UEA has been installing trenchless sections of steel enveloper pipe to encase DICL water main crossings on the new Rapid Transit Light Rail System under the Gold Coast Highway in Broadbeach. Working for CLM Infrastructure, UEA used a Pilot Guided Boring Machine (GBM) to drill a laser guided pilot hole achieving on target accuracy of less than 10mm. The installation auger followed the pilot bore pushing out the 100mm pilot tube and replacing it with the 550mm steel enveloper pipe. This pilot tube microtunneling method can be used for trenchless installations up to 600mm diameter and up to 80 meters in length depending on ground conditions, and is ideal for critical on grade projects requiring a high level of accuracy.
Ground conditions consisted of unstable fine sand which has seen other contractors undermine the main highway throughout the Gold Coast precinct. UEA Trenchless did not experience any undermining or over excavation subsidence on the drives using the pilot tube microtunneling method giving the principal contractor Baulderstone confidence that strict tolerances of grade and safe clearance from existing infrastructure could be constantly met.
Once the steel enveloper pipe was installed the DICL pipe was inserted using an auger boring machine to jack the pipe through, after which the annulus was filled with an approved grout mix.
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Image Caption: Guided Boring Machine in the entry pit inserting the pilot tube.