Several gold mining operations around the world have been using geosynthetic liners for the last thirty years for control and reinforcement applications. Probably, gold heap leaching operations are the main consumers of this type of products. Basically, the applications have been growing due to environment regulations and economical aspects. One important option in the liner selection are geosynthetic clay liners, which is a high quality and high-swelling sodium bentonite clay adhered or attached to manufactured geotextiles of flexible geomembranes. These liners have been manufactured for many years and the initial design was a double-lined landfill liner system.
Geosynthetic clay liners are fabricated in two types, unreinforced and reinforced liners. The first one are made using a special glue or pressure system and has a flexible geomembranes to hold the clay. This type of liner is employed on slopes gentler than 9:1 (e.g. heap leaching, reclamation caps). The second type are made by needle punching or stitch-bonding the top and bottom of geomembranes and the union between both geomembranes is a key aspect to improve the resistance to shearing.
The main properties of geosynthetic geomembranes are low permeability, better composite liner leakage protection, excellent resistance to desiccation, resistance to differential subsidence and freeze-thaw, and easy installation. It has been noted that geosynthetic clay liners are easy of construction respect to install compacted clay liners. Most manufacturers are used to prepare rolls 13.8 to 15.5 feet wide by 150 feet long. These rolls may weigh more than 1,500 kg and it is important to have equipment to handling the rolls. The liners are overlapped 15 to 22 cm depending upon the final application.
If the liner is not self-seaming, a thin layer of granular clay is added in the overlap seam at a typical rate of 100-120 g per lineal feet of seam. It is important to mention that field quality assurance is minimized with geosynthetic clay liners due to the quality of the burden is passed onto the liner manufacturer to certify that the product has the required performance properties. This is a much different scenario than constructing a low permeability soil liner where field characteristics have an impact on the life and efficiency of the liner.
The main application of geosynthetic clay liners are gold heap leaching processes, barren solution ponds, pregnant solution ponds, overflow ponds, waste water septage ponds, storm water ponds, diversion channels, secondary containment for tanks, tailings pond, waste rock deposition, solid waste landfills, and tailing impoundment caps.