Geosynthetics for retaining walls

With complete geosynthetic system solutions, noise barriers, retaining walls, reinforced embankments or other structures with inclinations of up to 90° can be built.

Reinforcement

The use of Secugrid® geogrids for the reinforcement of steep walls and retaining structures is necessary in cases where the shear strength of the soil material alone is insufficient to provide the required stability. Uniaxial Secugrid® R geogrids are designed, and especially well suited, for this purpose. They are made from high strength polyester (PET) or polypropylene (PP) resin which has been extruded into flat monolithic bars, and welded together to create junction stiffness.

This special grid design provides an immediate interlocking with the surrounding soil. Its frictional properties further enhance the structural strength of the application. Secugrid® is designed to accept high construction stresses with low elongation, as it is necessary to minimise unacceptable deformation. A tensile strength of up to 400 kN/m can be achieved with an extremely low strain at failure of ≤ 8 %.

In addition to bearing capacity as well as frost and drainage behaviour, the bond strength and robustness of the reinforcement should also be taken into consideration when installing the backfill. The required compaction of the backfill material will typically create high installation loads. Due to their large surface area and as demonstrated in numerous tests as well as field trials, the flat monolithic bars of Secugrid® are extremely robust and resistant to dynamic installation loads.

Secugrid® geogrid design and specification recommendations are available in our Secugrid® Design Manual.

Construction of a wall facing

To create low impact structures that blend into the landscape, there are different types of faces for reinforced steep slopes and walls that can be constructed. For steep reinforced slopes with inclinations up to 45°, Secugrid® can be installed horizontally, without special face elements. For protection against potential wash-out of the fill soil between the reinforcing layers, a filter-stable soil or Secumat® erosion control mat infused with grass seed is especially well suited.

On steeper slopes with inclinations up to 60°, the enveloping method for Secugrid® geogrid installation is necessary. To facilitate this construction technique, temporary or expendable formworks must first be installed. To prevent erosion or soil wash-out, it may be necessary to use a Secutex® nonwoven geotextile on the inner side of the reinforcement. The filter stability calculation of Secutex® is described in the chapter “Filtration with geotextiles”. Using vegetated Secumat® erosion control mats may also prevent soil washout.

The facing of steep walls with inclinations of up to 90° can also be designed to use natural stones, gabions, broken rocks and prefabricated concrete units. If one of these me thods is desired, it should first be determined if these materials can be vegetated. The outer face/geosynthetic connection is made with either factory-made connections or with special clamping or on-site fastening methods.

Foundation of massive face elements

Foundation requirements for massive face elements are described in the different national recommendations for geosynthetic reinforcement. In principle, the general engineering standards for earth and concrete construction are valid. In wrap-around walls, a special foundation is not typically required.

Conclusion

The robust Secugrid® products excel with their superior chemical resistance, low creep tendency, and their extremely low elongation (high initial modulus). Secugrid® geogrids, Secutex® filter non wovens and Secumat® erosion control mats are all used for the construction of reinforced steep slopes and walls. These geosynthetic systems are easy to install compared to con ventional construction techniques and can accommodate differential settlement without any damage. The wall facing can also be connected to the geosynthetics without performance complications.