Old factory sites and abandoned industrial areas are often redeveloped for new uses by the reclamation of the contaminated area. Geosynthetic systems are an effective solution to prevent the discharge or emission of contaminants into the environment.

Complete geosynthetic solutions from NAUE save natural building material resources while making expensive processing of rubble and decontamination measures unnecessary.

Encapsulation of contaminants

The encapsulation of polluted areas is necessary to prevent the
discharge of contaminants. To ensure long-term effectiveness of the
liner system, high-quality geosynthetic materials should be selected and
rigorous construction practices should be followed. This is achieved
with the installation of quality-assured, 2 mm thick (80 mil) Carbofol®
high-density polyethylene (HDPE) geomembranes. Carbofol® HDPE
geomembranes are produced to the highest quality standards and have the
chemical resistance necessary to contain contaminated soils or liquids.
Secutex® protection nonwovens and Secudrain® protection and drainage
systems guard the Carbofol® geomembranes from damage. Secugrid® geogrids
are used to prevent settlement or deformation of the contaminated
subsoil. These products protect the other liner components from damage
during the installation process as well as over the operational life of
the liner system under subsequent long-term loads.

When the geosynthetic liner system will be subjected to high normal
loads, the efficiency of a protection or cushioning material is tested
in a cylinder test (EN 13719). The results of this test determine the
minimum mass per unit area that should be used for the protection
component. Under lower confining stresses, a minimum mass per unit area
for the protection component of no less than 800 g/m² is recommended.

  Design cross sections

 

Due to the location and topography of many remedial sites, construction on steeper slopes is often necessary. With structured Carbofol® geomembranes, the frictional requirements of demanding steep slope applications can be accommodated. With the proper selection and product specification, the long-term performance and optimum transmission of shear forces is assured. As a replacement to compacted clay liners, Bentofix® is also well suited for the encapsulation of contaminated areas.

By means of needlepunching, the high-swelling sodium bentonite sealing layer is safely encapsulated between the cover and carrier geotextiles, fully capable of long-term transfer of shear forces through the fibre reinforcement. The robust cover and carrier geotextiles used in Bentofix® are designed to resist the physical stresses of the installation process and prevent damage to the seal. Depending on the existing soil conditions and slope lengths, the cover and carrier nonwoven geotextiles also make many applications possible, such as with slopes greater than 2.5h:1v.

Earth stabilisation

In some cases, a contaminated area has no bearing strength and conventional construction methods are not possible. In these instances the liner system must be capable of supporting itself and the overlying soils.

In dredged lagoons for example, the area to be sealed cannot be subjected to vehicle or pedestrian traffic due to the lack of bearing strength in the “subgrade”. By first deploying Combigrid®, a monolithic extruded geogrid with an integrated nonwoven geotextile, it is possible to traffic over the surface immediately after installation or upon the placement of a mineral levelling layer.

Combigrid® provides long-term stabilisation of soft subgrades by distributing the overlying loads and provides a firm foundation for subsequent layers of fill or other geosynthetics.

As compacted clay liners are difficult to construct, and can form preferential flowpaths with only small amounts of deformation, Carbofol® geomembranes or Bentofix® geosynthetic clay liners are the materials of choice when lining over soft subgrades.

Decommissioned industrial and mine sites with abandoned shafts, underground voids and inhomogeneous areas with low bearing capacity require an encapsulation system that ensures sufficient load distribution in the event of changing subsoil properties.

Secugrid® geogrids are especially well suited for these applications due to the ability of the grid mesh to interlock with the subsoil. The low initial elongation enables Secugrid® to immediately transfer or distribute stresses between the geogrid and subgrade or cover material.

With complete geosynthetic solutions from NAUE, highly efficient, thin-profile sealing and drainage systems can be installed that do not require substantial excavation and recompaction or the placement of voluminous mineral layers.

Slope stability

When remediating areas on steep slopes, Secugrid® geogrids can support the down-slope forces in most situations while protecting the sealing elements from potentially harmful stresses as in landfill applications. On steep or long slopes, Secugrid® geogrids can be used to improve the stability of soil veneers or entire lining systems.

Conclusion

Complete geosynthetic solutions from NAUE are more economical than expensive in situ treatments or excavation and removal techniques. If the available “airspace” or construction volume is limited, geosynthetic solutions from NAUE offer high performance in a thin profile system. Carbofol® geomembranes and Bentofix® geosynthetic clay liners are cost-effective sealing products that are more efficient as well as more economical than conventional compacted clay liners. With Secudrain® drainage systems, additional “airspace” can be recouped by effectively replacing mineral drainage layers that are typically 300 – 500 mm thick.

The high tensile strength of Secugrid® geogrids enables the construction of space-saving steep slopes. By using Combigrid® with its rigid junctions and integrated Secutex® geotextile, even extremely soft subsoils can be built upon.