Controlling erosion on highway slopes

TERRAM geocells are three-dimensional blankets of interconnected cells which are placed on slopes, secured in position using pins, and filled with friable topsoil.

The geocells are supplied flat packed, ready to be opened out into their distinctive honeycomb array. Once installed, a geocell provides immediate stability by confining the fill and greatly improves resistance to wind and run-off.

With a topsoil fill, the stability is further enhanced as vegetation becomes established and a geocell can be used to establish vegetation on slopes where establishing cover would otherwise have been a problem. The honeycomb of cells provides protection for the vegetation during the early, sensitive period of germination and growth.

The cells are formed from geotextile to confine the fill and the permeable walls allow drainage from cell to cell down the slope. Other geocells achieve this cell-to-cell drainage by perforating the walls but this process can lead to weaknesses. Geocells fabricated from impermeable materials suffer from weiring - water cascading down the slope from cell to cell – and this causes ongoing loss of soil from the cells.

Many variables affect the installation and performance of a slope-protection geocell, including slope angle, slope stability, the infill type, rainfall levels and irrigation (if included). It is important therefore that due consideration is given to all relevant criteria on a project by project basis.

Typical applications include:
• Cuttings and embankments
• Noise-deflection and environmental bunds
• Abutments
• Steepened slopes
• Soil nailing cover
• Drainage ditches
• Balancing ponds

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