3439
Bearing capacity of shallow foundation under eccentrically inclined load
Capacité portante d’une fondation superficielle sous une charge inclinée excentrique
Atalar C.
Near East University, Nicosia, North Cyprus
Patra C.R.
National Institute of Technology, Rourkela, India
Das B.M.
California State University, Sacramento, USA
Sivakugan N.
James Cook University, Townsville, Australia
ABSTRACT: Laboratory model tests were conducted in a dense sand to determine the bearing capacity of shallow strip foundation
subjected to eccentrically inclined load. The embedment ratio (ratio of the depth of embedment
D
f
to the width of the foundation
B
)
was varied from zero to one. Load eccentricity
e
was varied from zero to 0.15
B
and the load inclination with the vertical (α) was
varied from zero to 20 degrees. Based on the results of the present study, an empirical nondimensional reduction factor has been
developed. This reduction factor is the ratio of the bearing capacity of the foundation subjected to an eccentrically inclined load
(average eccentrically inclined load per unit area) to the bearing capacity of the foundation subjected to a centric vertical load.
RÉSUMÉ: Des essais ont été réalisés sur un sable dense en utilisant des modèles au laboratoire afin de déterminer la capacité portante
d’une fondation superficielle filante sous chargement inclinée excentrique. Nous avons fait varier le rapport d’encastrement de la
fondation (rapport entre la profondeur d’encastrement
D
f
et la largeur de la semelle
B
) entre 0 et 1. Nous avons également fait varier
l’excentricité de la charge
e
de 0 à 0.15
B
et l’inclinaison de 0 jusqu’à 20 degrés. Sur la base des résultats de cette étude, un facteur
empirique de réduction adimensionnel a été développé. Ce facteur de réduction est le rapport de la capacité portante d’une fondation
soumise à une charge inclinée excentrique (charge excentrique inclinée moyenne par unité de surface) par rapport à la capacité
portante d’une fondation soumise à une charge verticale centrée.
KEYWORDS: Load eccentricity, load inclination, sand, shallow foundation, reduction factor, ultimate bearing capacity
1 INTRODUCTION
On some occasions shallow foundations are subjected to
eccentrically inclined load as shown in Fig. 1 for the case of a
strip foundation of width
B
supported by sand. In Fig. 1,
Q
u
is
the ultimate load per unit length of the foundation applied with
an eccentricity
e
and inclined at an angle α with respect to the
vertical. Meyerhof (1963) proposed a relationship for the
vertical component of the average ultimate load per unit area of
the foundation based on the effective area concept. For granular
soil it can be expressed as
)
5.0
(
αcos
) ,(
idNB
idNq
B
B
B
Q q
qq q
u
euv
(1)
where
q
uv
(
e,
α)
= average vertical component of the ultimate load
per unit area with load eccentricity
e
and load inclination α,
q
=
γ
D
f
, γ = unit weight of sand,
D
f
= depth of foundation,
N
q
,
N
γ
=
bearing capacity factors,
B'
= effective width =
B
� 2
e
,
d
q
,
d
γ
=
depth factors, and
i
q
,
i
γ
= inclination factors.
Figure 1. Shallow foundation on granular soil subjected to eccentrically
inclined load.
The relationships for bearing capacity, depth and inclination
factors are as follow,
sin 1
sin 1
tan
e N
q
(2)
)4.1 tan( )1 (
q
N N
(3)
) 10
for (
2
45 tan
1.01
B
D
d d
f
q
(4)
2
90
1
q
i
(5)
and
2
1
i
(6)
where
= soil friction angle.
Purakayastha and Char (1977) conducted stability analyses
of eccentrically loaded strip foundations (α = 0) supported by
granular soil using the method of slices proposed by Janbu
(1957). Based on their study it was proposed that, for a given
D
f
/
B
,
c
euv
euv
B
e b R
q
q
1
)0 ,0 (
)0 ,(
(7)
