Levee strengthening in the early 1950s.
A great deal of effort was directed at improving Yellow River's levees ever since the 1950s when the national economy was still weak and resources scarce. In this picture, work progressed with no mechanized equipment in sight anywhere.
Ground was compacted by dropping a stone plunger. It doesn't seem like a very efficient procedure to me. I still don't see why couldn't sheep's-foot roller type of equipment be constructed and used for compacting soil at the time.
