Evaluation of the underground space safety resilience of Chinese urban agglomerations based on the “Pressure-State-Response”: A case study of underground rail transit in 26 cities

Urban underground space disasters exhibit characteristics including complex causal mechanisms and high risk. They also present unpredictability and risk coupling amplification. Differences in underground space safety resilience (USSR) and key pathways of urban agglomerations are issues that remain under-discussed. This study is based on the perspective of resilience genesis, and it constructs a Pressure-State-Response (PSR) analysis framework. This study employs methods such as the composite index method, Dagum Gini coefficient, and fuzzy set Qualitative Comparative Analysis (fsQCA) to explore the differences in safety resilience levels and key pathways of underground spaces of urban agglomerations. The study offered several findings: (1) The safety resilience index rankings of the five major urban agglomerations, from highest to lowest, are as follows: Chengdu-Chongqing City Group, Pearl River Delta urban agglomeration, Beijing-Tianjin-Hebei urban agglomeration, Triangle of Central China and Yangtze River Delta urban agglomeration. In addition, the underground space safety resilience systems of cities were clustered and categorized into demonstration and leadership type, striving catch-up type, and stable development type. (2) Overall differences between urban agglomerations are reflected in the differences between individual urban agglomerations. The internal development imbalance is the primary reason for the more significant differences in and between the Pearl River Delta and Yangtze River Delta urban agglomerations. (3) High-level safety resilience of urban underground space is the result of a multi-factor combination in the PSR framework. In addition, there are four high-level safety resilience configuration paths, and these paths are categorized into three modes: "state-driven response", "pressure-triggered response", and "autonomous response". Policy implications and countermeasures for urban underground space development are proposed for each mode of urban underground space safety resilience. These proposals offer theoretical references for optimizing the safety resilience of underground spaces of urban agglomerations.