Geology Reference
In-Depth Information
medium —passes a No. 10 (2.00-mm) sieve and is retained on
a No. 40 (425-µm) sieve.
fine —passes a No. 40 (425-µm) sieve and is retained on a
No. 200 (75-µm) sieve.
(8) Silt —soil passing a No. 200 (75-µm) sieve that is nonplastic or
very slightly plastic and that exhibits little or no strength when air
dry. For classification, a silt is a fine-grained soil, or the fine-
grained portion of a soil, with a plasticity index less than 4, and the
plot of plasticity index versus liquid limit falls below the “A” line
(see Figure 11-3).
The visual-manual procedure covered in this chapter for describing
and identifying soils utilizes the following group symbols (see Chapter 11
for more details):
G
gravel
S
sand
M
silt
C
clay
O
organic
PT
peat
W
well graded
P
poorly graded
Normally, two group symbols are used to classify a soil; for example,
SW indicates well-graded sand. ASTM D 2488-00 provides “Standard
Practice for Description and Identification of Soils (Visual-Manual
Procedure).”
Pocketknife or small spatula
Small test tube and stopper (or jar with lid)
Small hand lens
Water
Hydrochloric acid (HCl), small bottle, dilute, one part HCl (10 N) to
three parts distilled water
APPARATUS AND
SUPPLIES [1]
Note —Unless otherwise indicated, references to water mean
water from a city water supply or natural source, including
nonpotable water. When preparing the dilute HCl solution,
slowly add acid to the water, following necessary safety pre-
cautions. Handle with caution and store safely. If the solution
comes in contact with the skin, rinse thoroughly with water.
Do not add water to acid.
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