坑こう内ない掘ぼり

noun

underground mining

Mining method where ore is extracted from underground shafts or tunnels, as opposed to open-pit mining (露天掘り).

See also: 露天掘り

• この地ち域いきでは坑こう内ない掘ぼりが主しゅ流りゅうだ。

  Underground mining is the main method in this region.

• 坑こう内ない掘ぼりは露ろ天てん掘ぼりよりコストがかかる。

  Underground mining costs more than open-pit mining.