Tunnel borers instead of U-Boats

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Gorque
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Tunnel borers instead of U-Boats

#1

Post by Gorque » 07 May 2020, 20:52

What if the Third Reich invests in a fleet of tunnel-boring machines instead of U-Boats and these machines are used to pop out of the ground in rural areas, preferably in the middle-of-the-night. This would allow for a large build-up of men, material and machines prior to beginning offensive operations?

Feasible?

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Re: Tunnel borers instead of U-Boats

#2

Post by Carl Schwamberger » 07 May 2020, 21:39

At what tunneling rate or speed of digging? 2-3 meters per day?


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Re: Tunnel borers instead of U-Boats

#3

Post by OpanaPointer » 07 May 2020, 21:55

You know a few tall boy bombs would have an interesting effect on those tunnels, right?
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Re: Tunnel borers instead of U-Boats

#4

Post by Carl Schwamberger » 07 May 2020, 22:07

Depends on how deep they are. & the soil conditions. Some ground bears shock better than other.

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Re: Tunnel borers instead of U-Boats

#5

Post by Carl Schwamberger » 07 May 2020, 22:10

Heres a question. How much more efficient is the Allied cargo fleet sans losses & the need to run in convoys? Do deliveries to the UK increase 20% or 30%.

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Re: Tunnel borers instead of U-Boats

#6

Post by T. A. Gardner » 07 May 2020, 22:46

Here's how this would have to play out.

First, in peace time, Germany would have to do extensive core sampling across the channel to determine the soil conditions they would be boring through. At the time there was an old (1846?) survey of soil conditions that relied more on observation of both sides of the Channel on land with nothing being done to do at sea core sampling. This is necessary to know the conditions under the Channel and the proper depth to bore the tunnel at.

Next, somebody or company in Germany would have to invent, build, and test the boring machine(s) to be used. At the time, tunnel boring machines were known, but few were in use and none existed to bore through harder rock.

Then the Germans would have to stockpile the materials to line the tunnel, ventilate it as they progressed, pump water out as it seeped in, etc.

They would next have to come up with a way to keep the boring machine going in the correct direction at the correct angle and depth as the tunnel progressed.

And, of course, there is the rate of advance. Let's assume they can advance at a rate of one a meter an hour on average. This includes stops to change cutting tools, service the machine, etc., and that the intended tunnel is 50 km long. It would take at that rate about 6 years to bore the tunnel out...

They also better hope the British don't figure out where the tunnel is being built (highly likely to happen). Because if the British do (an virtual certainty) I could see them waiting until the tunnel is like halfway across the Channel and then sinking a ship on top of it with say 10,000 tons of explosives in it to set off an earthquake-like effect and either collapse it or flood it, or both...

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Re: Tunnel borers instead of U-Boats

#7

Post by Terry Duncan » 07 May 2020, 23:12

I think this was dealt with in the film and series of Dads Army. To be honest it is a non-starter for many reasons. It is also not really fully filled out to fit the requirements of a What If.

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Re: Tunnel borers instead of U-Boats

#8

Post by Gorque » 08 May 2020, 00:23

Terry Duncan wrote:
07 May 2020, 23:12
I think this was dealt with in the film and series of Dads Army. To be honest it is a non-starter for many reasons. It is also not really fully filled out to fit the requirements of a What If.
True. It was more of a lark on my part, but considering some of the ideas presented...why not. :D

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Re: Tunnel borers instead of U-Boats

#9

Post by Gorque » 08 May 2020, 00:25

Carl Schwamberger wrote:
07 May 2020, 21:39
At what tunneling rate or speed of digging? 2-3 meters per day?
No idea Carl. The white cliffs suggest a good possibility of encountering clay.

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Re: Tunnel borers instead of U-Boats

#10

Post by Gorque » 08 May 2020, 00:26

OpanaPointer wrote:
07 May 2020, 21:55
You know a few tall boy bombs would have an interesting effect on those tunnels, right?
They'd have to know where the tunnels would be. And did the Allies have tall boys in 1940? I can't answer it as IDK.

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Re: Tunnel borers instead of U-Boats

#11

Post by Gorque » 08 May 2020, 00:29

Carl Schwamberger wrote:
07 May 2020, 22:10
Heres a question. How much more efficient is the Allied cargo fleet sans losses & the need to run in convoys? Do deliveries to the UK increase 20% or 30%.
That is a good counter to not having U-Boats. However, the surprise of waking up and seeing a division or two or perhaps more in ones rear....

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Re: Tunnel borers instead of U-Boats

#12

Post by Gorque » 08 May 2020, 00:35

T. A. Gardner wrote:
07 May 2020, 22:46
Here's how this would have to play out.

First, in peace time, Germany would have to do extensive core sampling across the channel to determine the soil conditions they would be boring through. At the time there was an old (1846?) survey of soil conditions that relied more on observation of both sides of the Channel on land with nothing being done to do at sea core sampling. This is necessary to know the conditions under the Channel and the proper depth to bore the tunnel at.

Next, somebody or company in Germany would have to invent, build, and test the boring machine(s) to be used. At the time, tunnel boring machines were known, but few were in use and none existed to bore through harder rock.

Then the Germans would have to stockpile the materials to line the tunnel, ventilate it as they progressed, pump water out as it seeped in, etc.

They would next have to come up with a way to keep the boring machine going in the correct direction at the correct angle and depth as the tunnel progressed.

And, of course, there is the rate of advance. Let's assume they can advance at a rate of one a meter an hour on average. This includes stops to change cutting tools, service the machine, etc., and that the intended tunnel is 50 km long. It would take at that rate about 6 years to bore the tunnel out...

They also better hope the British don't figure out where the tunnel is being built (highly likely to happen). Because if the British do (an virtual certainty) I could see them waiting until the tunnel is like halfway across the Channel and then sinking a ship on top of it with say 10,000 tons of explosives in it to set off an earthquake-like effect and either collapse it or flood it, or both...

They were in it for the long-haul to begin with. It started in September '39 and ended in 5-45; So whats that 5.75 yrs vs 5.7077 years. :D

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Re: Tunnel borers instead of U-Boats

#13

Post by OpanaPointer » 08 May 2020, 02:19

Gorque wrote:
08 May 2020, 00:26
OpanaPointer wrote:
07 May 2020, 21:55
You know a few tall boy bombs would have an interesting effect on those tunnels, right?
They'd have to know where the tunnels would be. And did the Allies have tall boys in 1940? I can't answer it as IDK.
It was an example. But for fun, do this. Drill through to England, how many tunnels? How wide? How long to do it? I've seen Hitler's preps for a reverse D-Day and they were just sad.
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Re: Tunnel borers instead of U-Boats

#14

Post by Carl Schwamberger » 08 May 2020, 02:51

Back in the Autum of 1984 the battalion staff of 2/12 Marines took a tunnel tour of a interdicted NKPA tunnel . It was wide enough two files of infantry wi equipment could double time under the DMZ to the South. We were told some tunnels were identified as wide enough for four NKPA soldiers abrest. The ROKs tour guides would not tell us how many tunnels had been interdicted, tho I suspect at least two, or how many had been identified.
Last edited by Carl Schwamberger on 08 May 2020, 03:48, edited 1 time in total.

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Re: Tunnel borers instead of U-Boats

#15

Post by Kingfish » 08 May 2020, 02:58

Given the difficulties in navigation there stood an even money chance the Germans would emerge somewhere on the moon, and that would be enough to make an infuriated Donitz flip his desk.
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