Osberstown Rail Underpass
As part of the R407 Sallins Bypass, a new underbridge was required at Osberstown, on the main Dublin to Cork railway line. The installation of the precast underbridge structure was completed over a 78-hour rail possession during Easter 2018. Several months of preparatory piling works were carried out in the lead up to the possession to ensure the works could be completed within the tight possession window. John Sisk & Son were the main works contractor with Murphy Ground Engineering completing the piling works.
ByrneLooby were appointed as specialist consultants to design the embedded secant pile wall on behalf of Murphy Ground Engineering. The pile wall consisted of 1200mm diameter piles in a traditional secant arrangement installed using bored piling techniques. The secant pile wall was designed to cantilever for an excavation depth of up to 8m to facilitate the construction of the underbridge. The approach walls were installed during normal working hours, with the lengths crossing the railway line installed during shorter night time possessions in the lead up to the main possession.
Given the limited timeframe to complete the excavation and underbridge installation, it was imperative that the design of the secant pile wall and associated temporary works were sufficiently robust, with detailed sequences and methods identified prior to the works commencing. This involved rigorous planning and a series of design and construction workshops with the extended construction team. ByrneLooby worked in close collaboration with the main contractor, the piling contractor and the client (Irish Rail) to ensure successful completion of the scheme.