Mullum Mullum
Background
The Mullum Mullum & Melba tunnels are a 1.6 km long tunnel system
that travels under the environmentally sensitive Mullum Mullum valley.
The tunnels were constructed in 2006 and service up to 115,000 vehicles
a day.
Challenge
The tunnel’s 45m high ventilation stacks are lined with a fireproof
vermiculite which began to deteriorate, posing a risk of falling debris
onto the roadway below. Spire was contracted to design , supply and
install a debris netting system that would capture falling materials.
Installation works were logistically constrained, fitting in with scheduled tunnel and lane closures and being performed in tandem with existing night works.
Process
Spire sourced and supplied all materials including 5500m2 of debris
netting, 2500m of cable, and 36,000 geo-stabilisation fixings along with sufficient staff, vehicles, and plant to allow two crews to work continuous night shifts and complete the installation without the need for any
unscheduled lane or tunnel closures. To safely place supporting cable
anchorages, Ground Penetrating Radar was utilised to locate prestressed cables which ran through the structurally vital concrete beams.
The netting was required to be installed above the mechanical and
electrical services to ensure functionality of tunnel lighting and traffic monitoring equipment was maintained. EWPs were utilised to position
the nets with pneumatic tools used to efficiently fix nets onto the
quaternary cables.