UEA Trenchless recently completed a 110 metre 450mm diameter bore using pilot tube microtunneling methods beneath the Bruce Highway at Dakabin, 26km North of Brisbane in Queensland. UEA worked successfully with CLM Infrastructure to deliver an innovative solution for inserting small diameter pipe on very flat grades over long distances.
The proposed pipe alignment for Unitywater cut through unstudied strata under the Bruce Highway and adjacent creek. UEA Trenchless proposed trialling a horizontal investigative bore using HDD instead of the traditional and more costly down hole coring method. The horizontal investigative bore was completed successfully, confirming ground conditions as clay and decomposed sandstone.
UEA Trenchless used a Guided Boring Machine (GBM) to accurately place pilot tubes along the centre of the alignment. The pilot tubes were followed by a traditional 450mm diameter auger bore which placed a steel case ready to envelop the DN350 polycrete product pipe. The accuracy of the pilot bore allowed the insertion of a comparatively small diameter enveloper which allowed a 30mm annulus to the product pipe. A traditional steering method would have required a 600mm diameter enveloper at minimum to allow for vertical inaccuracies.
The product pipe was inserted and grouted into position marking the completion of a highly cost effective, low risk carrier pipe installation.
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Image Caption: UEA microtunneling crew set up a guided boring machine (GBM) to install a 450mm steel case enveloper under the Bruce Highway at Dakabin, QLD.