坑内こうない Noun Noun English jmdict 1 noun (common) (futsuumeishi)nouns which may take the genitive case particle 'no' within a pit or (mine) shaft
坑内掘りこうないぼり Noun English jmdict 1 noun (common) (futsuumeishi) underground mining See also: 露天掘り (ろてんぼり)