Objective In the safety risk assessment of metro shield tunnel construction, it is challenging for the traditional models to effectively quantify the risks due to the significant spatial heterogeneity of risk events. Therefore, it is necessary to consider the above spatial heterogeneity and establish a safety risk assessment model for metro shield tunnel construction based on the dual-dimension coupling of risk event attributes and spatial distribution characteristics, thereby realizing predictability, early warning and controllability of risks and meeting the differentiated decision-making needs of project management and on-site operation levels.

Method Based on engineering geology, design, construction and environmental constraints, the principles for dividing tunnel risk sections are proposed. The core concepts of risk events and spatial heterogeneity are defined, and the risk probability and consequence of each section are integrated through the event-section risk matrix. The information entropy theory is introduced to establish a spatial heterogeneity index to quantitatively characterize the uneven spatial distribution of risks. A section risk aggregation operator is developed based on the worst-case principle, to calculate the comprehensive risk level of sections and establish the risk rating criteria. In the practical case study of a Shanghai metro project, the scientific validity and practicality of the model is verified.

Result & Conclusion The proposed assessment model enables simultaneous characterization and integrated assessment of risks in the dual-dimension of event and space, facilitating a transition from traditional general assessments to precise risk profiling. It provides an operable methodology and tool support for the differentiated and refined risk management and control in complex tunnel engineering.