unnel basics

huangyhg

tunnel basics
i've started researching tunnels a bit lately.  if anybody in here designs tunnels, i'd appreciate a quick lesson on the very basics: what codes/specs are used, the basic types of construction and which is more common, etc.  
i'm especially interested in fire protection, so if anybody has links to insulation or coating products, i'd appreciate it.  also, aside from nfpa 502, what fire provisions and guidance are out there?
thanks in advance.
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i am designing subway tunnels. can you please be precise what you want to know in structural design aspect of it? i do not know a whole lot on fire proofing but all structure is usually of concrete and any steel section used in encased well in concrete.