On May 15 a drilled shaft rig operated by Mid America Drilling Corp was nearly swallowed by the 9-ft diameter hole it was drilling for a cell tower foundation near Harlan, Iowa. Fortunately nobody was injured and the truck did not suffer any significant damage.
In Arizona, the standard of practice is to use a temporary surface casing to prevent dangerous failures like that. I once saw pictures of a drilling contractor superindendent almost get sucked into a collapsing shaft, even with the temporary casing. Pretty scary stuff. Source: Harlan Tribune. (Photo by Samantha Bruck)