Detonating Underground Mines

[SimPar]

Hi folks,

Just watched and enjoyed Beneath Hill 60 and was wondering about the technology. Does anyone know how wiring circuits were tested prior to detonation? And, just for good measure, how long before detonation would all the final connections be made and the mine be ready for firing?

I know there are a few good books out there on the underground war which I will hunt down in due course but I've run out of book money for the moment.

Any guidance much appreciated.

Simon

[Rockdoc]

The detonators were electrical and linked together in sections so that it would be possible to check for a continuous circuit in each of the sections, with the full circuit only being connected together at the last moment. It would be important to keep the sections separate for testing for as long as possible so that any fault could be traced quickly.

Keith

[Tom Morgan]

I've read an account of officers nervously testing and re-testing their detonator circuits in the last few minutes before firing. They used a torch battery which gave a feeble current, just enough to light a bulb, but not enough to fire the detonators.

Tom

[Gunner Bailey]

My Grandfather was a sapper and he did all sorts of elecrical work. He apparently did something in the mines at Fricourt in July 1916. Whether it was lighting or doing the wiring for the detonation I don't know. If only they had told their stories in detail!

John

[calibre792x57.y]

I believe the circumstances dictated the time that all detonators and firing circuits were readied. The mine charges in each chamber would genrally have two sets of detonators fitted, one set being fired electrically and the second set by safety fuze, burning at 23-37 inches per minute, as back up. The detonators would be fitted and connected as the charge was placed because there would be a couple of sandbag barriers with an airspace between to act as tamping, to prevent the charge simply blowing back along the tunnel. Not easy to remove. The electrical circuits were checked by using a low power current, sufficient to light a torch bulb. Some of the Messines mines were thus fitted a year in advance of the battle and there were constant worries about these being affected by the damp. Ammonal has to be kept dry as it absorbs moisture and becomes less sensitive as it does so. Eventually it reaches the point that the detonator and primers will not provide sufficient energy to fire the charge. None the less the main charge was likely to stay good for many years in the rubberised bags used. Others were only finished a day or so before kick off. So the mines would only need the exploder box connecting in the case of the eletrical detonators and the fuze lighters fitted to the safety fuze immediately before the detonation to go. S.W.

[TonyE]

Can I suggest you buy a couple of the Durand Group's DVDs. "Fighting the Germans underground" and "One of our mines is missing" would be a good start. I can supply these or you can get them from Amazon.

When the group defused the last sizeable mine it had four detonators, two electric and two safety fuze as sommewalker says, and these were encased in glass jars to protect them from the damp.

There was no shortage of power for the detonators when the unused Messines mine went off in 1955 after the armoured firing cable was struck by lightning!

Regards

TonyE

[SimPar]

Hi all,

Thanks for all the great answers. I shall certainly take a look at the DVDs in due course.

Thanks to all of you for taking your time to answer the query.

Regards

Simon

[leighc]

Also highly recommend Crumps and Camouflets by Damien Finlayson for a detailed account of the day to day challenges of tunnelling, including keeping charges and circuits viable for months at a time and the pressure on the man with his hand on the plunger.

Crumps and Camouflets