In the case of the construction of a tunnel for the construction of a road in the basement of the land, what compensation is reasonable in view of the preservation of the road structure on the ground where the tunnel is laid and due compensation to the landowner. The issue relates to how far land ownership is effective in the use of underground land. First of all, Article 207 of the Japanese Civil Code stipulates that "the land falls within the limits of the statute to the upper and lower levels of the land," and since the clause does not limit the scope of "Shangha," it can be interpreted that the power of land ownership goes to almost limitless underground.
In addition to Article 207 of the Civil Act, laws restricting land ownership include the Urban Planning Act, the Building Standards Act, the Farmland Act, the Mining Act, and the Hot Water Act.
The depth of depth that can be used underground will be determined in consideration of the situation in the region, which is also called "limit depth" in practice in Japan. In general, the development potential of land is classified in depth according to the potential of land development, but areas with high development potential, such as housing sites, are subject to compensation by viewing the depth up to 20 meters below ground level as the limit depth.
In the judgment of the compensation target in the underground road project, the limit depth is set at 40m in reference to Article 2 subparagraph 1 of the Deep depth land' Use Act and Article 1 of the Enforcement Decree as there is no use of land exceeding 40 m below ground, considering the future availability and the surrounding conditions.
In conclusion, landowners need to be compensated because less than 40meters from the surface becomes a critical subdivision, allowing them to use as roads without compensation, thus falling under the ‘limit depth’ that is available to landowners up to 40 meters below the surface.