Stone revetments, a proven method of shoreline protection, are durable and can be relatively
inexpensive with a local source of suitable armor stone. Such stone should be clean, hard, dense,
durable, and free of cracks and cleavages. Figure B-3 shows a typical cross section of a stone rubble
revetment. Table B-1, which gives the required weight of armor units for a given design wave height,
was developed for a 1:2 bank slope and a stone unit weight of 165 lbs/ft3. If your bank slope is
something other than 1:2, find the value on Table B-2 and multiply the stone weight from Table B-1 by
this factor. Flatter slopes require smaller rock sizes. Table B-3 contains a second correction factor to be
applied when the unit weight (density) of the rock varies from 165 lbs/ft The tables contain an
illustrative example of their use.
Since it is not possible to obtain quarrystones of exactly the same weight, one must specify a range
of permissible sizes. For any given required weight, W, stones ranging from 0.75W to 1.25W can be
used, but at least 75% should weigh W or more. For example, if 100-pound stones are required, the
armor stones may range from 75 to 125 pounds, as long as 75% weigh at least 100 pounds. If graded
stone filter material is used, it generally will be much finer than the armor stone. An intermediate layer
of stone, between the armor and filter, one-tenth as heavy as the armor units (100/10 = 10 pounds in the
example), should provide the necessary transition to the filter material.
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