huangyhg

pre-cast segmental tunnel lining selection
i'm begining work on a transit tunnel project and am looking for info on the various types of tunnel linings available. being new to tunnel work i'm looking for pros and cons between linings such as:
one-pass system vs. two-pass with an initial junk segmental and secondary cast-in-place finish.
bolted segmentts vs. doweled.
trapizodal sections vs. non-trap.
etc.
the tunnel has an approx. 19' id, soils are consolidated clays, invert well above the water table, 130' depth to crown.
info on tbm's/shields would be helpful, too.


wow, what a lot of questions. where to start?
to answer all of these questions would take an age so i suggest you need to do some reading. ther are quite a few books on the pro's and cons of tunnelling methods. a good place to start is "the art of tunnelling" by szechy published by balkema but is now out of print so you'll need to visit a technical library.
for your particular tunnel. if you are well above the water table and in a stable clay stratum then a shield is what you need. in terms of cost it is an order of magnitude cheaper than a tbm (which generally you will only need when tunneling below the water table.
as for the ring type, well this will depend on the client's specification for the finished tunnel. if the client doesn't mind the joints being visible then the obvious option to take is the one pass bolted segmental in terms of speed of construction and cost effectiveness. you may wish to consider dowels on the circle joints to enhance construction cycle time.
regards
andy machon

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