Transmission And Substation Foundations - Technical Design Manual (TD06088E)
Bearing Capacity Factor Curve for Cohesionless Soils
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DESIGN METHODOLOGY
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10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 Angle of Internal Friction, degrees
Figure 4-5 Recommended Bearing Capacity Factor Nq for Deep Screw-Piles and Helical Anchors in Sand.
Mixed Soils φ ’ > 0; c’ > 0 The ultimate capacity of a deep screw-pile in mixed-grain soils can be taken from traditional bearing capacity theory using Equation 5-11: Q H = A H (cNc + q’Nq + 0.5 γ BN γ ) Note: The term 0.5 γ ’BN γ is typically ignored for helical piles because the helix plate is small.
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