Geotechnical Engineering

DHARM

582 GEOTECHNICAL ENGINEERING

140

120

100

80

60

40

(^0) 28 30 32 34 36 38 40 42 44 46
Angle of internal friction,f
Bearing capacity factors, N and N
q
g
Loose
Ver y
dense
01535
Medium Dense looseVer y
65 85 100
10
20
30
40
50
60
70
20
SPT value, N
N
Ng
Nq
Fig. 14.19 Correlation between N-value, φ, and the bearing capacity
factors (Nq and Nγ) (After Peck, Hanson, and Thornburn, 1953)
700
600
500
400
300
200
100
01 23 4 56
Width of footing, m
Allowable bearing pressure, kN/m
2
N=60
50
40
30
20
10
5
(settlement > 25 mm)
Fig. 14.20 Allowable bearing pressure for 25 mm settlement from
SPT values (After Terzaghi and Peck, 1948)
These charts have been prepared on the assumption that the water table is at a depth
greater than the width of the footing below the base of the footing. If the water table is located
at the base of the footing, the allowable pressure is taken as half that obtained from the charts.
For any intermediate position of the water table, linear interpolation may be made. Similarly,
if the allowable bearing pressure is required for any settlement other than the one for which
the charts are prepared, linear interpolation is suggested.