The long-term behaviour of retaining walls in Dublin

The performance of retaining walls in Dublin Boulder Clay under undrained conditions is relatively well understood. These structures show very modest lateral movements; this is attributed to the inherent strength and stiffness of the boulder clay and the very slow dissipation of excavation-induced pore water suctions. There are few data available on the long-term behaviour of such walls, however, both in Dublin and elsewhere. The economic downturn in Ireland provided a unique opportunity to improve understanding of the long-term behaviour of these types of excavations. Several temporary works retaining walls remained in place for long periods due to work on the projects having been suspended. The paper gives details of several such projects but focuses on the performance of the 14 m high secant piled wall with a single row of ground anchors at Heuston South Quarter. It was designed as temporary works but remained in place for about 7 years, with movements increasing to over 50% more than those predicted at design stage. The paper will present a detailed account of the Heuston wall design, construction and performance and the subsequent remedial works, which were carried out to ensure its long-term stability.