Gabion systems NEED GEOTEXTILES As soil separation, drainage, water filtration and allied protection interventions, geotextiles play crucial roles in the overall integrity and performance of gabion systems. The starting point is a soil analysis, followed by optimal design, correct product specification, and best practice installation techniques, says Louis Cheyne, managing director, Gabion Baskets. By Alastair Currie
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here are two main types of geotextile employed in the construction of gabion structures that enhance their structural stability – namely woven or needle-punched non-woven, which are produced using materials like polyester and polypropylene. Both materials are designed to provide some form of controlled permeability since a typical gabion basket is composed of 35% voids and 65% rock. Non-woven mesh products are ideally suited for sandy soil-type environments, plus riverine structures. Examples include bridge abutment protection, weirs, riverbank erosion control and retaining walls. Here, these non-woven geotextiles are highly effective in countering the migration of fines that would otherwise undermine these structures. They can also perform optimally in reducing water velocity below and around submerged gabion systems. In contrast, woven geotextiles are better suited to soils with a high plasticity. Clayey soils are a prime example. Where the
Laying geotextile sheets is the essential starting point for ensuring a sound base on which to build gabion basket and/or gabion mattress structures
Geotextile installed behind and below this gabion wall structure helps to prevent soil loss that could potentially undermine the structure
plasticity is very high, however, a geotextile may not be required, but the soil analysis will determine this. “Installing a non-woven mesh in a clayey scenario will result in progressive clogging of the liner via fine particle build-up over time. This will make the geotextile progressively impermeable. Subsequent water pressure build-up could then potentially push over the structure,” Cheyne explains. Gabion Baskets provides turnkey solutions for all projects. This scope encompasses the manufacture of gabion baskets and/or gabion mattresses, the supply of specialist geotextiles, plus the rock fill material. Design recommendations, plus contractor and installer training are also provided.
Selecting the right liner specification Choosing the right geotextile layer thicknesses and strength is essential. The general specification supplied by Gabion Baskets ranges between 200 g/m2 and 270 g/m2. As Cheyne points out, lighter-weight fabrics at around 140 g/m2 are fine for roadway and sports field subsoil drainage, but far too thin and lightweight for gabion installations. “The most common fill source is blasted rock from a commercial quarry,” Cheyne explains. “These rock fragments tend to be angular in shape, often with sharp edges that
