The resultant load and its position are determined for the critical load case.
While with the rectangular base the balancing is done by varying the cantilever and with the trapezoidal base by varying the end dimensions, in this case the balancing is done by forming a hole in the base positioned so as to move the centroid of the base to coincide with that of the resultant load (see Fig. 9.19).
Fig. 9.19 Holed balanced pad foundation.