Concrete wall project

[Sonny Jim]

Hello everyone.

A long running objective of mine has been to blast a good chunk out of a derelict concrete wall. It's a remenant from long disused mining equipment in my 'blasting area'.

It's 14 inches thick, and has a very convenient hole that goes two thirds of the way through that is about 2" thick at the opening but getting narrower further in. This is my target. The hole is about 24 inches from the edge of the wall, and about a 12 inches from the top. I'm looking therefore to blow off the top corner of the wall.

I'm wondering what you think would be a good choice of explosives.

The things to consider are:

The hole is not an equal width all way in, but varies erratically over about half an inch or so. Therefore I can't insert any form of casing into the hole very well.

I want to fill the hole with explosives, to ensure that the wall is destroyed in an exciting display. Therefore I will need quite a large volume of explosives.

A form of AN dynamite (ANNG) crossed my mind, but i would have to 'poke' the explosives into the hole leading to a high density. Would this screw up ANNG's performance

I dont want to make a lot of plastic explosive.

One way or another, the wall will go, and on tape for you all to watch. I just thought I'd see if any of you have some suggestions that could help ensure success. Thanks. SJ.

[Anthony]

If the width of the hole varies by 1/2", I would get some 1 1/2" plastic pipe from your local DIY shop/plumbers, cut it ~12" long and fill it with with ANNM. The explosive won't get squashed and the rigidity of the tube means you can force the charge in if neccessary.

It won't have perfect contact with the target like if the hole was stuffed with explosive, but I think the gap is small enough and the charge large enough to make practically FA difference.

[Desmikes]

hmm... you'll have about 1.25" of actual ANNM inside a pipe... I'd go with nitromethane plastique b/c it has better density, higher VOD and brisance too, it can be packed in filling up the entire available space. You could even "pump" it in via some pipe starting from the far back to make sure that you don't get any air left inside.

[zaibatsu]

None of the options are very adventurous, instead I'd use it to test a HE squash-head round ;) Seriously though, you could have a look at the damage something like that'd have, even if you have to place it on the target prior to detonation. If done correctly, it should blast big chunks from the wall.

[Sonny Jim]

Thanks for the ideas. I know this sounds pathetic but I've never seen NM anywhere. Not through lack of trying. I've scoured the earth looking in every motor store in my area for it, and not found anything. Maybe I've seen it but thanks to the UKs habit making of crappy, undetailed labels, I wouldn't have known.

I know a lot of you are in the UK. I don't mean to be a pest but you couldn't post the brand name of the stuff you use and where you got it could you? That would be of great help. :)

Assuming I don't get any NM, what viable alternatives would you say exist?

[DBSP]

APAN, really easy though not very powerful but still powerful enaugh I'd say since it's an enclosed hole you are going to pack it into. It could be loaded into the hole by inserting a piece of tubing and then pouring some APAN into it and then showing it into the end of the tube into the holes aft end by pushing it through the tubing with a rod which has been given a blob of cotton or similar to seal the tube so that nothing gets left behind in the tubing and then gets pulled out of the hole when you pull the rod out again. When one portion of explosive has been pushed into the hole the tubing is pulled back a few inches and then another portion of explosive is added and the process repeated. It will take some time to fill the hole this way but you can be shure to get the whole hole filled with explosive.

The best option would be a liquid or slurry explosive but thats a bit to expensive for something like this.

Hope you understood that.

[Efraim_barkbit]

Pressed APAN would be what I´d go for if I couldn´t get NM, at least in my current situation, it´s both easy and quite powerful.

I don´t know how you´d feel towards handeling these quantitys of explosives containing AP, (personally, I´m not to worried about this mixture) If you´d go for the 1½" pipe, and can get it all the way in to the bottom, you´d have almost 200ccm to fill,
I dont know the critical diameter of other AN mixtures, like the ANWAX, but you could always set off a smaller charge first to make room for any wider casings needed.

Edit: went offline when writing, and DBSP got before me

[Sonny Jim]

APAN? I think I read 12% AP was the optimum for APAN, rjchie posted it I do believe. You agree with this? APAN never really impressed me a great deal when I made it a while back, and I've never experimented with it since.

I have this looming feeling of dobt that APAN would be capable of destroying the wall; I'm probably wrong, but it's a feeling I'd rather not have if I'm going to undertake a rather large project like this.

I think this feeling may be something to do with the initial suggestion of ANNM as the charge. APAN seems quite a demotion relative to the reported power of ANNM.

[Nihilist]

what about MEKP? it's a liquid explosive, and it's not overly expensive(i've never made it, but I don't think any of the precursors are all too expensive). And yes, I agree liquid or slurry explosives would definitely be the best. Or anything unsensitive enough that it could be ground into a very fine powder(not sure what you could do this to, but if you could it would work similar to a liquid).

[Mr Cool]

80:20-ANNG

"leading to a high density. Would this screw up ANNG's performance"

Ammonia dynamites aren't too fussy when it comes to loading density ;). I would pack the explosive into a pipe and insert that, like Anthony said.

I would also play with the rest of the wall, like Zaibatsu suggested.

[Sonny Jim]

I think I'll go for Mr. Cool's idea. That's not to say I don't appreciate everyone else's suggestions though.

It's basically because I can manage AN and NG without too much trouble. I've ironed out the many creases in my understanding of NG since my first meddlings with it, so that's not an issue anymore.

I have all the resources I need for ANNG right now also, another pull factor. Therefore I should be able to get this underway very soon. At bear minimum, I should be able to take a soundless clip off my friend's digicam, but if I pull some strings I might be able to borrow a proper one from yet another aquaintance.

Just a quick thought though. I have an early stone age video camera about somewhere. I could perhaps use that, but would need to convert the analogue format to digital. I'll learn to fly before I become good with technical gizmos, so I must ask if there's a feasible way to convert the analogue format without being a millionaire.

Thanks again for your efforts. SJ.

[zaibatsu]

I really do think that you're not looking hard enough sonny jim, but I'll give you some tips. To my knowledge, "nitro" is used as a fuel additive to model cars and you'll be wanting to find a supplier in the UK. Now, using some of these words in a search on google should bring up some websites, and if you went to the products section, and looked for some section on fuel or fuel additives, no doubt you'll see "nitro" mentioned somewhere. It is possible to get 100% NM as a fuel additive, but mainly you see lower %s, around 30%. But keep looking!

In fact, I was bored, so did a little search, and have found a 100% supplier for you. Check your mail soonish. But next time, please do a little searching first.

[0EZ0]

None of the options are very adventurous, instead I'd use it to test a HE squash-head round Seriously though, you could have a look at the damage something like that'd have, even if you have to place it on the target prior to detonation. If done correctly, it should blast big chunks from the wall.
Well at least zaibatsu is being a little imaginative:). Come on guys, what is more fun?

a) Blasting the poopey out of a concrete wall with bulk explosives. One blink and she's dust.

b) Being imaginative and using shaped/projectile charges of sorts.

c) Using a method which has been described as 'scabbling' (by nbk I think) with a thinned liquid explosive. Scabbling has remarkable effects if the surface to be blasted is covered in a network of cracks:cool:. Just allow some time for the liquid explosive to accumulate inside the voids/cracks on the target.

d) Using multiple high velocity charges to defeat the wall with minimal amount of explosives.

e) Construct a huge charge (FAE, Dust or similiar) that would deliver enough overpressure to significantly weaken it's structure. Follow with a strategically placed charge to finish the job.

f) Experiment with different explosively propelled projectiles. Eg backing large chunks of metal with a moderate sized charge of composite.

And thats only a few suggestions:D. There are many different ways you could take out that wall. But for us to suggest something a little more specific, maybe you could take some pictures of the wall.

Some good bed-time reading 'The Blasters's Training Manual' by R.K Ken House. Chart below is taken from page 211.

'The Blaster's Training Manual' Chart (http://www.boomspeed.com/0ez0/Chart.jpg)
(Note: The image is a large 141kb, to preserve clarity. Manual resizing made some parts unreadable)

[Blackhawk]

mm, cant wait to see that wall go down ::D Why don't you try a linier shaped charge along the bottom to cut the wall in half, or a bunch of conical charges near the base to knock out big chunks of it.

[nbk2000]

The guys barely managing AN dynamite, so let's not tax his resources by suggesting EFP's and FAE's, eh? ;)

I'd go with a very sturdy ballon filled in place with liquid NG, and set off with a boosted detonator, with the stemhole being sealed with clay. For concrete work, you need highly brisant explosives to shatter it, especially given the small hole dimensions, which wouldn't allow for maximum VOD with AN based explosives.

"Scabbling" uses micro-fine PETN in a PBX binder that is HVLP sprayed onto the concrete, prior to a flying plate detonator setting it off, no cracks required. :)

[EP]

An idea perhaps too obvious to be mentioned: Why not make the hole bigger to accomodate a larger charge? A hammer and chisel will work as long as it's already started like that...

[Tuatara]

I've no idea just how big this wall is, but for a real challenge forget blowing chunks out and see how far you can "throw" the entire wall. I'd love to see that!

[0EZ0]

Alright, so scabbling with binded PETN sprayed over a brick/concrete/stone surface would most certainly be out of reach for the average member;). But does that mean producing similiar end results is out of reach? You could easily adapt the idea, and thats how thinned NG comes about.

I guess if you don't want to complicate things, just go for the big charge. But why not have a crack at a few abstract/different things. You might surprise yourself. EFP's and shaped charges aren't out of reach, they just require a little more effort and thought. Not everything has to be as complicated as mil-spec ordnance to work.

Try and think outside the square. What are some other suggestions/ideas?

[DBSP]

Well on the subject of SCs. A simple small winebottle SC could be detonated against the wall. Not that it would be extremely interesting but it would be nice to see how an simple improvised SC could afect the wall. It's always good to have some info on such things, if not just for the fun of it.

[Sonny Jim]

The wall is big enough to survive having one side blew off it, so all of these more adventurous ideas can be tried at a later date. I'm always up to try new and more complicated stuff; I'm not stupid or incapable, but am just beginning to scratch the surface of the more 'advanced' level of explosives, so give me time :D

I'm really happy with the response I've got here. You've all been great :) . With a bit of luck, a nice vid of a doomed wall will repay your efforts!

EDIT: Pics of the wall:

http://vectec.net/angryjack/wall.html

[Tended Tripod]

I think a satellite charge would be very interesting for something like this. Set up several shaped charges in a circle on the wall, and when detonated the shockwaves would collide and turn everything to dust. Somebody mentioned this in a post a while back, probably nbk.

A question: I didn't want to start a new topic, and searching (including google, stupid government censorship) showed nothing, so here goes.
Does anyone know how Timothy Mcveigh detonated all of that anfo he had? I also heard there was a charge inside the building. Seems to make sense since anfo has more of a push effect, rather than shatter. Anyone know anything on the subject?

[McGuyver]

Read the rules dude, just start a thread in the water cooler. Anything goes there. I'm not trying to be mean, just a heads up. You can ask any questions you want there. For the record though, obviously it wasn't just the truck, because the windows just a few yards away on the other side of the street weren't even cracked.

[THErAPIST]

As you seem to be able to make NG why not make some NC too? mix em together and you'll have yourself a nice lump of (I think its called ballistite) or blasting gelatin.
If you mix out the proper proportions yoi might get a putty like substance which would be places in the hole easier and would fill up all spaces. Even though i know you dont want plastick explosives it'd be easy. Have it in little bars that you could simply push into the hole and they would mold.

just my $.2 though. disreguard if you wish.

[PasstheDutch]

uh, i seen a picture of this wall , it being covered by soil for a great part on the front. Maybe you could try digging a hole (or a trenchlike hole) in so that you get a gutter in which you can pack full of (some sort of) brisant H.E and after that tamp it with the soil you previously removed.

is this an idea?

[DBSP]

It's not really something new, used all the time. It's just a way of directing more of the energy from the explosive against the target. Defeating that wall would require quite a decent charge though. I don't know if it is reinforced in any way but I emagine that it is. A kg or two of ANNM might just do the trick.

I don't know that post was any good, but I just don't give a fuck right now cause I'm in a badd mood right now..

[PasstheDutch]

Just trying to help.. I know its not new, but the purpose of this thread is to get that fuckin' wall down right?

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This site isn't run by Disney, so please spell out your obscenities, OK? Thanks. NBK

[alhazred]

Here is a formula for calculating the needed explosive mass:
M= t^3 * mf * a

M= mass of explosive in [kg]
t= thickness of the object (to the next free surface) [m]
mf = material factor
a= arrangement of the charge (from 1 for a closed hole to 4,5 for open charge)

The smallest distance from middle of the hole to next free surface is 7" * 0,025 m/" = 0,17 m.
The material factor for concrete is about 4 (can range from 3 to 5,5).
a is and 1 in a closed hole.

M= 0,17^3 * 4 * 1 = 0,02

So you will need 20 g of an AN / gelantinized NG explosive (70/30, standard explosive for blasting works). If want to try it with PETN, you need 20 % less.

[bobo]

have you got a reference Alhazred?

[alhazred]

The formula is originally used by military pioneers to calculate the needed explosive mass. If I remember right it is called "Maurersche Sprengformel". I used the formula serveral times with good results.
You can find these or similar caculation methods in "Heinze: Sprengtechnik- Anwendung und Verfahren, Leipzig 1993" or in "Militärische Sprengtechnik, 1985". I am sorry but I don´t know a good blasting- book in English.

You can find the "Blaster´s Training Manual" here:

http://internettrash.com/users/altreal/files.html

It includes some methods for estimating the explosive mass, but on quiet low level.