Is a curved tunnel stronger than a straight tunnel?

Answer 1

YES! The sharp corners concentrate the stresses in the structure. If you were to push down on a square tunnel made of paper, you will see that the corners 'flex' the most, bearing most of the pressure your hand exerts. In a round tunnel, the whole structure distorts to accommodate the pressure. This simply means that the pressure isn't being 'focused' on one part of the structure.

This is why the Roman's made extended use of the arch, and why any pressure vessel is always a cylinder. Look at cannisters, pipes, airplanes, and anything that has to store pressure.

By the way you do NOT want to use a triangle for a tunnel. A triangle is good as a support for a bridge because all the force on the structure comes from one point -- the apex. In a tunnel, there is force distributed all along the top, like a pressure vessel.

Also, composites are EXPENSIVE and are not the answer. The stress concentration does not go away; the material is simply strengthened to handle it. Composites are used in military aircraft where aerodynamic constraints conflict with pressure design requirements. The military can afford to decide to spend loads of money on composites if it means the plane is invisible to sonar or it flies better. An engineer who has to design a tunnel is not going to ask for composites. That would be a disgrace to his intelligence and his profession.

Answer 2

A cylindrical tunnel is stronger than an avoid one. Just look at old castles. The corners were always cylindrical because they were stronger than a sharp edge. Basically, wherever you have an edge or corner it is supposedly weaker than a round edge or corner. However, this doesn't necessarily apply today with modern composites, etc.
On the other hand, just look at underground tunnels. They're cylindrical right? There must be a good reason for that.

If you're talking about a bend in a tunnel versus a straight bit of tunnel i would say the straight bit is stronger.

Answer 3

there is very little difference in strength between a straight tunnel and a curved tunnel, however, as far as the shape of the tunnel itself then an ovoid tunnel is stronger as the majority of the load on a tunnel comes from above. if you dont believe me check out Brunell's sewers in london, they are Ovoid, the only reason modern tunnels are round is because modern tunnels are bored out using rotating machinery which by there nature produce circular holes

Answer 4

Regarding some of the answers all the old tunnels I've seen were ovoid like an egg shape with the pointy end at the top. I think modern tunnels, certainly those that were bored are round but ovoid must have had something going for it.

Answer 5

look around you, you dont find straight tunnels often, thats your answer. Curved tunnels are stronger because the load is spread out and stretch wil in a straight one its just in one place.

Answer 6

What's that got to do with anything?

Regardless of direction up down or sideways, the only thing concerning the engineer is the load carried and the soil mechanics for each portion of the terrain passed through.
There are many other aspects to design for but none concerning strength.

Answer 7

It depends on the make up of the rock it is penetrating and the materials and design. Also the geology of the whole area. Just an educated guess.

Answer 8

hmmmm yes??? although...a triangular tunnel would be stronger than both

Answer 9

Not necessarily.

Answer 10

depends on the materials used... and the structure.....