SCOPE OF WORKS
- The installation of a 1025mm diameter steel case to accommodate the 750mm DICL at the two state highway crossings
- A 900mm diameter steel casing to accommodate the 600mm DICL for seven Yeppoon Road crossings
- A 450mm diameter steel casing 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.
CONSTRUCTION
UEA used its 80 tonne and 160 tonne auger boring machines to compete the scope, with bore lengths ranging from 24 metres to 60 metres. The client required the drilling phase of the project to be completed in readiness for the open cut contractors to connect to all crossings.
A unique requirement for this project was that each installation had 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.
CHALLENGES
UEA encountered several challenges along the way:
- Monsoon season commenced 18 metres into the first bore with a subsequent eight week delay
- Large cobble was encountered on several bores, not previously picked up in the geotechnical data
- Changing ground conditions required innovation around cutting heads and the installation process
