blasting smallish tunnels in hard rock

No. Not one bit. I suspect small shaped charges might be the ticket if blasting were the only option, but the little bit of blasting I've been around used "cruder" explosives due to cost. Things like bags or urea dropped down a hole with diesel and blasting caps. Somewhere around my dad's house is a VHS tape I recorded out in the desert from when Western rock removed almost the entire south face of Aztec hill. I don't recall how much urea they said they used any more, but it was a lot. Not much of a show. Three little puffs of dust out the bore holes, a hint of movement, and then 30-45 minutes waiting for the dust to clear even though it was a windy day.

They'd spent weeks talking up their big blast in local stores and bars...

I might see if my dad still has that tape. It might be fun to digitize and put on YouTube....

350LB of Urea & Diesel GOES POP!

Sorry - that's "ANFO", as you point out.

"Little puffs of dust" - apparently (my local connections) that's exactly what you should get. Exasperated comment that many Company "buy our wonderful product" videos have plumes of ejected material because it looks good - but is technically wrong and misleading.

Urea - I was thinking ammonium nitrate? Apparently mining companies using tonnes of the stuff do their own mixing. However there are the made-up "prills" - seen as pink "bits" - for more modest users it seems.

Shaped charges - not in this application? The pattern the holes are drilled is doing all the "focusing" to get optimal result. Cylindrical holes metres long filled with blasting agent.

The thrill about using the Holman rock-drill - the "Holman Silver 3 Airleg" - N.Am. = "jackleg"

which I didn't mention (?) because I could find no good photos and didn't take a camera with me down the mine because didn't know I would be in the granite section (dry - killas section is like being in a shower at times) and having my first go with a rock-drill - anyway I ran a hole the size of a stick of gelignite (about 35mm?) 1~1/2metres into the hard granite wall of one of the levels in minutes -- that was promising with the ex-miner stepping-away after about a minute, satisfied to leave me running the hole -- the drilling being parallel in the horizontal and vertical planes to the central "reference" hole

lead to this next thought - the purpose of hole-drilling which can now be done is blasting. And there is hope of finding a lode to the side of the existing workings. Clear so cannot disturb historical workings.

The folk here damn' well know about all this stuff, but looking to other views. Other cultures of mining. Looking to learn.

I have seen videos of blasting "panels" of rock in quarries. This was done in quarries near where I grew-up. When I was ill off school at home during the day, you would hear the siren going for a couple of minutes, then a "bang". From the limestone area a few miles away...

As I mentioned, the overall pattern of this blasting here in mining is radial, about the lengthwise centre of the level being extended (if I understand rightly - mainly from Geevor Mine museum).

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There are old catalogs and books at Archive.com that might be of interest. This search should get you started:

"mining+tools"

Looks interesting - will come back to this.

Yup , ammonium nitrate as the oxidizer , fuel oil as the fuel . I had a couple of years back in the late 70's working with some very good engineers of various disciplines at Thiokol Chemical's Wasatch Division . A couple of things I learned about ANFO is that the AN will absorb just exactly the right amount of FO to be perfectly oxygen balanced and that you've got to hit it pretty hard to make it detonate .

Shaped charges are easy and very effective . Stick a funnel in the end of a tube with the pointed end in the tube . Fill the tube with explosive and initiate from the opposite end from the funnel . Crude and there's a lot more science involved to get the exact results you want but you just built a shaped charge . Probably not effective for the type of tunneling you're doing .

Happy blasting ! You mentioned at some point in this discussion "small puffs" coming from the blasting holes . Actually those holes should be packed with material to confine the blast . Anything being ejected into open air is wasted energy that was not used for the primary task of (in this case) shattering rock . (I also studied Dad's copy of the DuPont Blaster's Handbook whenever I could sneak a peek.)

Further to original post: I have looked on-line. Going for the very specific search "electronic timer blasting" lead me to "electronic detonator blasting" with many relevant finds. Seems is a big industry. Hopefully by what I learn and by going for more very specific searches I can find my way into this topic.

One example find is

they list many products for blasting.

Different "takes" on the matter are appreciated.

I think urea is the same as ammonium nitrate. A lot of companies mix it up on site because of transport regulations. In the states many explosive components require little or no licensing to transport. They would still need licensing for the blasting caps.

There is a watch on buying quantities of ammonium nitrate since the Oklahoma Federal building truck bombing, but its still no more difficult to transport than any other relatively safe farm chemical.

Here is an interesting aside. I can legally make a few explosives on my own property for use on site for entertainment purposes only, but if I put them in a strong container with a fuse or igniter they are a destructive device which is required to be registered individually. I can't legally make a pipe bomb, but I can legally make black powder (and a few other things) as long as I don't transport it on public roads or government regulated transport. (planes, trains, etc.) Now if I buy that black powder at a store I can carry it around in my truck all day long if I want to. LOL.

Being lazy, and wanting to take my Pennsylvania rifle to where the deer are I buy my black powder (substitute) from a store.

Going back before my time farmers used to keep dynamite for blasting out trees. My mom told me her dad blasted out trees on their farm because it would pop giant stumps right out of the ground and it left the earth nice and soft for cultivation.

My dad tells a story about when he was a kid. I might have retold this one here before. Near where he grew up he and his buddies used to play and swim in French Creek. They had a spot they call their swimming hole. It was the biggest pool on the creek, but there was a stump right in the middle of it. The bunch of them griped about it for a while, and one of the kids mentioned his dad had a case of dynamite in the garage. It took them a while to work up their nerve, but they planned one day to meet up at the creek, dig in under that stump, and blast it out. As my dad and his buddy Tom where headed to the creek with tools to meet up with the other guys the kid who had the dynamite came running back up over that hill yelling, "Get down its about to blow!"

(My dad tells the story better.)

They all hit the ground and felt the earth shake from the explosion. They saw the stump flying through the air back towards the main rode where it landed in the driveway of the kid who brought the dynamite. It just barely missed his dad's car as he was pulling in from the road.

They got to talk to him for a minute to ask how much he had used before they heard his dad yelling for him.

He had debated about how much to use. He didn't want to go to light and have to blast again. He knew after the first blast he'd have to clear out because people might come to see what was going on if only to help a neighbor drag out a stump in a field. He kept adding more, and before he knew it he had packed the whole case under the stump.

My dad said after that they didn't have a swimming hole in the creek anymore. They had a swimming pool, but they didn't see the kid with the dynamite for the rest of the summer.

Kids... We've all done it...

black powder...

I have fired some black-powder firers in the UK. Replicas.

I was surprised to see black powder listed in current stock with a wholesaler when looking yesterday for timers, etc. What??! :-) Amazed, I looked with curiousity - and find it has a niche. Masoned stone. Quarries for, I assume (?) Avoid shattering the rock you want to extract in big "as it's been for hundreds of millions of years" blocks. Well, well, well - always a surprise.

Anyone here know about blasting person-height&width tunnels in hard rock? ... Then there is hard granite. Very hard. A 4-carbide-teeth drill bit cannot touch some when driven by a rock-drill which can go 1~1/2metres in minutes with a simple chisel-edged carbide-tipped drill bit.

------------------ I can't help with this. My only rock drilling experience is on granite boulders with a Makita HR3851 rotary hammer drill I was given because it had broken. I use it with wedges and shims to trim inconveniently protruding outcrops.

Your comments on your technohistorical wanderings are always interesting.

author was a rare example of a scientifically literate historian:

I've seen breaking boulders by drilling a hole, putting in semicircular taper wedges and driving a metal solid cylindrical wedge down the middle (low friction?).

Seen chalcopyrite (sulfide copper ore) glistening in the fractured section where it has been there hermetically sealed in the granite for the 300million-ish years since it was deposited (not commercially viable extraction, but there)

Thanks for the Ancient-Engineers-Astonishing-Wonders-Creators L._Sprague_de_Camp hint - looks a good book to get.

I've just had a good week teaching welding (I said "No way!", they said "Yes it will be fine", so I gave it a whirl and it worked).

So looking forward to finding out blasting as a part of mining over the Christmas period. "Busperson's holiday" from what I have devoted myself to (metallurgy and welding) over the decades.

Best wishes and season's greetings

Urea /= Ammonium Nitrate. See Wikipedia: AN is mixed with diesel to make an explosive; urea is inert of itself, & must be reacted with nitric acid to give urea nitrate, which is explosive (needing no oil).

As stated, large mining operations use ANFO (ammonium nitrate - fuel oil) in ton lots. Here in Perth (Australia), we often follow a "B-double" (semi-trailer with 2 trailers) with a big hazmat plate on the back warning of ammonium nitrate. It's not unknown for these trucks to be involved in an accident, & the whole lot goes bang. See

The mines mix AN & fuel oil in what's basically a truck-cement mixer, & pump it straight down the holes. The holes are wired together, with a sub-second delay between each, so you get a ripple effect, rather than one big bang.

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Suspect you may find the book "The Anarchist Cookbook" of interest:

several copies, different formats there. This maybe a decent pdf🤷

Has quite a bit of info on explosives...

I've often wondered if there is a legit copy of the anarachist cookbook that isn't explicitly dangerous to the reader. The reason I say this is I have never held a print copy. However many years ago with a different frame of mind we once logged onto a server in France through a relay that appeared to be a black market trading board. Lots of early scripts and hacking tools, trading stolen credit card and bank account numbers. That sort of thing. One thing in the archives was a text file claiming to be the Anarchist Cookbook. We read many recipes, and most appeared to be more annoying than anything else. A few were downright dangerous to follow. I don't recall reading anything that was really good nuts and bolts of destructive mixture/devices.

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The original (Powell) was from 1971. Amazon reviewers (1 star) don't think much of it... Thought it might give Richard a few grins or possibly some ideas to search for better info😉

I see Amazon has several "More items to explore" that might treat explosives in a better manner:

:-)

Job done well! :-)

With houses only a few 10's of metres overhead, might be looking for a more sophisticated timing sequence than that.

Perth - sounds like the place to be a miner. One tin mine is going to reopen here in Cornwall, UK. Is South Crofty. Being pumped. Over a year to go before down to the sump and can tunnel deeper going for tin down there.