Scope:

The aim of the project is to capture sewage, that would otherwise flow into Sydney Harbour during wet weather, and store it until it can be treated at the North Head Sewage Treatment Plant.

Project Details:

• 16 km of hard rock tunnel in diameters ranging from 3.8 m to 6.5 m
• Extensive underground caverns and associated structures at the existing North Head Plant

Concrete floor construction was required in the access decline roadways and the tunnel invert.
The current design was to use steel fibre reinforcing at 30kg/m3.

Solution:

The project team was interested in synthetic fibre because of durability concerns with steel reinforcing in a corrosive environment.

Site trialling confirmed that 6kg/m3 of Barchip fibre would provide the same level of flexural toughness as 30kg/m3 of the intended steel fibre reinforcement with the added benefit of reduced cost.

Northside Tunnel