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My mine is looking to install a 600 mm open borehole to drop particles up to 150 mm through. It's a 320m shaft to drop ballast down to save time compared to using the drift.

When it gets blocked they typically take a water truck out and that works. They have used explosives to clear a blockage before but that was a decade ago.

Some of the seniors have rough rule of thumbs on the borehole diameter required to drop particles without causing a blockage but I'm unable to find any references. And it is based on experience and what they've always done. I'm unaware of any design work for this beyond "this should be large enough", but believe there should be more behind it than that.

Is there a formula available to determine the borehole diameter required to safety drop in the particles?

Scott
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  • Spacing between particles? 1 per minute or all crammed together? – Solar Mike Sep 12 '18 at 05:47
  • Crammed together, pretty much dropped from a dump truck. – Scott Sep 12 '18 at 05:53
  • What other boreholes exist, with length and what diameters of particles are put through them. You should have this info, at least for your mine, and that may give you an idea of what works – Solar Mike Sep 12 '18 at 06:10
  • I searched on GoogleScholar for "particles clogging millimeter diameter pore". Do you not find anything at all useful by a comparable approach? Do your "seniors" say their guidelines are from empirical observations, gut feelings, or vague memories? How much do trust them? Why 600 mm for 150 mm particles? This sounds like a "let's hope we don't blow ourselves up" plan, and you are asking us how much it will hurt when it does explode. Why not just dump the particles down the main shaft and avoid the problem? What are you really trying to do here that sets the limits in the first place? – Jeffrey J Weimer Sep 13 '18 at 03:03
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    Useful Papers, probably has your answer as well, check it out: [Flow in packed tubes with a small tube to particle diameter ratio](https://onlinelibrary.wiley.com/doi/pdf/10.1002/aic.690350116) [Radial porosity peak at the centerline of packed beds with small tube to particle diameter ratios](https://www.sciencedirect.com/science/article/pii/S0032591017305302) [Experimental study of flow transitions in random packed beds with low tube to particle diameter ratios](https://www.sciencedirect.com/science/article/pii/S0894177715000874) – K. Furkan BEK Sep 14 '18 at 07:47
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    part2: [Clogging of granular materials in narrow vertical pipes discharged at constant velocity](https://www.researchgate.net/publication/281202100_Clogging_of_granular_materials_in_narrow_vertical_pipes_discharged_at_constant_velocity) [Particle Clogging in Radial Flow: Microscale Mechanisms](https://pdfs.semanticscholar.org/4c7f/f24af12627abe63c0e13765569e93ea6973a.pdf) [Clogging in micro-channels: from colloidal particle to clog](https://tel.archives-ouvertes.fr/tel-01188553/document) _pretty interesting topic, have fun_ – K. Furkan BEK Sep 14 '18 at 07:49
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    One line of inquiry would be to look into ore/muck/waste pass design criteria. Another one would be to look at technical papers, particularly from the 1980s & 1990s, which discuss back filling of stopes directly from the surface using vertical drill holes. Symposia volumes from the Society of Mining Engineers (US), Canadian Institute of Mining, Metallurgy & Petroleum & the Australasian Institute of Mining & Metallurgy may be useful. – Fred Sep 14 '18 at 15:19
  • I take you're either back filling a stope or dropping material to a stockpile that will then be used as stope back fill via loaders, or loaders & trucks, or the material will be used as road base for surfacing the drift roadways? Does the dumped material have a consistent moisture content? Also, the distribution of particle sizes will be important. – Fred Sep 14 '18 at 15:23

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