strip mine vs workings

strip mine

noun
  • A mine where the material above the ore is removed (stripped) to expose it for removal and use. 

workings

noun
  • The parts of a quarry or mine that are being (or has been) worked. 

  • The internal mechanism of some device or system. 

How often have the words strip mine and workings occurred in a corpus of books? (source: Google Ngram Viewer )