Continuous Flight Auger(CFA) Piles

Also known as augercast piles, augeredcast-in-place piles (ACIP), auger-pressuregrout piles, drilled displacement piles and

screw piles

Geotechs seem to like lots of names forsimilar things, e.g., drilled piers, drilled

shafts, caissons and cast-in-drilled-hole(CIDH) piles (CALTRANS)

What is a CFA pile?“A type of drilled foundationin which the pile is drilled toits final depth in onecontinuous process using acontinuous flight auger.While the auger is drilledinto the ground, the flightsof the auger are filled withsoil, which provides lateralsupport and maintains thestability of the hole.”

What is a CFA pile?“At the same time the augers arewithdrawn from the hole, concrete orgrout is placed by pumping theconcrete/grout mix through the hollowcenter of the auger pipe to the base. Thegrout/concrete mix is placed as the augeris removed, and the hole is never leftopen or unsupported. Reinforcement isthen placed into the fluid concrete/groutfilled hole to complete the pile.”

What is a CFA pile?

What is a CFA pile?

What is a CFA pile?

Private sector uses CFA piles for multi-story buildingsFLDOT uses CFA piles for standard soundbarrier wall foundationCommonly used when vibration or noisefrom pile driving is a concernGEU Support Services is considering usefor sound barrier wall foundations, endbents or footings on piles and pile bents

Applications

Advantages

Low vibrations and noiseQuick installationEconomical?Can see soil conditionsDo not require temporary casing in unstablesoilsCan be installed on a batterCan be installed in low headroom

Disadvantages

Cost? (need a lot of them with easy access)Soil mining can cause settlement anddamage to adjacent structures if the properauger rotation and penetration rate are notmaintained (stronger soils less likely to mine)Generates spoilsLimited to weak rock and soil; notrecommended for muck or alternating hardand soft layers

DisadvantagesRequires a specialty subcontractor (critical)Extensive testing and monitoringrecommended to ensure quality control andstructural integrity

Monitoring during drilling and grouting(including auger rotation speed andpenetration rate, torque, applied crowdpressure, grout pressure and volume factorLoad testing (verification and proof testing)Integrity testing (CSL)

GEC 8 coming soon!

Grout for Structures PSPGrout for use in continuous flight auger (CFA) piles,micropiles, soil nail and permanent anchor tiebackretaining walls and backfilling crosshole sonic logging(CSL) tubes or grout pockets, shear keys, dowel holesand recesses for cored slabs and box beamsAddresses sampling, placement and materialsEventually add to Standard SpecificationsUse approved packaged grout or submit mix designwith gradation, shrinkage, compressive strength andfluidity test resultsIncludes default strength and shrinkage requirements