Risk assessment in construction of small-diameter deep drainage tunnel

In order to identify construction risk of small ̄diameter deep drainage tunnel shields and accurately evaluate risk levelꎬ a HAZOP ̄based risk identification method and an evaluation method based on rough sets and cloud models were proposed. Firstlyꎬ construction risks were identified comprehensively by using HAZOP and an evaluation index system was established according to attribute reduction theory of rough sets. Thenꎬ a risk assessment model for small ̄diameter tunnel shield construction was established by combining rough sets and cloud model. Finallyꎬ the model was verified with deep tunnel project of East Lake as an example. The results show that evaluations of the model are basically consistent with actual situationꎬ and major factors causing high ̄ level construction risks include delayed adjustment of tunneling parametersꎬ deficient training and evaluationꎬ clogged grouting pipesꎬ falling down of hoisting equipmentꎬ and unspecific engineering geological and hydrogeological surveysꎬ and they should be checked and avoided.