UEA Trenchless was awarded two 66 metre bores beneath the Nepean Highway for Comdain Infrastructure (Comdain) on behalf of Multinet Gas to facilitate the relocation of natural gas infrastructure on the 5th November 2015. UEA is contracted to install 66mm of DN450 and DN600 S Series Class 4 RC Jacking Pipe (RCP).
Comdain, on behalf of Multinet Gas, is responsible for the relocation of natural gas infrastructure currently located on Crown land at 1138 Nepean Highway in Highett, Victoria, to a new location approximately 450 metres southeast at Sir William Fry Reserve.
Scope of Works
To facilitate the relocation of natural gas infrastructure, two gas pipeline crossings of the Nepean Highway are required. The scope of works to be undertaken comprises these two trenchless crossings of the Nepean Highway:
- 1 x DN300 Steel Licensed Transmission Pressure (TP) pipeline within a DN450 reinforced concrete casing
- 1 x DN450 Steel High Pressure (HP) pipeline within a DN600 reinforced concrete casing
The reinforced concrete casing pipes will be installed by pipe jacking and microtunnelling, and prefabricated sections of pipeline will be installed within these casings.
The geotechnical information provided indicated the ground conditions would be sandy clay and very dense. For this bore UEA proposed to use the Akkerman Laser Guided Boring Machine (GBM) to complete an on grade pilot bore. Following the completion of the pilot bore UEA will use a conventional Auger Boring Machine to install a steel enveloper pipe which will follow the pilot bores alignment.
Once the steel enveloper is installed, UEA will jack in the RCP to replace the steel enveloper, which will be removed in 3 metre sections from the receipt pit as the RCP progresses.
The critical element of this bore is to avoid ground syphoning and heave, which would be detrimental to the Nepean Highway. UEA was awarded the boring works when the team presented the GBM’s capabilities and showed that it is specifically designed for displaceable ground.
This project is expected to be completed by the end of July 2016.