utility tunnel - emergency escape tunnel

adit adjacent alignment blast bolt bolting boring breackthrough cavern cavity concrete construction crete crosscut cut cutter drill drilling drinking emergency energy escape excavated excavation gallery grade granite gunit hard head headrace heavy hole hydro indicator invert lined long machine man measures mining molasse plant power pressure profile project proximate renewable road rock round save serves shaft shelter shot shotcrete single site slope small support sustainable system tbm tube tunnel tunneling tunnelling utility