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Prototyping RQD for better decision making

In response to interest from rock engineers in the geotechnical potential of the GeoCore X10 scanner, Orexplore’s software team are busy working on new features which will broaden the existing emphasis of the Orexplore Insight® software package on geochemistry and structural geology.

"We've just prototyped a user-interactive feature that digitally calculates RQD for a scanned borehole."

What kind of rock engineering applications are you working on right now?

We’ve just prototyped a user-interactive feature that digitally calculates RQD for a scanned borehole. We did some testing to make sure these semi-automated calculations match the manually compiled logs from clients. So far so good!

What is RQD?

RQD stands for ‘Rock Quality Designation’, a percentage measure of the extent of fracturing in the rock sampled by a borehole. It is a primary input to rock mass rating systems that are used in making engineering decisions. For example: Is it safe to build a tunnel here? Will this rock support an electrical pylon? 90-100% means, of course, excellent quality, and a lower percentage means lower quality. This is very important for rock engineers who are using data to plan a mine shaft, for example. RQD has several definitions: high-quality rock has a RQD of more than 75%, while low quality has less than 50%.

So beyond RQD, what else is needed for rock mass rating? Any further information to be had via a GeoCore X10 scan?

There are a couple of out-of-scope things like intact rock strength and water inflow which don’t really bear any direct relation to the scan data. Others, like mineral composition of the fracture fillings, while not yet feasible for us, might become more so down the road if and when our efforts elsewhere on 3D mineral mapping reach fruition. For the time being, probably the most promising practicable candidate for a next geotechnical feature is to identify joint systems from the GeoCore X10 scans.

Adding new geotechnical data sets is an on-going process, and will start with RQD being made available to beta test sites during the early autumn.

What is a joint system?

Rock fractures which resemble evenly spaced parallel planes are said to comprise a joint set. And if you have multiple joint sets criss-crossing one another then that is a joint system. For an engineer the nature of the joint system might determine, for example, whether they ought to think of their rock foundations as stacked plates or oblong blocks. Here in Stockholm where the bedrock is generally very visible, studying a joint system can be a very interesting way to pass the time while waiting for a bus!

What challenges have you had during the process so far?

The challenge is to have good data to compare and calibrate with. We are fortunate enough to have partners on the client side willing to share data and procedures with us. There still has to be some leeway in the configuration of the software, since every mine has their own, slightly different, way of performing RQD logging.

Read More → The benefits of taking mining off-site