EM 1110-2-1100 (Part III)
30 Apr 02
h. Laboratory procedures.
(1) Several techniques are available to analyze the size of beach materials, and each technique is
restricted to a range of sediment sizes. Pebbles and coarser material are usually directly measured with
calipers. However, this is not practical for sediments smaller than about 8 mm. Coarse sieves can also be
used for material up to about 75 mm.
(2) Sand-sized particles (medium gravels through coarse silt) are usually analyzed using sieves. This
requires an ordered stack of sieves of square-mesh woven-wire cloth. Each sieve in the stack differs from
the adjacent sieves by having a nominal opening less than the opening of the sieve above it and greater than
the opening of the sieve below it. A pan is placed below the bottom sieve. The sample is poured into the top
sieve, a lid is placed on top, and the stack is placed on a shaker, usually for about 15 min. The different
grains fall through the stack of sieves until each reaches a sieve that is too fine for it to pass. Then the amount
of sediment in each sieve is weighed. ASTM Standard D422-63 (Reapproved 1990) is the basic standard for
particle size analysis of soils, including sieving sedimentary materials of interest to coastal engineers. The
application of D422 requires sample preparation described in Standard D421-85 (Reapproved 1993). The
wire cloth sieves should meet ASTM Specification E-11.
(3) Sieves are graduated in size of opening according to the U.S. standard series or according to phi sizes.
U.S. standard sieve sizes are listed in Table III-1-2, and the most commonly used sieves are shown in
Figure III-1-1. Phi sized sieve openings vary by a factor of 1.19 from one sieve size to the next (by the fourth
root of 2, or 0.25 phi units); e.g., 0.25, 0.30, 0.35, 0.42, and 0.50 mm.
(4) The range of sieve openings must span the range of sediment sizes to be sieved. Typically, about 6
full-height sieves or 13 half-height sieves plus a bottom pan are used in the analysis of a particular sediment.
If 6 sieves are used, each usually varies in size from its adjacent neighbors by a half phi; if 13 sieves are used,
each usually varies by a quarter phi. Normally, about 40 grams of sediment is sieved. More is needed if there
are large size fractions (see ASTM Standard D2487-94).
(5) Determination of sediment size fractions for silts and clays is usually not necessary. Rather it is
normally noted that a certain percentage of the material are fines with diameters smaller than the smallest
sieve. When measurements are needed, the pipette method or the hygrometer method is usually used. Both
of these methods are based upon determining the amount of time that different size fractions remain in
suspension. These are discussed in Vanoni (1975). Coulter counters have also been used occasionally.
III-1-3. Compositional Properties
a. Minerals.
(1) Because of its resistance to physical and chemical changes and its common occurrence in terrestrial
rocks, quartz is the mineral most commonly found in littoral materials. On temperate latitude beaches, quartz
and feldspar grains commonly account for more than 90 percent of the material (Krumbein and Sloss 1963,
p.134), and quartz, on average, accounts for about 70 percent of beach sand. However, it is important to
realize that on individual beaches the percentage of quartz grains (or any other mineral) can range from
essentially zero to 100 percent. Though feldspars are more common on the surface of the earth as a whole,
comprising approximately 50 percent of all crustal rocks to quartz's approximately 12 percent (Ritter 1986),
feldspars are more subject to chemical weathering, which converts them to clay minerals, quartz, and
solutions. Since quartz is so inert, it accumulates during weathering processes. Thus, feldspars and related
silicates are more commonly encountered in coastal sediment close to sources of igneous and metamorphic
rocks, especially mountainous and glaciated coasts where streams and ice carry unweathered sediment
III-1-14
Coastal Sediment Properties
Previous Page
