Glossary of Terms

The depth of seasonal soil moisture variation. Sometimes referred to as the zone of seasonal fluctuations.

Watering sufficient to stop or arrest settlement brought about by soil shrinkage resulting from loss of moisture.

The load which may be safely transmitted to a foundation member.

A pile or pier connected to a structure by one or more ties to furnish lateral support or to uplift. Also, a reaction pile or pier for load testing.

The maximum pressure which can be applied to a soil mass without causing shear failure. The pressure or stress is created by applied loads and transmitted to the soil by the foundation.

A large-diameter shaft hand- or machine-excavated to bearing stratum inside a protective casing. The shaft may require a cutting shoe to penetrate obstructions.

A soil that has the finest possible particles, usually smaller than 1/10,000 in (2.5×10⁻⁴ cm) in diameter, and often possesses the capacity for extreme volume changes with differential access to water.

The result of expansive soils exerting nonuniform pressure against a constant downward loading. Such loading causes a pier to deviate further from vertical until it can no longer support the structural load.

Soil susceptible to substantial reduction in void ratio upon addition of water.

Removal of excess existing soil (cut) to low or deficient areas (fill) for contouring purposes.

A design whereby structural load is transmitted to soil at some depth, usually through piers, piles, or caissons.

A steel shaft containing one or more helixes which is screwed into the earth to provide a retention system against uplift forces.

Measurements taken by instruments (usually optical) to establish grades.

Soil added to provide a level construction surface or desired grade.

A member, usually concrete, that distributes the foundation load over an extended area and thus provides increased support capacity on any bearing soil.

The part of a structure in direct contact with the ground which transmits the load of the structure to the ground.

Water which can be taken on or lost by the soil without corresponding soil volume change.

A perforated pipe installed in a cut to intercept and divert underground water. The cut is below the level of the intruding water and graded to drain accumulated water away from the site. A catch basin and discharge pump may be required if a natural grade doesn't exist.

Expansion that results when a mixture of soil and water freezes. Upon freezing, total volume may increase by as much as 25 percent, depending on the formation of ice lenses at the boundary between frozen and unfrozen soil.

A coarse-grained soil containing both large and small sizes but a relatively low proportion of intermediate sizes.

The level of ground surface. Also, the rise or fall per given distance (often per 100 ft or 30 m).

Highly plastic clay from the southern and/or western United States.

Water situated within the crystalline layers of the clay that provides the bulk of the residual moisture contained within the intermediate belt.

A means of imposing a static driving force on a pile by jacks. Used extensively to install piles in underpinning existing structures and in static load testing.

A process whereby a water and soil-cement or soil-lime-cement grout is pumped beneath the slab, under pressure, to produce a lifting force that floats the slab to the desired position.

A soil in which there is no attraction or adhesion between individual soil particles.

A dimensionless constant bearing a direct ratio to the affinity of the soil for volumetric changes with respect to moisture variations. Determined as the difference between the liquid limit (LL) and the plastic limit (PL).

A coarse-grained soil in which a majority of particles are of one size. Often described as uniform or gap-graded.

The condition reached when a pile being driven by a hammer has zero penetration per blow (as when the point of the pile reaches an impenetrable bottom such as rock), or when the effective energy of the hammer blow is no longer sufficient to cause penetration. Overdriving of piles after essential refusal can damage them seriously.

The drop of some portion of the foundation below the original as-built grade.

One or another variety of concrete foundation that is supported entirely by the surface soils. It probably constitutes the majority of new residential construction in areas with high-clay soils.

All the loose material constituting the earth's crust in varying proportions, including air, water, and solid particles formed by the disintegration of rocks.

The vertical section that can contain capillary water available from rains or watering. Unless this moisture is continually restored, the soil will eventually desiccate through gravity, transpiration, and/or evaporation.

A procedure for improving the natural properties of soil to make it a more adequate base for construction.

Footings generally consisting of two structural components: steel-reinforced pads sized to adequately distribute the foundation load over the supporting soil, poured at a depth relatively independent of seasonal soil moisture variation; and a steel-reinforced pier tied into the footing and poured to the bottom of the foundation beam.

The removal of soil moisture by vegetation.

Soil that contains a high proportion of particles with narrow size limits.

The situation in which areas of the foundation (usually internal) are raised above the as-built position.

The ratio of combined volume of water and air to the total volume of the soil sample.

Water from any domestic source which accumulates under the foundation. Any water under the foundation, regardless of source, tends to accumulate in the plumbing ditch, of greater concern with slab foundations.

The upper surface of water saturation in permeable soil or rock.

A soil with a fairly even distribution of grain sizes: no excess of one size and no intermediate sizes lacking.