Project Description

The project involved the construction of a new mooring dolphin at the end of Berth 7 at Tasports Burnie Facility. The completion of the dolphin permits the use of the wharf by much longer and larger ships, including Cruise Ships.

Cruise ships have become increasingly important to the Tasmanian economy delivering a significant economic injection into a regional economy. Newer cruise ships are increasing in size, meaning some of the newest were unable to visit. The completion of this project will allow cruise ships to visit Burnie for many years to come and deliver their much needed economic injection.

Technical Details

The construction of a Dolphin of this nature is extremely challenging.

Burnie, Tasmania, has significant tidal movement, up to 4m per day in fact (by comparison, Hobart is about 1.5m per day). This large tidal movement makes driving raking (on an angle) piles extremely difficult as the reference frame is constantly moving.

The way to overcome this tidal movement is through the use of a Jack Up Barge. That is a barge that has legs and lifts itself up off the water. Thereby eliminating the effect of the tide, and rough seas and minimising the effect of winds. All challenges present themselves at this location.

There are only a few of this type and size of the barge in Australia, and certainly none in Tasmania. Its relatively small size meant it could operate at the port without interfering with other port users, and its modular nature enabled it to be configured in a unique way which provided significant benefit to the construction

We used Down the Hole Hammer (DTH) Drilling in heavily raked piles to great effect. The use of raked piles meant traditional drill rigs could not be used. We developed a unique, single-length drill string over 3om long to drill the piles. Into the drilled holes, we installed 30+m long pile anchors.

The dolphin was formed and poured in situ using over 70m3 of concrete. The formwork for the dolphin required significant falsework construction to support it on the heavily raked piles. In order to deliver the concrete to the dolphin, it had to be pumped along 120m of concrete pump line, which was ultimately controlled by the crane on the jack-up barge.

Relevance to B3, R2 Prequalification Categories

• Very heavy foundations, including complex rock sockets > 10m (B4)
• Pile installation from floating equipment (B4)
• Difficult installation conditions, including ‘grouting’ piles in wet conditions (B4)
• Large/significant concrete pours (B4)
• Construction over water using floating cranes (B4)
• Construction ‘over’ navigable waterways (B4)