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Hilliard Ltd – Casagrande C6XP-2 Soil Nailing

Hilliard Ltd are using a brand new Casagrande C6XP-2 to perform soil nail slope stabilization at EFW Enabling works, Colchester on behalf of principal contractor PJ Hegarty UK Ltd.

The new Indaver Site is constructing an incinerator for the burning of municipal waste, turning it into energy. The site was a disused sand and gravel quarry. Prior to that it was an old World War 2 airfield where mainly an American Squadron operated from.

Due to planning constrains the chimney of the incinerator had to be just over the tree line which would be approx. 10 m above current ground level.  Therefore, the plant itself had to be sunk into the ground. To facilitate this the whole site was excavated further requiring slopes to be supported. In the original design proposed a soil nail solution with a hard shotcrete facing. Hilliard Worked with designers AGL of Dublin to use innovated products from Maccafferri, offering a bespoke solution, eliminating 80% of the shotcrete facing and providing  vegetated slopes. Environmental friendly overall solution.

The ground conditions are glacial till for approx. 2 m, overlying sands and gravels, for up to 8 m, with an overlying London clays.  The excavation at the deepest location was 26 m vertically.  The slopes were cut between 45 and 60 degrees. Hilliard worked with Casagrande drilling rigs from the top down, working off of benches cut by Tom Blackwell the site ground works crew. As excavation increased in depth Hilliard soil nailed and meshed as the bench level dropped.

For the soil nailing Hilliard primarily used R32-280 and R32-400 self-drilling bar supplied by a UK based company Geostrong Ltd. Towards the end of the project installing some R38-500 bar.

Once complete Hilliard will have installed approx. 87,000 m of bar. The depths of the soil nails ranged from 15 m to 25.

At the height of the production, Hillard will be using Casagrande C6XP-2 and M6A drills, with 2 excavator-based drill mast attached rigs. Hilliard currently have a Casagrande M6A and a new C6XP-2 on site and are achieving production of 500 to 650 m of Soil Nail daily. The C6XP-2 achieving about 60% of the meterage.

The facing once completed will cover approx. 12 hectares