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[protab]

Hello,

I wonder if you could help me out with a topic:

I am studying tunnel planning. I have to plan works for a narrow tunnel. I have a problem to expedite excavation as only one dumper at a time can transport materials out of the tunnel. Would it be possible to dig sidewards and build some kind of niche to able dumpers to cross inside the narrow tunnel?

Thank you.

Protab

[webmaster]

Hello Protab,

You have basically two alternatives:

A) Build niches along the tunnel.

Becareful, depending on the size of the niche and type of soil/rock, a designer should look into the impact of such niche to the statics of the tunnel and check whether the given lining can remain or has to be reinforced with additional lining locally. This being done, you could build a niche locally fitting your dumpers turning radius +/- tolerance. The number of niches along the tunnel has to be assessed carefully on a time-distance diagram taking the loading and travelling time of each dumper into account so as to get the full picture of where to place the crossing points, i.e. niches.

In practice, this involves usually extra costs not covered in Contracts because part of the Contractors method.

B) Simple method: Lease special dumpers.

A lot of dumper suppliers offer to lease dumpers with 180 degrees rotating cabins which ables the dumper to drive forward in both directions of the tunnel without the need to turn the dumper. If the tunnel is long and you still require niches to speed up the process, then these dumpers will let you minimise the number and width of niches.

In practice, a cost analysis of both methods would tell you which one to take.

Hope the above is of an help to you.

[protab]

Many thanks for the dumper tip. I will probably follow this alternatives.

Thanks for this forum ,

Greetings

Protab

[webmaster]

Good luck for your tunnel studies...

[webmaster]

A link to this query is also placed in the "Tunnel specific queries" forum.