Nine underpasses on the Dundalk Western By-Pass Project

In May 2004 the Reinforced Earth Company Ireland Limited was awarded the contract for the design and supply of Reinforced Earth materials for 9 underpasses on the Dundalk Western By-Pass Project. Seven of the underpasses were road over road structures and two structures were road over river.

The Reinforced Abutments (Sub structure) were comprised of precast cruciform panels with a Bossage relief pattern. Panels were manufactured using 50 N concrete with 50% Ground Granulated Blast Furnace Slag. (GGBFS). The Superstructure was supported by driven 305*305 ‘H’ piles spaced at 3m centres. The ‘H’ piles were driven until refusal. Plastic pipes 0.6m in diameter were placed over protruded piles which rose 6.5m above ground level. The Reinforced Earth abutments were constructed with straight abutment walls and wings walls that were curved on a radius of 30m.

Granular 6i/6j backfill was reinforced by ribbed galvanized steel reinforcing strips. The reinforcing strips were placed perpendicular to the back face of the concrete panels and at some locations the reinforcing strips were splayed around the plastic pipes. When the 6m high abutment was completed, the last 0.5m of the steel ‘H’ pile was cast into a 1.1m wide 30m long pilecap/bankseat.

The centre line of the ‘H’ piles was located 0.85m heading the front face of the panels. This ensured that the shortest possible bridge beams were used on this project. The clear span between the precast concrete panels of the underpass bridge varied from 10m up to 18m. It took approximately 10 days to construct one abutment. The average surface area of the abutments was 289m2.

The construction of the 18 Reinforced Earth Abutments with a panel surface area of 5200m2 were completed within 6 month including panel and precast coping manufacture.