settlement_of_shallow_foundations_on_granular_soils (Lutenegger ang DeGroot)

5.2.14 Peck et al. (1974)
In their foundation engineering textbook, Peck, Hanson and Thornburn (1974) suggested a
modification to the Terzaghi and Peck (1948, 1967) method by primarily adding a blowcount
correction factor for overburden stress and a correction for groundwater located near the base of the
footing. The expressions for settlement are:
s = (q)/(0.11 N, ew) (for medium sized footings (B> 2ft.))
s = (q)/(0.22 N, ew) (for rafts)
[5.50]
[5.51]
where:
s = settlement (in inches)
q = footing stress (in tsf)
N, = corrected blowcount = Nen
ew = water table correction
= 0.5 + 0.5 (W/(D+B))
[5.52]
The overburden correction to field blowcotints can be obtained from the expression:
en= 0.77 log (20/p')
[5.53]
where:
p' = effective overburden stress (in tsf) for the measured blowcount at D + B/2 ;, 0.25 tsf
For effective overburden stress less than 0.25 tsf (generally in the upper 1. 5 m (5 ft) a value of en
between 1.5 and 2.0 may be assumed.
5.2.15 Meyerhof (1974)
Meyerhofs most recent expressions for settlement are further modifications of the earlier
equations given (Meyerhof 1956, 1965) which are generally considered to be conservative. In this
case, the settlement is given as:
s = [( q) (B) 112 /(2N)] [ed]
s = [( q) (B) 112 /N] [ed] (for very fine or silty submerged sand)
[5.54]
[5.55]
where:
s = settlement (in inches)
q =footing stress (in tsf)
B = footing width (in inches)
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