Gregadoo Bridge

Backfilling

This was the first of more than 15 bridges designed and constructed by Waldren Bridges using reinforced earth abutments.

The entire superstructure; steel girders and columns, precast concrete decks, abutment and wing walls was erected on concrete pile caps supported by steel piles. Soil reinforcement behind the abutments was provided by “Tensar” polyethylene geogrid layers, one end embedded in the precast walls. On arrival at site the walls were placed in position, the Tensar was rolled out and pulled taut while backfill was placed and compacted for each layer. Both abutments were completed within a couple of days.

Proof of the soundness of reinforced earth came soon afterwards, when the abutments had to withstand the very high point loads from the outriggers of the crane placing the steelwork and concrete deck slabs.

”Laying
”Tensar”
”Abutment