In geotechnical investigation, determination oftheseismic bearing capacity of foundation soil
constitutes an important task. The bearing capacity of soil under static loading has been extensively
studied since the early work of Prandtl (1921).Design of foundation in seismic areas needs special
considerations compared to the static case. The inadequate performance of structure during recent
earthquake has motivated researches to revise existing methods and to develop new method for
seismic resistant design. For foundation of structure built in seismic areas the demands to sustain load
and deformation during earthquake will probably be the severe in their design life. Due to seismic
loading foundation may experience decreases in bearing capacity and increases in settlement. Two
source of loading must be taken into consideration inertial loading caused by lateral forces imposed on
the superstructure, kinematic loading caused by the ground movement developed during earthquake.
Many techniques used for studying the effect of seismic forces on the soil bearing capacity such as, limit
equilibrium method, kinematic approach of yield theory, a variational approach, and unified theory of
stress, which the shape of failure surface has been assumed. The seismic forces are considered as pseudostatic
forces acting both on the footing and on the soil under the footing. However, finite element and
stress characteristics methods shape of the failure is not required to be assumed.
In the present paper, a theoretical analysis has been performed on the basis of Krey's method
(friction circle method) with radius of friction circle equal to = 𝑟 sin (∅ − tan−1 𝑘ℎ
1−𝑘𝑣
)where r is the
radius of the circle slip surface to determine the influence of the earthquake acceleration coefficients
on the seismic bearing capacity of foundation with assisted by a computer program. The present
study is compared with the various theoretical solutions. The comparison of that the present study
predicted values of ultimate seismic bearing capacity of soil are less than others theories of ultimate
seismic bearing capacity. In order facilitate the calculation of seismic bearing capacity, using the
proposed equations. It is a function of (B, Rf, , tan ∅ , 𝑘ℎ and c)