AMS No-Dig has recently completed a difficult scheme installing a 300mm gravity sewer as part of a culvert replacement project under railway lines close to our offices in North Lincolnshire.
The main challenge faced by the AMS engineers was the achievement of the tight tolerance in the gradient necessary to ensure that the system would flow properly after completion.
Although not ideal, the topography of the site and ground water levels meant that the pipe would be just 600mm below the tracks once installed. To further complicate matters, the work was to be carried out whilst the lines were in use and not during a ‘no trains’ period as would be normal for such work.
A special dispensation was granted by Network Rail to allow the installation to go ahead at the reduced cover, but only when a strict installation and monitoring regime was agreed and in place.
The work was completed over a two week period during January 2012. Twenty four hour track monitoring was in place throughout and work was paused every twenty minutes or so when a train went by.
A 2 inch pilot string was installed to line and gradient before the critical auger and jacking process could commence.
Because of the limited ground cover, in order to minimise the risk of lifting or moving the lines, the auger process was slowed to 300mm per hour. Requiring great patience, the 15 meter crossing was completed with minimal ground movement.
Now in commission, this is the shallowest trenchless installation completed by AMS to date.
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Guided Auger Boring Rig