Geotechnical Terms and Methods

foundation

The part of a structure that supports its weight and the weight of applied loads.

spread footing

The simplest and most common type of building foundation that includes individual footings, combined footings, and mat foundations.

mat or raft foundation

A heavily reinforced concrete slab extending under the entire structure, used to spread the structure's load over a large area.

floating foundation

A type of mat foundation in which the weight of the soil excavated approximately equals the weight of the structure being erected.

ground modification

The process of improving soils in place, also known as soil stabilization.

pile

A column driven into the soil to support a structure by transferring building loads to a deeper and stronger layer of soil or rock.

precast concrete piles

Piles that may be manufactured in almost any desired size or shape.

cast-in-place concrete piles

Piles constructed by driving a steel shell into the ground and then filling it with concrete.

steel piles

Piles made of steel that are capable of supporting heavy loads, can be driven to great depth without damage, and are easily cut and spliced.

composite piles

Piles made up of two or more different materials.

bulb piles

A special form of cast-in-place concrete pile in which an enlarged base (or bulb) is formed during driving.

pier

A column, usually of reinforced concrete, constructed below the ground surface.

caisson

A structure used to provide all-around lateral support to an excavation. Caissons may be either open or pneumatic.

liquefaction

A condition in which the water pressure exactly equals soil weight, causing the soil to behave like a liquid.

boiling or piping

A condition in which the water pressure is strong enough to move subsurface soil up through the bottom of a cut.

shoring

A method of providing lateral support for the sides of an excavation.

lagging

Sheet placed horizontally for shoring.

sheet piling

Sheeting of concrete, steel, or timber that is designed to be driven by a pile driver.

trench shields or trench boxes

Used in place of shoring to protect workers during trenching operations.

dewatering

The process of removing water from an excavation.

soil permeability

The ease with which water flows through soil, primarily a function of the soil's grain size distribution.

wellpoint

The perforated assembly placed on the bottom of the inlet pipe for a well.

vacuum wells

Wellpoints that are sealed at the surface by placing a ring of bentonite or clay around the well casing.

electroosmosis

The process of accelerating the flow of water through soil by the application of a direct current.

grouting or pressure grouting

The process of injecting a grouting agent into soil or rock to increase its strength or stability, protect foundations, or reduce groundwater flow.