It seems that they have rubber gaskets on the ends. Once the sections are in place, friction (from the foundations and overburden of that segment and the rest o

It seems that they have rubber gaskets on the ends. Once the sections are in place, friction (from the foundations and overburden of that segment and the rest of the tunnel) would hold it in place. There do also seem to be systems that have cables to keep the segments in tension. https://www.penta-ocean.co.jp/english/business/civil/crawnciel.html https://www.penta-ocean.co.jp/english/business/civil/crawnci...