(a) Sands Containing Little or No Fine Material. Sands made up of less than five percent, by
weight, of fine particles (materials with diameters less than the size of the openings in a Number 200 sieve) may
be classified as well-graded or poorly graded.
Well-Graded Sands. Sands that contain a relatively uniform distribution of a wide range of
particle sizes are referred to as well-graded sands or gravelly sands. As previously mentioned, well-graded soils
are symbolized by attaching the letter "W" to the symbol for the predominant soil type; therefore, the symbol SW
signifies a well-graded sand.
Poorly Graded Sands. Sands that do not contain a relatively uniform distribution of a wide
range of particle sizes are said to be poorly graded. As stated previously, poorly graded soils are symbolized by
attaching the letter "P" to the symbol for the predominant soil type; therefore, the symbol SP signifies a poorly
graded sand or a gravelly sand.
(b) Sands Containing Appreciable Amounts of Fine Material. Sands made up of greater than 12
percent, by weight, of fine particles may be further classified based on the predominate type of fines present.
Silty Sands. A sand containing greater than 12 percent, by weight, of fine material, with silt
being the predominant type of fine present, is called a silty sand or a sand-silt mixture. Because the letter "M" is
used to represent silts, silty sands are designated by the symbol SM.
Clayey Sands. A sand containing greater than 12 percent, by weight, of fine material, with
clay being the predominant type of fine present, is called a clayey sand or a sand-clay mixture. Because the letter
"C" is used to represent clays, clayey sands are designated by the symbol SC.
(c) Sands Containing Moderate Amounts of Fine Material. Sands that contain between 5 percent
and 12 percent, by weight, of fine material are considered to be borderline soil types and are assigned a dual
symbol. For example, such a soil with a well-graded coarse fraction and a fine fraction predominantly composed
of silt would be identified by the symbol SW-SM. Other possible soil types are SW-SC, SP-SM, and SP-SC.
b. Fine-Grained Soils. If more than half of the material, by weight, of a soil is made up of particles that are
smaller than the openings in a Number 200 sieve, the soil is considered to be fine-grained. Fine-grained soils are
further classified based on their positions as plotted on the ENG Form 4334 (see figure 3-4, page 3-9).
(1) Liquid Limit Less Than 50. Soils that have a LL less than 50 (those that plot to the left of the
vertical line representing a LL of 50 on ENG Form 4334) are said to have low plasticity. These types of soils are
symbolized by using a two-letter designation, with the second letter being an "L" indicating that the soils exhibit
low plasticity. Soils with low plasticity may be further classified based on their plotted positions relative to the
"A" line on ENG Form 4334.
(a) Silts With Low Plasticity. Fine-grained, inorganic soils that plot to the left of the vertical line
representing a LL of 50 and below the "A" line on ENG Form 4334 are referred to as silts with low plasticity. As
mentioned previously, the letter "M" indicates silt-sized
EN5341
3-14
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