How They Built the Chunnel

How the Channel Tunnel was built: two crews dug toward each other under the sea from England and France, and met only about 36 cm off. Eleven tunnel boring machines cut three tunnels through a layer of chalk marl under the English Channel. They steered blind with lasers, satellites and gyroscopes, and on 1 December 1990 Graham Fagg and Philippe Cozette shook hands through the last wall of chalk, about 40 meters under the seabed. This is how the rock was chosen, how the machines dug and lined the tunnel at the same time, how they were steered, and how the two sides met without crashing into each other. Chapters 0:00 Two tunnels meet under the sea 0:38 Digging blind 1:14 A very old idea 1:43 Three tunnels, not one 2:44 Four problems 3:07 Problem one: the rock 4:34 Problem two: the machines 5:22 Building the walls as it digs 6:17 The French sealed machines 6:41 Where the chalk went 7:03 Problem three: steering blind 7:27 The laser and the target 8:22 Problem four: the meeting 8:44 36 centimeters 9:27 The handshake, 1 December 1990 9:49 The rail tunnels meet 10:15 What happened to the machines 10:26 Opening day, 1994 Sources P.-J. Pompée, "Channel Tunnel: tunnels construction" (1995), Amicale des Bâtisseurs du Tunnel sous la Manche N. Korittke, "Procedure and accuracy in the Eurotunnel breakthrough", Glückauf 127 (1991) (DMT; abstract via OSTI ETDEWEB) Getlink (Eurotunnel), "Our history" timeline Wikipedia, "Channel Tunnel" (construction, geology, tunnel boring machines) HISTORY.com, "Chunnel makes breakthrough" (1 December 1990) MoneyWeek, "1 December 1990: breakthrough in the Channel tunnel" Discovery UK, "How the Channel Tunnel was Built: Ten Remarkable Facts" KentOnline, "£40,000 buys Channel Tunnel drill" (2004) Breakthrough offset: 358 mm sideways and 58 mm in level (Pompée 1995); 361 mm and 58 mm (Korittke 1991). Photo credits (Wikimedia Commons) Tunnel boring machine T4 "Virginie", Coquelles (2013): Lionel Allorge, CC BY-SA 3.0 Channel Tunnel Exhibition Centre, Folkestone 1992, a Tunnel Boring Machine: Ben Brooksbank, CC BY-SA 2.0 Along shore from Dover to Shakespeare Cliff, 1990: Ben Brooksbank, CC BY-SA 2.0 Site of the Channel Tunnel Construction in May 1991: The Basingstoker (Terry Foulger), CC BY-SA 2.0 Samphire Hoe country park: Immanuel Giel, CC0 Eurotunnel Class 9705 at the tunnel exit, Coquelles (2014): Florian Fèvre, CC BY-SA 4.0 Speech of Queen Elizabeth II for the opening of the Channel Tunnel (1994): Thierry Dauwe / European Communities, CC BY 4.0 Beaumont tunnel boring machine plan (1880s) and Illustrated London News, 4 March 1882 (reception in the Channel tunnel): public domain 3D reconstructions and graphics: How'd They Build It (our own) Narration: AI voice (Google Gemini TTS). Music: "Aha!" (Suno, licensed). how the Channel Tunnel was built, how was the Channel Tunnel built, how'd they build the Channel Tunnel