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)