Throsby Creek, Gungahlin

UEA’s Trenchless Division has successfully completed four 60 metre bores beneath Horse Park Drive in Gungahlin for Woden Contractors, in a mixture of hard clay and rock ground conditions.

In February 2016 UEA was contracted to bore and install 240 metres of DN225 UPVC sewer pipe within a steel enveloper beneath Horse Park Drive in Gungahlin, NSW. The works consisted of four number grade critical bores at four separate locations – one of the bores was in hard displaceable clay ground, one of the bores was in a hard shale ground and the remaining two bores were in hard rock ground.

UEA used a combination of their Akkerman Guided Boring Machine and their laser guided Rock Case Boring Machine to complete the required on grade pilot bores and then their McLaughlin Auger Boring Machine was used to install the steel enveloper pipe.

UEA successfully completed the bores to the correct alignment and 0.5% grade and installed the client’s DN225 UPVC Sewer Pipe on 31st March 2016.

Scope of Works

The scope involved the supply and installation of approximately 240 metres of DN225 UPVC sewer pipe by trenchless methods under Horse Park Drive. The proposed sewer pipe will be a gravity main that will connect into existing services and must be installed at 0.5% grade. The contractor has to demonstrate their capabilities on delivering on grade bores in hard clay/shale/rock ground conditions.

Technical Details

The geotechnical information provided indicated each bore had different ground conditions and UEA Trenchless had to ensure their methodology allowed for these changing ground conditions:

  • Bore 1 – Hard clay
  • Bore 2 – Hard clay changing to Class III shale
  • Bore 3 – Rock ground up to 40mpa
  • Bore 4 – Combination of Class III shale to rock

Pilot Bores

UEA used their Akkerman Guided Boring Machine to complete an on grade pilot bore on bore 1. For bores 2,3 & 4 UEA used their in-house designed Rock Case Boring Machine (RCBM) to complete on grade pilot bores. The RCBM is highly suited for ground conditions from 4mpa to 40mpa where it guarantees grade accuracy similar to the GBM which is +/- 25mm for bores up to 120 metres in length.

Lead Case

When the pilot bores were complete, UEA used their conventional auger boring machine to install a steel encasing pipe which followed the pilot bores’ alignment on each of the four number bores.

Completion

The project was a success with UEA completing all bores on the correct grade and alignment. The project was completed within five weeks of commencement, on Monday 4th April 2016.

Completed installation of the steel enveloper pipe in rock ground
Completed installation of the steel enveloper pipe in rock ground