Patent classifications
E
FIXED CONSTRUCTIONS
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E21
EARTH OR ROCK DRILLING; MINING
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E21D
SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
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9/00
Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
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E21D9/14
Layout of tunnels or galleries; Constructional features of tunnels or galleries, not otherwise provided for, e.g. portals, day-light attenuation at tunnel openings
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