An arched tunnel is driven in moderately blocky and seamy, wet ground at a depth of 1,970

Question:

An arched tunnel is driven in moderately blocky and seamy, wet ground at a depth of 1,970 ft. The tunnel is 14 ft wide by 11 ft 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.