Pile Design and Construction Practice, Fifth edition

Pile groups under compressive loading 245

where c cohesion intercept of soil

Nc, Nqand N bearing capacity factors

sc, sqand s shape factors

dc, dqand d depth factors

ic, iqand i load inclination factors

bc, bqand b base inclination factors

 density of the soil

po pressure of the overburden soil at foundation level.

For undrained conditions ( 0 ) the second term of the equation is omitted and cu
is substituted for c.For drained conditions, c(the cohesion intercept in terms of effec-
tive stress) is used instead of c.Values of the factors in equation 5.1 are shown in
Figures 5.6 to 5.10.

0

250

200

160

120

100

80

60

40

30

20

16

12

10

8

6

4

3

2

(^15101520)
Ground level
Ground surface
D (not greater
than B)
Equivalent horizontal base
Key to dimensions
V D
V
B/2
B
B

H H
25 30 35 40 45
Angle of shearing resistance, f (°)
Nc
N
Bearing capacity factors, Nq
Nc
, N
, q
N
Figure 5.6Bearing capacity factors Nc,Nqand N (after Brinch Hansen(5.4)).