On the back of four successfully completed projects in Australia’s eastern states, Downer PipeTech has used an innovative, patented structural concrete-lining system, called Tunneline System, to complete the first structural culvert lining project of this kind in Western Australia.
Developed and widely used throughout the United Kingdom, the award-winning Tunneline System is a simple in situ concrete-lining technique utilising lightweight manhole-accessible formwork and high-strength pressure-injected concrete to provide an additional 100 years of service life.
The unique features of the Tunneline System combine the use of conventional steel reinforcement, high-strength concrete and lightweight formwork to form a fully independent stand-alone structural lining – the smooth internal finish providing an enhanced hydraulic flow delivering an increased discharge velocity despite the reduction in diameter. The system can also be designed to accommodate internal pressures from sewers and water mains up to 12 Bar.
The Tunneline System is able to line all existing profiles, such as round ovi-form, box and elliptical, and will also accommodate both vertical and horizontal bends, as well as size and shape transitions within the existing hosts. It can be used to line all known host culvert material types from 1200mm to 9000mm.
Working with the M3 Group (the technology patent owners), Downer PipeTech was engaged by BHP Billiton Iron Ore to design and install a fully structural stand-alone lining to a quadruple cell culvert 1500mm diameter, each 30m long, in Cowra, just to the north of Yandi, in the Pilbara region of WA.
For design purposes, each cell was considered separately. M3, the UK-based technology owners, developed the design to Australian Standard 5100-2, resulting in a 150mm 40MPa concrete, steel-reinforced structure.
The project involved the relining of four 1500mm id corrugated steel culverts, each 30m long. The cover above the culverts to the tracks was 1.5m and separation between the units at one metre dictated that each cell was considered as a stand-alone structure. As such, a 150mm-thick lining was proposed with twin 12mm diameter reinforcement cages with hoop bars and distribution steel set at 220mm.
The cages were staggered to provide a 360-degree, 110mm grid. The final diameter of each cell was 1200mm.
Works commenced on 28 May 2013 with the installation of the rebar, and were completed in all four cells within a week. Placement of concrete commenced 5 June, with two pours per culvert required. The project was completed on 12 June – about a week ahead of schedule.
The project scope included:
- Full Structural design to Australian Codes & Standard AS 5100;
- Design of shutters;
- Hydraulic gradient calculation;
- Concrete mix design;
- Reinforcement scope and design;
- Production of Work Health and Safety plan;
- Environment assessment and management plan;
- Procurement of suppliers;
- Installation of the reinforcement;
- Installation of the designed lining;
- Commissioning and handover.
The use of the Tunneline System has resulted in substantial time and cost savings over conventional lining systems with no impact to the operation of the railway above.
Other key advantages include:
- No advance repairs required to the existing host structures;
- Reduced carbon footprint from less site traffic and operation;
- Significant time saving from one pass operation.
- 100-year design life;
- Compliance with Australian Codes and Standards;
- No LTIs