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South Yarra Substation


Metro Tunnel


3 x 750mm diameter bores


Clay geology Red Bluff Sands / Sandstone


220m, 223m , 235m

Project Overview:
Jelmac Australia contributed our experience and expertise to assist RIA in the design of the bore path. Including all horizontal and vertical alignments to avoid all existing and newly installed services while maintaining separation between each bore.


The number of ppl required / team:
Average team of 9 personnel

Dealing with variable geological conditions our experienced team was able to overcome significant challenges of the various types that arose during the construction of the bores.

Skills, knowledge, experience and planning by the team resulted in delivery as per design.

Our crews were able to deliver this project on time without delay to the project due to planning, constant communication and strong work ethic.

RIA Staff – excellent to work with – preparation and daily support of the highest level, which permitted prompt positive delivery of required build.

Techniques required, materials required:
Construct using American Auger DD10 Horizontal Directional Drill

  • Utilise BoreTrak2 Magnetic locating to steer drill head and As-built due to depth and existing services.
  • Defined Mud mix to suit known Geological Conditions
  • Adequate water and Mud mix resources to permit consistent supply as required upon demand. Utilise a recycling system to minimise waste.
  • Ample Vacuum Trucks to ensure a smooth transfer of drilling slurry to Tip site without incurring delays to the process
  • Special purpose tooling – reamers
  • Skilled Team
  • Precise planning pre-commencement

Clay geology
Red Bluff Sands / Sandstone

Learn more

Each bore 8 x 180mm Poly PN13 conduit. Conduit lengths 12 metres welded to 3 strings – 2 x72m, 1 x 84m due to restricted space on site. Once pulling started these strings were welded together to make a complete string.

Directionally Drill and Construct HV Supply Bores parallel to the rail corridor and under all existing and newly installed services.

Due to restraints of the tight corridor, 2 bores ran parallel while the 3rd bore running centrally below.

However, each bore essentially parallel to each other inverts varied to maintain separation between one another in the tight rail corridor.

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