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is a Japanese concept for the public use of deep underground, enabled by a 2001 law. It was first thought of in the late 1980s as Japan faced ever increasing land values in the economic bubble, to allow the utilization of heretofore unused deep underground for necessary water and utility ducts and other city tunnels. However, due to technical difficulties in ventilation, emergency procedures and other safety-related issues and also relatively high cost, no projects utilizing deep underground have been completed as of 2010. ==Definition== * Depth greater than 40 meters or * Depth 10 meters greater than the layer on which deep foundation rests In the case of public use, no compensation to the land owner is required. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「deep underground」の詳細全文を読む スポンサード リンク
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