142_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011

142_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011 -...

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DF21 Pile Driving Formulae (from Das, 1995) To develop the desired load-carrying capacity, a point bearing pile must penetrate the dense soil layer sufficiently or have sufficient contact with a layer of rock. This require- ment cannot always be satisfied by driving a pile to a predetermined depth because soU profiles vary. For that reason, several equations have been developed to calculate the ultimate capacity of a pile during driving. Three dynamic equations are widely used in the field to determine whether the pile has reached satisfactory bearing value at the predetermined depth. One of the earliest of these dynamic equations-commonly referred to as the Engineering News Recard (ENll) formula-is derived from the work- energy theory. That is, Energy imparted by the hammer per blow = (pile resistance)(penetration per hammer blow) According to the ENR fonnula, the pile resistance is the ultimate load
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Unformatted text preview: Q", expressed as Q = WRh II S+C (8.99) where W R = weight of the ram (for example, see Table 8.6) h = height of fall of the ram S = penetration of pile per hammer blow C = a constant The pile penetration, S, is usually based on the average value obtained from the last few driving blows. In the equation's original fonn, the following values of C were recommended. For drop hammers: C = 0.1 inch (if the units of Sand h are in inches) For steam hammers: C = 1.0 inch (if the units ofS and II are in inches) Also, a factor of safety, FS = 6, was recommended to estimate the allowable pile capac-ity. Note that, for single- and double-acting hammers, the term WRh can be replaced by EH s (where E = hammer efficiency and HE = rated energy of hammer). Thus (8.100)...
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This note was uploaded on 02/10/2012 for the course CEG 4012 taught by Professor Staff during the Fall '08 term at University of Florida.

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