Surface Armor for Erosion Protection
Rubble from demolition of pavement or other source;
Slag from steel furnaces; and
7.2.1 CONCRETE BLOCKS
The discussion here will focus on armor revetments composed of blocks which are
placed as individual components. Additional discussion of concrete blocks fastened together
in flexible mattresses is provided in 7.4.1.
A wide variety of block shapes and placement techniques can be used. Some have
evolved from engineering analyses, some from observation and empiricism, and some from
improvisation using readily available materials.
Blocks designed specifically for bank armor are commercially available. Forms for
casting concrete blocks locally are often available from distributors, and may be an
economical alternative to purchasing and transporting precast blocks.
Concrete blocks are durable, provide permeability for bank drainage, and are amenable
to complementary vegetative treatment. Most designs provide easy pedestrian access to
water's edge, and may be more aesthetic than other materials. Channel boundary roughness
is less than with many other techniques. Hand-laid blocks will fit irregularly shaped areas, and
do not demand access by heavy construction equipment.
A fabric or granular underlayment ("filter") is often required. Successful performance
of the underlayment is more critical than with a riprap armor. In areas of high turbulence or
waves, displacement of one block can lead to successive displacement of adjacent blocks.
If blocks are cast on-site, delays from inclement weather may be a problem.
At sites that are subject to theft or vandalism, blocks of an attractive size and shape
may suffer serious attrition.