper drainage at the mine’s tailings dam.

Without proper drainage, the water pressure would have increased along the toe of the dam wall, causing water to seep through the toe and the wall. This increase in water pressure would also have resulted in a decrease in the shear strength of the material deposited and, ultimately, would have affected the stability of the dam, Kaytech says.

“Kaytech’s products are specifically suited to this application, as they are lightweight, compared with conventional drainage materials comprising stone, aggregate and sand, which eased transportation to site and reduced the carbon footprint,” states Kaytech marketing director Garth James, adding that this system is particularly suited to restricted access areas such as raised tailings storage facilities.

The synthetic filter drain was designed by Kaytech and mining solutions company Fraser Alexander using Zipcore, Bidim A6, Megaflo and Kaytape products from Kaytech.

James points out that only products manufactured or supplied by Kaytech were used for this installation, as their properties and performance are best suited to such installations.

“Kaytech’s products also did not have to be modified to suit the mining environment, as they comprise geosynthetic materials that are inert to the pH and chemical conditions [associated with] mineral tailings,” he adds.

Installation
Kaytech provided the materials for installation and Fraser Alexander’s tailings division, which has vast experience in this field, carried out the construction.

While Kaytech does not carry out the actual installation of its products at mine sites, it is involved in application suggestions relating to project design requirements and, should Kaytech’s application suggestion be accepted, the specification is drawn up to optimise Kaytech’s products’ performance and durability, James says.

“Kaytech only supplies its products to experienced and well-established contractors with whom it has a strong relationship,” he adds.

To prepare for Kaytech’s product installation at the Millsell operation, the area around the dam wall perimeter was first cleared, shaped and then compacted. A central longitudinal groove was then dug, into which the Megaflo pipe was inserted on top of the Zipcore sheeting.

ZipCore Pro N, which was laid on the prepared area, is a high strength, robust, preformed drainage system that comprises a 2-m-wide horizontally aligned, single cuspated, high-density polyethylene sheet.

The ZipCore sheeting acts as an impermeable barrier, directing the entrapped water flow to the spinal 150-m-deep Megaflo panel drain, comprising a high-strength slotted high-density polyethylene (HDPE) core, completely wrapped in a bidim geotextile filter, provid- ing optimum filtering performance in most soils.

The Megaflo pipe has a formed invert at the bottom of the panel to prevent loss of water into base soils and an open waterway with little restriction from support legs allows for high flow rates. The HDPE core provides high chemical resistance, which is especially important for leachate collection and heap-leaching applications. It is cost effective, easy to install and offers a subsoil drainage solution in a wide variety of applications.

The Megaflo panel drain and ZipCore sheeting were then covered with a layer of Kaytape S270, a heavy-woven geofabric that spans the Zipcore cusps, retaining an open flow path above the ZipCore Pro N system. The Kaytape S270 is complemented by a layer of Bidim A6, which was tucked underneath the sides of the ZipCore sheeting. Bidim A6 is a nonwoven, continuous filament needle-punched geotextile that has high drainage capacity in transmissivity and permittivity planes. Compatibility testing of the tailings and Bidim A6 was conducted in Kaytech’s laboratory, in KwaZulu-Natal, to select the most appropriate grade to ensure durability of the fabrics’ filtering capacity.

For the total project, Kaytech supplied 640 m of Megaflo piping and 3 000 m2 each of ZipCore, Kaytape and Bidim A6 products for the project.

Once the drain had been installed, coarse tailings were cycloned to cover and extend beyond the newly installed drain, ultimately forming the perimeter wall.

Water flowing from the new system into the collector drains, without signs of water seepage on the dam wall, proved the efficacy of the design and the performance of Kaytech’s products.

James points out that Kaytech previously installed similar systems at the Ergo Complex’s Brakpan tailings storage facility, among other sites, and that the system has attracted attention, especially from Australia, which might lead to further installations.