[marktwain]

A sponge bomb does not collapse a tunnel. A sponge bomb seals a tunnel.

[Signalman]

A sponge bomb does not collapse a tunnel. A sponge bomb seals a tunnel.

Correct. In the video, the narrator does correctly state that the bomb "sealed" the tunnel. Obvious mistake made in the heading.

[kaktuskid]

Like that insulation foam spray that expands?