An Assessment of the Contribution of Widely Spaced Pairs of Raked Bearing Piles in the Design of a Quay Retaining Wall Using 2D and 3D Finite Element Methods

Quay side structures typically include piled crane rails set-back a short distance from the quay wall to support large dockside cranes for loading and unloading of container ships. These crane piles may intercept the critical deep rotational slip surfaces analysed as part of the ultimate limit state (ULS) design of the quay retaining wall structure, resulting in reduced earth pressures on the wall and potentially allowing a reduction in the wall section modulus, increased wall efficiency and reduced costs. However, the contribution of the bearing piles to the overall stability of the quay wall is often ignored due to uncertainty of the effect of increased lateral spacing of the crane piles in comparison to piles used to reinforced slopes for stability purposes. This paper presents a case study of the contribution of open-ended steel crane rail piles to the design of the new quay structure in Dublin Port, Ireland. The crane piles were driven at a raked angle at 11 degrees to the vertical, with a lateral spacing between pairs of piles equivalent to eight pile diameters. Analyses were carried out using the finite element software programs Plaxis 2D and 3D to assess the contribution of the crane rail piles to reducing the structural forces in the sheet pile combi-wall. The results showed that, despite the wide spacing of the piles, the effect of dowel action of the crane rail piles within the critical slip surface provided substantial reductions in design bending moment in the combi-wall in order of 40%