Backreaming for Service Holes

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Today, we’re going to be discussing BACK REAMING FOR SERVICE HOLES.

So, let’s get right to it.

We regularly drill standard breakthrough holes for various reasons in the mine. Some of these holes we call Out of Scope drilling.

These holes can be drilled a standard size of NQ2 which is 76mm in DIA and these holes act as a drain holes between levels. These holes are normally from sump to sump or breakthrough into ore drives to drain water from the levels.

We can also drill first pass with HQ which is 96mm in DIA to hole breakthrough point and then attach our custom built oversized 152mm back reamer which screws onto the turnaround sub. This is a custom-built product from Brownie and the team at Hard Core Diamond Products in Adelaide. Most back reaming service holes are for HV power cable runs between levels.

These back reaming holes can be opened up from HQ to either 123mm DIA or to 152mm DIA and can be up to 100m in length as seen in this video. – The hole in this video was collared HQ and as a guide the accuracy and breakthrough point is approximately 800mm away from the marked up red X as seen in this video which is the planned breakthrough point.

Once the HQ core barrel has broken through in the designated breakthrough area the turnaround sub is attached. The turnaround sub has a 152mm bit screwed on, and is then screwed directly onto the HQ reamer and barrel so its sits tight in the hole once back reaming begins. This is the advantage of using HQ as there are no need for stabilisers on the rods and we keep the annulus tight.

We pull that all the way back to the collar and leave a nice clean 152mm diameter hole to run your services through. As a guide backing reaming – on average, is about 18-20 metres per shift if in competent ground.

Depending on your mine design and layout, the benefits for service holes is the ability to run less high voltage cable on the decline backs and keep them out of the way operations and level access turn outs. I am sure the bogger operators will appreciate this.

So that’s BACK REAMING FOR SERVICE HOLES and if you have any more questions, feel free to reach out – would love to help.

That’s a wrap!

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Jared Webb

CEO, Webdrill

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