Abstract

The ultimate bearing capacity of shallow foundations under axial vertical loads on dense sand overlying deep loose deposit has been investigated. In the literature, several theories can be found using simplified failure mechanisms in conjunction with the punching shear failure. Accordingly, assumptions were used to simplify the evaluation of the level of mobilization of the shear strength on the punching column. This is mainly due to the complexity of modeling the earth pressure distribution on the punching column. In this study a numerical model was developed to investigate the case of continuous footing on dense sand overlying loose sand. The model utilizes the powerful software "PLAXIS" version 8.6, which is capable to model such complex interaction in two-dimensional stress analysis. The model was validated with the prototype test results of Meyerhof and Hanna (1978) and Hanna (1981- a). The results of this investigation showed that the shear strength mobilized on the punching column depends on the relative strength of the two layers, the width of the footing and the thickness and angle of shearing resistance of the upper layer. Design procedure and design charts have been presented to assist foundation engineers to predict the bearing capacity of footing on dense sand overlying deep loose deposit.