Ground helix pile for construction
Ground helix pile for construction, sometimes referred to as screw anchors, screw-piles, helical piles, and helical anchors are a steel screw-in piling and ground anchoring system used for building deep foundations. Ground helix pile for construction are manufactured using varying sizes of tubular hollow sections for the pile or anchors shaft.
General Bearing Capacity Equation
At the present time, the design of Ground helix pile for construction generally follows the traditional theory of General Bearing Capacity used for compression loading of foundations. Terzaghi’s general bearing capacity equation for determining ultimate bearing capacity, as given in most Foundation Engineering textbooks is often stated as:
qult = c’Nc + q’Nq + 0.5γ’BNγ
qult = Ultimate Unit Bearing Capacity
c’ = effective cohesion
q’ = effective overburden stress = γ’D
γ’ = effective unit weight of soil
D = depth
B = diameter of helix
Nc, Nq, Nγ = bearing capacity factors
Notes on use of Terzaghi’s General Bearing Capacity equation:
1. Because B is considered very small for Ground helix pile for construction, relative to most concrete footings, some engineers choose to ignore the term 0.5γ’BNγ in design.
2. In saturated clays under compression loading, Skempton’s (1951) Bearing Capacity Factor for shallow round helical plates may also be used: NC = 6.0(1 + 0.2D/B) < 9.0
3. The unit weight of the soil is the total (wet) unit weight if the helical plate is above the water table and the buoyant unit weight if the helical plate is below the water table.
4. For saturated clay soils with φ’ = 0, Nq = 1.0; For sands, Nq is a function of friction angle, φ’
5. In all cases, for both compression and tension loading, the upper limit of capacity is governed by the mechanical strength of the Screw-Pile or Helical Anchor as provided by the manufacturer.
The main benefits of Ground helix pile for construction include: shorter project times, ease of installation, ease of access, reduction of the carbon footprint, ease of removal when the foundations are no longer required, reduced risk to the workforce, and reduced costs.
They are also suitable for both tensile and compression loads, so they are also used for masts, signs, and retaining structures.