NEW ESTATE ROAD | ROYAL ALBERT BASIN, LONDON

The use of LECA® geotechnical fill (LWA) as a lightweight fill solution for infrastructure works at the Royal Albert Basin helped to cut a whole week off an already short earthworks programme.
Main contractors Birse Civils faced the challenge of mitigating the impact of a new highway built over existing twin 2,100mm diameter sewers in soft ground conditions where there was a risk of damage and settlement.

Leca® LWA was specified as the solution to providing a ‘load neutral’ design, preventing any additional loading on the Thames Water storm sewers. These are situated four to six metres below final ground level, above Thames gravel and a combination of soft clays and made ground.

An assessment of the sewers revealed them to be in good condition, although it was felt that any further loading might cause failure, resulting in an estimated replacement cost of £2 million.

Civil engineers Clarke Bond Group Limited and Birse Civils devised a scheme to remove the existing overburden and replace it with Leca® LWA 10-20mm fill to achieve ‘load neutral’ status. Approximately 4700m³ of Leca® LWA was used to create the mass fill for the highway, with loads delivered by high sided, 60m³ articulated tipper vehicles from stockpiles shipped directly into a local port.
The Leca® LWA was tipped into the void, levelled by a tracked earth moving blade or dozer and compacted in one metre layers using the same vehicle.

A geotextile layer was placed to separate the Leca® LWA from the sub-base material. The cohesion of Leca® LWA of 0kN/m2 and the ability to compact it in one metre layers, allowed it to be placed onto wet, boggy sub formation that would usually prevent normal earthworks operations due to fear of heave and compaction time, delaying an already stretched construction program.