High-capacity ribbed pile foundations

This research concerns the influence of ribs on the ultimate capacity of a bored pile in overconsolidated clay. Ribbed bored piles are known to give increased shaft capacity in comparison to conventional straight-shafted bored piles. The investigation seeks to explore the effectiveness of ribs at increasing the ultimate capacity of a pile, and furthermore to understand how this enhanced capacity is derived. The scale pile test results are analysed using several industry standard methods. A plastic failure envelope for the base of the pile rib is identified. This plastic failure envelope is used to provide a detailed design solution for the ultimate capacity of a ribbed pile. The design solution is simple and requires a summation of the constitutive contributions from each rib and from the base and shaft of the pile. This method has been used successfully to predict the ultimate capacity of any pile tested to within ± 8%.