Elastoplastic Finite Element Analysis of Pile-Supported Circular Footing on Cohesionless Soil Using PLAXIS 2D

Abstract

In an established foundation design, it is usual to consider initially the use of shallow foundation. If shallow foundation is not adequate, deep foundation such as a pile foundation is recommended. Unlike the predictable pile foundation design in which the piles are designed to carry the major amount of load, the design of a Piled Footing allows the load to be collectively transferred between the footing and pile as well increase in capacity due to confinement below footing. Hence, it is important to take this complex soil–structure interaction effect into account. The present work is an attempt to determine the increase in capacity of piled footing due to the increase in skin friction of the pile beneath the shallow footing due to the confinement offered to the sand by the shallow footing. A parametric study is carried out only for cohesionless soil. The foundation type is circular footing over the circular pile of uniform cross-section. For this, different geometrical data viz. diameter of footing and diameter & length of the pile has been chosen after a review of different researches carried out in this area. To handle such type of soil–structure interaction problem, numerical simulation is done with the help of FEM software, PLAXIS 2D. While using PLAXIS 2D, the axisymmetric condition for modelling the pile, 15 nodded triangular elements, and Mohr–Coulomb model for the soil properties are used. After analyzing sets of problems in PLAXIS, it is concluded that Piled Footing proves to be advantageous for footing resting on loose sand rather than dense sand due to enhancement of skin friction beneath footing. The skin friction is increased even in dense sand, but at the cost of losing the capacity of shallow footing.