I tap my anchor bolts with a small sledge hammer, they make a unique sound when the threads are pulled or the bolts are fractured, My anchor bolts are about 1 1/2’ diameter. They anchor tall silos.
I remember when Oldsmobile tried converting a gas engine to a diesel, we mechanics would literally pull the rocker covers off, tap each head bolt and often they would just pop up with a thunk, all it took was a hammer tap. Too much compression in a diesel for gasoline engine sized head bolts.
Wow. One and a half FEET? Those must be some damn big silos.