Team uses thrust boring
under flood embankment
A Jackson team working on behalf of the Environment Agency has used thrust boring to install a drain underneath a flood embankment in Northampton.
The team has been working at the Northampton Washlands site next to the River Nene replacing damaged drainage pipes.
It was decided that thrust boring (also known as guided auger boring) was the best approach to take in this case to preserve the embankment infrastructure. This tunnelling project is relatively long in distance and involved installing a pipeline 52 metres in length under the embankment.
Jackson appointed auger boring specialists HB Tunnelling and drainage contractors GAM Civil Engineering based at nearby Northampton to carry out the work.
Thrust boring
Initially, a guided, soil-displacing 100mm pilot drill was sent through to create a target shaft. The direction and inclination of the pilot drill were monitored precisely using a laser guided probe
This was followed by an auger drill situated inside a 300mm steel casing, which created the way for the drainage pipe sections and also removed the spoil material as it drilled through. The ceramic drainage pipes were then pushed through in sections forcing the steel casing through and out the other end.
The purpose of the toe drain (named because it’s at the toe of the embankment) is to allow any water seeping through the reservoir embankment when it is storing water, be removed from the area. It also takes away surface water so it does not impact on the reservoir embankment
Video: Team use thrust boring under flood embankment

Although a simple cofferdam was required it was particularly challenging in terms of space for installation and ecological constraints. The team have worked well within these constraints and works have been delivered on programme

Brendan Saunders, project manager, Jackson Civil Engineering
Temporary Works
The project involved significant temporary works including digging out two work pits either end of the pipeline. The entry pit was shored up with steel piles and a temporary concrete base and thrust wall constructed for the guided auger boring machine to work from.
Manholes are being installed when these two pits are no longer needed while plastic perforated drainage pipes will be used for the remaining length of the new toe drain running alongside the embankment.
Video: Team use thrust boring under flood embankment