Underground Utility Tunnel Expansion Joints

[KHoff]

I am working on a project that includes an underground CIP concrete tunnel connecting three different structures. The tunnel houses utility piping and will also be used by staff to cart laundry/food between buildings. The tunnel makes a "T" shape, with the stem of the T being approximately 200 feet, and the top of the T being approximately 370 feet. The question was raised as to whether or not we need to have expansion joints in the tunnel at intermediate locations between the three ends.

I have designed underground tunnels without intermediate expansion joints in the past, but not tunnels this long and with intersecting tunnel segments. However, I would not expect much thermal expansion with the tunnel being buried underground. Does anyone have any input on this issue? Are there any references that may be of use?

 

[TehMightyEngineer]

I do a lot of work with precast concrete culverts that are in that range of length. Typically each section is about 5 to 8 feet long with a shear-keyed cold joint. 2 strips of sealant are placed between each section and they are clamped together with carbon steel bolts grouted into bolt pockets. If moisture entering the structure must be avoided then they usually damp-proof the exterior. I've never considered thermal expansion or contraction beyond temp. and shrinkage rebar as the cold joints prevents that from becoming an issue.

Have you considered precast sections rather than CIP?

Maine EIT, Civil/Structural.

 

[BUGGAR]

Once everything is backfilled, temperature changes mostly go away of course. During construction, however, you have to allow for all the short time shrinkage. You could consider pouring the tunnels with closure pour strips every so often (depending on your conditions).

Any moisture conditions to deal with? In my experience, it takes a true construction master to correctly install waterstop.

 

[KHoff]

Precast seems like it might be a good option. I imagine that could significantly cut down on construction time.

There are not any unusual moisture conditions to deal with on this project.