Geotechnical

Geotechnical engineering is a subcategory of civil engineering that analyzes the mechanics of soils and rocks in the building and excavation for a site.  Every construction design infrastructure that is supported by foundations, above or below ground such as bridges, dams, plants, slopes, structures, tunnels, etc. uses geotechnical engineering.

Geotechnical Engineering Subtopics

 Geotechnical Engineering Earthwork Building Foundation Geosynthetics Geotechnical Investigation Ground Improvement Lateral Earth Support Offshore Slope Stabilization Soil Mechanics

Geotechnical Nomenclature & Symbols

• $$\rho_w$$  (Greek symbol rho) = density of water
• $$GI$$ = group index
• $$LL$$ = liquid limit
• $$m_l$$ = mass of liquid
• $$m_s$$ = mass of solid
• $$w_n$$ = natural water content
• $$PL$$ = plastic limit
• $$Y_{sat}$$ = saturated bulk density of soil
• $$K$$ = soil erodibility factor
• $$M_t$$ = total mass of soil
• $$\gamma_m$$  (Greek symbol gamma) = unit weight of solid mass
• $$\gamma_s$$  (Greek symbol gamma) = unit weight of solid soil
• $$V_a$$ = volume of air
• $$W_a$$ = weight of air

Geotechnical Terms

A

• Aggregate  -  A mixture of sand and stone with the major component concrete.
• Aquifer  -  A layer of rock or sediment that holds groundwater within.
• Alluvium  -  Soil that has been transported to its present location by water.
• Asphalt concrete  -  A hot mixture of asphalt cement, rubber, fine and coarse aggregate, and a mineral mixture.
• Atterberg limits  -  The basic measure of the critical water contents of a fine-grained soil.  The water contents where the soil behavior changes are liquid limit, plastic limit, and shrinkage limit.
• Basic types of rock  -  Igneous rock, Metamorphic rock, and Sedimentary rock.
• Bearing capacity  -  The maximum average load per unit area of a footing that will not produce failure by rupture of the supporting soil.
• Boulder  -  Fragments greater than 256 mm.
• Bulk density  -  The ratio total weight of soil to the total volume of soil.

C

• Capillart water  -  Water that is under tension in a soil due to stresses produced by menisci forming in the soil pores as water recedes into the voids from evaporation or is lost other means.
• Clay  -  Particles ranging in size from 0.002 mm and smaller.
• Cobble  -  Rock ranging in size from 65 mm to 256 mm.  Larger than a pebble and smaller than a boulder.
• Cobblestone  -  Rounded or partially rounded stones used in paving roads and streets.
• Coarse aggregate  -  Particles ranging in size greater than 4.75 mm.
• Coarse sand  -  Particles ranging in size from 0.50 mm to 1.00 mm.
• Colluvium  -  Soil that has been transported by gravety.
• Collapsible soil  -  Low density soils that have considerable strength when dry of moist.
• Compaction  -  Is rearranging the particles and reduce the voids and increase the density of the soil.
• Compressibility  -  Measures the change in volume under external forces for any liquid.
• Compression  -  Squeezing rocks togeather, causing rocks to fold or fracture.
• Confined aquifer  -  Layers of impermeable rock or sediment that prevent water from seeping into the groundwater from above.
• Confined stress  -  A deeply buried rock is pushed down by the weight of all the material above.  Since the rock cannot move, it cannot deform.
• Consistancy index (CI)  -  The range of water content to the firmness of the soil.
• Consistancy limit (CL)  -  The water content at which the soil changes from one state to another state.
• Crest  -  Land that stands above or almost above surrounding terrain.

D

• Darcy"s law  -  The rate at which a fluid flows through a permeable medium.
• Darcy velocity  -  The volumetric flow per unit area of a porous mediun.
• Density  -  The ratio of the amount of matter in an object compared to its volume.
• Dry soil  -  Contains only air and voids.
• Ductile strain  -  A rock that does not go back to its origional state.  Remaines deformed when strain stops.

E

• Elastic strain  -  A rock that goes back to its origional state.
• Emissivity  -  The surface depends on the material effectiveness in emitting energy as thermal radiation and varies between 0.0 and 1.0.
• Erosion  -  The natural wearing away of the earth's surface by rainfall and surface runoff.

F

• Falsic  -  Magmas that are rich in silica and aluminum.
• Fault  -  A rock fracture showing evidence of relative movement.
• Fine aggregate  -  Particles sand or crushed stone ranging in size less than 9.55 mm.
• Fine sand  -  Particles ranging in size from 0.10 mm to 0.25 mm.
• Footing  -  A structural member used to distribute the loads to the soil in such a way that the load bearing capacity of the soil is not exceded.
• Fractured  -  A rock that has broken abruptly into pieces.

G

• Glacial till  -  Soil that has been gouged out of the earth's crust by ice at one location and deposited at another.
• Gravitational water  -  Water that is free to move through a saturated soil mass under the influence of gravity.
• Groundwater  -  Water that has traveled down from the top soil to fills the cracks and openings in the rocks and sand.
• Gully  -  A channel from errosion during intersmittent and concentrated flow of water during heavy rain.

H

• Heat capacity  -  The ratio of heat transferred to raise the temperature of an object.
• Hydraulic gradient  -  A dimensionless number expressing the change in height (pressure) to length between any two points.

I

• Igneous rock  -  Formed from the cooling and solidification of hot liquid magma.
• Intermediate rock  -  Between mafic and felsic rocks.
• Irrigation  -  Applying water to crops by means of canals, ditches, pipes, sprinklers, etc. to meet their water requirements.

K

• Kinetic energy  -  The energy in moving objects or mass.  If it moves, it has kinetic energy.

L

• Latent heat  -  The energy absorbed or released by a substance during a constant temperature or phase change from a solid to liquid, liquid to gas or vise versa.
• Leaching  -  The removal of material from soil and materials by the constant movement of water.
• Liquid  -  A liquids molecules are close together with no particular pattern and continually move past each other, this allows it to flow and move about.  Having little space between the molecules leaves little room to compress.
• Liquid index (LI)  -  The range of water content to the liquid limits.
• Liquid limit (LL)  -  The minimum water content at which soil just begins to flow.

M

• Mafic  -  Magmas that are rich in iron, magnesium, and calcium.
• Marble  -  Result of heat and pressure imposed on limestone or dolostone.
• Marsh  -  Wetlands that features permanent large areas of land with shallow bodies of water that include a large amount of grasses.
• Mass flow rate  -  The average velocity of a mass that passes by a point.  In engineering, mass flow rate is often used, along with the conservation of mass to determine how much product moves through a pipe or duct.
• Medium sand  -  Particles ranging in size from 0.25 mm to 0.50 mm.
• Metamorphic rock  -  Started as some other type of rock, but has changed substantilly from its earlier metamorphic form.
• Mineral  -  A naturally occuring inorganic element or compound having an orderly internal structure.
• Mulch  -  An organic or inorganic material applied around plants or to the top of the soil.

N

O

• Organic material  -  Decomposing animal and plant material.
• Organic soil  -  Contains a high percentage of organic material.
• Quartzite  -  Result from the deformation of sandstone.

P

• Perched water table  -  The saturation point where the downward flow action in the soil is by the force of gravity.
• Permeability  -  The quality of the soil to enable water to move downward through the soil.
• Plastic index (PI)  -  The range of water content over which the soil remains in the plastic state.
• Plastic limit (PL)  -  The water content at which the soil changes from semi-solid state to solid state.

• Plasticity of soil  -  The soils ability to undergo deformation without cracking of fracturing.  At this state the soil can be moulded into different shapes.
• Ploughing  -  Turning the soil by mechanical cultivation of agricultural soils to a depth of 20 to 30 cm deep.
• Ponding  -  Standing water on soil in a closed depression.
• Porosity  -  A measure of a rocks and soil capacity to store fluids.
• Post  -  A timber used in a vertical position.
• Precipitation  -  Water that falls to earth from the atmosphere.

Q

• Quarry  -  An open pit where fill, gravel, minerals, sand, and/or stone is taken from.

R

• Relative density  -  The density or ratio of any substance relative to another substance.
• Rock  -  An aggregate of one or more minerals.
• Runoff  -  The water that flows off the ground surface without sinking into the soil.

S

• Sand  -  Soil particles ranging in size from 0.05 mm to 2 mm that do not shrink or swell when drying or wetting.
• Sandstone  -  Rock composed of sand sized particles.
• Saturated soil  -  Has its voids completely filled with water.
• Sediment  -  Solid material deposited or transported by ice, water, or wind.
• Sedimentary rock  -  Formed from pre-existing rocks or pieces of once living organisms.
• Seepage velocity  -  The actual velocity of a fluid flowing through the void spaces in the soil.
• Shear  -  Pushes one side of the rock in one direction, and the other side of the rock in the opposite direction.
• Shear stress  - Tends to deform the material by breaking rather than stretching without changing the volume by restraining the object.
• Schist  -  A cource-grained to medium-grained rock.
• Shrinkage limit (SL)  -  The maximum water content at which further reduction in the water content will not cause decrease in volume of soil.
• Silt  -  Particles ranging in size from 0.002 mm to 0.05 mm.
• Silt clay  -  Particles ranging in size from 0.002 mm to 0.05 mm.
• Slate  -  Fine-grained rock derived mainly from shale.
• Slump  -  The measure of consistancy of newly mixed concrete.
• Soil  -  Sediments or other unconsolidated solid particles produced by the physical and chemical decay of rocks.
• Soil solids  -  Mineral particles resulting from the physical decay of the parent rock.
• Solid waste  -  Waste other than sewage, mostly solid material.
• Span  -  The distance between supports.
• Specific gravity  -  A dimensionless number, is the density or ratio of any substance to another substance.
• Storm water  -  Surface run off after a rainfall.
• Stress  -  The force per unit area of cross-section.
• Surface tension  -  The energy or force at the surface of a liquid that holds it together.
• Swamp  -  Wetlands that features permanent large areas of land with shallow bodies of water that include a large amount of trees.

T

• Temperature gradient  -  Describes in which direction and what rate the temperature changes in a given area.
• Tension  -  Rocks that are pulled apart, break apart, or lengthen under tension.
• Terrace  -  A conservation practice for soil and water management to prevent rainfall runoff on sloping land from causing serious errosion.
• Tillage  -  Turning the soil by mechanical cultivation of agricultural soils to a depth of 20 to 30 cm deep.
• Topsoil  -  The top layer of soil that contains most of the nutrients that normally occuring in the soil, usally between 2 to 10 inches.
• Trace element  -  Naturally occuring elements found in small amounts in the soil.

U

• Unconfined aquifer  -  Water that seeping into the groundwater from above.
• United Soil Classification System (USCS)  -  A method for identifying and grouping soil.  Coarse grained, Fine grained, and Highly organic.  Only particles smaller than 3" are considered USCS.

V

• Very coarse sand  -  Particles ranging in size from 1.00 mm to 2.00 mm.
• Very fine sand  -  Particles ranging in size from 0.05 mm to 0.10 mm.
• Void  -  Spaces between particles.
• Void ratio  -  The ratio of the volume of voids to the volume of solids.

W

• Water content  -  The ratio of weight of soil to the weight of water or the quantity of water contained in a material.
• Waterlogged  -  Saturated with water
• Water table  -  The underground boundary between the surface of the soil and the area where groundwater fills the cracks and openings in the rocks and sand.
• Weathering  -  A breakdown in the chemical or physical changes in rocks or sediments at or near the earth's surface by atmospheric changes.

Z

Display #
Title
Air Content
Bulk Density
Bulk Unit Weight
Buoyant Unit Weight
Consistancy Index
Curvature Coefficient
Degree of Saturation
Discharge Velocity
Dry Bulk Density of Soil
Dry Unit Weight
Liquid Index
Moisture Unit Weight
Normalized Water Content
Permeability Coefficient
Plastic Index
Porosity
Runoff
Saturated Unit Weight
Shrinkage Limit
Solid Unit Weight
Specific Gravity of Soil
Total Volume of Soil
Total Weight
Total Weight of Soil