Helical Pile Torque-to-Capacity
Ultimate axial capacity from torque × Kt and allowable from factor of safety.
Example
You enter
- Shaft type 1.5_inch_solid
- Installation torque (ft·lb) 5000
- Factor of safety 2
You get
- Torque-to-capacity factor Kt 10
- Ultimate axial capacity 50000
- Allowable capacity 25000 lb
Checked against published worked examples from: Hubbell Power Systems, Inc. (CHANCE).
Details, formula, and sources
ScopeEngineer of record governs.
Formula or tableUltimate axial capacity = Kt × installation_torque (lb-ft). Allowable = ultimate / factor_of_safety. Kt by shaft type (ICC-ES AC358 defaults): 1.5 in solid 10, 1.75 in solid 10, 2.875 in pipe 9, 3.5 in pipe 7.
Source and editionICC-ES Acceptance Criteria AC358 (helical foundation systems) by name; manufacturer technical bulletins (CHANCE, Magnum, Ram Jack, AB Chance) by name.
Free accessICC-ES AC358 free at icc-es.org. Manufacturer Kt values free in each manufacturer's published evaluation report.
What governsEstimate. Engineer of record governs the design and acceptance. Verify against the project structural drawings and the manufacturer's published capacity / chart.
API field namesshaft, torque_ft_lb, factor_of_safety, Kt, ultimate_lb, allowable_lb
- Kt table data/construction/helical-pile-kt.json keyed to shaft typemanufacturer technical bulletins
- Default factor of safety 2.0 unless user supplies (engineering-practice default for axial helical piers)ICC-ES AC358 typical