Abstract: In order to promote safety risk assessment of the operational tunnel structure health, the cloud model was adopted to discuss the randomness and fuzziness in the uncertainty information. And a level of safety risk evaluation method was worked out based on two-dimensional and multidimensional cloud reasoning. On the basis of establishing the evaluation index system, cloud digital features were used to describe the safety risk level, probability and loss degree, and to implement the two-dimensional cloud reasoning of the third layer evaluation index safety level. And the multidimensional cloud reasoning of the second and the first evaluation index safety levels was realized by ideology of fuzzy reasoning after establishing a reasoning rules base. The results show that the safety evaluation method based on cloud reasoning is helpful in realizing expression of the uncertainty problem,and that the final result of the safety risk hierarchy is in accordance with the actual situation.

Key words: operating tunnel, could model, two-dimensional cloud model, uncertainty reasoning, risk assessment