settlement_of_shallow_foundations_on_granular_soils (Lutenegger ang DeGroot)

capacity is reduced, the allowable bearing pressure should be reduced with position of the water
table as indicated above for the ultimate bearing capacity."
Meyerhof (1965) gave essentially the same expressions for allowable bearing pressure as:
p, =Ns,/8
p, = (Ns,/12)((B+ 1)/B)Z
p, = Ns,/12 for rafts
where:
(forB ;; 4ft.)
(forB> 4ft.)
[6.11]
[6.12]
[6.13]
p, = allowable bearing pressure (in tsf)
N = SPT blowcounts (corrected for compact and dense, submerged silty sand)
B = foundation width (in ft.)
s, =allowable settlement (in inches)
Meyerhof noted that these relationships are "sensibly independent of the shape of the foundation,
and for a foundation depth approaching the width B, an increase of the allowable pressure by
approximately one-third is sometimes made." It was also noted that "Even without making any
allowance for the ground-water conditions, which are already reflected in the measured values of
N, ... the method still furnishes conservative bearing pressures."
6.5 Teng (1962)
The empirical allowable bearing pressure chart for a settlement of 25 mm (1 in.) of Terzaghi
and Peck (1948) was put into equation form by Teng (1962) as:
q, = 720 (N- 3) [(B+ 1)/(2B)]' R'w
[6.14]
where:
q, =net allowable bearing pressure (in psf)
B =footing width (in feet)
N = SPT blowcount
R'w =reduction factor for water level
The water table adjustment factor R'w is shown in Figure 6.7.
146