Effect of Construction Procedures on the Performance of Bored Piles

The load-displacement performance and the working load of bored piles are critically affected by its construction procedure; nevertheless, current design methods do not take into account these effects. These effects include relaxation of soil due to excavation of the borehole, roughness of borehole sides, recompression of soil by fluid concrete placement, intermixing between concrete and drilling fluid, and numerous other factors. Due to these factors, conservative design parameters for soil are implemented in pile design and consequently a conservative approach to design is therefore pursued. This conservativeness, which has no theoretical bases, is different from one country to another all over the world. Well-trained personnel and expert engineers can eliminate some of the construction effects totally or partly: The paper presents case studies on full scale loading tests on bored piles, constructed at different subsoil conditions. The results confirm that a close coordination between the designer and the construction team, along with loading tests on piles, can increase the reliability in assessing the pile capacity and significantly reduce the effects of construction procedure on the performance of bored piles. Finally, the paper outlines that improper sub-surface soil investigation results in a defected bored pile.