A NUMERICAL STUDY ON INTERFERENCE EFFECTS OF CLOSELY SPACED STRIP FOOTINGS ON SOILS

Foundations of structures often need to be placed close to meet the architectural as well as the functional requirements. In such cases, the combined action of footings is different from a single footing. It causes interference of the stress zones. In the present study, the interference effects of two closely spaced strip footings on the surface of cohesive and cohesionless soils are being investigated. Parametric studies are done for two footings by varying the spacing between the footings and the width of the footings. The results are presented in terms of efficiency factors. In the first case, both the footings are loaded simultaneously up to failure. In the second case, one of the footings representing an already existing foundation is loaded with half of the estimated failure load of isolated footing and adjacent footing loaded up to failure. The effect of interference is observed to be particularly significant in terms of the settlement. Effect of shear keys placed beneath the footings, at different locations beneath the footing and the interference of such footings is also studied in case of stiff clay. It is found that the presence of shear keys has a significant effect on the interference between the footings, compared to without the shear keys, especially in reducing the tilt of foundations.