Lock Block Ltd. uses a mortarless stone concrete block system to assemble enormous and strong forms. The truck in particular in this demonstration video is a fascinating design. The back appears to be covered with rollers that serve as braces as the blocks are set into an interlocked arch. The roller back looks like it’s tapered, so the truck smoothly exits a section of tunnel by driving forward.
Also, the construction blocks look almost exactly like Lego pieces:
No, really! And they’re used to assemble large forms like Lego pieces, too. Once they’re set in place, they’re strong enough to hold up the digger in the video.