Geosynthetics

At landfills, HDPE geomembranes with a thickness greater than or equal to 2.0 mm are used almost exclusively. In groundwater protection, HDPE geomembranes with a thickness of 1.0 mm are mainly used. In applications in tunnels, geomembranes with a signal layer are most often installed. Steeper slopes can be adjusted by installing geomembranes with structured surfaces. Needle-punched geosynthetic clay sealing liners with mechanically bonded nonwovens (300 g/m2) as cover and load-bearing geotextiles are particularly suitable for steeper slopes because they typically achieve higher interface friction angles compared to other geotextiles.

Sealing is necessary for the protection of the environment and groundwater and significantly contributes to the usability and service life of buildings. Geomembranes of different thicknesses, depending on the purpose, are used as barriers for liquids and gases, mainly in landfills, in tunnel construction and in hydraulic engineering. Geomembranes produced from different formulations of polyethylene (eg different densities) are usually used. Thicknesses are generally greater than 1.0 mm. Geomembranes are installed and welded by authorized installers. In areas with lower loads, plastic sheets with a thickness of 0.3 mm to 1.0 mm can be used, which is applicable for temporary covers and, for example, for pond applications. Geosynthetic clay sealing liners are used in specific areas, with bentonite performing the sealing function.

Products:

• Carbofol®
• Bentofix®

In order to enable the long-term drainage functionality of the percolation layer, filtration geotextiles are used to transfer shear stresses to the percolation layer. Mechanically bonded nonwovens (see filtration) are particularly suitable for filtration functions. Randomly interlaced mesh matrices are particularly suitable as drainage layers because they have a stable three-dimensional static structure. Shear stresses can be transferred without damage, thus maintaining long-term hydraulic efficiency.

Drainage includes the collection of precipitation, groundwater, and other liquids or gases that must be drained. Drainage systems are supplied as individual elements or composites consisting of at least one filtration layer and one percolation layer. The percolation layer takes the liquid and drains it away with minimal pressure loss. Surface drainage systems are often combined with sealing systems, for example in landfills, and in waterproofing applications, such as underground car parks or tunnels. Geosynthetic drainage systems replace expensive mineral drainage layers.

Product:

• Secudrain®

Mechanically bonded nonwovens are particularly suitable for this function because they adapt very well to irregular substrates as well as soft soils, thanks to their high elongation capacity. This ability to elongate is important to accommodate stone penetration. The fibers wrap around the stone and prevent damage to the structure of the non-woven material.

Geotextiles separate adjacent soil types or bulk materials, preventing them from mixing with each other. They are used in the form of durable, robust non-woven or woven fabrics and/or composites produced from synthetic raw materials that can withstand high loads. Common applications include road and railway construction, hydro engineering projects and the construction of equestrian and sports fields. The selection of the appropriate product depends on the grain size distribution of the base layer material and the expected operating loads.

Product:

• Secutex®

Thick mechanically bonded non-woven materials have proven to be very good protective layers. For example, Secutex® PP non-woven materials with a weight per unit area greater than 800 g/m² are used as the only protective layer for geomembranes. However, in areas of application where lower loads occur, mechanically bonded non-woven materials with a mass per unit area greater than or equal to 300 g/m² are used.

Geomembranes, coated and uncoated structures must be protected from mechanical damage. Without protective layers, there would be damage caused by sharp irregularities of the substrate or filling material. Non-woven materials and composites are used as protection against mechanical damage. Composites include nonwovens reinforced with woven materials, double-sided woven materials, and composite nonwovens with mineral fillers. The effectiveness of the protection depends on the thickness of the geosynthetics, their mass per unit area, as well as the resistance to perforations caused by impacts or compression. Nonwovens and composites are used in a variety of applications, including landfills and tunnels, to protect geomembranes. Such protective elements have also been successfully installed in the construction of pipelines.

Product:

• Secutex®

Mainly, geogrids and woven materials are used as reinforcement elements. Reinforcement elements, where the reinforced parts are made from strands of cut films (eg woven materials), are more susceptible to damage during installation than reinforcement elements made from polymer ribs with solid intersection points. In addition, stretched geogrids have smaller initial elongations compared to woven materials, for example, and therefore immediately transfer forces without elongation during construction.

When used for reinforcement purposes, geotextiles, geogrids and composites are placed under or between soil layers to absorb tensile forces and thereby improve mechanical properties. Preference is given to their use in a supporting structure based on the principle of “reinforced soil” or for stabilizing earth embankments on soils with poor bearing capacity. In many cases, this makes expensive structural measures, soil replacement or the installation of an additional soil layer unnecessary.

Products:

• Secugrid®
• Combigrid®

Mechanically bonded nonwovens are particularly suitable for this function if the thickness of the nonwoven is at least 30 times greater than the selected opening size. This has been established by inspections of mechanically bonded nonwovens that have been in use for relatively long periods. The thickness adapted to the size of the opening enables deep filtration and prevents the formation of a filter cake at the interface between the geotextile and the soil, which would reduce water permeability. This ensures long-term water permeability of mechanically connected non-woven materials adapted to the soil.

The geotextile filtration layer retains solid particles, while allowing liquids to pass almost freely perpendicular to the filtration plane. A distinction is made between the mechanical strength (holding capacity of soil particles) and the hydraulic efficiency of the filter, with the aim of achieving water drainage with minimal pressure loss.

The requirements can also be met with a mineral filter, but geotextile filter layers have proven to be the most suitable and economical alternative.

As with mineral filter layers, the thickness of geotextile filters can affect the long-term mechanical and hydraulic efficiency of the filter. Filters are mainly used in hydrotechnical and drainage systems.

Products:

• Secutex®
• Terrafix®

Because of their very good flexibility, mechanically bonded nonwovens are particularly suitable as they enable robust handling thanks to optimal stress/stretch behavior and adapt well to substrates. In addition, the flexible system optimally deforms during the impact of waves, absorbing impact forces. Three-dimensional needle punched nonwovens are also particularly resistant to abrasion.

In geotechnology and hydrotechnics, earth materials are specially “packaged” in flexible pipes, bags and containers. Here, geosynthetics perform the functions of separation, filtration, protection and/or reinforcement, depending on the type of application. Materials used include non-woven fabrics, woven materials, geogrids and composites.

Product:

• Soft Rock® (Terrafix®)

Erosion of slopes can be very effectively prevented by the use of interlocking mesh structures, especially during the vegetation phase, because the soil filled in the three-dimensional static structure of the random interlocking mesh is securely held in place and becomes relatively resistant to washing.

Three-dimensional geosynthetics and composites prevent the removal of soil particles due to the action of water and wind. In nature, plants prevent soil erosion with their roots. The natural process of forming layers of vegetation, which often takes years, can be accelerated and enhanced by the use of erosion control mats.

Product:

• Secumat®