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 Surface Armor for Erosion Protection
broken into blocks by driving heavy equipment over them. Sizes of the
broken blocks will vary according to the thickness of the slabs and the
distance between scarification lines.
Careful quality control during construction is vital
to insure that
specifications are met.
7.2.4 RUBBLE FROM DEMOLITION
7.2.4.1 Description
The ideal rubble for erosion protection is a dense, durable material such as concrete
or asphalt with a size gradation similar to riprap.
7.2.4.2 Advantages
Rubble is economical, and recycles material that otherwise might be wasted.
7.2.4.3 Disadvantages
Even dedicated advocates of economy and recycling are likely to view rubble on a
stream as unesthetic at best. Leachates from some rubble may pose a water quality problem.
Since rubble is usually available only on a "take it or leave it" basis, it may be too
small and/or too large. Losses of finer material due to piping, overbank drainage, and
streamflow is likely. Conversely, larger rubble precludes attaining a uniform and efficient
layer thickness.
7.2.4.4 Typical Applications
Rubble would be considered where the justification for a more sophisticated but
expensive armor does not exist, suitable rubble is available, and the environmental
shortcomings are acceptable. It is often used in windrow form.
7.2.4.5 Design Considerations
Although precise control is likely to be impossible, the same general principles as for
riprap will apply to weight, gradation, and durability requirements for rubble. The layer
thickness should be equal to at least 1.5 times the maximum block size, although controlling
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