and 6.13, this method should only be utilized if the load Q is located within the middle one-third of
the footing.
Once the new dimensions of the footing have been calculated (i.e., L′ and B′), then Eq. 6.1 can
be used by substituting L′ for L and B′ for B.
Footings at the Top of Slopes. Although methods have been developed to determine the allowable
bearing capacity of foundations at the top of slopes (e.g., NAVFAC DM-7.2, 1982), these methods
should be used with caution when dealing with plastic (cohesive) soil. This is because the outer face
of slopes composed of plastic soils may creep downslope, leading to a loss in support for the footing
constructed at the top of such slopes. Structures constructed at the top of clayey slopes will be
further discussed in Chap. 10.
Inclined Base of Footing. Charts have been developed to determine the bearing capacity factors
for footings having inclined bottoms. However, it has been stated that inclined bases should never be
constructed for footings (AASHTO, 1996). Sometimes a sloping contact of underlying hard material
will be encountered during excavation of the footing. Instead of using an inclined footing base
along the sloping contact, the hard material should be excavated in order to construct a level footing
that is entirely founded within the hard material.