achieve their blocky shape, but this was not necessary. When installed properly, stacked bag groins have
performed well. They should only be considered a short-term solution, however, when filled with sand.
Gabions. Gabions were described earlier in the revetment section. When used to construct groin,
the gabions should be underlain with filter cloth to inhibit settlement and all baskets should be made
from PVC-coated wire mesh. They must be tightly filled to eliminate deformation and possible breakage,
and the tiers of baskets should be wired together to prevent shifting of the upper tiers over the lower tiers.
As with other structures, adequate toe protection is required to prevent settlement and basket distortion.
Thin gabion mattresses are ideal for this purpose.
Steel Fuel Barrels. The use of steel fuel barrels for construction is economical only in remote
arctic areas where corrosion rates are low, and used barrels are readily available and have no other
salvage value. Barrel groins have worked well where littoral transport characteristics are suitable for
shore stabilization with a low groin. When used to construct a groin, the barrels should be completely
filled with gravel to prevent crushing by ice floes or damage from floating debris. For additional
strength, the barrels should be capped with concrete. Also, they should be entrenched sufficiently to
prevent undermining by scour on the downdrift side.