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In the design and construction of earth retaining systems, the use of geosynthetics has become essential. Geosynthetics often deliver durable, economical and flexible solutions when compared to alternate gravity structures.
Typical categories of earth retention systems include reinforced soil slopes, embankments and retaining walls. These systems use geosynthetics to mitigate for erosion, improve drainage and filtration, and for soil reinforcement.
Geosynthetics that are typically used include geotextiles, geogrids, geocells, geonets and erosion control products. Some materials are combined into a composite product, for instance geotextiles and geonets which become a very efficient drainage blanket.
These products interact with the surrounding soil. For instance, geogrids and geotextiles act as tensile elements within the reinforced fill, creating a composite material, similar to how steel reinforcement improves the behavior of concrete.
This composite behavior is referred to as mechanically stabilized earth (MSE). MSE is used for walls, embankments and slopes, as well as other geosynthetically reinforced soil applications such as pavement bases and load-transfer platforms. In earth-retention applications, horizontal reinforcement elements are connected to a facing component to provide confinement and to facilitate placement and compaction of select backfill.
For steeper and more exposed structures, facing and surface measures also provide protection from weathering and erosion. These systems can be constructed to significant heights and can carry large loads.
Retaining wall facings are typically rigid elements such as concrete panels and modular blocks. More flexible components such as wire baskets, geosynthetic wraps or gabions are used as well when greater deformation tolerances are required or when aesthetics are not critical. This is one of the primary benefits of using more flexible MSE-type structures. This allows their use, in many cases, without additional foundation improvement which can significantly improve schedule, cost, and performance.
Slopes typically use flexible facing elements because there is little to no surcharge load near the face; the primary concern is erosion control and long-term weathering. Slopes with inclinations of approximately 45 to 70 degrees typically require a form system to support the placement and compaction of the fill. Typical components used to form the face and contain the fill include wire baskets, geocells, and gabions. Depending on local climate and project requirements, slope faces may be vegetated or a hard facing.
A primary benefit of geosynthetics is their low weight, which makes them easy to handle and transport. Combining geosynthetics with locally available soils can reduce project costs and improve sustainability. This is particularly important in remote locations, where steeper reinforced structures can minimize footprint, excavation and the volume of imported materials.
These advantages reduce truck traffic, fuel consumption and construction time which in turn improve project efficiency while supporting sustainability. Together with their ability to accommodate deformation, these benefits have made geosynthetics a standard solution for earth retention systems.
For additional information, see:
- Design and Construction of Mechanically Stabilized Earth (MSE) Walls
- GEC 11, FHWA-HIF-24-002
- Reinforced Soil Slopes
- Geosynthetic Design & Construction Guidelines, August 2008, Publication No. FHWA-NHI-07-092
Daniel Alzamora, P.E., is a contributing editor for Geosynthetics and has spent more than three decades in the geosynthetics industry in both the public and private sector.