Gabion is a simple solution yet tackles a complex problem – soil retention. It is just a box made of hexagonal shaped double/triple twisted wire meshes. The box is then filled with anything that can retain the soil behind while keeping the system in place. Many fillers have been used in practice – stone, concrete block, geobags, compacted sand, steel slag etc. The boxes are placed side by side and in height one above another like steps. A geotextile is placed between the gabion boxes and backfill soil to protect the soil from being washed out.
Gabion boxes are made of low carbon steel wires. There are three types of wires in a gabion box.
|Wire Type||Wire Dia. (mm)|
These wires are heavily galvanized with Zinc coating with almost 250-300 gsm. These heavily galvanizing coating help the wire from being corroded. Gabion also has a unique double/triple twist pattern which prevents the structure from being torn apart throughout the whole area. However, there are many alternatives to soil retention systems like RCC Retaining Wall, Cantilever walls, MSE walls etc. Gabion has few advantages that makes it stand apart.
- It is flexible in nature, not rigid like RCC systems. This allows the construction easier and faster. Moreover, flexibility of gabions allows it to retain itself during differential settlement of soil. While in case of differential settlement, RCC structures may crack.
- Another important advantage of Gabions, probably the most significant one is its permeability. As the Gabion boxes are filled with relatively bigger size stones it allows the water from the soil to pass through the box. The geotextile layer behind the box allows the water pass through but keep the soil protected from being washed away.
- Gabion solution reduces the CO2 emissions up to 80% according to many studies. In this modern era of environment friendly solutions, Gabion solutions are indeed environment friendly.
- Gabion can promote vegetation if there is provision. This will be an added advantage regarding environment friendliness.
Gabions are flexible, environment friendly and a scalable solution. Especially in context of Bangladesh, in hilly terrains Gabions can be a good alternative solution to RCC retaining walls.