Introduction: This project involves the cutting of a concrete dolphin to enable the removal of the structure from the end of the Gelibrand Pier at Williamstown Victoria.

Client: KV Johnson Constructions Pty Ltd

Equipment: Barry Bros. 450 Hp High Pressure Water - Hydrojetting Aquacutter

Problem:

Over the past few years Gelibrand Pier has been undergoing some major works to upgrade and improve the functionality of the pier. The pier is used by Mobil as a dock for their oil tankers as they unload oil before the processing.

The docking point or Dolphin as they are known is the first point of contact with the pier by the tankers and over the years its functionality has deteriorated and there has been some damage to the structure.

A new high tech Dolphin has been manufactured and installed at the end of the pier which will accommodate a broader range of vessels. The problem then was how to remove the existing Dolphin structure most effectively. This reinforced concrete structure weighed in at over 150 tonnes and was connected to a range of pylons.

Solution:

Following a site inspection with the contractor it was decided that the most effective method of removal of the Dolphin was to cut the Dolphin into 10-12 tonne pieces and then these pieces would be barged around to a concrete recycling plant.

The method of cutting, initially was going to be via core drilling but following discussions with Barry Bros. the Aquacutter was chosen as the most effective method of cutting the concrete.

Each section of the Dolphin was around 1.0 metre in depth and around 1.8 metres in width, so the ability to cut all through to the full depth was a challenge for any system.

Several logistical problems needed to be overcome, including the location of the Aquacutter on the Dolphin, the cabling for the supply of water and power to the unit.

In addition to these problems there was also a time constraint of 4 days prior to a tanker coming to dock at the wharf as no work is allowed when a ship is in dock.

A crane was used to locate the Aquacutter system on the Dolphin and a barge was used to support the power and other cables across a 50 metre stretch of water.

The benefits of the Aquacutter came clearly into play in this project. They include:

> Safe and remote working environment.

> Use of high pressure water a time effective method of cutting concrete.

> Alternative methods were labour intensive and time consuming.

> The flexibility of the cutting depth. We cut up to 1 metres depths in this case.

> Difficult access was made easy by the set up process.

> Meeting the time constraints of the project.

> Leaving a structurally intact Dolphin (held together by exposed reinforcement bars) which would not collapse into the bay if bumped by a docking ship.

> No concrete debris goes into the sea.