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Expansive clay is a clay soil that is prone to large volume changes (swelling and shrinking) that are directly related to changes in water content. [1] Soils with a high content of expansive minerals can form deep cracks in drier seasons or years; such soils are called vertisols .
A soil survey should list the coefficient of linear extensibility (COLE) value. [2] Professional soil scientists can also analyze samples of a soil to determine its shrink-swell capacity. [2] Expansive soils will form large cracks, in roughly polygonal shapes, on the surface of the soil during dry periods. [3]
LECA can be mixed with heavy soil to improve its aeration and drainage. In the horticultural practice of hydroponics , LECA is a favored medium for growing plants within; the round shape provides excellent aeration at the root level, while the LECA clay pieces themselves become saturated with water and plant food, thus giving the roots a ...
Distinctions in soils are used in assessing soil which is to have a structure built on them. Soils when wet retain water, and some expand in volume (smectite clay). The amount of expansion is related to the ability of the soil to take in water and its structural make-up (the type of minerals present: clay, silt, or sand). These tests are mainly ...
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. Soils high in swelling clays (expansive clay), which are clay minerals that readily expand in volume when they absorb water, are a major challenge in civil ...
Soil bulk density, when determined at standardized moisture conditions, is an estimate of soil compaction. [3] Soil porosity consists of the void part of the soil volume and is occupied by gases or water. Soil consistency is the ability of soil materials to stick together. Soil temperature and colour are self-defining.
The Unified Soil Classification System (USCS) is a soil classification system used in engineering and geology to describe the texture and grain size of a soil. The classification system can be applied to most unconsolidated materials, and is represented by a two-letter symbol. Each letter is described below (with the exception of Pt):
Soil types by clay, silt and sand composition as used by the United States Department of Agriculture. Loam (in geology and soil science) is soil composed mostly of sand (particle size > 63 micrometres (0.0025 in)), silt (particle size > 2 micrometres (7.9 × 10 −5 in)), and a smaller amount of clay (particle size < 2 micrometres (7.9 × 10 −5 in)).