Surface Armor for Erosion Protection
Advantages are: Flexibility to adjust to scour or settlement and still remain
in contact with the bed and bank is the most obvious shared trait. Most
mattress materials which are sold under trade names share another advantage
- they are available in various configurations, thus can be applied to a variety
of situations.
Flexible mattresses can be placed underwater with a relatively high degree of
confidence. If properly anchored to a geotechnically stable bank, they can be
placed on steep slopes.
They can be walked upon easily, thus are suitable for slopes used by
pedestrians.
Disadvantages are: Mattress components are subject to deterioration from the
elements and vandalism. However, the damage is often within acceptable
limits, and, since the various types are affected differently, identification of the
hazards enables the designer to select an appropriate mattress for a given
application. The construction of some types of mattress is labor intensive, and
may require skills not commonly available. However, the labor intensive
aspect may not be a disadvantage in all cases, and may be an advantage in
some cases.
Typical applications are: This compromise between adjustable armor and
rigid armor is most attractive when economical materials can be used for the
mattress. In fact, the origin of some variations can be traced directly to
creative use of local materials where no protective material of local origin was
adequate to withstand the erosive forces in a given application, and where the
most suitable method was the one which required the least amount of costly
imported material, a requirement which is often met by a flexible mattress.
Some types of mattress are suitable for use where erosive forces are so severe,
or construction operations are made so difficult by great depth and/or high
velocity of flow, that other types of armor are not effective or cannot be
placed reliably. An example is the articulated concrete mattress developed by
the U.S. Army Corps of Engineers for the Lower Mississippi River over the
last 60 years. The ACM has evolved into a highly efficient product placed by
specialized floating equipment adapted to operation under severe conditions
of velocity and depths.
Some types of mattress are suitable for use in areas which are to be used by
pedestrian or vehicular traffic.
Design considerations are: Beyond the general considerations discussed
below for the various types of mattresses, the manufacturers of commercial
mattresses have developed very detailed design guidance for their products.
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