Innovative ideas for underground tunnel repair 1

[pbc825]

I'm working on a project for a mining operator. They have a reinforced concrete tunnel under a product storage structure, and the tunnel is highly chloride impregnated. Replacement in-kind of the tunnel is an option, but the price tag is rather high and indirect costs from lost production make it extremely unattractive to the client. The tunnel was constructed by excavating to the floor elevation, prepping for a floor, placing a floor, then walls, then roof (all with shear keys at the interfaces) to make a rectangular opening for several hundred feet then back-filling on top then constructing the storage structure above the tunnel. All tunnel elements are about 20" thick with two layers of reinforcing steel. Inside dimensions are about 11' tall and 9' wide.

I've had the ideal of constructing an internal tunnel, but we may not be able to consume that much room internally.

I've had the idea of encapsulating the tunnels, then raising the internal gauge pressure (as was done for caisson construction, Brooklyn bride towers for example), but I don't like the safety challenges associated with it (I think the/a Brooklyn bridge engineer died of the bends).

If anyone has experience with innovative repair/replacements of underground tunnels in-situ (i.e. without excavating to the top), I am interested in discussing with you.

Thank you in advance.

 

[amlinerrichard]

Miningman, I didn't realize that only mining people understood that only miners can send a possibility of a fix.

 

[LittleInch]

Well until you can determine whether the current tunnel is still structurally capable or not, what the minimum internal space would be and how big an access hole you can make I think we're going to have difficulty here coming up with sensible solutions.

If all you really need to stop the thing falling down is a whole set of acrow props and a bunch or either timber or steel support frames then you should be able to erect those in situ around what ever is there.

I can't see anything external to the current tunnel being strong enough if the current structure is as bad as is being reported.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[cvg]

perhaps build a new product storage building, new tunnel, install a new conveyor and abandon the old? this might eliminate a long shutdown

 

[FacEngrPE]

Consider building a new tunnel - with new material handling equipment. This approach could reduce the out of service time. If the big cost is loss of production, a new tunnel might wind up costing less than repairing the existing one.

 

[miningman]

Just goes to show theres nothing new in this world........ cvg's idea is pretty much what my surface colleagues did while I was playing silly buggers with the underground production conveyors 2010-2014.

 

[bridgebuster]

Take a look at this contractor, Sovereign Hydroseal. They made a presentation at my office back in December. They have a lot of experience with tunnels.

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