Interference of the footings

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The Interference of the footings is a phenomenon that is observed when two footings are closely spaced. The buildings when are to be constructed nearby to each other, the architectural requirements or the less availability of space for the construction forces the engineers to place the foundation footings close to each other, and when foundations are placed close to each other with similar soil conditions, the Ultimate Bearing Capacity of each foundation may change due to the interference effect of the failure surface in the soil.

The figure illustrates stress isobar of an isolated footing carrying structural load.

The figure illustrates the isobars when two footings carrying structural load placed close to each other. Due to interference the stress isobars of individual interacting footings coalesce to form a single isobar of larger dimensions altering the characteristic behaviour of an isolated footing.


1 Introduction
2 Previous studies
3 Observed results
4 References

Foundations or group of foundations are important components of the structure through which the superficial structural loads are transmitted to the underlying foundation soil or bed on which the foundations are laid. The structural loads are transmitted to the foundation soil safely such that neither the foundation fail nor the foundation soil fails either in shear or in excessive settlement. The foundations are basically designed based on two criterion namely Bearing Capacity and Settlement criterion. Many classical theories have been postulated for the isolated foundations by many pioneers like Terzhagi (1943), Meyerhoff (1963), Hansen (1970) and Vesic (1973). In general as per the Terzaghi (1943), when an isolated shallow foundation is loaded, the stress or the failure zone in the foundation soil extends in horizontal direction on either side of the footing to about twice the width of the footing and in vertical downward direction to about three times the width of the footing. Unless until the stress or failure zone of individual footings do not interfere, the individual footings behave as an isolated footing. However, in many a situations such as lack of construction space, structural restrictions, rapid urbanization, architecture of the building, structures cl