Longest micro-tunnelled span at Perth Airport

Civil engineering contractor DJ & MB MacCormick has successfully completed the longest span of slurry shield micro-tunnelling within an airport in Australia.

Perth International Airport is one of the busiest Australian airports in terms of both passenger and air traffic and operates 24 hours a day throughout the year. International flight arrivals and departures along average 164 a week.

The 1.32km of 450 Hobas GRP jacking pipe supplied by Iplex Pipelines was micro-tunneled between the international and domestic terminals as a service conduit.  The project was completed in just over 2 months.

In total 10 drives were successfully completed, the longest drive being 157.5 metres below the main international runway.  All drives were in high risk locations including two under international runways and several under domestic runways, taxiways and apron areas.

Due to the importance and critical nature of the works, the client opted for specialist tunnelling contractors DJ & MB MacCormick.

As air traffic screamed overhead and as many as six planes lined up for takeoff, the works proceeded.

Prior to commencing, the works design input was submitted to the client to develop the best route to suit the methodology used.  In addition, eight of the 10 drives were 150 meters minimum length due to restrictions on proximity to runways which resulted in a special bentonite polymer mix being developed for the project to ensure jacking pressures were minimised and modifications were required to the tunnelling head including new types of cutters designed and developed in-house to cope with the long drive lengths and ensure successful completion of all drives.

The construction of thrust and receival shafts and dewatering were undertaken in-house.  Ground conditions encountered along the pipeline route varied considerably and included wet sands and clays and rock at depths of 3.5 to 4.5 metres.

Accuracy of plus or minus 20mm over drive lengths was a pre-requisite for the work.  Strict security and escort procedures were necessary in undertaking the project.

Article by DJ & MB MacCormick

Last Updated on 9 December 2001