The RMS required a new culvert to be installed alongside an existing one under Lawrence Hargrave Drive at Austinmer. The RMS awarded the work to Interflow who then sublet the microtunnelling work to Pezzimenti Tunnelbore.
The ground conditions were very poorly compacted backfill material consisting of boulders in a loamy matrix. Old bottles, plastic and other general waste material was encountered under the road formation. No access to retrieve the microtunnelling head was possible on the exit side. The carrier pipe was designed to be 600mm dia concrete RRJ jacking pipe.
Retractable Cutters allows head to be retrieved
It was decided to pipejack a 830 mm diameter steel casing first. Retractable cutters were fabricated which allowed for full face support of the poor ground and then were designed to retract to allow the head to be pulled back to the jacking shaft after breakthrough at the exit end.
Interflow managed the construction of the jacking shaft and pipework which was completed by Athassel P/L. The work took 3 days to complete the drilling and another 3 to install pipes and grout..
The contruction site was between Austinmeer Beach and Lawrence Hargreaves Drive.
The vacuum truck is in place as microtunnelling proceeds
The setup pit was very shallow.
The 830mm diameter casing was pipejacked as the first stage. The operator closely monitors spoil removal back through the 125mm vac line.