Muck in the construction trades refers to waste in general, usually in bulk form. A representative use from a company's website:
The Danjo's Skip Hire grab truck service covers Croydon, Sutton & Kingston, providing a muck away service, removing all rubbish & construction waste
It also refers to mining waste in the form of loose rock.
Muck away is a common use.
Muck out as a phrasal verb in construction seems vanishingly rare in writing. Attempts to track down this usage are more likely to turn up quotes like solutions for conveying muck out of tunnels. (i.e. muck as a noun).
However there are quotes like:
If successful we will muck out and pour. If unsuccessful we will get divers, muck out, and pour.
From Bridging the Imjin: Construction of Libby and Teal Bridges during the Korean War (October 1952-July 1953) (from an appendix that's a log from 1953). This is an American use (84th Engineer Battalion officers), unlike my other hits which were British. So the phrasal verb has some history. It's not common though.