Commercial Foundation Repair in TN, including Richmond, London & Somerset.

Commercial Helical Anchors / Tiebacks

Helical Ancors and Tiebacks

Helical Anchors (also referred to as tiebacks) provide lateral stability to foundation walls and retaining walls with unbalanced earth pressures. Helical anchors can be installed with hand-held equipment, mini-excavators, skid steers, backhoes, trackhoes, or crane-supported rigs so the anchors can be installed in almost any application. This versatility, along with the ability to immediately load and test the anchors, make helicals a convenient and economical solution for a wide variety of projects.

Advantages

  • Predictable capacity
  • Helix blade configuration selected to achieve design embedment and capacity
  • All-weather installation
  • Can be installed in areas of limited or tight access
  • Installation does not generate spoils
  • Clean installation with no messy grout
  • Load tests can be performed immediately following installation
  • Available with optional hot-dip galvanizing for added corrosion protection

Design Considerations

Helical anchors 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, welded to the lead section. Extension shafts, with or without additional helix plates, are used to extend the anchor into competent load-bearing soils. Helical anchors 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 foundation system loaded in axial compression, while the term "anchor" more often refers to a helical foundation system loaded in axial tension.

Determination of Capacity

The ultimate capacity of a helical anchor may be calculated using the traditional bearing capacity equation:

Qu = ∑ [Ah (cNc + qNq)]

Where:
Qu = Ultimate Anchor 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 anchor installation.

Another well-documented and accepted method for estimating helical anchor capacity is by correlation to installation torque. In simple terms, the torsional resistance generated during helical anchor installation is a measure of soil shear strength and can be related to the bearing capacity of the anchor.

Qu = KT

Where:
Qu = Ultimate anchor 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 anchor shaft. Load testing using the proposed helical anchor and helix blade configuration is the best way to determine project-specific K-values. 

Helix Blade Geometry

Helical anchors feature blades manufactured with a true helix. The leading and trailing edges of true helix blades are within one-quarter inch of parallel to each other and any radial measurement across the blade is perpendicular to the anchor shaft. A true helix shape along with proper alignment and spacing of the blades is critical to minimize soil disturbance during installation.

Conversely, blades that are not a true helix shape are often formed to a 'duckbill' appearance. These plates create a great deal of soil disturbance and do not conform to the helix geometry requirements since their torque to capacity relationships are not well documented.

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Serving TN including the Greater Richmond area
Our Tennessee Service Area
Cities in Anderson County, TN
Andersonville
Briceville
Clinton
Lake City
Norris
Oak Ridge

Cities in Bledsoe County, TN
Pikeville

Cities in Blount County, TN
Alcoa
Friendsville
Louisville
Maryville
Rockford
Tallassee
Townsend
Walland

Cities in Bradley County, TN
Charleston
Cleveland
Mc Donald

Cities in Campbell County, TN
Caryville
Duff
Jacksboro
Jellico
La Follette
Newcomb
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Cities in Carter County, TN
Elizabethton
Hampton
Roan Mountain
Watauga

Cities in Claiborne County, TN
Arthur
Clairfield
Cumberland Gap
Eagan
Harrogate
Lone Mountain
New Tazewell
Pruden
Shawanee
Speedwell
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Cities in Clay County, TN
Celina

Cities in Cocke County, TN
Bybee
Cosby
Del Rio
Hartford
Newport
Parrottsville

Cities in Cumberland County, TN
Crab Orchard
Crossville
Pleasant Hill

Cities in Fentress County, TN
Allardt
Clarkrange
Grimsley
Jamestown
Pall Mall

Cities in Grainger County, TN
Bean Station
Blaine
Powder Springs
Rutledge
Thorn Hill
Washburn

Cities in Greene County, TN
Afton
Chuckey
Greeneville
Midway
Mohawk
Mosheim

Cities in Grundy County, TN
Altamont
Beersheba Springs
Coalmont
Gruetli Laager
Monteagle
Palmer
Pelham
Tracy City

Cities in Hamblen County, TN
Lowland
Morristown
Russellville
Talbott
Whitesburg

Cities in Hamilton County, TN
Apison
Bakewell
Birchwood
Chattanooga
Collegedale
Harrison
Hixson
Lookout Mountain
Lupton City
Ooltewah
Sale Creek
Signal Mountain
Soddy Daisy

Cities in Hancock County, TN
Kyles Ford
Sneedville

Cities in Hawkins County, TN
Bulls Gap
Church Hill
Eidson
Mooresburg
Mount Carmel
Rogersville
Surgoinsville

Cities in Jefferson County, TN
Dandridge
Jefferson City
New Market
Strawberry Plains
White Pine

Cities in Johnson County, TN
Butler
Laurel Bloomery
Mountain City
Shady Valley
Trade

Cities in Knox County, TN
Corryton
Heiskell
Knoxville
Mascot
Powell

Cities in Loudon County, TN
Greenback
Lenoir City
Loudon
Philadelphia

Cities in Marion County, TN
Guild
Jasper
Sequatchie
South Pittsburg
Whiteside

Cities in Mcminn County, TN
Athens
Calhoun
Englewood
Etowah
Niota
Riceville

Cities in Meigs County, TN
Decatur
Georgetown
Ten Mile

Cities in Monroe County, TN
Madisonville
Sweetwater
Tellico Plains
Vonore

Cities in Morgan County, TN
Coalfield
Deer Lodge
Lancing
Oakdale
Petros
Rugby
Sunbright
Wartburg

Cities in Overton County, TN
Allons
Allred
Alpine
Crawford
Hilham
Livingston
Monroe
Rickman
Wilder

Cities in Pickett County, TN
Byrdstown

Cities in Polk County, TN
Copperhill
Delano
Farner
Reliance
Turtletown

Cities in Putnam County, TN
Cookeville
Monterey

Cities in Rhea County, TN
Dayton
Evensville
Grandview
Graysville
Spring City

Cities in Roane County, TN
Harriman
Kingston
Oliver Springs
Rockwood

Cities in Scott County, TN
Elgin
Helenwood
Huntsville
Oneida
Robbins
Winfield

Cities in Sequatchie County, TN
Dunlap
Whitwell

Cities in Sevier County, TN
Gatlinburg
Kodak
Pigeon Forge
Sevierville
Seymour

Cities in Sullivan County, TN
Blountville
Bluff City
Bristol
Kingsport
Piney Flats

Cities in Unicoi County, TN
Erwin
Flag Pond
Unicoi

Cities in Union County, TN
Luttrell
Maynardville
Sharps Chapel

Cities in Van Buren County, TN
Spencer

Cities in Washington County, TN
Fall Branch
Johnson City
Jonesborough
Limestone
Telford

Cities in White County, TN
Sparta

Cities in Bland County, VA
Bastian
Ceres
Rocky Gap

Cities in Bristol City County, VA
Bristol

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Big Rock
Davenport
Grundy
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Mavisdale
Oakwood
Pilgrims Knob
Raven
Rowe
Vansant
Whitewood

Cities in Dickenson County, VA
Bee
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Clinchco
Clintwood
Haysi
Mc Clure
Nora

Cities in Grayson County, VA
Elk Creek
Independence
Mouth Of Wilson
Troutdale
Whitetop

Cities in Lee County, VA
Blackwater
Dryden
Ewing
Jonesville
Keokee
Pennington Gap
Rose Hill
Saint Charles

Cities in Norton City County, VA
Norton

Cities in Russell County, VA
Castlewood
Cleveland
Dante
Honaker
Lebanon
Rosedale
Swords Creek

Cities in Scott County, VA
Duffield
Dungannon
Fort Blackmore
Gate City
Hiltons
Nickelsville
Weber City

Cities in Smyth County, VA
Atkins
Chilhowie
Marion
Saltville
Sugar Grove

Cities in Tazewell County, VA
Amonate
Bandy
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Bluefield
Broadford
Cedar Bluff
Doran
Falls Mills
Jewell Ridge
North Tazewell
Pounding Mill
Richlands
Tannersville
Tazewell

Cities in Washington County, VA
Abingdon
Bristol
Damascus
Glade Spring
Meadowview
Mendota

Cities in Wise County, VA
Appalachia
Big Stone Gap
Coeburn
East Stone Gap
Pound
Saint Paul
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Cities in Wythe County, VA
Cripple Creek
Crockett
Rural Retreat
Speedwell

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Cucumber
Jenkinjones
Newhall
War
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