Maybe you could add tunnel faces, shaft faces, drift faces, mine faces, which are all terms used in underground mining? Still, wouldn't it be helpful to know that one meaning of "face" (when used, alone, in underground mining) is Ortsbrust? You could mark it [Untertagebau] on the German side if necessary.
"Surrounded by steel props which support the roof, crouched into a few feet of space, Tommy Shotton gets down his job of drilling coal from the face
with the aid of his 'windy pick' (pneumatic drill). " http://www.cmhrc.co.uk/site/literature/minersday/
SUPPORT SYSTEM STANDARDS FOR MINES OF COAL
SUPPORT SYSTEM STANDARDS FOR FACE WORKINGS http://www.opsi.gov.uk/si/si1999/uksi_1999246...