The Study of Behaviour of Pile-Cap in Expansive SoilsUsing a Finite Element Softening Model

Abstract

The behavior of pile-cap in expansive soils layers under axial loading was investigated using axi-symmetric state , finite element model, these consists of soil continuum elements, with material non-linearties for the soil, and the pile-cap is simulated as linear elastic material. The simulation of soil swelling is based on the softening model to determine swelling potential and hence upheaval deformation in pile-cap-soil system. The literature review was undertaken in order to provide a framework of available information regarding expansive soils and pile foundation on them. The behavior of pile-cap has been studied extensively using different load, pile diameter, cap diameter and thickness of cap. It is found out from the results of simulation analysis that the addition of a cap to a pile and taking advantage of the axial load resistance of pile cap have been found to increase the axial load carrying capacity of pile-cap system. The increase in size of pile cap has been found to increase the axial load carrying capacity of pile significantly. Axial behavior of a pile-cap system is directly related to the axial capacity of the piles. Also, the results obtained using the softening model confirm the fact that the cap on expansive soils increases upheaval deformations in Pile-Cap-Expansive soils systems and induces high tensile stresses in piles.

Key words: expansive soil, swelling potential, softening model, upheaval deformation, pile-cap through expansive soil.