The ultimate bearing capacity of a single/isolated footing has been investigated intensively by many researchers. Although a lot of studies considered different aspects affecting the bearing capacity, only very few focused on the influence of an existing footing on the bearing capacity of a new footing in its close proximity. In this study, the influence of an existing footing on the ultimate bearing capacity of a recently constructed footing in a close spacing has been investigated with respect to different sizes of the footings, spacings between the footings, friction angles of the subsoil and loads applied on the existing footing. Numerical simulations based on finite-element limit analysis (FELA) are utilized to determine lower and upper bounds of the ultimate bearing capacity which bracket the exact solution from below and above. The results for isolated footings are compared with selected data from literature in terms of the bearing capacity factor Nγ indicating good agreement of both, lower and upper bound values. Accuracy of the results was enhanced by applying an adaptive mesh refinement technique which enabled a more precise approximation of the failure mechanism and a better estimation of the exact solution due to smaller differences between the lower and upper bound solutions. The results for footings placed next to an existing footing are discussed with regard to the interference factor ξγ as well as the shape and size (extend) of the failure mechanism. The results illustrate that two types of failure mechanisms may develop which either extend up to the front edge of the existing footing or pass underneath. Comparisons with previous studies revealed that interference factors have been improved significantly due to utilization of adaptive mesh refinement technique. Moreover, design charts for an estimation of ξγ are presented for variable footing width ratios, spacings between the footings, friction angles of the subsoil and loading factors of the existing footing.
- Adaptive mesh refinement
- Design charts
- Finite element limit analysis
- Interference effects
ASJC Scopus subject areas
- Civil and Structural Engineering
- Geotechnical Engineering and Engineering Geology