tunnels shape

[ngangey]

We are currently planning a tunnel for a small hyro project and one of our engrs. recommended to use rectangular shaped tunnel instead of an arc roof tunnel to save money for tha arc rib support..what would be the disadvantage if we use rectangular shaped when it comes to quality of the support..

 

[hokie66]

The appropriate shape depends on the method of tunnel construction. Using a tunnel boring machine dictates a circular shape. If a cut and cover tunnel, then a rectangular shape could be appropriate. For a water conduit, you might consider a performance document, leaving the method to the tunnel builder.

 

[csd72]

Agree with hokie, the ground will dictate the asppropriate options and then from those options you should try and pick the one with the simplest most straight forward construction method.

This usually gives you the cheapest option rather than choosing the cheapest materials.

 

[cvg]

arched roofs will handle higher loads than flat roofs as they reduce the amount of bending and shear stress. So if you can do it, it might result in thinner structural sections with less reinforcement and possibly cheaper.