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A pipe cracking effort

Australian trenchless expert Harris Civil has completed a challenging pipe renewal project on the outskirts of Melbourne, Victoria, relying on the power and dependability of a TRACTO-TECHNIK Goliath machine.

Yarraville is located on the western fringes of Melbourne’s bustling metropolis. Under the administration of the local municipality the City of Maribyrnong, the suburb features a chequered streetscape, with detached houses, garden beds and rows of trees. Local residents frequent parks and recreation areas, with sports grounds, playing fields, animal recreation areas and adventure playgrounds, regularly used by residents.

On Benbow St, which runs east to west on the outskirts of Yarraville, close to the McIvor nature reserve, a sewer was discovered to have reached the end of its service life. A 99 m stretch of ND750 ferroconcrete pipes, which had previously been rehabilitated with a glass-fibre reinforced plastic liner (GFRP), had to be replaced.

It soon became clear that trenchless pipe bursting was the only viable and economical solution for all parties involved.

The decision was made to replace the old pipe with a new PE pipe, sized ND800, in the existing path, without using any open cut trenching along the almost 100 m long section. Harris Civil, who specialises in Trenchless Technology applications, were awarded the contract to renew the sewer by the local water utility City West Water. The replacement project posed several challenges, including:

  • its proximity to a highly sensitive nature reserve, in the middle of a residential area
  • an open rainwater drainage system running parallel to the sewer
  • the position of the old pipes, at a depth of 4-5 m
  • the 800 mm diameter of the new polyethylene (PE) pipe (the old diameter ferroconcrete pipe had a smaller diameter of 750 mm).

Meeting these challenges required far-sighted planning and preparation.

The pipe was delivered in 12 m lengths and welded together to form a string for the pipe bursting installation, which was to be performed by plastic pipe specialist GEM Industrial Services, using a butt welding technique.

On the completion of the welding works, the launch and exit shafts were excavated and the flow control system for the existing sewer was initiated by establishing a bypass, operated by two fully silenced 150 mm pumps. An inspection of the ground where the existing pipe laid showed that it was bedded on sand and rubble, which meant the soil was left undisturbed during the installation.

Due to the large diameter of the new pipelines, the project team decided to use a TRACO-TECHNIK-manufactured GRUNDORAM Goliath pipe ramming machine as a pipe cracker, and a Bagela winch for pipe pulling.

The old ferroconcrete pipe with GRP liner was burst using the GRUNDORAM Goliath.

The GRUNDORAM Goliath is traditionally used for the installation of steel pipes over lengths of 80 m, under roads, waterways, railway tracks and parks. It is equipped with technology that provides thrust forces up to 40,000 Nm, which enables the installation of open end steel pipes, up to 4,000 mm diameter, in soil classes from one to five, without the need for jacking abutments.

For this particular application, the machine was also pre-stressed by a winch with a maximum pulling force of 200 kN, which guaranteed safe guidance in the old bore path and the optimal leading-in of impact for bursting and expanding the old line.

Temperatures on-site, which climbed as high as 38°C, aided the progress of the job, increasing the flexibility of the prepared PE pipe string, which made pulling the pipe into the existing bore path considerably easier. The TRACTO-TECHNIK machine managed the task without issue, and after less than three hours, the pipe renewal had been completed and the line’s capacity raised from ND750 to ND800.

However, the project was not without its difficulties. The GFRP hose liner used in a previous rehabilitation project was not laying close enough to the existing pipe wall, and as a result it was displaced during the process of cracking. The issue required several stops to remove the liner pieces from the exit shaft, slowing down project progress.

As well as the pipe renewal, the connections to the manholes lying in front and behind the new line also had to be re-established. Two 800 mm PE couplings were installed using a heating coil welding technique. A CCTV inspection of the pipeline was necessary to make sure that the new pipe was in the correct location and in perfect condition.

According to Harris Civil, this was the first time that an Australian project used pipe bursting to complete a pipe renewal for a line with a diameter of ND800. The infrastructure owner, City West Water, was so impressed with the benefits of the Trenchless Technology and the final results of the project, that it immediately invited tenders for the renewal of an additional 79 m section of sewer connected to the replaced line.

Project quick facts
Location: Melbourne, Victoria, Australia
Length: 99 m
Method: Sewer line renewal applying dynamic pipe bursting method
Old pipe: 750 mm ferroconcrete with GRP liner
New pipe: 800 mm high-density PE
Ground conditions: Rubble, reinforced concrete pipes bedded on sand
Machinery: GRUNDORAM Goliath, Bagela winch
Installation time: 2.5-3 hours
Client: City West Water
Contractor: Harris Civil Pty Ltd
For more information visit the TRACTO-TECHNIK website.

This article was featured in the Spring 2017 edition of Trenchless International. To view the magazine on your PC, Mac, tablet, or mobile device, click here.

If you have a project you would like featured in Trenchless International contact Assistant Editor Nick Lovering at nlovering@gs-press.com.au

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