Looks like a pipe cover. Possibly for irrigation piping, or rain piping? I found one of those just yesterday in the ground at a muni park (not exactly the same), still connected to the pipe. It clearly was designed to simply keep rodents and stuff OUT of the pipe, while allowing the water to freely run out.
That's my guess, anyway. I'd not seen one before. I simply laid the sod back down, and thought it was an interesting experience... Funny that it showed up today on the forum. :0)