IMPORTANT NOTE: The build's floor should be y=11 when looking for diamonds to prevent lava from setting off the TNT. (y=12 should be air, and y=13 should be the first layer of blocks in the build).
In this video, I give an explanation and tutorial (15:18) for an expandable tunnel bore designed in 1.15.2, though it should work in earlier 1.15 versions and in 1.16. The design takes inspiration from designs on Rays Works' and ilmango's channels.
World Download: http://www.mediafire.com/file/tierwaa...
Litematic: http://www.mediafire.com/file/ggm20um...
Get the Mods I Use (Fabric Mod Loader):
https://masa.dy.fi/mcmods/client_mods/
https://github.com/gnembon/fabric-carpet