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Situated to the south-east of Melbourne, the Mornington Peninsula is best known as a popular tourist region often frequented by residents of the Victorian capital for its famous beaches and calm waters, sheltered between Port Philip and Western Port.
The peninsula is accessed via the M11 or Mornington Peninsula Freeway which features several sections of Motorway and standard trunk route between Frankston and Rosebud.
One section, between Moorooduc highway and the Nepean Highway, close to the town of Mount Martha, transverses two natural water courses over the Devilbend and Tuerong Creeks. These watercourses drain the Moorooduc Estate and Devilbend Reservoir encompassing approximately 6000 ha, an important wine region for Chardonnay and Pinot Noir vintages as well as a significant Natural Feature Reserve. Maintaining a serviceable drainage corridor is essential to the ecosystem and sustainability of this sensitive area.
Both of the creeks flow beneath the freeway and were culverted using corrugated steel plate units in 1993. Devilbend Creek was constructed as a triple cell array at 3000mm id and 137m long with Tuerong Creek as an 1800mm id triple cell at 120m long. Both culvert sets had substantial cover in excess of 4m to the road surface above.
Over the years both culvert sets had suffered from erosion with damage to the inverts, loss of plate thickness and some circular deformation to the side walls and obvert with visible rusting and serious wear in both.
Vic-Roads identified the need for a structural rehabilitation to both culvert sets and offered the project as a design and construct tender to industry towards the end of 2015. The main stipulations were that the solution must not
aff
ectthe passage of traffic above, must be fully structural and independent of the existing structures and must have a design life of at least 100 years with design conformance to current Australian Standards.
ITS PipeTech submitted a proposal to use a bespoke Tunneline®
castinsitureinforced concrete lining for both culvert sets using design criteria to AS5100 and AS3725 to comply with the scope and proposed final lining diameters of 2700mm and 1500mm which
conformed with the overall hydraulic requirements together with a flow management proposal to undertake the works without having to restrict existing flows as the construction progressed.
Vic-Roads awarded the works to ITS in February 2016 and construction work commenced in late May
Design was based on ITS PipeTech’s engineered technology Tunneline®, using a high strength pump mix concrete that was specifically developed with Vic-Roads for this project with concrete being pumped into a bespoke Tunneline® formwork system designed to AS3610 compliance encompassing a bespoke HY steel reinforcement cage to cater for the load distribution that was scoped as SM1600 with a B2 exposure classification for durability.
The principle of Tunneline® is to create an independent structural element inside the existing host structure that is able to take
thefullactive and passive loading without any recognition of existing strength in the existing structure. The design assumes a fully deteriorated host condition and requires no additional treatment of the surrounding soils regardless of
voiding or loss of material. Designing to AS5100 and AS3725 produces a rigid structure rather than a flexible lining such that assumptions based on AS2566 part 1 are not required and a design life in excess of 100 years can be assured.
The hydraulic efficiency of the final linings achieved a slight improvement against the existing CSP due to the improved friction coefficient that is achieved withTunnelineas there are no joints in the lining and precise control of invert levels and gradient can be achieved through the adjustable formwork system.
A significant factor in the project development was the management of existing flows and the preservation of the environment, neither of which could be affected by the works at any stage and this had to be balanced with the construction program as works progressed across the three separate cells on each of the crossings with flows being diverted to whichever cell that was not being actively worked on at the time.
Tunneline® is a one pass system requiring no pre-treatment, advanced grouting or post lining treatment. The project commenced in May and lining works were completed by the end of July despite the onset of the winter rains which resulted in some severe flooding to both culvert sets.
The highlights of the project can be summarised as:
- Providing a 100-year design life;
- Full Compliance with Australian Codes and Standards;
- No disruption to the operation of the Freeway;
- Flood immunity was not compromised;
- No lane restrictions or closures;
- No speed restrictions, and
- No LTIs or accidents.
Images:
1: Existing cells
2: Formwork at Devilbend Creek
3: Completed lining