Interference of Two Closely Spaced Footings: A Finite Element Modeling

The study pertains to finite element modeling of two closely spaced footings resting on linearly elastic foundation soil whose modulus of elasticity is either constant or linearly varying with depth. The problem is considered either 2-D (two-dimensional) or 3-D (three-dimensional), depending on length to width ratio of two footings and the analysis is made accordingly. The medium is discretized into a mesh of isoparametric 4-noded rectangular elements (2-D analysis) or 8-noded brick elements (3-D analysis). The necessary code has been developed in MATLAB 2008a and its accuracy checked by calibrating with existing benchmark problem. Parametric study has been carried out to study the effect of various parameters like width, spacing between the footings, length to width ratio, modulus of elasticity variation with depth etc. and these are found to greatly influence the load-settlement behavior of the footings. However, Poisson's ratio does not have much of influence on the same. In general, it is found that settlement increases with decrease in spacing between footings, decreases with increase in slope angle of linearly varying soil modulus with depth. At length to width ratio 10 and above the decreasing rate in settlement at center of footing is at most constant.