Hello

Being relatively new to the Great War I wondered if fellow pals could enlighten me about the following?

I am reading "They called it Passchendaele" by Lyn Macdonald and in it she says that of the 21 mines laid,two failed to go off. Apparently one went off in 1955 and at the time of writing her book the other one was still there but the exact location was unknown. The date of the book was 1978.

Does anyone know what happened to the unexploded mine? Has it subsequently been identified or exploded?

Apologies if I am asking a very simple question but as yet my reading isnt that extensive!

Regards

Jayne

I think it's still there ...

I think I read somewhere that the 1955 one killed a cow.

[QUOTE]I think I read somewhere that the 1955 one killed a cow.

Yes a Belgian Blew (blue)

Lightening set it off, the other remains awaiting a similar event.Believed to be under a farm.


Roop

Six months ago (27 May), Iain (McHenry) and I were there, on the exact spot where (according to plans) the unexploded mine is sleeping. And we had a nice semi-French, semi-Flemish, semi-English chat with the farmer, who was very interested (and also a bit uneasy) to hear about the mine over which he had ploughed his field all these years.
I saw Iain today shortly before noon, and I can assure Forum members that this is a proof that we survived.

Aurel

IIRC there was a documentary on the very subject of the rogue mine shown quite recently.

"One of our mines is missing" (?) ... available from DD video.

Dave.

Would it be possible to provide a link to a source for the DVD or rebroadcast for us cousins across the pond?

I am curious as to why there has not been a concerted effort to find the mine. Yes, yes I know it it is dangerous, but could not modern drilling techniques lower the risk? I have not been to the area myself but if it were to pop would there be danger to locals?

Finally, how often do munitions from the great war go off during plowing or from being mishandled during recovery?

Thanks,

Bert

I can't answer the question about munitions going off during ploughing. But I don't think the mine will be disturbed by ploughing. My understanding is that the mines were at least 90 feet or more under the ground. The depth of the British and Dominion forces' mining efforts was one of the factors that enabled them to plant so many mines and have them remain undetected for the relatively long period leading up to the attack in June. It would not surprise me if the subterranean effects of the other mines going off caused the approach to the unexploded mine to collapse.

Robert

I understand the two didn't fail to explode, it was decided that their positioning was not suitable for the current operation so they weren't blown... then in the chaos of war the British forgot where they'd put them. Another issue - most accounts report 10,000 German dead in the blast.. I've never seen any supporting evidence. It sounds like a suspiciously round number, and it wasn't like the Germans to hold the front line in such strength. Anybody got any info ? Whatever the number, the site is an enormous mass grave.

Thanks everyone for your interesting posts. If I were the farmer in question I would feel really uneasy.

Dave
Where or what is DD Video? Could you point me in the right directionas I wouldnt mind seeing it.

Many thanks

Jayne

Does anyone know what explosives were used in these mines?

The reason I ask is that some of the military high explosives are much more stable than the commercial ones, but the commercial ones are best for a lifting effect.

If, for instance, they used TNT, then it might still be quite stable.

Hello Angie

I think that the explosive used was called aminol.

Andy

The most common explosive used was Ammonal and Gun Cotton; occasionally they were mixed if a certain effect was needed. Another called blastine was also used. Initially gunpowder had been used, but the previously named explosives were found to be at least three times more powerful so quickly replaced gunpowder.

After nearly 90 years in the ground the Ammonal is not very stable, and attempts to move might result in disaster. I suspect that while the location of these mines is known, they will never be investigated for this reason. The Petit Douve farm mine is right under the modern farm; where would you begin! (considering the tunnels were flooded in 1916)

The documentary about these Messines mines is not 'One of our Mines is Missing' - that is about Vimy. It was a programme in a Ch4/5 series about 'Histories Largest Explosions' or somesuch.

Mines were charged with whatever was available: huge and unusual quantities were needed so it was not uncommon to have several types in one mine. All RE calculations were based on using gunpowder, and other [more powerful] modern HEs were expressed in terms of a multiple of powder when the calculations were done. In contradiction to what is widely believed, the RE had studied mining and explosives [not on the scale used in the Great War of course] and the complicated theoretical equations used were based on much experiment at Chatham around the turn of the century. I have the relevant text books.

The factors that principally determine the diameter of the 'ole are:

power of the HE used
efficiency of tamping and concentration, together with simultaneous initiation
character of rock/clay/soil/gravel: geology in a word
depth of charge.

Or, you could decide on size of your desired 'ole and work backwards, which needed to be done if mine near your own lines: 'own goals' were not encouraged..

Whereas the calculation is rather empirical, it usually worked, with one notable exception.

You certainly would not get me tampering with old ammonal.

By the way, when it is said "under the farm", is it under the land or under the buildings? If the latter, how would you sleep at night?

Angie

I suspect that, with the amount of ammonal that is packed into the mine, it won't matter whether the mine is under the land or the buildings. The latter will be seriously damaged even if some distance from the mine.

Robert

The mixture of various explosives as LB has inferred is related to the geology primarily.

The size of the ole theoretically is a 90 degree arc vertically related to its depth, from this the amount of ground to shift is calculated.

The calculation is derived from the velocity of the given explosive and the resilience of the ground. Hard rock needs higher velocity but less explosive than heavy clays.

The largest part of these immense quantities buried under Flanders were required just to shift the earth and probably (apart from displacing the enemy directly above) did little relative damage in the immediate surrounds.

The mixtures for this type of mining could , due to the nature of the ground, be of moderate velocity if that was what was available but needing high gas production to create the necessary heave.

From LB's notes it is apparent they achieved both a decent velocity and the heave factor, hence the large oles.


Roop

There seems to be a bit discussion about the number of mines which are still charged.

24 Mines were prepared, one of them (Petit Douve) was discovered by the Germans who broke in the tunnel (August 1916, almost one year before the attack). They were blown up by a British camouflet (whilst trying to remove the explosives?) . Later the whole tunnel was destroyed by a German camouflet and that one was abandoned. Is the mine still charged?

So 23 left. At one moment the plans for the Battle of Messines changed and the last four mines in the Ploegsteert area were designed to be kept as a kind of reserve. In my opinion these are the four "Birdcage" mines.

The other 19 mines were effectively used.

This brings us to the discussion how many are left? Indeed one of these four was blown up in '55 by a lightning. This makes three other in the Birdcage-area. Personally I wonder why one of them would be charged and the other two not. In my opinion the story that only one is charged (apart from the doubt concerning Petit Douve) comes from the idea that Birdcage is seen as one mine instead of four. So I think it is very well possible that all three others are still charged.

Are they still dangerous? I'm not an expert in explosives, but I learned that ammonal, which is the main explosive type used for the battle of Messines, is losing it's explosive nature from the moment it becomes moist . Probably it is accepted that it's much safer to let it underground than to try to evacuate the charge. The fact that the mines are in rural country will add to the fact that no plans are made to excavate the mine.

Conclusion: relatively unharmless. But when you go walking over there remember that people had the same opinion in 1955!

Erwin

Forgot to react on this. Absolutely true on the interaction between geology and explosives. A good example : although Ontario Farm was a one of the deepest and quite heavily charged (about 60.000 pounds of Ammonal- compare with St Eloi which had the largest charge- 95.600 lbs) it didn't made an such an impressive crater or large ole as some other similar charges did.

Erwin

One account suggests no 'ole at all, just a seething mass of porridgy muck.

Ayup Chums

The biggest problem even today with blasting muck is that over half lands back in the ole!!

Similarly the shock waves travelling laterally from the explosion turn the earth to a loose tilth at great depth and thus allows the water inherent in the soil structure to be released.

Given that water or any fluid under pressure will travel towards the line of least resistance it would eventually ( and possibly very quickly in Flanders) migrate to the crater being the easiest route.

Roop

Re the safety or otherwise of living above the unexploded mine - the mines were fired electrically and there were also old-fashioned fizzing fuses in place just in case. Both electric and fuse methods set off a detonator which fired the charge. The 1955 mine was detonated during a thunderstorm when a lightning-strike earthed directly above the mine. Am I right in thinking that barring a similar event or an underground fire, the remaining mine(s) can't be detonated?

That is - the eexplosive can't go off all by itself without any outside intervention?

Tom

[QUOTE]A good example : although Ontario Farm was a one of the deepest and quite heavily charged (about 60.000 pounds of Ammonal- compare with St Eloi which had the largest charge- 95.600 lbs) it didn't made an such an impressive crater or large ole as some other similar charges did.

Hi BSM

Yes a good example.

Now the reason for either of these scenarios ie big (wide ole) little (small ole) is again related to geological structure, depth and size/type of charge.

If a small charge is buried too deep there will only be a porridgy mass as LB has inferred happened to one such.With inherent water problems.

If a large charge is not deep enough it takes the direct vertical line which creates a steep sided small surface area ole.Conversly the same charge at the same depth in a diferent geology can create a very large surface area ole .

If a charge is correctly placed it should in theory be near 45 degree sides (theories are never bourn out in practice).

Roop

I have heard differing opinions as to the stability of the explosives in the 'Missing Mine'-some people have told me that ammonal becomes less likely tro go off with age, others the reverse. When we were standing at Prowse Point looking over to La Petite Douve farm in October, some of the boys asked me in their ghoulish way whether we would have been in serious danger there if the mine went up. I suspected so but have no idea of the likely blast radius/debris effect of a mine like that exploding.
Incidentally has anyone visited the site of the amazing Fauld crater in Staffordshire, caused by the explosion of an underground ammo dump in November 1944? I'm surprised I didn't hear anything on the 60th Anniversary. The story goes that the dump was relatively low on stocks at the time-had the accident occurred prior to D-Day the explosive force would potentially have been greater than Hiroshima.

as a matter of interest the Fauld crater fits the theoretical RE calculations rather well: the maths works on small and big 'oles.

I am assuming that there are no detonators in place, as these would have been inserted shorly before the mine was due to be detonated.

The problem with ammonal is that it is TNT with ammonium nitrate and aluminium added.

The aluminium acts to slow down the speed of detonation and increase the lifting effect. It is used for this purpose in a range of commercial explosives.

The ammonium nitrate is basically a bulking agent which, added to high explosive, makes what you have go further. It is also used in amatol, a WWII mortar bomb filling, and in many of the large improvised explosive devices made by terrorists, where it needs a good quality high explosive as an initiator and needs to be mixed with various other substances.

Ammonium nitrate can simply leech out, but under the right conditions, it can also form sensitive crystals which can be initiated by friction. One of the standard inspection points in amatol filled 3" mortar bombs was to check for AN crystals in the fuze cavity threads.

So, no telling, except that after 90 years the TNT may be OK, but the AN may not.

As far as I understand the explosives used are reasonably stable. Wet Guncotton is relatively safe and can be sawn, drilled or hit with a hammer - these are High Explosives and need a considerable detonation force to trigger them. Ammonal (a mixture of 65% Ammonium Nitrate, 17% Aluminium, 15% TNT and 3% Charcoal) is less safe.

Guncotton (formed by the action of Nitric and Sulphuric acids on cellulose - cotton wool or similar and then pressed and dried in blocks) was able to be used wet and in this manner actually produces more explosive force. It is harder to detonate and in this scenario a primer of dry guncotton is used, itself triggered by a conventional fulminate of mercury detonator. There is a block of this explosive in the La Targette museum, it looks like a small flat brick with a central hole.

Early mines were charged with 100 lb bags of black powder. According to A. Barrie (War Underground) later mines used 50 lb boxes of Ammonal sometimes supplemented with Guncotton and occasionally Blastine. This was detonated with 25 lb primer charges fitted with electrically fired detonators. Considering some of these mines had more than 50 000 lbs of charge that is a lot of boxes!

Spanbroekmolen was charged with 1800 sealed tins of Ammonal, and at 91 000 lbs they must have been large tins...

I believe the largest mine was produced by the Canadians at St Eloi with a charge of 95,600 lbs of explosive 125 feet down.

Many of the charges were contained in waterproof bags clamped with wooden battens at the top. A friend in France has one of these immaculately preserved with Gov. arrow and date. Apparently there is a very large supply available when his colleague gets the time to recover them.......

The really unstable explosives left as a legacy of the Great War are mainly shells charged with Picric Acid based explosives which form highly un-stable compounds by reaction with the metal casing.

Thanks, Pals, for the interesting technical info.

Tom

[QUOTE]Guncotton (formed by the action of Nitric and Sulphuric acids on cellulose - cotton wool or similar and then pressed and dried in blocks)


Leave out the Nitric acid and you have cigarette filters!!

I have just built a machine making this filter stuff in one of the original factories that made gun cotton.


Roop

"Gentlemen I do not know whether we shall change history tomorrow but we shall certainly alter the geography"

Maj-Gen Sir Charles Harington June 6th 1917.

Bob.

With all this discussion about explosives, perhaps it is worth mentioning the Royal Gunpowder Mills at Waltham Abbey. During the Great War there were 5000 people working there making explosives for the Western Front.

www.royalgunpowdermills.com/

As their website says, they do not open again until next April but they have interesting exhibits including descriptons of ammonal, TNT etc.

It is an interesting place, much of it derelict and a large amout more suitable for birdwatchers than Great War researchers, but worth a visit.

Howard