This is my 5 cents for tunnel breakthroughs;
The second giant boring machine (TBM) building HS2 under the Chiltern Hills broke through at the tunnel’s northern portal, completing a journey that began in June 2021.
cover tunnel photo by: Matt Brown from London, England / CC BY
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Another good view
Moment machine digging HS2’s longest tunnel breaks through after 10-mile journey - video Dailymotion
www.dailymotion.comMoment machine digging HS2’s longest tunnel breaks through after 10-mile journeyPA