In solid-waste containment applications, ensuring the stability of the waste mass, the lining system and subgrade are critical to the success and longevity of the solution. Liners with a textured surface can improve the friction strength between the liner and the subgrade, or between liners in multilayer systems, thereby improving slope stability. But which liners offer the best outcomes?
The World Bank conservatively estimates current global waste generation at 1.3 billion tons per year for municipal solid waste alone. This is expected to increase to approximately 2.2 billion tons by 2025. With steep side slopes increasingly standard in landfills – as owners strive to increase capacity and revenues – a number of liner characteristics become important.
Landfill cell liners and closure solutions are massive, critical projects. While the geosynthetic-liner solution represents a small fraction of the overall cost, it is the greatest defense in a landfill, forming a powerful barrier between pollutants and the environment. It also contributes significantly to the stability of landfill structures.
For geomembrane, liner thickness, asperity height (the maximum variation in height between peaks and valleys on a given surface), interface-shear strength, seam integrity, and several other considerations all play a role in containment design. Decisions on the most appropriate lining system will also depend on factors such as the need for filtration, surface runoff and gas drainage, seepage prevention, and leak detection. In addition, the ability to accommodate differential settlement and gas venting – along with resistance to heat and corrosive, flammable and poisonous materials – need to be taken into account.
Geosynthetics are recognized for their ability to create safe and cost-effective barrier solutions. Geosynthetic clay liners (GCLs) act as a secondary or tertiary barrier, while geomembranes are used as primary and secondary barriers. However, in terms of stability (i.e. stability of the lining system on slopes), research1 has shown that a higher texture density provides the best performance in terms of achieving higher frictional resistance.
At a slope of approximately eight degrees the friction angle becomes critical, and your system could begin to slide. Textured membranes can give a friction angle of up to 35 degrees, improving the opportunity to design much steeper slopes.
