Rock bag innovation first for ports

A sustainable, civil engineering alternative to scour protection at Devonport East as part of Project QuayLink.


31 July 2023

For the first time on a major Australian wharf infrastructure project, a sustainable environmental civil engineering alternative to the more traditional concrete or blockstone, will be used for scour protection on TasPorts Project QuayLink at the Port of Devonport.

At QuayLink, we will be deploying rock bags for the first time.

As a significant innovation in scour protection, they will protect wharves and ship berths from erosion, especially as ships increase in size and thrust power.

Invented in Japan, the rock bag was used for the first time in 1987 to protect the foundations for the great Akashi Kaikyo bridge, the world's second longest suspension bridge, with a total length of 3.9 kilometres.

The bags are made from 100% recycled polyester, with a lifespan of 50 years.

They will contain locally sourced rocks from the Hazell Brothers Long Hill quarry, with an estimated weight of eight-tonnes.

It is estimated that 2,000 rock bags will be deployed, equating to 160,000 tonnes of rock. Due to the size and weight of the rock bags, the bags will be filled on-site.

The rock bags will be lifted into place at the berth by 500T barge mounted crane. This single-lift system makes deployment easier.

As well as preventing scour at the port, the rock bags are also used by endemic flora and fauna as new sea-port habitat.

Simulation testing | Rock bags

Simulation testing for the new berth at East Devonport commenced in March 2023 at the UNSW Water Research Laboratory, Sydney.

The focus at the laboratory was to undertake physical model testing of the planned rock bag scour protection to be installed. The laboratory placed rocks into mesh bags, to create a rock bag scour, as a method to help protect the berth and adjacent embankments.

A 1:20 scale model simulated the exposure from bow thrusters and main engine propulsion from TT Line's next generation of ferries. The model proved the design to be effective.

The Water Research Laboratory (WRL) is a world-leading fundamental and applied research organisation tackling the most challenging water engineering problems faced by the world today. The laboratory is home to state-of-the-art facilities, equipment and personnel comprising the most experienced and creative problem solvers in their respective areas of research and industry.