Bridge Abutment | A417 Gloucester South West Bypass

Lightweight fill for civil engineering

Contractors seeking a lightweight in fill for a bridge abutment on a new £18 million by-pass scheme on the A417 identified Leca® Lightweight Expanded Clay Aggregate as the optimum solution for speed and cost.

Main contractor Norwest Holst Construction Limited used some 840m3 of Leca® LWA to provide the infill behind sheet piling for the northerly abutment of the twin span Castlemeads Bridge which carries the new A417 Gloucester South West by-pass over the River Severn

Initially, polystyrene-based fill had been considered for the project but in a value engineering review Leca® Lightweight Expanded Clay Aggregate emerged as the preferred option, both for cost effectiveness and convenience. The material can be fully submerged and is free draining, making it ideal for applications adjacent to watercourses.

A417 Development

The sheet piles were retained using tie rods, which were installed in perforated ducts to protect the rods and assist drainage. Leca® Lightweight Expanded Clay Aggregate in 10-20mm rounded pellets was then tipped in 60m³ loads prior to compacting using traditional infill methods.

A spokesman for Norwest Holst explained: “Earlier in the project we used polystyrene but it is difficult to handle and needs protection from contaminants such as diesel. A value engineering exercise showed us that using Leca® Lightweight Expanded Clay Aggregate made commercial sense because it provides a quicker and more cost-effective solution.”

Leca® Lightweight Expanded Clay Aggregate is approved for both general fill and structural backfill applications by the Highway Agency. The new Gloucester South West bypass was built for Gloucestershire County Council with the first phase open in Spring 2005.