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Although many naturally occurring deposits include both silts and clay, clays are distinguished from other fine-grained soils by differences in size and mineralogy. Silts, which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays. Mixtures of sand, silt and less than 40% clay are called loam.
sand ≥ 50% of coarse fraction passes No.4 (4.75 mm) sieve clean sand SW well-graded sand, fine to coarse sand SP poorly graded sand sand with >12% fines SM silty sand SC clayey sand Fine grained soils 50% or more passing the No.200 (0.075 mm) sieve silt and clay liquid limit < 50 inorganic: ML silt CL lean clay organic: OL organic silt ...
Both extremes in soil have their advantages and shortcomings. Sand particles are relatively large (by definition from 2- to 5-hundredths of a millimeter across). Clay particles are very small (by ...
[11] [12] Sand is least active, having the least specific surface area, followed by silt; clay is the most active. Sand's greatest benefit to soil is that it resists compaction and increases soil porosity, although this property stands only for pure sand, not for sand mixed with smaller minerals which fill the voids among sand grains. [13]
If the percentages of sand, clay, and silt in the soil sample are known, then the triangle can be used to determine the soil texture classification. For example, if a soil is 70 percent sand and 10 percent clay then the soil is classified as a sandy loam. The same method can be used starting on any side of the soil triangle.
Silt-Clay Materials (>35% passing the 0.075 mm (No. 200) sieve) Group Classification A-1 A-3 A-2 ... fine sand silty or clayey gravel and sand silty soils
A poorly-graded soil is a soil that does not have a good representation of all sizes of particles from the no. 4 to no. 200 sieve. A poorly-graded gravel is classified as GP, while a poorly-graded sand is classified as SP. Poorly-graded soils are more susceptible to soil liquefaction than well-graded soils. [1]
The criteria for the different soil orders include properties that reflect major differences in the genesis of soils. [4] The orders are: Alfisol – soils with aluminium and iron. They have horizons of clay accumulation, and form where there is enough moisture and warmth for at least three months of plant growth. They constitute 10% of soils ...