DEM analysis of pile installation effect: comparing a bored and a driven pile

This paper presents a two-dimensional particle flow code (PFC2D) model of the discrete element method (DEM) that is used to study the effects of pile installation in deep foundation. It is accepted widely that installation method affects pile behaviour, but there are still limited studies that compare and analyse the impacts systematically. In this paper, the DEM is used to explain the pile behaviour installed in granular soils. A rigid bored pile and a rigid driven pile of the same geometry were installed into an assembly of granular soil modelled under a high gravitation force. Behaviour of the driven pile during penetration compares well with published data, and the numerical data also provides further insights of the soil-pile interaction during the penetration process. After pile installation, comparisons of the subsequent pile-loading behaviour were made, showing different contributions of shaft and end bearing resistance between the bored pile and the driven pile. Furthermore, the impacts of having different pile weights and different soil friction angles were discussed. When considering the same pile and soil friction, the driven pile performed better in the pile load test because the soil was compressed during the driving process. In particular, it was found that the soil friction affects the bored pile and the driven pile in a different manner such that soil friction will take effect after certain depth for bored pile, however, it will have an impact at the beginning for driven pile. Micro-scale sliding fraction of the particles near the two piles was also used to explain the observed phenomena.