Soil Particle Sizes

The study of the response of soils to loads = Soil mechanics Natural resources and complex materials consisting of solids, liquids, and gases = Soils Used before as construction materials for flood protection and shelters = Soils

Coulumb = First person to use mechanics to solve soil problems Roman Engineers = Recognized the importance of soils in the stability of structures

Stability, strength and deformation = Serviceability life of any structures Soil behavior and responses = Analysis and design systems

Human-made structures (buildings) = Loads Gravity (earth pressures) = Loads Natural phenomena (earthquake) = Loads

Residual soils = Soils that remain at the site of weathering Transported soils = Soils that are carried away by forces of gravity, water, wind and ice and deposited at another location Glacial soils = Formed by transportation and deposition of glaciers Lacustrine soils = Formed by deposition in quiet lakes

Igneous rocks = Formed by solidification of molten magma ejected from deep within the earth’s mantle Sedimentary rocks = Deposits of gravel, sand, silt and clay formed by weathering and compacted by overburden pressure and cemented by agents Metamorphic rocks = Either igneous or sedimentary rocks that have undergone considerable change in their constitution, shape, structure and mineral composition

Mechanical weathering = Caused by the expansion and contraction of rocks from the continuous gain and loss of heat, which results in ultimate disintegration Chemical weathering = The original rock minerals are transformed into new minerals by chemical reaction

Solid phase = May be mineral, organic or both Liquid phase = Usually the soil water that fills part or all of the open spaces between the solid particles Gaseous phase = Usually air, occupies part of the space between particles not filled with water

Gravel = Rounded and/or angular bulky rock Sand = Rounded and/or angular bulky hard rock Silt = Particles smaller than 0.075 mm, exhibit little or no strength when dried Clay = Particles smaller than 0.075 mm, exhibit plasticity when wet

Soil Mechanics = Deals with the study of the physical properties of soil and the behavior of soil masses subjected to various types of forces Geotechnical Engineering = Involves natural materials found close to the surface of the earth and includes the application of the principles of soil mechanics and rock mechanics to the design of foundations, retaining structures and earth structures Foundation Engineering = Deals with design, construction and maintenance of shallow footings and deep foundations and other structural members which comprise foundation of buildings and other engineering structures Karl Von Terzaghi = The undisputed father of soil mechanics who published the book 'Erdbaudmechanik' in 1925, laying the foundation for soil mechanics

Soil = Defined as an uncemented aggregate of mineral grains and decayed organic matter with liquid and gas in the empty spaces between the solid particles, and it supports structural foundations Rock = Defined as hard and compact natural aggregates of mineral grains cemented by strong and more or less permanent bonds Leaning Tower of Pisa = Famous example of a problem related to soil-bearing capacity, where the tower began to lean during construction due to soft ground Tower of Bologna = Another example of a leaning tower, located in Bologna, Italy, and consists of two towers, the Garisenda Tower and the Asinelli Tower

Coulomb = Tacitly defined a failure criterion for the analysis of soil failures Karl Von Terzaghi = The undisputed father of soil mechanics who published the book 'Erdbaudmechanik' in 1925, laying the foundation for soil mechanics Bonanno Pisano = Architect of the Leaning Tower of Pisa Families of Bologna = Traditionally credited and constructed the Garisenda Tower and the Asinelli Tower between 1109 and 1119

Soil Formation = Process where soils are formed from the physical and chemical weathering of rocks Rock Cycle = Process that describes how rocks change from one type to another over time Soil Engineering = Application of the principles of soil mechanics to practical problems Geotechnical Systems of Structures = Structures that involve the application of soil mechanics, geology and hydraulics to their analysis and design

Karl Von Terzaghi = The undisputed father of soil mechanics Bonanno Pisano = Architect of the Leaning Tower of Pisa Families of Bologna = Traditionally credited and constructed the Garisenda Tower and the Asinelli Tower Geotechnical Engineers = Provide solutions to soil problems and their work is often invisible once construction is completed

Organic silt = Fine grained, more or less plastic soil, containing an admixture of organic matter Clay = Composed of microscopic and sub-microscopic particles of weathered rocks Bentonite = Clay with high percentage of clay mineral, derived from chemical alteration of volcanic ash Black cotton soils = Inorganic in nature, exhibit high compressibility and swelling characteristics

Peat = Composed of fibrous particles of decayed vegetable matter, light brown to dark in color, very compressible Varved clay = Consists of alternating layers of medium gray inorganic silt and darker silty clay Caliche = Consists of gravel, sand and clay cemented together by calcium carbonate Expansive soils = Clays that undergo large volume changes from cycles of wetting and drying

Particle size = Used to distinguish various soil textures Clay minerals = Consist of silica and alumina sheets that are combined to form layers in the soil Montmorillonite = A type of clay mineral with very weak bond between its layers, causing swelling when water enters Fine-grained soils = Have much larger surface areas than coarse-grained soils and their properties depend mainly on mineralogical factors

Glacial till = Composed of material deposited by glacier and consists mainly of coarse particles Laterite soils = Residual soils that are cemented with iron oxides and found in tropical regions Gypsum = Calcium sulphate formed under heat and pressure from sediments in ocean brine Loam = A mixture of sand, silt and clay that may contain organic material

Water = A thin layer of it is bonded to the mineral surfaces of soils and significantly influences their physical and mechanical characteristics Fine-grained soils = Responsible for the major physical and mechanical differences between coarse-grained and fine-grained soils Engineering properties of fine-grained soils = Depend mainly on mineralogical factors Hard pan = Any stratum of hard and cohesive soil which offers exceptional resistance to penetration by normal drilling tools

Permeability = Ability of soil to let water pass through its pores Consolidation and compressibility = Deals with changes in volume of pores in a soil under load Shear strength = Measure of the ability of soil to sustain stresses without failure Base Exchange = Property of the soil to bind exchangeable base from a solution onto its surface

Bulky particles = Mostly formed by mechanical weathering of rocks and minerals Flaky particles = Have very low sphericity and are predominantly clay minerals Needle – shape particles = Much less common than the other two particle types, found in some coral deposits and attapulgite clays Silt = Fine grained soil with little or no plasticity, consists usually equidimensional grains of quartz

Sieve analysis = Consists of shaking the soil sample through a set of sieves that have progressing smaller openings Hydrometer analysis = Based on the principle of sedimentation in water Stokes’s Law = Equation to calculate velocity in relation to unit weight of soil particles, unit weight of water, viscosity of water, and diameter of soil particles Base Exchange = Property of the soil to bind exchangeable base from a solution onto its surface

Dry strength = The wet soil sample is molded to any convenient shape and allowed to dry in the air or by heating. A small fragment of the dried sample is obtained and passed between the thumb and forefingers Plasticity = If a sample of moist soil can be molded and rolled into threads without breaking or crumbling the soil. A thin thread of clay or foot or more can support its own weight or will not break when held Water mobility = A soil sample is mixed with water to the consistency of a thick paste, then it placed and shaken in palm of the hand Dispersion = A small quantity of soil is dispersed with water in a glass cylinder or tests tube and allowed to settle. The coarse particle will fall and the finer particles will remain in suspension, sand will settle 3 inches in about 10 seconds

Saturated = All voids are filled with water Dry = No water in the soil Moist = Soil has some water content, but not fully saturated Partial saturation = Some voids are filled with water

Saturated unit weight = Weight of soil per unit volume when it is completely saturated with water Void ratio = Ratio of the volume of voids to the volume of solids in a soil mass Porosity = Ratio of the volume of voids to the total volume of the soil Degree of saturation = Ratio of the volume of voids filled with water to the total volume of voids in the soil

Sandy soil = High permeability, low compressibility Clay soil = Low permeability, high compressibility Silt soil = Moderate permeability, moderate compressibility Peat soil = Very high water content, low shear strength

Mechanical weathering = Physical breakdown of rocks into smaller particles without any change in their chemical composition Chemical weathering = Transformation of rock into new compounds by various chemical reactions Biological weathering = Breakdown of rocks by living organisms Physical weathering = Disintegration of rocks due to physical forces without any change in their chemical composition

Dead load = Permanent load exerted on a structure Live load = Load that is not permanently attached to a structure Wind load = Load exerted by the wind on a structure Seismic load = Load exerted by an earthquake on a structure

Geotechnical engineering = Study of the behavior of earth materials Structural engineering = Design and analysis of structures Environmental engineering = Protection of the environment from the potentially deleterious effects of human activity

Gravel = Particle size > 4.75 mm Sand = Particle size 0.075 - 4.75 mm Silt = Particle size 0.002 - 0.075 mm Clay = Particle size < 0.002 mm

Solid State = Soil behaves more like a solid at very low moisture content Semisolid State = Soil and water may flow like a liquid at very high moisture content Plastic State = A gradual increase of water content may transform a dry soil into this state Liquid State = Soil and water may flow like a liquid when the moisture content is very high

Consistency = The term used to describe the degree of firmness of a soil Liquid Limit (LL) = The moisture content corresponding to the transition from liquid to plastic state Plastic Limit (PL) = The moisture content corresponding to the transition from plastic to semisolid state Shrinkage Limit (SL) = The moisture content corresponding to the transition from semisolid to solid state

Atterberg = A Swedish scientist who developed a method to describe the consistency of fine grained soils MBV = Contributed to the understanding of the behavior of soil with varying moisture contents

Water Content = Affects the consistency of a cohesive soil Liquid Limit = Corresponds to the moisture content at which soil transitions from liquid to plastic state Plastic Limit = Corresponds to the moisture content at which soil transitions from plastic to semisolid state Shrinkage Limit = Corresponds to the moisture content at which soil transitions from semisolid to solid state

Liquid State = Very high moisture content Plastic State = Gradual increase of water content from solid state Semisolid State = Gradual increase of water content from plastic state Solid State = Very low moisture content

Consistency = Degree of firmness of a soil Liquid Limit = Moisture content at which soil transitions from liquid to plastic state Plastic Limit = Moisture content at which soil transitions from plastic to semisolid state Shrinkage Limit = Moisture content at which soil transitions from semisolid to solid state

Water Content = Greatly affects the consistency of a cohesive soil Liquid Limit = Corresponds to the moisture content at which soil transitions from liquid to plastic state Plastic Limit = Corresponds to the moisture content at which soil transitions from plastic to semisolid state Shrinkage Limit = Corresponds to the moisture content at which soil transitions from semisolid to solid state

Liquid State = Occurs at very high moisture content Plastic State = Occurs after a gradual increase of water content from solid state Semisolid State = Occurs after a gradual increase of water content from plastic state Solid State = Occurs at very low moisture content

Consistency = The degree of firmness of a soil Liquid Limit = The moisture content at which soil transitions from liquid to plastic state Plastic Limit = The moisture content at which soil transitions from plastic to semisolid state Shrinkage Limit = The moisture content at which soil transitions from semisolid to solid state

Liquidity Index = A measure of the degree of saturation of a soil Liquid Limit = The moisture content at which a soil changes from a liquid to a plastic state Plastic Limit = The moisture content at which a soil changes from a plastic to a semi-solid state Plasticity Index = A measure of the range of moisture content within which a soil behaves as a plastic material

Liquidity Index = A measure of the relative consistency of a soil Liquid Limit = The moisture content at which a soil changes from a liquid to a plastic state Plastic Limit = The moisture content at which a soil changes from a plastic to a semi-solid state Plasticity Index = A measure of the range of moisture content within which a soil behaves as a plastic material

Plastic Limit (PL) = Moisture content at which the soil crumbles, when rolled into threads of 1/8 in. (3.2 mm) in diameter Shrinkage Limit (SL) = Moisture content corresponding to the final transition Liquidity Index (LI) = Ratio of the relative consistency of a cohesive soil in the natural state Specific gravity of solids (Gs) = Ratio of the density of the solids to the density of water

Plasticity Index (PI) = Difference between the liquid limit and the plastic limit of a soil Shrinkage Limit (SL) = Moisture content that caused the soil to change from a semi-solid to a solid state Liquidity Index (LI) = Measure of strength in a cohesive soil in the natural state Specific gravity of solids (Gs) = Ratio of the density of the solids to the density of water

Liquid state to solid state = Change that occurs at the shrinkage limit Semi-solid state to plastic state = Change that occurs at the plastic limit Plastic state to liquid state = Change that occurs at the liquid limit Semi-solid state to solid state = Change that occurs when the water content is below the plastic limit

Plastic state = Soil state with intermediate strength and deformation like a plastic material Liquid state = Soil state with low strength and deformation like a viscous fluid Semi-solid state = Soil state with high strength and brittle fracture when exposed Solid state = One of the four states fine-grained soils can exist