Earlsfort Terrace, Dublin

Feb 26, 2015

Byrne Looby has been working with the main contractor John Sisk and Son Ltd. as well as the piling contractor PJ Edwards Ltd. on the design and construction of an 8m deep double basement for a 6 storey commercial development on Earlsfort Terrace in Dublin. This project has provided significant challenges due to the proximity of the basement to existing buildings and roadways, as well as an ambitions cantilever section for which the observational method has been utilised to mitigate the risks involved.

A 30m length of secant pile wall, less than 1m from the adjacent footpath of Earlsfort Terrace has been designed as an 8m high cantilever with the support of a low level berm, with the male piles embedded 4m into rock below basement formation level. The absence of high level props in this area will help Sisk to stay on program during the bulk excavations. Due to the risks associated with the location of this wall, the observational method has been designed with the ability to implement contingency measures immediately should movement trigger levels be exceeded.


Byrne Looby detailed a comprehensive excavation sequence and monitoring requirements to be carried out during the bulk excavation, with a contingency propping solution to be readily available should excessive movements occur. On the remaining sides of the excavation the secant pile wall has been installed within 1m of adjacent building foundations and some protected Georgian properties. At these locations a Groundforce Shorco proprietary hydraulic propping arrangement has been chosen to allow for the pre-stressing of propping frame on installation in order to curtail wall movements.

The secant piling works is currently nearing completion with the initial bulk excavation and prop installation to commence in the coming weeks.

Byrne Looby have also undertaken the design of several temporary works elements for the removal of the existing basement structure, which included underpinning existing foundations of protected Georgian houses on Earlsfort Terrace and sequential removal of 3m deep reinforced concrete walls adjacent to the roadways, to allow installation of the secant piles in its place. No adverse movements of the adjacent road pavements or buildings have occurred to date.