THE PROBLEM

Local residents asked the client for a better looking alternative to the proposed incremental concrete panel walls for the highway bridge approach ramp. The existing road was required to remain open to traffic during the construction of the new bridge so the wall needed to be built in two phases and used as temporary support to the carriageway during traffic diversions.

THE SOLUTION

The Tensartech TW3 Keystone modular block wall system using multiple facing block colours, technically supported by Tensar’s Design and Supply service including detailed calculations, construction drawings and a fully indemnified design. The system was supplied in conjunction with TAL Distribution Ltd, the sole distributor of Tensartech systems in Ireland and Roadstone the local manufacturer of Keystone blocks.

PROJECT DESCRIPTION

As part of the Limerick Southern Ring road scheme, the proposed road required a new bridge at Ballykeefe over a single track rail line to replace a level crossing. The approach ramps had to be constructed with vertical retaining walls due to the close proximity of residential and commercial properties. The bridge abutment itself was piled and formed with a false abutment wall. The TW3 Keystone wing walls met this abutment with a project specific detail which included curtailing the reinforcing geogrid where it met the piles.

The Tensartech TW3 Keystone wall system is simple and rapid to install. It requires no propping or crane lifts and the blocks are dry laid. The walls, which were founded over cohesive soils, were constructed using granular fill reinforced with layers of Tensar uniaxial geogrids which were secured to the TW3 Keystone block face with high strength polymer key connectors. This wall system has BBA certification and will achieve a design life of greater than 100 years. It was selected following consultation with local stakeholders, primarily the residents, who were given various face options of colour, texture and unit size to choose from. Different colours of facing block were used at specified course layers to achieve the desired aesthetic finish.

At its maximum the wall is 7.4m high, and the versatility of the system enabled the geogrid soil reinforcement to be easily adapted around the abutment piles. In total around 450m² of wall face was constructed over a length of 120 metres.