Safety risk factors of metro tunnel construction in China: An integrated study with EFA and SEM

In this work, we proposed a systematic method by integrating exploratory factor analysis (EFA) and structural equation model (SEM) to examine the risk factors for the safety of metro construction. We collected 514 valid questionnaire responses from metro construction personnel in five cities, from which nine common risk factors out of 65 questionnaire items were extracted. The relationships between the individual factors were examined by SEM, and the established model was validated by hypothesis testing and goodness-of-fit tests. The influence of individual factors for the safety in metro construction was characterized by the path coefficient in the model. Real tunnel accident cases in the Wuhan Metro of China were utilized to demonstrate the feasibility and applicability of the proposed EFA-SEM approach. It was found that safety was profoundly influenced by the risks associated with the launching and arrival of tunnel boring machine (TBM) and the risks during tunnel excavation that involved special procedures and conditions. In contrast, the risks pertaining to shaft construction did not have a statistically significant impact on safety. The developed method clarified the causal relationships within a complex project and allowed finding the predominant risk factors, thus providing a guideline to improve safety management for metro construction.