Abstract: The development and utilization of urban underground space are reasonable strategies conforming to the law of urban development, and China has seen rapid expansion of underground development in urban construction in recent years. China has a vast territory with various types of cities distributed in various geomorphological regions. Therefore, before large-scale development, the underground space of various cities should be classified according to geological conditions to ensure that a geostructural engineering classification system can be established to guide engineering practice. Here, we classified 49 cities according to geomorphologic location, regional tectonic and lithospheric structural characteristics, current seismic activity, basement and soil structure, underground water depth and so on. Choosing the geomorphologic location as the top division unit, we can classify the tectonic environment, crustal and mantle characteristics, basement structure and surface fault activity and potential seismic source zone, as well as soil type and solid structure of surface rocks, in the same division unit for various cities. Classification of urban underground space is based on fine exploration of underground space. We summarized here the current methods for underground geostructural investigation including ground surface mapping, exploratory drilling, geophysical survey and model building. However, new methods and theories are still needed for conducting fine exploration of all elements in a structural system in complex geological environment and in deep underground space development. Breakthroughs are also expected in construction theory and descriptive method for different types of urban geostructural models. And the classification system and classification method for the geostructures of urban underground space also need to be further improved.

Key words: urban underground space, geostructure, underground structure, geological survey, underground space classification