Excavation, Fonnworks, Scaffolding and Staging

Excavation

The digging and removal of earth from its natural position, or the cavity resulting from such removal.

Minor Excavation

Excavation characterized as having independent and hollow block wall footing where the digging of the soil for the footing extends to a depth from 1.0 to 5.0 meters and about 0.5 meter for wall footing.

Major Excavation

An excavation which requires wide or total extraction of the soil.

Shoring

The process of providing temporary supports to the structure or ground during excavation.

Underpinning

The process of rebuilding, strengthening, or stabilizing the foundation of an existing building.

Tieback

Steel cables or tendons inserted into pre-drilled holes through sheet piling into rock or suitable soil, grouted under pressure and post-tensioned with a hydraulic jack to anchor the structure.

Foundation Wall

Part of the foundation system that supports the superstructure and encloses a basement or crawl space below grade, designed to resist earth pressure and anchor the structure against wind and seismic forces.

Slurry Wall

A concrete wall cast in a trench to serve as sheeting and often used as a permanent foundation wall.

Dampproofing

A method of protecting a foundation wall when subsoil conditions indicate that hydrostatic groundwater pressure will not occur.

Formworks

A system of temporary boarding, sheathing, or panels used to produce the desired shape and size of concrete until it gains sufficient strength.

Form

Boarding or sheeting of wood, metal, plastic, or fiberglass used to contain and shape newly placed concrete until it becomes self-supporting.

Scaffoldings

A system of temporary platforms supporting workers and materials while providing access to work areas above ground.

Falsework

Temporary bracing for supporting work under construction that cannot yet support itself.

Staging

A temporary platform for workers and materials used during building construction.

Shore

A piece of timber placed diagonally or obliquely to temporarily support a wall.

Wale

A horizontal timber or steel beam used to reinforce vertical members in formwork or sheet piling; also called Breast Timber, Ranger, or Waler.

Wedge

A slotted device used for tightening formwork and transferring force from a form tie to the wales.

Strongback

A vertical support used to align and reinforce wales; also called Stiffback.

Spreader

A wood brace used to keep wall or footing forms properly spaced; also called Spacer.

Grade Strip

A wood strip fixed inside a form to indicate the top of a concrete lift.

Bulkhead

A partition closing the end of a form or preventing the passage of freshly placed concrete at a construction joint.

Keyway

A longitudinal groove or channel formed in hardened concrete to provide a shear-resisting key for newly placed concrete.

Yoke

A clamping device used to prevent column or wall forms from spreading under the pressure of freshly placed concrete.

Formliner

Material lining the inside face of a form to provide a smooth or patterned concrete surface finish.

Form Tie

A metal tie that prevents wall forms from spreading under the pressure of freshly placed concrete.

Snap Tie

A form tie with notches or crimps allowing its ends to be snapped off below the concrete surface after form removal.

Cone Bolt

A form tie having cones at each end that also function as spreaders.

Cone

A truncated cone of wood, steel, or plastic attached to a form tie to space wall forms and leave a neat depression in the concrete surface.

She Bolt

A form tie consisting of outer rods threaded onto an inner rod, with the outer rods removed after stripping while the inner rod remains embedded in the concrete.

Chair

A device supporting reinforcing steel in its correct position before and during concrete placement.

High Chair

A tall chair used to support top reinforcing bars in concrete beams or slabs.

Bolster

A wide chair used to support and space bottom reinforcing bars in concrete beams or slabs.

Sonotube

A trademarked cylindrical column form made of compressed resin-impregnated paper.

Placement

The process of depositing and consolidating freshly mixed concrete in forms or its final position.

Direct Placement

The discharge of freshly mixed concrete directly into a form from a mixer, buggy, or crane.

Free Fall

The descent of freshly mixed concrete into a form without using a drop chute.

Drop Chute

A chute that directs falling concrete to prevent segregation.

Agitation

The gentle movement of mixed concrete sufficient to prevent segregation or loss of plasticity.

Segregation

The separation of coarse aggregate from mortar or water from other concrete ingredients due to excessive movement, free fall, or over-vibration.

Stratification

The separation of excessively wet or over-vibrated concrete into horizontal layers with lighter material rising to the top.

Bleeding

The emergence of excess water on the surface of newly placed concrete caused by settlement of solids; also called Water Gain.

Water Gain

Another term for Bleeding.

Laitance

A weak milky deposit of cement and fine aggregate on the surface of new concrete caused by bleeding, overworking, or improper finishing.

Dewatering

The pumping or removal of water from a construction site to maintain dry and stable working conditions.

Retaining Wall

A structure whose primary function is to provide lateral support for soil or rock.

Gravity Wall

A retaining wall that resists overturning and sliding by the sheer weight and volume of its mass.

Cantilevered Wall

A reinforced concrete retaining wall that resists earth pressure through cantilever action and is generally used for walls up to 20 ft high.

Counterfort Wall

A reinforced concrete retaining wall strengthened with triangular cross walls (counterforts) spaced at regular intervals to stiffen the wall and add weight to the base.

Crib Wall

A retaining wall formed from an open cellular framework filled with earth or stone to resist lateral earth pressure.

Slope Protection

The stabilization of slopes to prevent erosion caused by surface runoff.

Revetment

A protective covering placed on the face of an embankment to prevent erosion.

Riprap

A layer of irregularly broken and random-sized stones placed on the slope of an embankment to prevent erosion.

Cribbing

A cellular framework of squared steel, concrete, or timber members assembled in layers at right angles and filled with earth or stones.

Bin Wall

A gravity retaining wall formed by stacking modular interlocking precast concrete units and filling the voids with crushed stone or gravel.

Gabions

Galvanized or PVC-coated wire baskets filled with stones and stacked to form an abutment, retaining structure, or riprap.

Filter Fabric

A permeable fabric placed beneath riprap or drainage material to prevent soil migration while allowing water to pass through.

Soil Binders

Plant materials that prevent erosion by providing ground cover and forming a dense network of roots that bind the soil.

Batter

The backward slope of the face of a retaining wall as it rises, reducing the appearance of the wall leaning forward.

Drainage Mat

A drainage layer with filter fabric placed behind a retaining wall to relieve water pressure.

Weepholes

Openings through a retaining wall that allow accumulated water behind the wall to drain out.

Perforated Drainpipe

A perforated pipe installed behind a retaining wall to collect and carry groundwater away from the structure.

Control Joint

A vertical joint provided in a retaining wall at regular intervals to control cracking.

Expansion Joint

A vertical joint that allows movement caused by expansion and contraction of a retaining wall.

Dead Man

A timber, stone, or concrete mass buried in the ground and used as an anchor for retaining walls.

Horizontal Timber Wall

A retaining wall constructed from pressure-treated timbers laid horizontally with overlapping joints and secured together.

Brick Veneer Wall

A retaining wall finished with a brick veneer attached to a concrete masonry backing.

Dry Stone Wall

A retaining wall constructed of stacked stones without mortar.

Angle of Repose

The steepest angle at which soil remains stable without sliding.

Earth Pressure

The lateral pressure exerted by retained soil against a retaining wall.

Total Pressure or Thrust

The total lateral force exerted by retained soil on a retaining wall.

Surcharge

An additional load, such as earth or live load, applied above a retaining wall that increases lateral earth pressure.

Resultant

The single force representing the combined effect of soil thrust and wall weight.

Overturning

The failure of a retaining wall caused by rotation about the toe due to excessive earth pressure.

Sliding

The failure of a retaining wall caused by horizontal movement due to lateral earth pressure.

Settling

The downward movement of a retaining wall caused by excessive soil pressure exceeding the soil's bearing capacity.

Resisting Moment

The stabilizing moment produced by the weight of the wall and the soil over the heel to resist overturning.

Overturning Moment

The moment produced by lateral earth pressure tending to rotate the wall about its toe.

Coefficient of Friction

The ratio of frictional resistance between the base of a retaining wall and the supporting soil.

Passive Pressure

The resistance exerted by soil in front of the toe of a retaining wall that helps resist sliding.

Key

A projection below the footing of a retaining wall that increases resistance against sliding.

Bearing Capacity

The maximum pressure that supporting soil can safely sustain without failure.