The use of earth retention structures has expanded in recent years as civil construction work has spilled over onto sites with irregular topography, especially related to transportation upgrades. Retention walls are used in place of simple earth slopes, generally dictated by the severity of grade change and the availability or cost of land within the project site.
Conventional construction methods use heavyweight objects to hold back the soil, such as concrete cribs and steel sheet piles. These conventional earth retention structures are cumbersome and require multiple components to overcome the passive earth pressures and resist erosion due to stormwater runoff. However, this costly and time-consuming process is not applicable in all scenarios; a more versatile and lower environmental impact solution is required.
3D geocellular vegetated walls
A natural alternative to steel or concrete walls are GEOWEB geocellular walls. They offer green aesthetic appeal and a flexible nature that can be designed for a variety of wall configurations and conformance to native landscapes. Readily adapted to a wide range of site conditions, GEOWEB retaining walls are particularly suited for foundation conditions composed of predominately compressible soils. Their relative light weight and flexibility allow them to perform better than solid-faced mechanically stabilized earth (MSE) walls in soft soils and seismic zones, as well as tolerate greater differential settlements than rigid walls.
GEOWEB wall sections are also light and easy to install. Conventional wall units are heavy and unwieldy, contributing to potential worker injury. An interconnected cell structure allows cutting of GEOWEB sections to fit around pipes, guardrails, trees, and other obstructions without compromising the system’s structural integrity. This flexibility also allows conformance to landscape contours for a more organic wall design.
A unique feature of multi-layered geocellular walls are their horizontal terraces and exposed outer fascia cells at the wall set-back. This creates a natural environment for selected sustainable vegetation to grow. The open fascia is also highly permeable — acting as multiple “planting pots” where rainwater can infiltrate, minimizing runoff. This allows design for low-impact development and green infrastructure. Where vegetation is not desired, aggregate infill maintains the system’s permeability.
The HDPE GEOWEB material tolerates environmental stresses — it resists cracking, spalling, and corrosion that degrades concrete, steel, and timber-based systems; and also resists chemicals and freeze-thaw action.
Flexible geocellular walls are adaptable to specific wall types, including:
- Steepened slopes — Layered wall structure without requirements for additional earth reinforcement when over structurally stable soil embankment.
- Reinforced walls — fully confined wall facing that is united with the backfill using a variety of tie-back systems (e.g., geogrids).
- Gravity walls — Completely configured with geocell layers; effective when tight space constraints do not permit the use of reinforcement layers.
Selection of the appropriate earth retention system is influenced by a number of factors, including surcharge loadings, wall height and batter, reinforcement requirements, site soil conditions, space accessibility and restrictions, availability of suitable backfill materials, project economics, and the desired aesthetics of the completed project. A project evaluation from the manufacturer can determine design feasibility.
Information provided by Presto Geosystems (www.prestogeo.com).