The highway and road crossing designs specified the installation of a 1025mm diameter steel case to accommodate the 750mm DICL at the two state highway crossings and a 900mm diameter steel casing to accommodate the 600mm DICL for seven Yeppoon Road crossings. A 450mm diameter steel case was also required to accommodate a 355mm polyethylene pipe. The allowable tolerances for the crossings were +/– 300mm in the horizontal, +/– 100mm in the vertical and +/-0.5mm grade.
UEA used its 80 tonne and 160 tonne auger boring machines, capable of drilling 300mm to 1025mm diameter holes. UEA engaged local surveyors and construction companies who brought invaluable local knowledge. The bore lengths ranged from 24 metres to 60 metres in length.
The client required the drilling phase of the project to be completed in readiness for the open cut contractors to connect all crossings. UEA encountered several difficulties along the way:
- Monsoon season commenced 18 metres into the first bore with a subsequent 8 week delay
- Large cobble was encountered on a number of bores – not previously picked up in the geotechnical data
- Changing ground conditions across the project required innovation around cutting heads and the installation process
The contract required each installation to be independently pressure tested to 1600kpa prior to connection to the open cut sections. In conjunction with the DICL supplier, an end cap was designed and constructed. A reduced pressure test requirement of 800 Kpa was agreed upon with the final test to be completed as part of the overall pipeline test.
For more information about this project or UEA Trenchless, please send enquiries to Steven Hopkins.