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A tunnel is an underground or undersea passageway. It is dug through surrounding soil, earth or rock, or laid under water, and is enclosed except for the portals, commonly at each end.
Learn about the history, methods, uses, and facts of tunnels and underground excavations. Explore how tunnels have been built for mining, transportation, water, and other purposes since ancient times.
Learn the meaning, history, and usage of the word tunnel as a noun and a verb. Find synonyms, examples, phrases, and related words for tunnel.
Learn about the types, characteristics and challenges of tunnels, from mining to transportation. Explore the history, examples and future of tunnel engineering and construction.
May 11, 2024 · Channel Tunnel, rail tunnel between England and France that runs beneath the English Channel. It is 50 km (31 miles) long and consists of three tunnels: two for rail traffic and a central tunnel for services and security. Learn more about the Channel Tunnel, including its history.
- The Editors of Encyclopaedia Britannica
Basic tunneling system. Tunnels are generally grouped in four broad categories, depending on the material through which they pass: soft ground, consisting of soil and very weak rock; hard rock; soft rock, such as shale, chalk, and friable sandstone; and subaqueous.
Tunnel construction is a subset of underground construction. There are three basic types of tunnel construction in common use: Cut-and-cover tunnel, constructed in a shallow trench and then covered over. Bored tunnel, constructed in situ, without removing the ground above. They are usually of circular or horseshoe cross-section.
