The application and research progress of special underground space

Special underground space (SUS) is defined as a kind of underground space with special properties in terms of spatial form, distribution and structure. According to the source, SUS is classified into two types:naturally existent space and humaninduced one. The special properties and the suitable engineering applications of different SUS types are described in this paper. In addition, the status and prospects of natural gas underground storage, carbon dioxide geological storage, compressed air energy storage, deep-well waste reinjection and radioactive waste disposal are briefly analyzed. With the development of SUS research, it is necessary to explore different SUS development and utilization methods and modes according to local conditions, which can promote the efficient use of underground space.