> what if the Army could cut and cover 100 meters of precast tunnel segments in a day

If you have the precast tunnel segments to do that why wouldn’t you just plop them down on the ground? What benefit does cutting and covering provide?

Also how would you protect your construction crew and construction supply chain as they are slowly plodding along 100m a day?

Once built, could this cut and cover tunnel be disabled by hitting it anywhere along its length with a “bunker buster” amunition? Or a backpack full of explosives and a shovel? Or a few cans of fuel down the ventillation and a lit rag?

And if the answer is that you will patrol the topside to prevent such meddling, how do you protect your patrols? And if you can protect them why don’t you do the same for your logistics?

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jandrewrogers 4 hours ago | parent | next [-]

That cover dirt materially adds to the resistance of the structure.

This is why even above-ground bunkers are almost always buried underneath a giant mound of dirt instead of being bare concrete. It is a cheap structural multiplier that greatly increases the amount of explosive required to damage the insides. It is also very cheap. A bunker buster is a very heavy and specialized munition which limits its scope of practicality.

There are entire civil engineering textbooks that focus exclusively on the types of scenario you are alluding to. It is a very mature discipline and almost all of it has been tested empirically.

I used to have a civil engineering textbook that was solely about the design of structures to resist the myriad effects of nuclear weapons. It was actually pretty damn interesting. Civil engineers have contemplated at length just about every structural scenario you can imagine.

	▲	krisoft 4 hours ago \| parent [-]
		> Civil engineers have contemplated at length just about every structural scenario you can imagine. I bet. Do they recommend cut and cover highways in contested environments? Or do they recommend shooting back until the area is no longer contested? (Which you practically have to do anyway to build the cut and cover tunnel in the first place.) I don’t doubt that it is a good idea to cover with earth C&C bunkers and launchers and such. But those are point installations. Miles and miles of tunnels used for logistics are lines. They scale very differently.

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PaulDavisThe1st 5 hours ago | parent | prev [-]

> If you have the precast tunnel segments to do that why wouldn’t you just plop them down on the ground? What benefit does cutting and covering provide?

I have no opinion on this, but TFA makes it pretty clear: visibility and susceptibility to attack.

TFA also makes it clear that cutting and covering is weak sauce compared with actual tunnels "30-40 feet below the surface".

	▲	krisoft 3 hours ago \| parent [-]
		> I have no opinion on this Use your mind and develop an opinion. I read the article too, i’m just disagreeing with it. > visibility There are two kinds of visibility to be had. Not knowing where the tunnel is, and not knowing who and when passes in it. Cut and cover doesn’t help with the first kind of visibility. Disturbed vegetation and soil will reveal your tunnel’s path to even a senile adversary. One who somehow missed your whole construction. If you just want to hide your movements and somehow you have the budget for hundreds of miles of prefab concrete tunnel you can hide inside it without it being burried. > susceptibility to attack Undoubtedly burrying the precast concrete segments under dirt makes it harder to attack, but it won’t make it impenetrable. And once the enemy cracked it the whole tunnel becomes useless for transportation. On the surface you can just buldozer a way around the damage and keep on trucking. Underground you need to excavate, re-line with precast concrete and cover again, under enemy fire. > TFA also makes it clear that cutting and covering is weak sauce I think they could have just left the mention of cut and cover out and the article would have been stronger for it.