Micropile, Screw Piles, and Helical Piers in New Jersey
Helical piles are a factory-manufactured steel foundation system consisting of a central shaft with one or more helix-shaped bearing plates, commonly referred to as blades or flights, welded to the lead section. Extension shafts, with or without additional helix blades, are used to extend the pile to competent load-bearing soils and to achieve design depth and capacity. Brackets are used at the tops of the piles for attachment to structures, either for new construction or retrofit applications. Helical piles are advanced (screwed) into the ground with the application of torque.
The terms helical piles, screw piles, helical piers, helical anchors, helix piers, and helix anchors are often used interchangeably by specifiers. However, the term 'pier' more often refers to a helical pile loaded in axial compression, while the term 'anchor' more often refers to a helical pile loaded in axial tension.
Design Considerations
Helical piles are designed such that most of the axial capacity of the pile is generated through bearing of the helix blades against the soil. The helix blades are typically spaced three diameters apart along the pile shaft to prevent one blade from contributing significant stress to the bearing soil of the adjacent blade. Significant stress influence is limited to a 'bulb' of soil within about two helix diameters from the bearing surface in the axial direction and one helix diameter from the center of the pile shaft in the lateral direction. Each helix blade therefore acts independently in bearing along the pile shaft.
Multiple piles shall have a center to center spacing at the helix depth of at least four (4) times the diameter of the largest helix blade (ICC-ES AC358). The tops of the piles may be closer at the ground surface but installed at a batter away from each other in order to meet the spacing criteria at the helix depth. For tension applications, the uppermost helix blade shall be installed to a depth of at least twelve (12) diameters below the ground surface (ICC-ES AC358).
Supportworks Model 287 Helical Pile System
Technical Specifications
Outside Diameter (O.D.) = 2.875"
Wall Thickness = 0.203"
Pile Shaft Yield Strength = 60 ksi (min.)
Coupling Hardware: (2) ¾" Grade 8 Bolts with Nuts
Available Helix Blade Diameters = 8", 10", 12", and 14"
Helix Blade Thickness = 0.375"
New Construction Bracket: ¾" x 6" Square A36 Plate (for
allowable compression capacities up to 60.0 kips)
New Construction Bracket Hardware: (2) ¾" Grade 8 Bolts with
Nut
External Sleeve: 3.50" OD x 0.216" wall x 30" long with
sleeve collar welded to one end.
Yield strength = 50 ksi (min.), tensile strength = 62 ksi
(min.).
Bracket Cap: 5.0" wide x 9.0" long x 1" thick plate with
confining ring welded to one side.
Yield strength = 50 ksi (min.), tensile strength = 65 ksi
(min.).
External Sleeve: 3.50" OD x 0.216" wall x 30" long with
sleeve collar welded to one end.
Yield strength = 50 ksi (min.), tensile strength = 62 ksi
(min.).
Bracket Cap: 5.0" wide x 9.0" long x 1" thick plate with
confining ring welded to one side.
Yield strength = 50 ksi (min.), tensile strength = 65 ksi
(min.).
External Sleeve: 3.50" OD x 0.216" wall x 30" long with
sleeve collar welded to one end. Yield strength = 50
ksi (min.), tensile strength = 62 ksi (min.).
Bracket Cap: 5.0" wide x 9.0" long x 1" thick plate with
confining ring welded to one side. Yield strength = 50
ksi (min.), tensile strength = 65 ksi (min.).
External Sleeve: 3.50" OD x 0.216" wall x 30" long with
sleeve collar welded to one end.
Yield strength = 50 ksi (min.), tensile strength = 62 ksi
(min.).
Bracket Cap: 5.0" wide x 9.0" long x 1" thick plate with
confining ring welded to one side.
Yield strength = 50 ksi (min.), tensile strength = 65 ksi
(min.).
External Sleeve: 3.50" OD x 0.216" wall x 30" long with
sleeve collar welded to one end.
Yield strength = 50 ksi (min.), tensile strength = 62 ksi
(min.).
Bracket Cap: 5.0" wide x 9.0" long x 1" thick plate with
confining ring welded to one side.
Yield strength = 50 ksi (min.), tensile strength = 65 ksi
(min.).
Maximum Allowable Mechanical Shaft Capacities
(3,5)
Default Torque Correlation Factor (6) Kt (ft-1)
Maximum Installation Torque (ft-lbs)
Maximum Ultimate Torque Correlated Soil Capacity
(6,7)Qu = Kt X T
(kips)
Axial Compression (kips)
Axial Tension (kips)
HA150
10
6,500
65.0(8)
26.5(1,8)
26.5(1)
HA175
10
10,000
100.0(8)
65.7(8)
53.0(1)
HP287
9
5,600
50.4
46.4(4)
23.6(2)
HP288
9
7,900
71.1
65.4(4)
34.1(2)
HP350
7
16,000
112.0
107.8(4)
62.5(5)
Governed by AISC allowable capacity of single Ø3/4" (HA150) or (2)
Ø3/4" (HA175) Grade 8 bolt(s) in double shear.
Governed by bearing at the bolt holes.
Capacities include a scheduled loss in steel thickness due to
corrosion for black, uncoated steel. Scheduled thickness losses are
for a period of 50 years and are in accordance with ICC-ES AC358.
Allowable compression capacities are based on continuous lateral
soil confinement in soils with SPT blow counts ≥ 4.Piles with
exposed unbraced lengths or piles placed in weaker or fluid soils
should be evaluated on a case by case basis by the project engineer.
Listed mechanical capacities are for the shaft only. System
capacities should also not exceed the installed torquecorrelated
capacity or those listed in the respective bracket capacity tables.
Listed default Kt factors are widely accepted industry standards.
They are generally conservative and are consistent with those listed
in ICC-ES AC358. Site-specific K t factors can be determined for a
given project with full-scale load testing.
Soil capacities listed are ultimate values at maximum installation
torque. Allowable soil capacity values are obtained by dividing the
ultimate values by the appropriate factor of safety (FOS). FOS is
most commonly taken as 2.0, although a higher or lower FOS may be
considered at the discretion of the helical pile designer or as
dictated by local code requirements.
Square shaft piles may be considered for compression applications in
soil profiles that offer sufficient continuous lateral support;
e.g., in soils with SPT blow counts ≥ 10. Even in these higher
strength soil conditions, buckling analyses should be considered,
taking into account discontinuities and potential eccentricities
created by the couplers
The ultimate capacity of a helical pile may be calculated using the traditional bearing capacity equation:
Qu = ∑ [Ah (cNc + qNq)]
Where:
Qu
=
Ultimate Pile Capacity (lb)
Ah
=
Area of Individual Helix Plate (ft2)
c
=
Effective Soil Cohesion (lb/ft2)
Nc
=
Dimensionless Bearing Capacity Factor = 9
q
=
Effective Vertical Overburden Pressure (lb/ft2)
Nq
=
Dimensionless Bearing Capacity Factor
Total stress parameters should be used for short-term and transient load applications and effective stress parameters should be used for long-term, permanent load applications. A factor of safety of 2 is typically used to determine the allowable soil bearing capacity, especially if torque is monitored during the helical pile installation.
Like other deep foundation alternatives, there are many factors to be considered in designing a helical pile foundation. Supportworks recommends that helical pile design be completed by an experienced geotechnical engineer or other qualified professional.
Another well-documented and accepted method for estimating helical pile capacity is by correlation to installation torque. In simple terms, the torsional resistance generated during helical pile installation is a measure of soil shear strength and can be related to the bearing capacity of the pile.
Qu = KT
Where:
Qu
=
Ultimate Pile Capacity (lb)
K
=
Capacity to Torque Ratio (ft-1)
T
=
Installation Torque (ft-lb)
The capacity to torque ratio is not a constant and varies with soil conditions and the size of the pile shaft. Load testing using the proposed helical pile and helix blade configuration is the best way to determine project-specific K-values. However, ICC-ES AC358 provides default K-values for varying pile shaft diameters, which may be used conservatively for most soil conditions. The default value for the Model 288 Helical Pile System (2 7/8-inch diameter) is K = 9 ft-1.
Cities in Atlantic County, NJ Absecon Atlantic City Brigantine Buena Cologne Dorothy Egg Harbor City Egg Harbor Township Elwood Estell Manor Hammonton Landisville Leeds Point Linwood Longport Margate City Mays Landing Milmay Minotola Mizpah Newtonville Northfield Oceanville Pleasantville Pomona Port Republic Richland Somers Point Ventnor City
Cities in Bergen County, NJ Allendale Alpine Bergenfield Bogota Carlstadt Cliffside Park Closter Cresskill Demarest Dumont East Rutherford Elmwood Park Emerson Englewood Englewood Cliffs Fair Lawn Fairview Fort Lee Franklin Lakes Garfield Glen Rock Hackensack Harrington Park Hasbrouck Heights Haworth Hillsdale Ho Ho Kus Leonia Little Ferry Lodi Lyndhurst Mahwah Maywood Midland Park Montvale Moonachie New Milford North Arlington Northvale Norwood Oakland Oradell Palisades Park Paramus Park Ridge Ramsey Ridgefield Ridgefield Park Ridgewood River Edge Rochelle Park Rutherford Saddle Brook Saddle River South Hackensack Teaneck Tenafly Teterboro Township Of Washington Waldwick Wallington Westwood Wood Ridge Woodcliff Lake Wyckoff
Cities in Burlington County, NJ Beverly Birmingham Bordentown Browns Mills Burlington Chatsworth Chesterfield Columbus Cookstown Delanco Delran Florence Hainesport Jobstown Joint Base Mdl Juliustown Lumberton Maple Shade Marlton Medford Medford Lakes Moorestown Mount Holly Mount Laurel New Lisbon Palmyra Pemberton Rancocas Riverside Riverton Roebling Shamong Southampton Tabernacle Vincentown Willingboro Wrightstown
Cities in Camden County, NJ Atco Audubon Barrington Bellmawr Berlin Blackwood Camden Cedar Brook Cherry Hill Clementon Collingswood Gibbsboro Glendora Gloucester City Haddon Heights Haddonfield Lawnside Magnolia Merchantville Mount Ephraim Oaklyn Pennsauken Runnemede Sicklerville Somerdale Stratford Voorhees Waterford Works West Berlin Winslow
Cities in Cape May County, NJ Avalon Cape May Cape May Court House Marmora Ocean City Ocean View Rio Grande Sea Isle City Stone Harbor Strathmere Villas Wildwood Woodbine
Cities in Cumberland County, NJ Bridgeton Cedarville Delmont Greenwich Heislerville Leesburg Millville Newport Port Norris Shiloh Vineland
Cities in Essex County, NJ Belleville Bloomfield Caldwell Cedar Grove East Orange Essex Fells Fairfield Glen Ridge Irvington Livingston Maplewood Millburn Montclair Newark Nutley Orange Roseland Short Hills South Orange Verona West Orange
Cities in Gloucester County, NJ Bridgeport Clarksboro Clayton Deptford Franklinville Gibbstown Glassboro Grenloch Malaga Mantua Mickleton Mount Royal Mullica Hill National Park Newfield Paulsboro Pitman Sewell South Harrison Township Swedesboro Thorofare Wenonah Westville Williamstown Woodbury Woodbury Heights
Cities in Hudson County, NJ Bayonne Harrison Hoboken Jersey City Kearny North Bergen Secaucus Union City Weehawken West New York
Cities in Hunterdon County, NJ Annandale Asbury Bloomsbury Califon Clinton Flemington Frenchtown Glen Gardner Hampton High Bridge Lambertville Lebanon Milford Oldwick Pittstown Pottersville Ringoes Stockton Three Bridges Whitehouse Station
Cities in Mercer County, NJ Hightstown Hopewell Lawrence Township Pennington Princeton Princeton Junction Robbinsville Titusville Trenton Windsor
Cities in Middlesex County, NJ Avenel Carteret Colonia Cranbury Dayton Dunellen East Brunswick Edison Fords Helmetta Highland Park Iselin Keasbey Kendall Park Metuchen Middlesex Milltown Monmouth Junction Monroe Township New Brunswick North Brunswick Old Bridge Parlin Perth Amboy Piscataway Plainsboro Port Reading Sayreville Sewaren South Amboy South Plainfield South River Spotswood Woodbridge
Cities in Monmouth County, NJ Allenhurst Allentown Allenwood Asbury Park Atlantic Highlands Avon By The Sea Belford Belmar Bradley Beach Brielle Cliffwood Colts Neck Cream Ridge Deal Eatontown Englishtown Fair Haven Farmingdale Fort Monmouth Freehold Hazlet Highlands Holmdel Howell Keansburg Keyport Leonardo Lincroft Little Silver Long Branch Manasquan Marlboro Matawan Middletown Millstone Township Monmouth Beach Morganville Neptune Oakhurst Ocean Grove Oceanport Port Monmouth Red Bank Roosevelt Rumson Sea Girt Shrewsbury Spring Lake West Long Branch
Cities in Morris County, NJ Boonton Brookside Budd Lake Butler Cedar Knolls Chatham Chester Denville Dover East Hanover Flanders Florham Park Gillette Green Village Hibernia Kenvil Lake Hiawatha Lake Hopatcong Landing Ledgewood Lincoln Park Long Valley Madison Mendham Millington Mine Hill Montville Morris Plains Morristown Mount Arlington Mount Freedom Mount Tabor Mountain Lakes Netcong New Vernon Parsippany Pequannock Pine Brook Pompton Plains Randolph Riverdale Rockaway Schooleys Mountain Stirling Succasunna Towaco Wharton Whippany
Cities in Ocean County, NJ Barnegat Barnegat Light Bayville Beach Haven Beachwood Brick Forked River Island Heights Jackson Lakehurst Lakewood Lanoka Harbor Lavallette Little Egg Harbor Twp Manahawkin Manchester Township Mantoloking New Egypt Ocean Gate Pine Beach Point Pleasant Beach Seaside Heights Seaside Park Toms River Tuckerton Waretown West Creek
Cities in Passaic County, NJ Bloomingdale Clifton Haledon Haskell Hawthorne Hewitt Little Falls Newfoundland Oak Ridge Passaic Paterson Pompton Lakes Ringwood Totowa Wanaque Wayne West Milford
Cities in Salem County, NJ Elmer Monroeville Pedricktown Penns Grove Pennsville Salem Woodstown
Cities in Somerset County, NJ Basking Ridge Bedminster Belle Mead Bernardsville Bound Brook Bridgewater Far Hills Flagtown Franklin Park Gladstone Hillsborough Kingston Lyons Manville Martinsville Neshanic Station Peapack Raritan Rocky Hill Skillman Somerset Somerville South Bound Brook Warren Watchung Zarephath
Cities in Sussex County, NJ Andover Augusta Branchville Franklin Glenwood Hamburg Highland Lakes Hopatcong Lafayette Layton Montague Newton Ogdensburg Sparta Stanhope Stockholm Sussex Vernon
Cities in Union County, NJ Berkeley Heights Clark Cranford Elizabeth Elizabethport Fanwood Garwood Hillside Kenilworth Linden Mountainside New Providence Plainfield Rahway Roselle Roselle Park Scotch Plains Springfield Summit Union Vauxhall Westfield
Cities in Warren County, NJ Allamuchy Belvidere Blairstown Columbia Great Meadows Hackettstown Johnsonburg Oxford Phillipsburg Port Murray Stewartsville Vienna Washington
Cities in Rockland County, NY Bear Mountain Blauvelt Congers Garnerville Grandview On Hudson Haverstraw Hillburn Monsey Nanuet New City Nyack Orangeburg Palisades Pearl River Piermont Pomona Sloatsburg Sparkill Spring Valley Stony Point Suffern Tallman Tappan Thiells Tomkins Cove Valley Cottage West Haverstraw West Nyack
Cities in Berks County, PA Bally Barto Bechtelsville Hereford New Berlinville
Cities in Bucks County, PA Bensalem Bristol Buckingham Carversville Chalfont Croydon Doylestown Dublin Erwinna Fairless Hills Feasterville Trevose Fountainville Furlong Jamison Kintnersville Langhorne Levittown Line Lexington Milford Square Morrisville New Hope Newtown Ottsville Perkasie Pipersville Point Pleasant Quakertown Richboro Richlandtown Riegelsville Sellersville Silverdale Southampton Springtown Trumbauersville Upper Black Eddy Warminster Warrington Washington Crossing Wycombe
Cities in Chester County, PA Parker Ford
Cities in Lehigh County, PA Allentown Center Valley Coopersburg Emmaus Zionsville
Cities in Montgomery County, PA Abington Ambler Bala Cynwyd Blue Bell Bridgeport Bryn Athyn Cheltenham Collegeville Colmar Conshohocken Dresher East Greenville Elkins Park Flourtown Fort Washington Frederick Gilbertsville Gladwyne Glenside Green Lane Gwynedd Gwynedd Valley Harleysville Hatboro Hatfield Horsham Huntingdon Valley Jenkintown King Of Prussia Lafayette Hill Lansdale Merion Station Montgomeryville Narberth Norristown North Wales Oaks Oreland Palm Pennsburg Perkiomenville Plymouth Meeting Pottstown Red Hill Royersford Sassamansville Schwenksville Skippack Souderton Spring House Telford Willow Grove Wyncote Zieglerville
Cities in Northampton County, PA Bethlehem Easton Hellertown
