Note for Geotechnical Engineering- 1 - GTE-1 by Prashanth mj Prashu

Topics ( 3 )

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An Introduction to Soils and Soil Terminology A PowerPoint resource to accompany the posters available at: http://www.macaulay.ac.uk/soilposters/1.pdf http://www.macaulay.ac.uk/soilposters/5.pdf

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Soil: some definitions Soil can be defined as the solid material on the Earth’s surface that results from the interaction of weathering and biological activity on the parent material or underlying hard rock. The study of soils as naturally occurring phenomena is called pedology (from the Greek word pedon, meaning soil or earth). Pedology takes into account: • factors and processes of soil formation • soil characteristics • distribution of soil types

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The basic unit of study: Soil Profiles TOPSOIL, upper or A horizon SUBSOIL, middle or B horizon PARENT MATERIAL, lower or C horizon This diagram shows simplified soil horizons A soil profile is a vertical crosssection of a soil. It is divided into a number of distinct layers, referred to as horizons. The horizons are normally designated by symbols and letters. The presence or absence of particular horizons allows pedologists (soil scientists) to classify the soil. In addition, the organic or O horizon can form above the mineral soilcommonly in forested areas, resulting from the dead plant and animal remains.

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Soil Horizons The horizons may be further subdivided. Fresh vegetation For example, in this soil profile the A horizon has been divided into 4 further pedological horizons: Dead vegetation-Litter (L) Humus (H) A horizon Fermenting litter (F) • (L) leaf litter • (F) fermenting leaf litter • (H) humus • (E) eluvial Eluvial horizon (E) These lie above the (B) or illuvial horizon. Illuvial horizon (B)