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A recent drilling project crossing under the N1 in Centurion, near the active Gautrain high speed rail, proved tricky until the right contractor for the job, armed with the right equipment, managed a breakthrough.

The project involved the installation of four ducks of 110 mm in diameter over a distance of 130 m through solid rock, crossing under N1 in Centurion and under the very active Gautrain rail lines. “Several companies had failed and the project had been waiting for a year or two for the right contractor,” says Robert ‘Chico’ Garcia, JCS Pipeline’s operations and horizontal directional drilling (HDD) manager, adding that the evidence of previous contractors’ attempts to get all the way across were cleary visible.

Challenging conditions

The biggest challenge on-site was the hard rock. “South Africa has some of the hardest rock in the world,” says Garcia. The majority of the bore was solid rock, tested at over 300 MPa. The continuous traffic on the N1 was also challenging, according to Garcia, as well as the fact that the drilling had to cross under the tracks of the Gautrain line. “All of these are very different obstacles that not everybody can overcome, but we did,” states Garcia.

The equipment of choice in this challenging context was a downhole hammer supplied by Vermeer’s alliance partner Pioneer, on a Vermeer D130x150 drill rig, which Craig Burnie, MD at Vermeer Equipment Suppliers, says was sourced from Vermeer’s Beijing Factory. The rig itself was designed for large-diameter HDD projects and, according to Burnie, has “the features and power needed for demanding job site conditions”.

In addition, the open-top vice increases visibility for the operator and offers the ability to set large tooling in the vice with ease.

The hammer in this case was used to traverse the approximately 130 m of solid sub-surface rock, after the initial hole was opened to a diameter as prescribed by the consulting engineers. “Using the hammer was Step 1 ‒ the hammer is only 160 mm in diameter ‒ but it allowed us to get all the way across, which then allowed us to proceed with the rest of the project,” explains Garcia.

The entire drilling process took only 15 days for Garcia and his team from JCS Pipelines, with the pilot bore itself done in only a couple of days. Several days were required for a sizeable single jump to the final 355 mm hole opener (rock reamer). “The hammer and rig worked very well in the South African conditions,” adds Garcia.

Training essential

“Not many people have the experience to use the hammer and the related equipment. This takes a lot of specialised skill,” warns Garcia, adding that the hammer and rig that Vermeer supplied was supported by training from a Pioneer specialist from the US, with Vermeer assistance, who showed Garcia and his team exactly what the hammer and rig were capable of. This allowed the already highly skilled team to push the equipment to the limits of its capabilities on-site in order to deliver on time and according to exacting specifications.

“I was very impressed with the team from Vermeer. They always give us outstanding service and their aftersales service is also excellent,” concludes Garcia.