Geotextiles and geosynthetic solutions provider Kaytech supplied 100 000 m2 of its heavy-duty high-density polyethylene (HDPE) Geocell reinforcement structures to London-listed Glencore’s Tweefontein complex, near the town of Ogies, in Mpumalanga, to reinforce two newly designed canals, which form part of the complex’s stormwater system.

The two adjacent canals, each 2.8 km long – one to channel dirty water and one to channel clean stormwater away from the workings at the mine – were constructed to ensure that there is no unnecessary contamination of the stormwater flowing through the plant and mining area.

The project, which started in March 2012 and will be completed at the end of this year, forms part of Glencore’s Tweefontein optimisation project.

Covering 113 km2, the Tweefontein complex consists of three differently structured coal mines. Coal is sourced from either opencast or underground mines, with contractor mining used at the opencast operations and continu-ous miners used in the underground mines.

A challenge during the project was that the canal system had to run through marshy areas. This factor prompted the main project contractor, the G4 Civbuild joint venture, to source a form of reinforcement that would prevent any movement over time and securely hold the concrete in place.

Project management company DRA Mineral Projects, which was appointed by Glencore to design the stormwater system, recommended the use of a heavy-duty Geocell for the project and Kaytech’s 80 mm and 100 mm HDPE Geocells were thus specified.

The Geocell is a honeycombed structure, manufactured from strips of a robust HDPE plastic that are welded alternately together to form three-dimensional diamond-shaped cells. This provides a strong structure that does not collapse when filled with concrete.

The sidewalls of the Geocell are textured and perforated for improved interlocking between adjacent cells.

Since the canals had to pass through areas containing clay, the flexibility of the HDPE Geocell system was ideal. Hydrostatic pressure is relieved through its joints, enabling the Geocell to be installed in high-water-table areas and, because of its geometry, it distributes vertical load and behaves like a semirigid slab, thereby limiting embankment and/or road settlement.

Since the Geocell can be used over soft compressible soils, or used to limit the thick-ness of the required subbase layer, no specific foundation was needed for this project.

A 17% cost saving was achieved using the Geocell on the project as opposed to using conventional mesh-reinforced concrete.

In addition to this saving, the canal was constructed significantly quicker, as the project team did not have to construct every second panel and return later for curing and jointing purposes.

The Geocell provides a flexible, effective erosion protection treatment for hydraulic structures, such as channels or canals, and can also be used as an on-site shuttering to cast continuous interlocking concrete paving for road construction.

A benefit of using Geocells is that the failure of a single cell does not compromise the integrity of the rest of the honeycomb structure, as it can be easily repaired.

The Tweefontein Waterpan mine produces 4.5-million of saleable tons of coal a year, which is exported through the Richards Bay Coal Terminal, sold domestically as well as to State-owned power utility Eskom.