CETN-III-4
Revised
3/85
and
C>2B
Figure 1 - Dimensions of quarry-
Figure 2 - Special placement method
stone required for use of
special placement method
armor units one at a time, or dumping by skiff, above and below water, present
the engineer with a difficult design problem. The extent of interlocking
achieved is unpredictable when using randomly sized (but still within speci-
fied limits) quarrystone. Generally, in specifying quarrystone armor units,
the dimensions of the maximum axis are no greater than 3 times the minimum
axis. This applies only to armor stone, as this ratio was devised to fore-
stall the use of flat or plate-like stone which, if laid flat on the structure
slope, would be less stable than a more cubic stone. It is rather obvious
that the greater the care in placing and obtaining a higher degree of
interlocking the higher the stability coefficient KD (Jackson 1968).
Because of these unpredictable variables, all methods of placement, except for
uniform and special placements, have been lumped together in the SPM to
encompass the range of placement methods.
This provides a conservative
structure design.
Many Corps of Engineers field offices use selected
SELECTED
PLACEMENT:
placement to increase structure stability.
Selected placement is the careful
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