Abstract:  To investigate the risk pattern and evolution conditions of accidents during the construction of urban large underground space(ULUS), engineeringresearch and statisticalanalysis methods are employed to study the risk characteristics and classification of ULUS construction. Risk assessment of ULUS is performed using theoretical analysis. Then, through an engineering case study, the definition of ULUS is proposed, and ULUS is divided into newlybuilt opencut, newlybuiltmined, and networkexpansion large underground spaces. The risk sources of ULUS include geological, environmental, survey and design, construction, and management factors, and their identification method is established based on a database. The unique characteristics of ULUS construction risks such as dynamic evolution, coupling amplification, and high risk are revealed. The ULUS risks are systematically classified according to their forms. Finally, a ULUS riskassessment method is proposed based on the theoryofindex system method.

Key words: urban large underground space, risk source, risk characteristics, risk classification, risk assessment