Collapsed segmental lined tunnel and its recovery

Round-13 hunt: picked; source: named-course long-video search (round-13 wave 2); channel screens (sellers/exam/re-upload/devotional/vendor/events), provenance check, vendor/seller/devotional recheck and quality tier C + tier-C depth check passed; strict per-title check + final strict pass; oEmbed verified.

A 84-minute video from British Tunnelling Society: “Collapsed segmental lined tunnel and its recovery”.

Video by British Tunnelling Society, played through YouTube's embedded player.