An arched tunnel is driven in moderately blocky and seamy, wet ground at a depth of 600 m. The tunnel is 4.3 m wide by 3.4 m high; the back arch is semi-circular.

(a) Specify a suitable steel set size (web depth, flange width, weight per foot), set spacing and maximum blocking point spacing for these conditions.

(b) Explain how one would handle a relatively high side pressure that may develop crossing a fault zone.

(c) What is the approximate thrust capacity, in lbf, required for equilibrium?