Spurs and dykes
Gabions
Gabions are rectangular wire cages containing rocks or
boulders. They are easily constructed units large enough
and heavy enough to remain stable in moving water.
These are the basic building blocks for spurs and dykes
and can be made locally by hand although this is
physically demanding for people doing the work. Either
square mesh or hexagonal mesh is used. Hexagonal mesh
is intrinsically stronger but more difficult to construct by
hand. If a simple rectangular mesh is used then there is
a tendency for the mesh to unravel, even if only a single
wire is broken, which will result in premature failure of
the structure.
Practical Action
Figure 5: Making gabion cages by
hand with a square mesh.
Photo: Practical Action Nepal
Figure 6: A basic gabion before loading with stones
Illustration: Practical Action / Neil Noble.
Figure 7: Hexagonal wire mesh with three twists.
Illustration: Practical Action / Neil Noble
Woven double twist or triple twist
design is used in commercial gabion
construction. The cost of commercial
gabions can be prohibitive to many
remote communities so alternative
approaches have been developed in a
number of regions. Hexagonal mesh
gabions can be made locally with
hand tools.
This hexagonal design can be
replicated using galvanised (zinc
coated) steel wire with a diameter of
2.7mm and simple tools such as vice
grips and jig to help construct them.
The hexagonal mesh size should be
approximately 10 to 12 cm. Heavier
wire can be used along the corners
and edges (4mm) to strengthen them.
For example in Sri Lanka a jig was
developed to improve local
manufacture of hexagonal mesh
gabions. The design of the jig used
steel pegs positioned on a metal back
plate allowing for flexibility in the
construction process (Figure 10).
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