Stress Analysis in the Combination of Footplate and Caisson Foundation

Currently, the combined footplate-caisson foundation has been used for some projects. This type of foundation is one of the chosen low cost foundations for the structure supporting medium load when the bearing capacity of conventional foundation is not sufficient. The inserted caisson underneath the footing enables to increase its performance; has a better bearing capacity and lower settlement. Unfortunately, the theoretical basic regarding this foundation is not available so that the design tends to use a conservative approach. For this reason, the study on footplate-caisson foundation is essential to obtain the information of its performances. In this study, the combined footplate-caisson was numerically modelled in plane-strain condition as a foundation resting on clay. The footplate was modelled in the depth variation of 0.75 m up to 1.5 m in fixed width of 1.5 m x 1.5 m; whereas the caisson was modelled in depth variation of 0.75 up to 4.5 m in fixed diameter of 1.0 m. The properties of soil and foundation are presented in the paper. The applied load on the model was varied from 60 kPa up to 1000 kPa. The result of the study indicates that the presence of caisson contributes to the decrease in contact pressure in footplate. The percentage of the contribution depends on the dimension of each element and the depth of caisson.