Transmission And Substation Foundations - Technical Design Manual (TD06088E)

can actually take more load, up to as much as 20% of the helix diameter. Using a ASD Factor of Safety of 2.0, the working load for this anchors would be equal to 19,500 lbs/2.0 = 9,750 lbs. Because the load-displacement curve of most helical piles/anchors is generally nonlinear it would be expected that the displacement at the working load would be less than ½ of the displacement at 1.20 in. In this case, the displacement at the working load of 9,750 lbs is on the order of 0.36 in. Using a lower Factor of Safety gives a higher displacement. For example if a Factor of Safety of 1.5 is used, the working load becomes 19,500 lbs/1.5 = 13,000 lbs and the displacement corresponding to this load is on the order of 0.55 in. Based on a review of a number of tests performed on single-helix pile/anchors in Colorado, Cherry and Perko (2012) recently suggested that for many anchors/piles, the displacement at the working loads (F.S. = 2) averaged about 0.25 in. Additional work is needed to determine how this may vary for multi-helix piles/anchors and if other soils show different behavior. References: 1. Specification ASTM D 1586, Standard Test Method for Penetration Test and Split-Barrel Sampling of Soils, American Society for Testing and Materials. 2. Abdelghany, Y, and El Naggar (2010), Full-scale Experimental and Numberical Analysis of Instrumented Helical Screw Piles Under Axial and Lateral Montonic and Cyclic Loadings – A Promising Solution for Seismic Retrofitting. Proceedings of the 6th International Engineering and Construction Conference, Cairo, Egypt. 3. Bjerrum, L., Norwegian Experiences with Steel Piles to Rock, Geotechnique, Vol 7, 1957. 4. Bowles, J.E., Foundation Analysis and Design, First Edition, McGraw-Hill, 1968. 5. Bowles, J.E., Foundation Analysis and Design, Fourth Edition, McGraw-Hill, 1988. 6. Brinch Hansen, J., The Ultimate Resistance of Rigid Piles Against Transversal Forces, Geoteknish Institute Bulletin No. 12, Copenhagen, 1961. 7. Broms, Bengt. B., Lateral Resistance of Piles in Cohesive Soils, Proceedings of the American Society of Civil Engineers, Journal of the Soil Mechanics and Foundations Division, Vol. 90, SM2, 1964. 8. Broms, Bengt B., Lateral Resistance of Piles in Cohesionless Soils, Proceedings of the American Society of Civil Engineers, Journal of the Soil Mechanics and Foundations Division, vol. 90 SM3, 1964. 9. Cadden, Allen and Jesus Gomez, Buckling of Micropiles, ADSC-IAF Micropile Committee, Dallas, TX, 2002. 10. Clemence, Samuel P. and others, Uplift Behavior of Anchor Foundations in Soil, American Society of Civil Engineers, 1985. 11. Das, Braja M., Theoretical Foundation Engineering, Elsevier Science Publishing Company Inc., New York, NY, 1987. 12. Davis, E.H., The Application of the Theory of Plasticity to Foundation Problems-Limit Analysis, Post Graduate Course, University of Sydney, Australia, 1961. 13. Davisson, M.T., Estimating Buckling Loads for Piles, Proceedings of the Second Pan-American Conference on Soil Mechanics and Foundation Engineering, Brazil, Vol 1, 1963. 14. Davisson, M.T., Laterally Loaded Capacity of Piles, Highway Research Record, No. 333: 104-112, 1970. 15. Design Manual DM7, NAVFAC, Foundations and Earth Structures, Government Printing Office, 1986. 16. Design Manual DM7, NAVFAC, Soil Mechanics, Government Printing Office, 1986. 17. Gouvenot, D., Essais en France et a l’Etranger sur le Frottement Lateral en Fondation: Amelioration par Injection, Travaux, 464, Nov, Paris, France, 1973.

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