Surface Armor for Erosion Protection
7.3.5 CHEMICAL SOIL STABILIZATION
A number of commercially available products, including lime, can be used to increase
cohesion of soil particles or to provide a hard film at the soil surface. Under favorable
conditions, even those products which eventually break down upon exposure to the elements
may be effective in providing erosion protection until vegetation becomes established.
Because specific site conditions can greatly affect performance, the feasibility of this
approach and appropriate design guidance for a particular project can be determined only by
obtaining evidence of satisfactory performance under similar conditions from previous users
or from the manufacturers.
7.3.6 CLAY BLANKET
When the upper slopes of a bank are exposed to small erosive forces, but the existing
soil has insufficient cohesion to resist them, it may be effective, environmentally beneficial,
and economical to utilize a clay blanket instead of a structural armor. The cohesive properties
of the clay provide resistance to erosion, and its moisture holding properties may enhance
vegetative growth. This approach would be prudent only on projects where the consequences
of failure in the event of unfavorable streamflow or weather conditions are low, or where
adequate monitoring, and reinforcement if required, are assured.
7.4 FLEXIBLE MATTRESSES
The following paragraphs outline the general description, advantages, disadvantages,
typical applications, and design considerations for most flexible mattresses used as a bank
stabilization method:
The basic concept of a flexible mattress is that material or objects which
cannot resist erosive forces separately can be fastened together or placed in
a flexible container to provide adequate resistance to erosive forces, while
partially retaining the desirable characteristics of adjustable armor, especially
that of flexibility.
The most common flexible mattress materials are:
Concrete blocks;
Fabric; and
Gabions.
Materials which have a more limited use are:
Grids (for confining earth or other fill material);
Used tires; and
Wood.
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