Landfill base lining systems provide permanent protection of soils and groundwater from the pollutants in a waste mass. Lining system requirements are often specified in national regulations and geosynthetics have become common components of these systems.
Geosynthetics fulfill the stringent containment parameters of landfill liner regulations. Geosynthetics provide an efficient, significantly effective and durable barrier for long-term environmental protection. But achieving this effectiveness requires proper design, specification and installation of the geosynthetic system. To remove waste for repair or remediation of an improperly designed or executed barrier system is technically difficult and expensive.
The geosynthetics utilised in a base lining system must be made from high-quality raw materials. The geosynthetics must be highly resistant to chemical and biological attack. For side slopes, the polymeric barrier must have the proper frictional characteristics for geosynthetic-geosynthetic and geosynthetic-soil. Understanding how to properly evaluate and select these materials will prevent unacceptable creep or the development of tensile stresses in the system. Creep and unpermitted stresses could lead to slope instability and possible failure.
The thickness of geomembranes in a base lining system is generally established in regulations. In the United States, for example, primary commonly call for 1.5mm HDPE geomembranes. In Germany, 2.5mm is standard, in other European countries such as the UK 2mm thick HDPE geomembranes are used. Compared to general construction solutions like an asphalt layer, both of these geosynthetic thickness ranges are significantly more cost-effective and they are far more impermeable and durable in containment.
In many countries, geosynthetic clay liners (GCLs) are also permitted to be used in a landfill lining system as an alternative to clay mineral layers. Systems may also include nonwoven geotextiles to protect impermeable barrier materials from installation damage and ballast-related overstressing. Protection layers are determined by the height of the landfill and the grain size and configuration of the drainage layer. Nonwoven geotextiles may also act as a separation and filtration layer between the mineral drainage layer and the waste.
Carbofol® HDPE geomembranes provide high chemical and biological resistance and exceptional long-term service lives for landfill security. Smooth-surfaced Carbofol® geomembranes may be used on slopes up to approximately 1:9. Structured (textured) Carbofol® geomembranes are used for steeper slopes.
Bentofix® geosynthetic clay liners are composite materials made of two layers of geotextile (cover and carrier layers) that encapsulate a core of highly swellable powder sodium bentonite. Needle-punching of the geotextiles in manufacturing firmly bonds the layers across the entire surface of the GCL. This prevents bentonite erosion and increases the durability of the material. Bentofix® GCLs are used as a mineral sealing layer in geosynthetic barrier designs.
Secutex® nonwoven geotextiles are mechanically bonded (needle-punched) to provide highly durable protection and long-term separation and filtration functionality. A variety of geotextile weights, such as 1.200g/m² and 300g/m², provides robust protection and optimal separation and filtration design usage. Secutex® enables engineers to specify the appropriate nonwoven to meet landfill performance needs and product approval authority guidelines.
Secugrid® and Combigrid® geogrids redistribute loads to stabilize and strengthen soil layers. This includes enabling the construction of steep embankments.