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The most common engineering classification system for soils in North America is the Unified Soil Classification System (USCS). The USCS has three major classification groups: (1) coarse-grained soils (e.g. sands and gravels ); (2) fine-grained soils (e.g. silts and clays ); and (3) highly organic soils (referred to as "peat").
In principle, soil type is a result of main soil forming process. Types of soil are grouped into soil orders. They are identified based on the presence or absence of diagnostic horizons and properties reflecting the effect of specific groups of soil forming processes. Soil types are divided into subtypes. [1]
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 ): If the ...
A taxonomy is an arrangement in a systematic manner; the USDA soil taxonomy has six levels of classification. They are, from most general to specific: order, suborder, great group, subgroup, family and series. Soil properties that can be measured quantitatively are used in this classification system – they include: depth, moisture ...
The physical properties of soil, in order of decreasing importance for ecosystem services such as crop production, are texture, structure, bulk density, porosity, consistency, temperature, colour and resistivity. [1] Soil texture is determined by the relative proportion of the three kinds of soil mineral particles, called soil separates: sand ...
The AASHTO Soil Classification System was developed by the American Association of State Highway and Transportation Officials, and is used as a guide for the classification of soils and soil-aggregate mixtures for highway construction purposes. The classification system was first developed by Hogentogler and Terzaghi in 1929, [ 1] but has been ...
The World Reference Base for Soil Resources ( WRB) is an international soil classification system for naming soils and creating legends for soil maps. The currently valid version is the fourth edition 2022. [1] It is edited by a working group of the International Union of Soil Sciences (IUSS). WRB, 4th edition (2022)
Soil gradation is a classification of the particle size distribution of a soil. Coarse-grained soils, mainly gravels or sands, are graded as either well graded or poorly graded. Poorly graded soils are further divided into uniformly-graded or gap-graded soils. Fine-grained soils, mainly silts and clays, are classified according to their ...