Shallow foundation reliability design

The increasing awareness that soils are highly variable in terms of their physical-mechanical properties, has boosted the development of probabilistic computational models in geotechnics. Moreover European geotechnical regulations as Eurocode 7 (for example) refers to “characteristic” values for soil resistance in statistical sense and the use of partial coefficients prove to be a significant step forward compared to the use of global safety factors. Furthermore Eurocodes introduce the reliability based design which can be effectively employed whenever accurate estimation of soil resistance has been achieved. As far as the bearing capacity assessment is concerned, some of the most significant studies carried out in the last years on probabilistic basis are here recalled. Especially the influence of correlation among friction angle, cohesion and unit weight on footing design was investigated by many authors. Hereinafter the influence of cross correlation between cohesion c and friction angle φ on reliability level of bearing capacity calculation has been investigated. Accordingly response surface method has been applied on Meyerhof formulation for bearing capacity of shallow foundations. Results show that the reliability index  decreases with the increases of applied pressure differently according to cross correlation values. Finally such results have been compared with the ones from Babu and Srivastava study and some hints for the use of cross correlation coefficients in shallow foundation design are drawn.