From the magazine, HDD, Microtunnelling, Pipe jacking, Tunnelling

Talking big rigs in NZ

Smythe Contractors, a multi-resourced trenchless construction company owned by Mike and Isobel Smythe, is a long standing member of the No-Dig community. In 2008, the company imported the largest directional drill seen in New Zealand – a 50 tonne American Augers DD440T maxi rig, capable of installing 1 m diameter pipe for a kilometre; a feat previously unheard of in New Zealand.

The machine lived up to its billing when it set a New Zealand record by installing 950 m of 560 mm diameter pipe in one continuous operation at depths of up to 32 m on an Auckland North Shore sewer replacement project.

The Birkenhead Project

North Shore City Council was experiencing capacity constraints to their wastewater systems, which had adverse effects on the local streams and beaches in the Birkenhead area.

As part of the Project CARE initiative to clean up these beaches by 2021, the second stage of the Birkdale construction program called for an innovative design solution to allow the installation of a pipeline under sportsfields, through bush reserves, driveways and a garage at depths of up to 32 m.

The initial pipeline was designed as a microtunnelling project, however, an innovative engineer pursued the horizontal directional drilling (HDD) option, and following many meetings and discussions, Smythe advised the client of its intention to purchase a maxi rig. This would provide a cost-effective alternative to microtunnelling, and the tender was awarded to Smythe.

The major challenge on the project was the 560 mm HDPE pipe aligning with 2,100 mm diameter manholes up to 32 m deep. Although the geology did change from sandstone to weak silts along the pipe route, the main challenge was steering the pilot hole to align with the manhole positions.

Conventional steering systems failed to provide the accuracy required, and ultimately Smythe engaged expertise from Australia who applied their Paratrack steering system, which brought the job home.

The Birkdale project spanned 15 months and the project ran overtime although caused no delays to the Project Care Scheme.

The maxi rig features

The maxi rig brings numerous benefits to projects, including its portability to transport on-site, and ability to be setup on sites with soft ground conditions. The torque and pullback figures are conservative, which allows Smythe to design installations with the knowledge that the machine has more in reserve. This rig also has the wiggle steer feature which is useful in hard drilling mediums.

The domain of the Maxi Rig is the larger and longer distance pipe installations, where fluid volumes and pullback pressures rise with every metre. Smythe always works by the policy that the drill rig should have a higher pullback capability than the yield strength of the product pipe. As the pipe sizes increase in size, so does its yield strength, so there is little point in attempting an HDD installation with a machine that has half the pullback load of the pipe you are proposing to install.

Since this baptism on the installation in Auckland 2010, Smythe’s maxi rig has installed 1,700 m of 710 mm diameter pipe as part of Tauranga’s Southern Pipeline Wastewater Scheme, and the Smythe team is about to embark on the next 1,200m stage.

With larger 1,000 mm and 1,200mm prospects currently in design phase, the future of maxi rig grilling is looking promising for Smythe, and the ground the company is breaking grows further and deeper with every project completed.

Distinctively Smythe

Smythe offers years of trenchless experience combined with a full range of HDD and pipe jacking services, enabling the company to tackle any project, no matter how challenging.

The majority of the company’s installations require accuracy of steering to gradients as flat as 0.33 per cent in urban environments where low impact on residents, road users and protection of the environment are key drivers for the client.

Smythe’s future lies with major project works utilising the medium and maxi drill rigs to deliver longer and larger diameter pipe installations that meet the growing demands of the underground infrastructure industry. The company is moving into larger HDD opportunities in Australia and the South Pacific.

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