The Structural Engineering section were asked to examine the structural integrity of a retaining wall that was tilting out onto a public footpath on Kilshane Drive. It was brought to the attention of the Structural Engineering section by the housing department during a routine inspection. The retaining wall is located between a housing development at Kilshane Court and the adjacent road on Kilshane Drive in Finglas. During inspection it was noted that the wall was rotating about its toe due to the active pressure from the 3.0m high retained fill.

The Structural Engineering section commissioned Byrne Looby to carry out investigations to determine the cause of the rotation, propose remedial works and project management the works. The retaining wall which is up to 3.5m was originally constructed in 2006. Following investigations it was proposed to underpin and modify the dimensions of the retaining wall to resist the overturning effects of the retained soil.

These works consisted of 33 mini piles at 700mm centres in front of the retaining wall. The mini-piles were self-drilling hollow bar mini-piles drilled to an approximate depth of 8m below ground level into stiff clay.  A concrete ground beam was then poured over the row of mini piles and doweled into the toe of the retaining wall to increase its resistance to overturning and tying the existing retaining wall to the newly installed mini piles and ground beam.

The ground works took four weeks and were completed in December 2017.

Retaining Wall on Kilshane Drive

Mini Pile Installation

Mini Piles Installed

Load Testing of Mini Piles