The mix was required to enable UEA to insert a very tight 405OD GRP pipe into a 450mm enveloper over 120m beneath the Bruce Highway at Dakabin, 26km North of Brisbane in Queensland. The 450mm steel enveloper was inserted as an alternative to the larger and more expensive 600mm enveloper which is currently specified by many local authorities.
A Guided Boring Machine (GBM) was used to accurately place pilot tubes along the centre of the proposed pipe alignment. The accuracy of the pilot bore allowed the 450mm enveloper to be installed with a 30mm annulus to the product pipe. A traditional steering method would have required the 600mm diameter enveloper at minimum to allow for vertical and horizontal accuracies. The smaller 450mm pipe presented several advantages including lower material and installation costs and greater strength.
This new flowable grout compliments several other mixes UEA Trenchless has developed to suit applications requiring low heat, no shrinkage and thermal resistivity as low as 0.47.