The effect of footing closeness (of three parallel similar strip footings at equal distance from each other) on soil bearing capacity is studied using the finite element method. Flexible and Rigid (surface and buried) footings resting on clayey (under undrained conditions) and sandy soils, are analyzed.
The effect on bearing capacity due to footings interference is expressed by the efficiency factor (Ef), which represents the ratio between the bearing capacity of the closely-spaced footings and that of a similar single footing under the same conditions.
The results show negligible effect of interference on the bearing capacity of flexible footings. The closeness of rigid strip footings, generally, results in increasing the soil bearing capacity. The embedment depth has a suppressing effect on interference when the footings are very close to each other.