Slope Protection with Gabion Sluice Reinforcement

Gabion walls are used mainly to retain soil behind the wall, but they also work as facing or cover walls. The wall is built from gabion baskets laid in one or more rows, depending on its height. Each basket is a cage closed on all sides, made of galvanized hexagonal mesh and filled with broken rock. Stacked in a planned layout, the baskets form retaining structures that are an alternative to concrete for soil stabilization. A non-woven geotextile is normally placed behind and under the baskets so that soil is not washed out through the stone.

Gabions protect ground from water damage and give vegetation a stable place to grow. They are widely used for slope protection, in five main forms: retaining walls, slope protection, bed (bottom) protection, toe protection and buried stone blankets. Gabion structures are stable and hold together under load, prevent soil erosion and keep the topsoil, and its nutrients, in place for plants.

Slope Protection with Gabion – functions

Gabions are used for slope protection in several ways:

Retention structures

Gabion retaining structures hold back soil on slopes, and because they are free-draining, they stay stable through heavy rain and snowmelt.

Dams

Gabion check dams slow runoff in gullies and streams and trap the sediment it carries. With an impermeable lining, gabions can also form small dams that store water.

Retention ponds

Gabions line the banks of ponds to stop erosion and damage to the surrounding area.

Erosion Control

Gabions and gabion mattresses protect riverbanks, channels and slopes for erosion control.

How Gabion Retaining Walls Moderate Landslides

Besides protecting slopes, gabions are used to reduce landslide risk. In landslide-prone areas, gabion check dams are built across gullies and drainage lines. They slow the water and control where it flows, so the soil does not become saturated and break away. Gabion walls at the toe of a slope add weight and support while letting groundwater drain freely, which keeps the soil in place.

The construction for the sluice reinforcement with gabion walls

• Clean the gabion slope

Clear trees and weeds from the slope as per the design. If the excavated ground does not match the geological investigation report, revise the design to suit the actual ground conditions.

• Install the gabion

Unfold the gabion on firm, level ground, keeping the folds neat, and place it tight against the prepared surface. Avoid damaging the mesh and its coating, and check the assembled shape matches the design. The binding wire lashing length is about 200 mm to 300 mm.

• Filling the gabion

The fill has to meet the material standard in the design. Fill the gabions one by one, and pack the gaps between stones as you work, before the lid is closed. Stone size should be about 1.5 to 2 times the mesh opening (so it cannot pass through), and the filled density should be more than 1.7 t/m3.

• The cover for the Gabion

Once the stone filling is done, level the top surface. Check that the gabion edges are straight and neat, then close the lid and lace it down.

• The gabion construction

Detailing matters: binding intervals should not exceed 20 cm. One typical fill specification calls for stone 90–150 mm in size with 50% of the stones larger than 120 mm; smaller stones used to pack the gaps should be at least 30 mm, and sand content should be below 5%. Make sure the filling is dense and matches the design.

• The sand is filling the gap

After the gabion has been inspected and approved, fill sand into the voids until it stops settling.

• The quality control for the Gabion box

Check that the mesh opening used on the slope matches the design. The front, back and end panels should stand vertical, and the lids should be laced securely to the sides and diaphragms. Build up course by course in sequence, from one end to the other, and place topsoil in the upper gabions where the slope is to be vegetated.

The advantages/Benefits of the gabion

Gabions withstand wave impact and can resist flow velocities up to about 6 m/s, depending on thickness and stone size. Because the structure is flexible, it settles with scour at its base instead of cracking the way masonry and plain concrete do.

Gabion structures are flexible yet stable: the mesh stretches and the basket deforms without losing strength.

Gabions resist corrosion. Where the water is aggressive or the river is polluted, PVC- or PE-coated galvanized wire is used, which gives a long service life by protecting the steel from corrosion.

Gabion boxes are simple to install. No cement, electricity or formwork is needed, work can go ahead in any weather, and the fill stone can come from local sources.

Using local stone and simple labour keeps construction costs low.

Gabions do not disturb the local ecology. They blend in with vegetation, which suits urban riverfronts, and plants can be grown in the gabions themselves to strengthen the bank against erosion.

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