Geotechnical Engineering

DHARM

628 GEOTECHNICAL ENGINEERING

the coefficient of friction between the base of the footing and the soil beneath it. This is illus-
trated in Fig. 15.20.

Janbu (1957) proposed an analysis which is a direct extension of the Terzaghi theory
with an additional factor Nh, in addition to Terzaghi’s factors Nc, Nγ and Nq:

(.)RN H

A

+ h = cN

c + γDf Nq +

1

2

γbNγ ...(Eq. 15.16)

where A = area of base of footing.

The notation and values are shown in Fig. 15.21.

300

200

100

50

20

10

5

2

1

N , N ,

and

(Log scale)

c

q

NNg

h

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

tanf

Nq Ng Nh

Ng

Nc

V

=cN + DN +– bN

H V tan

cfqg

f

g g

Df

b

R

H

Area of base = A

1

V+N .H 2

A

h

Fig. 15.21 Continuous footing subjected to inclined load (After Janbu, 1957)

Df a Vb=R.qi ult

R

V/b = R .qi ult

R

b

Df

V

b

a

1.0

0.8

0.6

0.4

0.2

(^0204060) 80 90
D/b=0f
Cohesive soil
Granular soil
D/b 1f ³
Inclination ° to verticala
(a) From AREA
Reduction factor, R
i
q =Ultimate bearing capacity of horizontal footing under vertical load
R = Reduction factor (given in the charts below)
ult
i
1.0
0.8
0.6
0.4
0.2
0
20 40 60 80 90
Loose
Inclination ° of load to vertical
(= inclination of foundation to horizontal)
a
(b) After Meyerhof (1953)
Cohesive soil
D/b 1f ³
D/b=0f
Dense
granular
soil
Fig. 15.22 Footings subjected to inclined load (a) Horizontal foundation (AREA)
(b) Inclined foundation (Meyerhof)