A 220 kV transmission tower footing rectification

Client: AusNet Services
Location: Victoria, Australia
Date: November 2011 – January 2014

Rectifying the corroded foundations of a 220 kV transmission tower to ensure structural integrity, reliable operation and public safety.

Background

AusNet Services identified that the underground elements of the foundations of a 220kV transmission tower inside the Heatherton terminal station in Victoria, Australia, were so corroded that the tower and transmission line were at risk of collapsing. This could lead to a power outage and/or significant public liability and financial impacts. In 2012, AusNet engaged Entura to  propose a suitable foundation rectification solution while evaluating the situation, associated risks and other constraints.

Solution

Entura formulated a range of feasible preliminary design solutions for the foundation rectification through load analysis, risk matrix analysis, and structural modelling and strength verification of the tower. Our solutions included clever methods to overcome significant complexities and challenges for design and construction, such as the need to limit excavation (as it would increase the risk of tower failure), and the limited construction space available and potential public risks due to the transmission tower foundations being located inside the Heatherton terminal station and adjacent to the Warrigal Highway (a major public road).

The selected solution involved constructing an ‘on-ground’ reinforced concrete raft footing connecting all four legs of the tower. To ensure  structural stability, the final foundation settlement and soil pressures underneath the new raft footing were assessed and verified by Entura through detailed finite element analysis and modelling. Specialist transmission line engineers  liaised continuously with the the client and construction team during construction to ensure that the structural integrity of the tower and footings was maintained.

Outcome

Entura's innovative design solution met the client's aesthetic, operational and safety expectations. Entura managed construction risks through minimising excavation works around the tower, and also minimised required power outages during construction. Structural integrity of the tower and its footings was maintained at all times, and continuous construction support have been provided until the project was complete.

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