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143_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011

# 143_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011 -...

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DF22 The ENR pile-driving fonnula has been revised several times over the years. A recent fonn-the modified ENR formula-is Q _EWRhWR+nzW p u- S+C W R + W p (8.101) where E = hammer efficiency C = 0.1 in. if the units of Sand h are in inches W p = weight of the pile n = coefficient of restitution between the ram and the pile cap The efficiencies of Jarious pile driving hammers, E, are in the following ranges. Hammer Type Single and double-acting hammers Diesel hammers Drop hammers Efficiency, E 0.70-0.85 0.80-0.90 0.70-0.90 Representative values of the coefficient of restitution, n, are given in the following table. Pile Material Cast iron hammer and concrete piles (without cap) Wood cushion on steel piles Wooden Piles Coefficiellt of restitutioll, n 0.40-0.50 0.30-0.40
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Unformatted text preview: 0.40-0.50 0.30-0.40 0.25-0.30 A factor of safety of 4 to 6 may be used in Eq. (8.101) to obtain the allowable load-bearing capacity of a pile. The Michigan State Highway Commission (1965) undertook a study to obtain a rational pile-driving equation. At three diverse sites, a total of 88 piles were driven. Based on these tests, Michigan adopted a modified ENR formula: Q _ 1.25H B W R + nZW p U-S+ C W R + W p where H B = manufacturer's maximum rated hammer energy Ob·in.) C = 0.1 in. The unit of S is in inches in Eq. (8.102). A factor of safety of 6 is recommended. (8.102)...
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