Megadeath: Breaching the Aswan Dam

Factual Questions
41

Okay, I’m getting something closer to 8895.992 m3 for a conic crater 80 feet deep x 100 feet across, but I’m not good with numbers.

Anyway, the idea isn’t to make craters. That requires deep penetration of the bomb and the force is used to move the material vertically, with lots of it coming back down into the crater. If it blows the crater out nearly clean, thats wasted explosive. Any explosion near the edge of the top of the dam will blow a lot more material out horizontally from the face of the dam. The bomb would probably need to penetrate the material about 1/2 of the depth to the water level. As you move down the channel your depositing a lot of the material back in the channel you’ve blown out already, but it’s loose and the water will penetrate it. A few extra bombs to start the trench deeper will allow more material to roll out of the trench and leave room for the excess without blocking the channel. Or you just drop a few more at the end to speed up the penetration of the water.

The clay/rock mixture is going to behave differently depending on the water content. The wetter the clay, the more elastic the material, which I’m guessing makes it harder to move, but it should go out in bigger chunks. If it’s dry enough, it could be very hard, but then subject to fracturing. So as the line of bombs progress, harder material will weaken. However, at 30 meters, if its very dry, it might harden under the weight of the material to ceramic or concrete strength and be much more difficult to penetrate.

Either way, 10 of those MOPs or Tallboys should do the job easily. It would make more sense to use smaller bombs and increase the number since you’d be blasting away a much wider channel than you need. Because of inaccuracy, you might need 2000 500 lb bombs to do the job, but that might cost less than 10 of the big firecrackers. If B52s carpet bombed the dam with 500 pound bombs, eventually it would go. Only the bombs landing near the front or back of the dam would move much material. But every one that hit in the middle would loosen the material allowing more penetratation by the next bomb, and water to penetrate when enough material is removed from the back of the dam.

Another way to breach the dam is with torpedos. This dam needs to be tunnelled out just a few meters below the water level. Most torpedos aren’t that large, but a series of them directed at the same location hitting the dam 3 meters below the water line might penetrate 3 meters into the dam with each hit. The backrush of water following the explosion would clear out most of the loose material and penetrate further into the dam. The top of the dam would collapse on the tunnel several times before the dam is completely breached, so it will end up taking a lot of torpedos to dig all the way through.

Either way, to excavate a trench with explosives, you need to move the material sideways and down. Using explosives to move it up will be very inefficient.

42

Certainly a gravity dam like the Aswan High Dam can fail catastrophically. However, it doesn’t fail due to a loss of compressive or shear strength through the thickness or at footings as an arch or masonry dam can. It restrains the water behind it by shear mass, it doesn’t really have discrete footings, and the stresses within the dam are negligible. It fails due to removal of material from the dam.

I’m not an expert on explosive demolition, either. However, I have analyzed the effect of shock and seismic loads on large earthen and reinforced concrete structures. I also have personal experience with small scale excavation using explosives. A 50 lb bag of ammonium nitrate fertilizer slurried with fuel oil, in a four foot deep borehole, overdriven by a couple of sticks of high yield dynamite creates a hell of a blast and a crater about thirty feet in diameter, but only five or six feet deep. Multiple ditch-line shoots would be required to accomplish the kind of removal I described above, and that is probably the minimum required to achieve a critical loss of structure required to result in catastrophic destruction of the dam.

Stranger

43

Forgive me for ignoring everything but this, but it is the crux upon which your arguments fail. Air-delivered ordnance explodes upwards and outwards in a roughly hemispherical way (yes, even torpedoes). The only air-delivered ordnance that explodes sideways is shaped-charge HEAT or HESH warheads, and they’re minuscule for this application.

This is a US soldier standing next to a 500# bomb crater. So, no, carpet-bombing with 500# bombs isn’t going to work on any reasonable time or monetary scale.

44

Bombs are not designed to blow up and out. That’s what happens when they strike the ground. They can’t penetrate deeply because they’re compressing the material underneath. They can’t blow material out sideways because the at the bottom of the crater the sides are getting compressed also. At the top of the crater material can be blown out sideways. That’s where the hemispherical shape comes from.

We’re not trying to make a crater in the middle of a flat field here. We’re dropping a bomb near the edge of a cliff. The side of the crater near the edge of the dam will not be very thick, and a lot of material will get blown out sideways, into midair along side the dam, where it will fall down. The blast will penetrate deeper on that side also. A curved gouge will be taken out of the dam that you progresively move inward with each succeeding explosion.

When you dig a trench in the ground, you don’t keep digging downward as you move along. You dig a hole, get in, and start pulling the dirt off the sides of the hole to extend the trench. With a trench you still have to lift the loose dirt out of the hole. But if you start digging a channel into the side of a hill, you won’t dig down at all, you’ll move all the dirt out sideways. The clay/rock combo isn’t dirt, but it’s not reinforced concrete either.

Even 500 lbs bombs hitting the edge of the dam are going to remove a lot of material. Carpet bombing is inefficient because bombs that don’t hit the edge or the slope side of the dam aren’t very effective. But each one hitting the edge or sloped side will narrow the dam wall, and the ones in the middle will keep loosening the material. The problem with 500 lb vertically dropped bombs is the lack of penetration. So it will take a lot more bombs to reduce the top of the dam down to the water level, and many times that because of the lack of accuracy.

Some torpedos are designed to direct the force of the explosion forward to penetrate ships. That would help, but the advantage of torpedos is the underwater explosions are more effective at penetration because water is heavy and incompressible, and the backrush of water into hole following the explosion will clear debris and further erode the hole.

In both cases, the catastrophic destruction is the result of just a small flow of water through the dam which will rapidly erode the dam.

45

Agreed.

46

It was their experimental album, I liked Youth in Asia better.

47

The Denver Water Department is VERY concerned about a possible terrorist attack on the Dillon Reservoir dam. They now prohibit all larger trucks and any vehicle towing a trailer from crossing over it (it has a road on top). At first, they closed the road to all vehicles, but that caused a hell of a stir in the County. It’s one of 3 east/west roads.
It is also an earthen dam. I’m a bit skeptical that even a semi full of explosives could do much to it, but DW has gone to the point of installing pop up vehicle barriers are not working on erecting guard towers at each end of the road.

It’s funny that they say they where worried about the town of Silverthorne. What they where worried about is loosing their water.

48

Doing some internet searching I did find a video compilation of various terrorist attacks. One such attack is the successful breach of a dam using explosives, albeit one a fair bit smaller than the aswan dam.

The dam breach is a smidge after 2:40 into the video. I know a better and longer video documentation of this attack is out there because I’ve seen it, I just couldn’t find it. Be warned, it has adult language (might want to put your speaker on mute) and is rather graphic in nature (poor bastard in the pickup truck).

49

Isn’t that the same thing? (Letting the water loose on Silverthorne) :stuck_out_tongue:

50

These two statements are completely backwards. You’re conceptualizing the Aswan High Dam *completely *wrongly and as a result you are clinging to a notion that has no reality.

Aswan High Dam is not a cliff-like structure like the Hoover Dam or whatever other dam you’re thinking of. It’s a big pile of dirt, rocks, and clay with a very, very shallow face angle (yes, that diagram is to scale at least in terms of external dimensions). Dropping bombs onto that 13 degree face that is almost exactly like dropping bombs onto a flat field.

51

There is no way at all that you could get a meaning full percentage of people out of Cairo in 2 hours. I would be amazed if you could get 5% out in a weeks time.

52

Ok, that is a shallower slope than I imagined, and it makes the cliff analogies poor. But it actually makes it easier to breach this dam with small bombs.

I’ll go with Stranger’s numbers, they seem to match what I saw on some web site yesterday.

“The Aswan High Dam is 40 m wide at the crest, 980 m at the base, and 110 m high”

So with a water level at 75% of the height of the dam, you need to excavate a channel about 300 meters long. It could be 1 inch wide, but lets call it 3 meters wide minimum which seems about right for a 500 lb bomb. You need to go about 30 meters deep from the top of the dam, but starting on the face of the dam (the dry side), if you hit the face at the water level, you need to go slightly more than 0 meters down. Even without penetrating the dam face, a 500 lb bomb will blow out material to a depth of a least 1.5 meters hitting a flat surface. On that slope it will probably blow out material down to 3 meters on the outside of the dam. It will also leave a near vertical face on the on the inside of the crater, a total of about 6 meters high. That’s with dumb iron bombs dropped vertically that explode on impact. If they are designed to penetrate the ground, even 1 meter, the crater will be deeper, and much more material will be blown out the side. The near vertical face you leave forms the cliff. As you progress by dropping bombs 3 meters apart, moving toward the center of the dam, the depth of penetration will stay about the same, so you are creating a sloped channel. That may seem to create a problem, but it’s actually allowing each blast to clear the material out the side because much more of it will roll and slide down the sloping channel. Now about 30 bombs later, and 120 meters in, your channel is less than 10% of the depth you need. So you need to go back to the new edge, now 3 meters further in, and run another series of bombs up to that point. So that will take between 500 and 600 bombs to get a channel 120 meters long and 30 meters deep. Why stop there? Because by that point you’ve already blasted a lot of material from the center of the dam out as the 30 meter high cliff face disintegrates from the blasts. You could continue the channel across the dam, but it isn’t necessary. What you do is cross over to the water side of the dam, and start the process from that side, moving in toward the center of the dam. The bombs are less effective because the water offers more resistance to the force of the blast than the air did on the other side. But the water infiltrating the channel as you go will help clear the channel. When you reach the tallest part of the dam 120 meters in from the water side, going 30 meters deep, you’re left with a 30 meter high vertical sided wall in the middle, and a channel full of water on one side of that wall. Now you have a simple dam to blow up. Drop bombs into the water filled channel close to the wall, and the concussion and backrush of water will cause a catastrophic failure of the wall. You are only a little below the water level, but the water will be running through that channel with enough force to erode it out faster than the water level drops.

That’s all just using 500 lb bombs. Use bigger bombs and you need far fewer. Use MOPs and you could do it with just 10 or less. You are still using explosives to blast material out sideways. Your first bombs are going to be hitting a shallow slope. Each subsequent bomb is hitting near the edge of a vertical cliff. It will take about 1200 500 lb bombs, maybe 2000 at the outside. That’s with bombs that explode on contact with the ground. Bombs that penetrate the material will be much more effective, and could cut the number of bombs in half.

That’s also based on accurate hits. I stated much earlier that accuracy was a necessity for doing this kind of excavation. I don’t know if anybody can place 2000 bombs with that accuracy for reasonable time and cost. With that shallow slope on the sides, the job could be done with excavators and bulldozers for much less money. Possibly in the same amount of time. If you had to just carpet bomb with little accuracy, it could take anywhere from 100 to 1000 times as many bombs to do the job depending on the level of accuracy. But bombs will blast a lot more material horizontally than vertically, even on a shallow slope. And all you need to do is open a narrow, shallow channel that lets water to flow through the dam for the water pressure to take the rest of it out.

This also all based on hitting the thickest, tallest part of the dam. If you look at an overhead picture, you’ll see a narrow, shorter section where there are spillways, and probably where the turbine generators are located. Thats where you want to bomb. 2 or 3 MOPS, or 200 or 300 500 lbs bombs, might cause a breach there that would result in eventual catastropic failure.

53

Good post Tripolar.

Thats the sort of thing I was thinking about but was too lazy to run the numbers with. And it brings up a critical number that I was unable to find. How much lower is the “pool” on the upside of the dam than the crest and what is the dam’s horizontal thickness at that point? Random pics I found online and google earth imagery made it look like the pool wasnt particularly low or the dam particularly thick at that level.

54

The narrow area of the dam where the spillways are located is the is the crest (the area that is 40 m wide); the thicker area of the dam is even more substantial. The dam is really like a small mountain plunked right in the stream of the Nile.

Stranger

55

My yard is 40 meters wide. That number isnt that impressive by itself.

56

40 meters wide at the crest, tapering down to nearly a kilometer wide at the base. Even a shallow channel would require removal of a large mass of material as previously described, and in a manner that is not consistent with aerial bombing in terms of precision.

Stranger

57

I’m honestly impressed by the effort, TriPolar, but bombs don’t blow neat channels that way. this is what happens when you drop one bomb next to the crater another has left. They tend to fill each other up with the material they displace.

Not to mention that the IAF has no B-52’s or B-2’s. They’re most capable “bomb truck” is the F-15I, essentially an Israeli-avionics version of the F-15E Strike Eagle. It can’t carry more than 9 GBU-12 500# LGB’s. Even under your (I’m still convinced over-optimistic assumptions), you’d need 150-200 bombing runs to do it.

It would be far, far, far, more feasible for the Israelis to put together an airborne engineer team with some infantry and AT and AA teams for protection and dig their way through.

In short, while the idea of bombing the dam is within the marches of possibility, it is a far way from the realms of the reasonable or feasible.

58

Those countries are upstream. The Nile, unlike most rivers, runs north.
P.S. don’t the posters here understand the difference between dam (holds water) and damn (holds hellfire)?

59

When somebody here besides you starts talking about digging a channel (a tunnel for pete’s sake) across the base let me know.

60

That’d be the ticket, drop some paratroopers and a boring rig at the site. Drill a hole through the dam and let water begin piping through. That would breach it in short order.