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Beating expectations in Bendigo with new drill rods

Edge Underground

As an old mining area, the ground conditions in Bendigo are known to be challenging for trenchless pipeline installations due to the high likelihood of hitting reinstated ground. 

Having the right drilling equipment is vital to ensuring a successful installation, especially when ground conditions aren’t optimal.

A project in the Bendigo suburb of Huntly was originally thought by engineers to be almost impossible, but Edge Underground was able to complete the job quicker than anticipated using its modified AXIS laser guided boring machine with new ground-supporting drill rods. 

Dealing with complex conditions 

Edge Underground was engaged in November 2023 to complete a 350mm pilot line to install a 60m 324 OD Hobas glass reinforced plastic (GRP) pipeline. 

Due to the ground conditions on-site, such as a previously excavated ground, wet sand, rock alluvial mix and a high-water table, the main concern was maintaining line and grade. 

Edge Underground director of microtunnelling Adrian Sneddon said the team had allowed a week to complete the bore, with an understanding that it could take longer depending on what ground conditions they hit. 

“We used new ground-supporting drill rods with the AXIS machine so despite the challenging ground conditions, we were able to complete the installation in three days,” Sneddon said.

“This was quicker than anyone was expecting and as a result we were ahead of the program. We had to wait for the program to catch up to us so we could continue.”

Edge Underground
Upgraded drill rods have allowed Edge Underground to expand the capabilities of its existing AXIS machines. Image: OptionX Group

Drill rods proven in Truganina

While Edge Underground was completing the pipeline in Bendigo, another project in Truganina, Victoria, was underway with the team also utilising the new drill rods.

“In Truganina, we were drilling through a mix of hard rock and clay,” Sneddon said.

“This combination of ground is always difficult, but there was further complexity as it was also water saturated.”

Sneddon added that these conditions were a concern for most contractors as it was difficult to maintain line and grade, but Edge Underground’s modified AXIS machines gave the team expanded capabilities in hard rock and hard rock mixes.

“The upgrades provide better vacuum, and the laser channel is insulated which reduces refraction and gives us greater accuracy,” he said.

“The tolerances within the rods also allow for less head roll and the rotation shafts are heavier duty, reducing wind up in the roads and maintaining a greater ability to feel the face as we’re drilling in complex conditions.”

Edge Underground
By upgrading its existing AXIS machines with drill rods developed for OptionX Group’s AdaptX machine, Edge Underground’s equipment can now do more than ever before. Image: OptionX Group

Greater capabilities than ever before

Edge Underground uses modified AXIS machines which include upgrades that allow the machine to do things that were previously thought to be impossible in microtunnelling.

Sneddon said added that the new ground-supporting drill rods were designed as prototypes of the AdaptX head.

“The rods are able to hold the ground open while we are drilling while still maintaining a vacuum,” he said.

The full faces on the dual rods also means that as the team pushes, the system is designed to go straight, with steering only needed to make minor corrections.

Sneddon said Edge Underground also have access to a range of cutting faces that can be selected depending on the prevailing ground conditions, including a semi-closed face cutter designed to pass material through. 

“The semi-closed face cutter gives us the ability to create ground pressure in situations where there is limited or minimal ground pressure,” he said. 

“This enhances our ability to steer, and in extreme circumstance we can semi force the drill head through the ground which creates some displacement and increases the ground’s load-bearing capacity, preventing the head from dropping.”

All AXIS machines are retractable, so even if the ground conditions change, users can retract and change the drill head to suit the new conditions without needing to dig a 911 shaft.

These modifications were originally developed and patented for Edge Underground’s parent company OptionX Group’s AdaptX machine, which is a new state-of-the-art modular drilling system. 

As an OptionX Group company, Edge Underground had first access to the upgraded components for the AXIS machine and currently has exclusive use of the AdpatX machine. As work continues to roll in for Edge Underground, management is looking to expand its workforce with those with a passion for highly accurate trenchless tunnelling, encouraging anyone interested to apply.

For more information, visit the OptionX Group website.

This article featured in the February edition of Trenchless Australasia. 

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