ABSTRACT
The focal point of underground space use is the regeneration of city by relocating numerous city functions underground in order to reinforce, develop and improve urban infrastructure for the future enrichment of society. Underground space is no more optional space but necessary space for the city. In the 21st century, the underground space will burst into use in many parts of the world. Subways will become common transportation means in most of large cities even in the developing countries, and public utilities and lifelines do the same. The major feature that will emerge in the 21st century is the network use for infrastructure system. Networks will be strengthened in the transportation systems as well as telecommunication and electric power networks. Sewerage and drinking water systems will be networked among treatment plants and purification plants. Storm water reservoir tunnels will also be networked. In order to respond to this need, new technologies have to be developed. First is the network development of infrastructure with the new modal shift concepts and technologies. Modal shift concepts and technologies that have already been adopted in the freight transportation systems will be applied to the network of underground infrastructures. Second is the methodological use of deep underground with geo-technology. Third is the geo-technical development to use deep and large underground space. Geo-technological issues are the design and construction technologies to use deep underground and to create the large caverns and tunnels.
