Analytical studies on the geotechnical performance of shell foundations

Shell foundations are economic alternatives to conventional plain foundations where heavy superstructural loads are to be transmitted to weaker soils. The use of a shell is a material-saving technique, and for foundations, only forms that are not labour intensive are adopted. Shell foundations of different geometrical shapes have been extensively investigated on the structural side, at both the elastic and the ultimate stages. However, corresponding studies on their geotechnical performance in terms of bearing capacity and settlement, which are the basic parameters for their geotechnical design, are scarce. Because closed-form solutions are extremely complex, even in the limited cases where they have been attempted, the present investigations have resorted to numerical analyses by the finite element method, using the advanced Numerically Integrated Elements for Systems Analysis package. Three configurations of the shell, conical, spherical, and hyperbolic paraboloidal, have been taken up for these studies. The influence of the coefficient of interface friction (µ), type of soil (c, φϕ, and c–φϕ), and different loading conditions, involving vertical and horizontal loads and moments, on the bearing capacity and settlement of the shells and their plain counterparts has been studied for the sake of comparison. The results presented reveal the general superiority of shell foundations.Key words: shell foundations, plain foundations, bearing capacity, settlement, finite element analysis, relative performance.