Effect of linearly increasing cohesion on the compression and uplift capacity of the under-reamed pile in clay

The present paper tries to explore the load-settlement behavior of an under-reamed pile subjected to either compressive or pull-out loading and installed in clay whose cohesion increases linearly with depth. In this regard, the finite element analysis was performed using OptumG2 software wherein the soil was assumed to obey Mohr-Coulomb's failure criterion under the undrained condition. For the selected pile geometry, the analysis was performed for the different values of linearly increasing cohesion and for the various shaft adhesion. The comparison of results for single and double under-reamed pile with a uniform diameter pile suggests that the provision of a bulb or under-reamed section to the pile helps in the increase in safe load and decrease in the settlement up to a certain value of the slope of linearly increasing cohesion. Additionally, the effect of no tension condition at the base of a pile on the safe and ultimate capacity was examined. The present results were found to compare well with that available literature.