How Greece Built a €1.8B Railway With an 11-Year Hole in the Middle of It

Greece's €1.8 billion railway spent 11 years with a hole in the middle of it. In 2002 the crews inside Mount Kallidromo walked out, and the tunnel did not break through until 22 May 2013. The line it belongs to replaces 122 kilometres of single track through central Greece with 106 kilometres of new double track, built for 160 to 200 km/h. On the old route trains could not pass each other, and every freight train that occupied it ran in place of a passenger train. Construction started in 1997 on a budget of approximately €1.8 billion: 49 railway bridges totalling 6,086.88 metres, and two single-track bores through Mount Kallidromo of about 9 km each, 35 metres apart — the longest railway tunnel in Greece and in the Balkans. Kallidromo is three grounds sharing one centreline. Most of it is limestone that stands on its own, and ophiolite that is awkward but manageable. The problem was a band of clay and clay-marl only 645 metres long — less than a fifteenth of the tunnel, and it took longer than everything else combined. Under 540 metres of overburden that clay behaved as squeezing ground: it did not fracture and settle, it kept coming. The floor of the tunnel rose by up to 3 centimetres a day, around 70 cubic metres of water an hour ran into the works, and the steel arches and sprayed concrete were crushed rather than cracked. In 2002, roughly a kilometre and a half in from each side, the work stopped — failures of the support that had to be dealt with in squeezing ground. Evert Hoek came to the site; his report is dated 3 June 2002. The remaining sections were designed again from the beginning, and the answer was the opposite of more strength. A yielding lining with ten slots around the ring let the tunnel shrink on purpose — built to accept convergence of up to a metre — with yielding anchors instead of rigid bolts, and a final 65 cm steel-fibre reinforced sprayed concrete lining cast only once the ground had finished moving. Excavation through the difficult sections then ran at 30 to 35 metres per tube per month, 24 hours a day, seven days a week: about one metre a day. The two headings met on 22 May 2013, eleven years after the work stopped. The line opened on 8 February 2018. €1.8 billion is the headline number. 645 metres is the number that tells the story. The mountain never stopped pushing. They stopped pushing back. CHAPTERS 0:00 2002 — the crews walk out 0:52 One track between Greece's two largest cities 2:46 1997: €1.8 billion to go through instead of around 4:29 Mount Kallidromo: two bores, about 9 km each 5:22 The 645 metres of clay 6:40 Squeezing ground: rock that does not stop moving 7:19 540 metres above, three centimetres a day 8:33 2002: the supports fail and the work stops 9:49 Evert Hoek, and a redesign from the beginning 10:53 A lining built to shrink by a metre 12:29 Eleven years at a metre a day 14:04 22 May 2013 — the headings meet, and the line opens 15:15 When force stops working #engineering #documentary #greece #railway #tunnel #infrastructure #megaproject #megastructure DISCLAIMER ____________________________________ This is not engineering advice. Everything here is for informational and entertainment purposes only. Contact an engineer licensed to practice in your area if you need professional advice or services. All non-licensed clips used for fair use commentary, criticism, and educational purposes. This video was made with AI-assisted tools: the narration is an AI-generated voice and the visuals are AI-generated illustrations, not documentary footage of the real Tithorea–Domokos railway or the Kallidromo tunnel.