M7/M8 Interurban Motorway Scheme | Dublin to Cork, Ireland



Interurban Motorway Scheme

Early in 2010 another section of Ireland’s M7/M8 motorway network was opened by An Taoiseach, Mr Brian Cowen, T.D.

The new Portlaoise to Cullahill/Castletown scheme completed the motorway link from Dublin to Cork, significantly reducing journey times between the capital and the country’s second biggest hub. This 491 million Euro project was built by the National Roads Authority and will be operated by the Celtic Roads Group. It was part funded by the EU.

Major civil engineer Coffey Construction had one particular water culvert on the M7 section at Anaholty, Co. Tipperary, where lower ground conditions were generally water logged soil and soft bog substrate in the vicinity of the newly installed concrete culvert. There was a requirement to close the excavation between the culvert and the motorway embankment without risking overload on the culvert opening. Structural engineers selected lightweight Leca® Lightweight Expanded Clay Aggregate as the most suitable material to achieve a stable fill and enhanced drainage of the embankment.

Leca® Lightweight Expanded Clay Aggregate is a lightweight expanded clay aggregate formed by heating and firing natural glacial clay in a rotary kiln at up to 1150°C. This process transforms the clay into lightweight ceramic granules that have a hard shell and porous core. The material is extremely light with a bulk density of a fraction of traditional fill material thus reducing loading on underground voids and abutments. The 10-20mm Leca® Lightweight Expanded Clay Aggregate has an average density after compaction of just 300kg/m3, 85% lighter than traditional crushed rock or gravel fill. Leca® Lightweight Expanded Clay Aggregate is free draining which was particularly beneficial for this project and has a high friction angle; the material can form a stable, 37° embankment.

Kevin Donelon, project manager, of Coffey Construction, Athenry, County Galway managed this culvert project and was impressed by the qualities of the Leca® Lightweight Expanded Clay Aggregate material in this application. “The bog conditions required that we found the lightest possible infill for use above the culvert construction to minimise the loading and Leca® Lightweight Expanded Clay Aggregate was very easy to handle. Its drainage performance will also be very valuable taking surface water quickly down to the culvert run. We installed 176m3 of Leca® Lightweight Expanded Clay Aggregate in this project.”