Abstract: The safety risks during long-distance small-diameter tunnel constructed by tunnel boring machines (TBMs) vary and always cause great loss. Based on the grounded theory, various risk factors in long-distance small-diameter tunnel constructed by TBMs are systematically and comprehensively identified. The analytic hierarchy process, entropy weight method, and game theory method are used to determine the risk factor weight, reduce the interference of experts′ subjective opinions, and improve the accuracy of weight determination. A set of risk assessment model of long-distance and small-diameter tunnel TBM construction is constructed based on cloud model theory. Finally, this model is applied in the TBM construction of a long-distance small-diameter tunnel in the west of Anyang, China, to validate its feasibility in risk assessment. The primary risk factors are determined to be wind duct damage and leakage, water gush on the tunnel surface, collapse, inadequate safety awareness, and insufficient allocation of emergency materials and equipment. Targeted risk prevention and control measures are proposed.

Key words: long-distance small-diameter tunnel, tunnel boring machine construction risk assessment, grounded theory, combinatorial empowerment, cloud model theory