In northeast England, the construction of a sea outfall was planned in order to divert treated sewage into the North Sea. The pipeline with a total length of 550 meters comprised three sections. The first 180-meter-long section had an inclination of eight degrees. The second section included a 120-meter-long vertical curve alignment with a radius of 1,200 meters. The final 250-meter-long section underpassed the beach and the North Sea at an inclination angle of 0.2 degrees.
The contractor opted for a Herrenknecht AVND1800AB in order to realize the project. Due to the geological conditions, the tunnel length and the vertical curve alignment five interjack stations were employed during pipe jacking. To reduce friction forces to a minimum, an automated bentonite pipe lubrication system was used. Position detection and tunnel surveying were provided by a well proven guidance system for pipe jacking. Prior to the recovery in the target shaft, the micromachine is secured against water ingress at an overpressure of approx. one bar.