UEA Trenchless Division awarded Guided Boring/Thrust Bore project within Port Botany for ELGAS

Posted 12 September 2014

The UEA Trenchless Division has been awarded a 120 metre underbore of Charlottes Road in Port Botany NSW for the ELGAS LPG Export Pipeline to Qenos using the GBM (Guided Boring Machine) and Thrust Boring Technology to achieve an on grade pipe install in sand.

The overall project involves UEA undertaking all civil works, including

  •  Supply all enveloper pipes
  •  Operation of a GBM to complete an on grade pilot bore
  •  Insertion of a 450mm Steel Case using a McLaughlin conventional Auger Boring Machine.
  •  Insertion of a secondary enveloper in the form of a 355mm SDR21 PN8 PE100 pipe  (installed on metal centralisers with the annulus between the PE pipe and the outside steel enveloper grouted.)

Construction technique

Pre works

Prior to commencing any excavation works UEA will pothole the entire bore path due to the amount of unrecorded services in the area.

Following the potholing process UEA will mark out the location of the launch and receipt pits. Due to the high water table UEA will need to install dewatering spear points around both pits and pump down the ground water into a  number of sediment tanks.

Pilot Bore

Once the ground water is under control UEA will commence works to install the  pilot bore using the GBM – a machine ideally suited to the soft displaceable ground conditions. It is UEA’s preference to both pilot bore and auger bore uphill (from the same pit) However due to limited space on site UEA intend to GBM uphill but auger bore from the opposite pit and install the steel case on a downhill grade.

UEA will use this set up to their advantage to avoid potential sagging of the pilot tubes in the very soft ground conditions over the 120 metres. UEA will pull the pilot tubes (which will be connected to the lead steel case) with the GBM whilst auguring keeping the tubes under constant pressure and therefore eliminating any chance of sagging which will guarantee grade meeting the designed invert level (IL)

After the installation of the steel case UEA will install a secondary enveloper in the form of a 355mm SDR21 PN8 PE100 pipe. This will be installed on metal centralisers with the annulus between the PE pipe and the outside steel enveloper grouted.

Once the secondary PE enveloper is installed and the annulus grouted UEA will excavate the back end of the Auger Boring pit and install the pre-welded metal ELGAS LPG Pipeline on client provided centralisers which are designed to fit inside the PE Internal Diameter. This pipe will be fully installed to extend 1.5m past either end of the bore.

ELGAS will then construct their own specialised designed concrete pits in the excavated UEA launch and receipt pits and make final connections to the installed LPG pipe.

Further information

For details about the Port Botany project, or for information about UEA Trenchless’ accreditation status, phone 02 9851 3000 or email us for a quick response. To find out more about Trenchless Technology, visit our Technical Centre.