Sound in relation to depth of a charge of APAN

[blindreeper]

Ok I am about to show my lack of experience when it comes to detonations but here goes. I have found a used cold pack at a rock climbing center which contains ammonium nitrate and have activated the AN. I am left with 130g of AN.
Since this is the first time I have ever accually had AN in a decent amount and known how to dry it properly and store it for it to remain dry, I have decided to do a 150g APAN. Not much compared to what some people have done around here.

Here is my question. I have just checked out my old blasting pit and dug it out to a depth of 50cm. I plan to detonate the charge here under ground. The bottom of the pit is sandstone and all around it is compacted dirt. If I bury the charge under this with about 10cm of extra material onto to make it 60cm under ground, would I still get the thunderous boom? I ask because I am detonating it in the middle of a 9 hectare property and I'm worried about sound.
Do you think I will just get a big upthrust of dirt when it goes off with a deep thud or a big boom and losts of dirt thrown skyward? Or just a little pop of dirt up? I don't think I'll get the pop because when I detonated a film can of AP 50cm down it made the pop and hardly moved the dirt.

I know there are lots of questions about this but I am a newbie when it comes to blasting.

[xyz]

OK, 150g of APAN will probably be louder 60cm underground than it will be above ground with no confinement, same goes for all low VoD AN based comps.

I have detonated 120g of APAN at approx the same depth and the blast was heard several kilometres away at my friend's house. A 120g charge above ground could only be heard for a few hundred metres. Both charges were inside 1" PVC pipe of approx 20cm in length and had been lightly pressed with a broomstick.

Underwater is the way to go if you want impressive results with reduced noise.

P.S. You don't need to activate AN for use in APAN, you only need to make it into a powder (doesn't have to be very fine either). Activating your AN is only useful if you want a sensitized ANFO mix (better contact between fuel and AN) without having to grind the AN into a fine powder.

[Snipie]

I’ve detonated several 100 and 500 gram charges of PNNM at 60 to 80 cm deep, and every time there was very little noise (and a big crater, between 40 and 90 cm in diameter :D ).

Based on the data provided by xyz, I think that the VOD really makes the difference, because the noise of my “experiments” wasn’t audible at 200 m.

[xyz]

What I was trying to say was that in my experience, AN comps are louder when buried due to the extra confinement.

[blindreeper]

But the sound that was heard over the 2km away was a dull thud not the thunderous boom right? I activated my AN cause I was bored. I got 2.5L of 100% NM today so maybe I should go ANNM with a 5g AP cap?

[Guerilla]

Burying the charge under ground greatly increases the blast effect, but the intensity of the sound will be reduced as the sound wave goes through the medium and gets absorbed (chances to heat energy). Lower sound waves get through more easily though, therefore its heard as a deep boom. Snow acts surprisingly effectively as a sound absorber btw, but maybe its not an option in your area. ;)

When 130g ANNM was detonated at around that depth(hard clay soil), a fairly loud and deep BUM resulted and earth was raining down.. it surely was heard in a radius of several hundred meters but in longer distances it becomes hard to locate the det site accurately...

5g is more than enough, even 1g will suffice.

[Efraim_barkbit]

I think you should use at least 5g in your det if you go with ANNM, I only had faliures with smaller dets. I usually use about 10-15g.

I set off ~120g APAN sitting in a container in the open, un top of a steel plate, and it´s thundering boom was loud as hell, echoing several times.
It makes no sense to me when xyz says that it´s louder if dug it down half a meter in the ground.

I won´t believe it until I have heard it with my own ears. If I have time this weekend, I may set off some Hg´s of APAN, then I´ll know…

[Anthony]

I buried 2kg of ANNM 45-60cm down in clay and retired ~150m the blast was a dull thud and actually quite unimpressive. 65gm of APANAL I had done before in the open in the same location was much louder.

I certainly wouldn't say that burying increased sound! I know for a fact that the same 2kg above ground would have been heard for miles, as a it was someone a few hundred yards away probably wouldn't have given it a second thought

[blindreeper]

Its probably 400m to the nearest house around my pit so I think it will be fine. I like the dull thud or "BUM" sound as you describe it. I just got turned of HE when I set off a film can of AP above ground and it was a loud thunderous boom. Because the pit in in between a valley. Accually it has hills on all sides and its sort of the gully in the middle, the sound echos off each of the "walls" and makes it go for ages. So I think I'll be trying some 130g of ANNM soon. But it will take me 3 days to make AP and dry it because its raining and will be raining for the next couple of days :mad:

[xyz]

Actually the sound heard was a boom, not a dull thud.

The soil that it was in was very hard and dry (this means it wouldn't absorb sound well), and although the charge was under the ground, the top was not entirely covered over as the charge was fused with a sparkler and it needed a little oxygen to burn. This meant that a hole about 1" in diameter had to lead from the charge up to the surface of the ground.

So those 2 reasons are probably why it was so loud, I would go for underwater or damp/muddy soil for your first tests.

[blindreeper]

It has been raining a week here so the soil is wet and muddy, perfect for sounds muffling :) May try out my new primary as a det :p

[0EZ0]

I think you are in for a surprise if you think that wet earth is going to provide more sound dampening than dry earth. Wet spongy earth (mud or almost mud) has a tendency to burst upward quite fantastically even with small charges. It traps alot of gas when the charge detonates and as the gas bubble rises to the surface it bursts apart quite nastily. There is quite a margin for the sound to reach the surface with still alot of intensity. Bury your charge very deep if you choose this type of soil.

The best type of earth for avoiding any spectacular productions of noise is moist to dry porous earth that tends to sink when walked on. Something similar to the soil in an aerated garden bed or plowed paddock. All high frequencies of noise are cut out and you are left with a deep sound that is not very audible outside 100 meters at the most, when dealing with small charges. Gas is not much of a problem if buried at the right depth. It is absorbed by the surrounding dirt and at most it will only lift the surface soil a few inches as a little of the gas escapes (the soil just jumps, more from the shock wave reaching the surface). You can bury charges closer to the surface with porous dry earth than wet soil without rupturing the surface.

You can get similar results in noise reduction when you bury your charge in tinder-dry crusty soil that has not been packed down. Packed earth tends to crack and shatter at the surface and burst upward. All the escape routes for gas are the same as above. The surface should stay quite intact still if buried appropriately as above.

Without an in depth description of your intended site of detonation it makes it a little hard to give you any good recommendations. Points like soil density, water saturation, main soil constituent (sand, clay etc.), vegetation (grass and plant roots) are key factors in determining the outcome. For example, grass gives soil quite a good surface structure that is more resistant to rupture than just straight soil.

Water would be by far the best as stated. It is the easiest to plant your charge in at a reasonable depth. It gives you some room for error, unless the charge floats on you:eek:. The sound produced is minimal too(low frequency/bass), at reasonable depths(1meter and up, much deeper with x00 gms). Although It's not very good for the fish as water is a very conductive medium for a shock wave:D. You can hear the hashing sound of it as it moves through the water.

AN based composites are very powerful when it comes to gas production. It's low VoD only means that it's brisance is not useful for any shattering or cutting effect. Exceptions are some of the binaries like Kinepak(even though it is at the very low end when considering cutting power). Be careful not to underestimate their power if you are intending to use them. Even with smallish amounts.