Glossary
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| A coefficient: | A coefficient proposed by Skempton to calculate the excess pore water pressure due to deviatoric stress. |
| Absorbed water: | Absorbed water is the water that enters the soil pores and can be removed by drying. |
| Activity: | A parameter reflecting the amount of clay particles in a soil. |
| Adhesion: | Interface force between soil and another material. |
| Adsorbed: | Adsorbed water is water bonded to the mineral surface. It cannot be removed by oven drying. |
| Alluvium: | Soil transported by water in suspension and deposited by sedimentation. |
| Angle: | Angle of friction or friction angle is a measure of the shearing resistance of a soil. It is the angle between the normal stress and the resultant stress on a plane. See also friction. |
| Anisotropic: | Anisotropic soil has different properties in different directions. |
| B coefficient: | A coefficient proposed by Skempton to calculate the excess pore water pressure due to deviatoric stress. |
| Blow count: | Used in connection with the Standard Penetration Test (SPT). It is the number of blows to penetrate 305mm (12 inches) of soil. See Standard Penetration Test. |
| Bulk modulus: | Is an elastic constant relating mean stress to
volumetric strain. |
| Calcareous soil: | A soil containing calcium carbonate and effervesces when treated with hydrochloric acid. |
| Caliche: | A soil that consists of gravel, sand and clay cemented together by calcium carbonate. |
| Capillarity: | The rise of water in soils caused by capillary action. |
| Clay: | A fine-grained geological material with particle sizes less than 2 microns and practically impervious. |
| Coefficient of Consolidation: | A soil parameter that gives a measure of the time rate of settlement. |
| Coefficient of permeability: | A measure of the rate of flow through soils under a unit hydraulic gradient and laminar flow at standard temperature and pressure. |
| Coefficient of uniformity: | A ratio of the particle size corresponding to 60% finer to the particle size corresponding to 10% finer. It helps to classify soils. |
| Coefficient of volume compressibility: | A soil parameter that gives a measure of the change in volume per unit effective stress level. |
| Cohesion: | The shear stress due to cementation or interparticle bonds in soils. |
| Collapse load: | The load that causes a soil to fail suddenly. The collapse load is associated with the peak load in dense sand and heavily overconsolidated clays. |
| Compaction: | The densification of soil by expulsion of air. The amount of compaction possible for a soil is determined using the Proctor test. |
| Compressibility: | The ability of soil to change volume. |
| Compression: | The decrease in volume of a soil. |
| Compression index: | An index that indicates the change in void ratio under effective stresses. It is the slope of the normal consolidation line in a plot of void ratio versus either the logarithm or the natural logarithm of effective vertical stress. |
| Consistency: | The relative ease by which a soil can be deformed. |
| Consolidation: | The time dependent process of reducing the volume of a soil (soil settlement) by expulsion of water. |
| Constant volume: | Zero change in volume. |
| Critical state: | The stress state attained by a soil whereby no change of volume occurs with further changes in shear strains. The soil mass behaves like a viscous fluid at the critical state. |
| Critical void ratio: | The void ratio when a soil reach critical state. |
| Deformation: | The change in geometry (size, shape) of a body from external forces. |
| Deviatoric strain: | The strain that results from distortion of a body. |
| Deviatoric stress: | The stress difference that results in distortion of a body. Deviatoric stress and shear stress are synonomous. |
| Dilatancy: | The ability of particles to move up relative to each other under shearing forces. |
| Direct shear: | A shear test in which shear forces and normal forces are applied to parallel faces of a soil. |
| Drawdown: | The vertical distance of the free water surface or ground water face after removal of water. |
| Effective size: | The size of particle corresponding to 10% finer. |
| Effective stress: | The stress carried by soil particles. It is the total stress less the pore water pressure. |
| Elastic limit: | The limiting stress beyond which a body will suffer permanent change in geometry. |
| Elasticity: | The ability of a body to regain its original geometry after imposed loads or stresses are removed. |
| Element: | An element is a base piece that may consist of an image, a text piece, a data file, etc. |
| Equilibrium: | A state of rest defined by Newton's second law. |
| Equipotential line: | A line along which the head is the same. |
| Failure: | The strength of the material is reached. In soils the failure strength is a constant stress at which no volume changes occur under further shear deformation. |
| Failure criterion: | A principle or statement defining the conditions (stresses and strains) that will cause a material to fail. |
| Falling head test: | A test used to determine the coefficient of permeabilty of a fine-grained soil. |
| Fill: | A man-made deposit of soil or other materials. |
| Filter material: | A coarse-grained soil or other material used to drain water from soils. |
| Finite element: | A numerical method of solving boundary valued problems by disretization of the body in question. |
| Flow channel: | The area between two consecutive flow lines. |
| Flow line: | he direction of flow of an imaginary particle of water. |
| Flow net: | A grid consisting of flow lines and equipotential lines. |
| Footing: | A structural member (slab) used to transfer loads from a structure to the soil. |
| Foundation: | A structural system through which loads from a structure are transferred to a soil. |
| Free water: | Water that is in excess of that required for saturating a soil. Also called ground water |
| Gap-graded: | A characteristic of soil in which certain grain sizes are absent. |
| Geogrid: | A polymeric product formed by joining intersecting ribs. |
| Geotextile: | A planar, textile, polymeric product. |
| Glacial clay: | Clays deposited in ancient lakes and subsequently frozen. |
| Glacial till: | Soils of various sizes deposited by glaciers. |
| Gradation: | he distribution of particle size usually shown on a graph of finer (ordinate) versus the logarithmic of grain size (abscissa). |
| Grain-size analysis: | A test using a stack of sieves to determine the particle size distribution of coarse-grained soils. |
| Gravel: | Particles of rock greater than 4.75mm. |
| Groundwater: | Water that is in excess of that required for saturating a soil. Also called free water. |
| Groundwater level: | The surface of free water (groundwater). Soils below the groundwater line are saturated. |
| GROW: | GROW is Geotechnical, Rock and Water |
| Gypsum: | Calcium sulphate formed under heat and pressure from sediments in ocean brine. |
| Head: | The mechanical energy per unit weight. It is the total pressure of a fluid expressed as a vertical distance. |
| Heterogeneous: | A soil mass with different properties in different directions. |
| Homogeneous: | A soil mass with the same properties in all directions. |
| Hydraulic conductivity: | The rate of flow of fluid through soils. |
| Hydraulic gradient: | The head loss per unit distance of flow. |
| Hydrostatic: | A stress state in which all the stresses are equal and are principal stresses. Hydrostatic is the water pressure above a given elevation. When a body is under hydrostatic stress, there is no shear stress and the stresses on the body are equal in all directions. |
| Illite: | A soil mineral formed by repeated layers of one alumina sheet sandwiched by two silicate sheets. |
| Isochrone: | A curve showing the variation of excess pore water pressure with time. |
| Isotropic: | A soil mass having the same properties in all directions. |
| Kaolin: | A soil mineral formed by repeated stacking one silica sheet and one alumina sheet. |
| Laterite: | Residual soils that are cemented with iron oxides and are found in tropical regions. |
| Learning unit: | A learning unit: Is a smallest self-contained learning lesson made from elements that has at least one learning outcome. Learning units within GROW are created using interactive multimedia technologies. |
| Liquefaction: | The sudden loss of strength of soil when the pore water pressure becomes equal to the total stress. |
| Liquid limit: | The water content at which a soil changes consistency from a plastic state to a liquid state. |
| Liquidity index: | An index quantifying the current state (water content) of a soil relative to the liquid and plastic limits. |
| Loam: | A mixture of sand, silt and clay that may contain organic material. |
| Loess: | A wind blown, uniform fine-grained soil. |
| Mean stress: | The average stress on a body. It is the sum of the three principal stresses divided by three. |
| Module: | A module is a collection of learning units with one or more learning outcomes. |
| Modulus of elasticity: | The ratio of stress to strain for an elastic material. Also called Young's modulus. |
| Modulus of volume change: | The ratio of volumetric strain to normal stress in one-dimensional consolidation of soils. |
| Mohr circle: | A circle that represents the stress state of a soil under two dimensional stresses. |
| Mohr-Coulomb failure: | A failure criterion combining Coulomb's frictional law with Mohr's representation of the stress state of a soil. |
| Mud: | Clays and silts mixed with water into a viscous fluid. |
| Normal force: | A force directed normal to the surface of a soil mass. |
| Normally consolidated soil: | A soil that has never experienced stresses greater than its current stresses. |
| Oedometer: | A device to apply vertical loads to a soil. |
| Optimum water content: | The water content attained by a soil at maximum dry unit weight in a Proctor compaction test. |
| Organic soil: | A soil in which the percentage of organic matter is greater than 25%. |
| Overburden: | The soil pressure at a depth of intertest. |
| Overconsolidated soil: | A soil that has experienced stresses greater than its current stress. |
| Overconsolidation ratio: | The ratio of the past effective stress (preconsolidation stress) to the current effective stress. |
| Penetration resistance: | The number of blows to drive a standard sampler a distance of 1 ft using a hammer 140lbs falling from a height of 30 inches. |
| Permanent strain: | The strain that remains in a body after imposed stresses have been removed. |
| Permeability: | The rate of flow of water through soils. |
| Phreatic line: | The free surface line in soil. |
| Piezometer: | An instrument to measure the pore water pressure. |
| Pile: | A long, slender structural element used to transfer structural loads deep within the soil. |
| Piping: | The pipe like removal of soil due to seepage forces. |
| Plane strain: | The stress state in which one normal strain is zero. |
| Plastic limit: | The water content dividing a soil in a plastic state from a soil in a semi-solid state. |
| Plasticity: | The property of a material in which the material does not recover its original geometry after imposed stresses are removed. It is also the consistency of a soil in which molding of the soil does not produce cracks. |
| Plasticity index: | The range of water content that a soil can be molded without cracking. |
| Pore water pressure: | The pressure of the water within the void space in a soil. |
| Porosity: | The ratio of the volume of voids to the total volume of soil. |
| Preconsolidation pressure: | The effective stress that a soil was subjected to in the past. |
| Preloading: | The densification or consolidation of a soil by the placement of temporary loads. |
| Principal plane: | The plane on which the principal stress acts. |
| Principal stress: | The stress on a plane in which the shear stress is zero. |
| Proctor curve: | A curve of dry unit weight versus water content for a given compactive effort. |
| Progressive failure: | Gradual movement of a soil along existing failure planes. |
| Quick clay: | A marine clay that flows like a viscous fluid when disturbed due to reduction of salt content. |
| Quicksand: | Static liquefaction. The upward pore water pressure is equal to the total vertical stress. |
| Relative density: | A measure of the current density of a soil realtive to its loosest and densest conditions. |
| Rock: | A hard mass consisting of minerals. |
| Sand: | Hard soil particles between 4mm and 0.075mm. |
| Sand boil: | The removal or ejection of soil due to seepage. |
| Saturation: | A condition in which the voids in a soil mass are filled with water. |
| Secant modulus: | The slope of a stress strain graph at peak or maximum stress or at other desired stress or strain. |
| Seepage: | The slow movement of water through soils. |
| Seepage force: | The force (frictional) or drag on soil particles caused by seepage. |
| Seepage velocity: | The velocity through the voids of a soil mass. |
| Sensitivity: | The ratio of the intact strength of a soil to its distrurbed strength. |
| Serviceability limit: | A tolerable limit for displacement. |
| Shear stress: | A stress that distorts a body. |
| Shrinkage limit: | The limiting water content at which a soil will change consistency from a semi-solid to a solid. |
| Silt: | A fine soil particle with sizes within the range 0.075mm and 0.002mm. |
| Simple shear: | The plane strain distortion of a soil. |
| Soil: | A geological material derived from the weathering of rocks. |
| Soil profile: | The straigraphic vertical layering of soils. |
| Specific gravity: | The ratio of the density of a body to the density of water. |
| Specific surface: | The surface of area per unit volume of particles. |
| Stability: | The condition though which a soil is capable of supporting loads without attaining failure. |
| Standard penetration resistance: | A test which gives the restistance of a soil to the energy delivered on a standard sampler by a hammer of weight 140lbs falling from a height of 30 inches. |
| Stiffness: | The ratio of force to deflection. |
| Strain: | The change in length per unit length. |
| Streamline: | The path followed by an imaginary particle of water. |
| Stress: | The load per unit area. |
| Stress path: | A graphical representation of stress history. |
| Texture: | The appearance or feel of a soil. |
| Theme: | A theme is a collection of modules that address a global topic. For example, one of the themes in GROW is 'Effects of Water on Soils'. Under this theme, the user can learn from a series of modules that provides a learning experience in a variety of related topics on the influence of water on soils from K-12 level to graduate and professional levels. There are three key characteristics of themes: 1) The hierarchy of knowledge in the themes provides learning flexibility and guided choices that allow a user to learn as much as he/she wants using the various modules in GROW. 2) The modular structure allows users, in particular educators, to select modules from within a theme or from several themes to build his/her own library or a course. 3) The themes and modules serve as gateways to links on similar topics. |
| Till: | A glacial soil consisting of rock debris, sand, silt, clays and boulders. |
| Time factor: | A dimensionless parameter used in the time -settlement(consolidation) behavior of soils. |
| Transported soil: | A soil transported by water or wind or ice. |
| Triaxial compression: | Axisymmetric compression. |
| Unconfined compressive strength: | Axisymmetric compressive strengthon without any lateral confinement. |
| Unit weight: | The weight density. Weight divided by volume. |
| Vane shear test: | A field shear test done by rotating a set of fins in the soil. The shear strength is determined from the soil's resistance to rotation. |
| Viscous flow: | Very slow moving mass. |
| Void: | The space betwen soil particles. |
| Water content: | The percent of water in a soil relative to its dry weight. |
| Weathering: | A process in which rocks are disintegrated into soils. |
| Yield curve: | A curve defining the stress state beyond which a material will deform permanently. Stress states below the yield curve produce elastic response. |
| Yielding: | The ability of a material to deform permanently. |
| Zero air voids: | A term used to describe 100% saturation. All the soil voids are filled with water. |
