emporary shoring - 30 diameter, 36 deep shaf

huangyhg

temporary shoring - 30' diameter, 36' deep shaft
i need to design temporary shoring for a 30' diameter, 36' deep circular shaft.  i'm thinking of using rolled steel beams with wood lagging.  any comments or other ideas?
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sheet piling, i think with the circular beams it would be expensive, plus i would still want to see some cross   
steel beams and wood lagging seem to be appropriate.  i suppose driven steel sheet piling might be an alternative but i don't think they would have adequate strength for that height without some kind of tieback.
ba
how is it going to be excavated?  does the shoring go in as the shaft goes down?  sheet piling may be the best approach and add walers & tie-backs as needed as the excavation proceeds.
soil type? radius of available land around?  
consider the activities inside.  will you be able to brace the inside?  sheet piling would likely be a better option, though you might have to go deep with the piling; however, you'll need to go deep with the wf sections to make them stable as well.
sheet piling is easy to install and extract.
why not cast concrete ring beams within the ring of sheetpiles. if the soil conditions are equal all around the exterior of the shaft, the ring beams will be in compression and act as an arch.
ring beams are cast as required during excavation. the spacing between rings will depend on soil conditions and pile section modulus. rings are connected  to the sheets to prevent them dropping down.