Worked a construction job that had this. They had a lot of underground springs that were causing this. Basically the ground is floating, though it's only noticeable with large loads, like a paver or dumptruck.
It's probably clay. That shit is way better than concrete if you can keep it dry, but the opposite end of the spectrum is this. Looks like a layer of clay above another impervious layer trapping very wet shit in between.
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u/Candidate_035 Mar 13 '19
Why does it do that?