Physical Modelling of High-Capacity Piles under Axial Loading

This paper presents selected aspects of an on-going experimental study on the enhanced capacity of deep foundations under axial loading. The research uses geotechnical centrifuge model testing to examine the behaviour of rotary bored piles in over consolidated clay. An increase in the shaft capacity of the pile was achieved by modifying the shaft geometry and thus the shear stress development under working load. In each test, internal consistency was achieved by simultaneously testing three modified piles and one conventional straight shafted pile. The experimental set up was designed to ensure the independent behaviour of each pile. The load applied and the pile head settlement were recorded. Encouraging results show that the changes to the shaft geometry increased the ultimate capacity of the pile by between 20% and 40% of the equivalent straight-shafted pile depending on the shape and the spacing of the enhanced geometry.