Landfill cap – Functions

Typically, a drainage layer is required for all major landfill classes (I, II, and III). This layer sheds precipitation directly, to avoid the buildup of a hydraulic head on the capping system. The drainage layer must be permanently protected against clogging from the cover layer’s soil particles. Drainage geocomposites with three-dimensional matrices and filter geotextile cover layers control seepage and properly designed fulfil design requirements in landfill caps.

Geosynthetic drainage systems of this nature are sufficiently protected against the damage risk posed by cover soil installation. This enables the geosynthetic system to ensure the requisite long-term drainage function.

When installing a mineral drainage layer over a geosynthetic seal, a needle-punched nonwoven geotextile can replace the otherwise necessary sand protective layer atop a geomembrane. In these situations, one should also evaluate whether a filter/separation geotextile would be an optimal solution between the drainage layer and cover soil.

In landfill closure projects, it is increasingly important to utilise steeper slopes to minimize the soil-disturbing footprint of the site. The multi-layer nature of sealing systems, however, complicates this space-saving goal. It represents a particular challenge to the shear strength between layers. Here, textured geomembranes provide enhanced frictional characteristics for slope stability. Additionally, geogrids can be used to enable cost-effective, safe engineering of steeper slopes.

NAUE Solutions: Protection, Filtration, Separation, Drainage, Reinforcement

Secudrain® is a composite material with a polymeric drainage core and at least one nonwoven geotextile outer layer to provide filtration functionality. The geotextile prevents soil particles from disrupting the pressure and flow of draining liquids. Installed atop a geomembrane, the geotextile side of the composite can act simultaneously as a protection layer. In Germany, the use of Secudrain® has been approved by BAM for Landfill Directive-guided systems.

Secutex® is a mechanically bonded (needle-punched) nonwoven geotextile that can be used as protection/cushioning or as a separation geotextile in landfill sealing systems. In Germany minimum requirement for the mass per unit area for a protection geotextil is 800g/m². For separation and filtration, the nonwoven must be 300g/m².

Secugrid® geogrids minimize or eliminate settlement and redistribute loads. They also enable the construction of steeper embankments. For reinforcement applications in landfill projects, NAUE Secugrid® meets BAM requirements.