Stability Assessment on Safety of Shield Tunneling Based on Game Theory and Extension Cloud

During the construction of the metro shield, the surrounding ground surface and buildings will settle due to the disturbance of sand and gravel during excavation. Therefore, it is essential to evaluate the safety and stability of shield tunneling. Aiming to address the ambiguity, randomness, and significance of each index in the process of evaluating safety and stability during shield tunneling, the study utilizes a method that combines game theory and extension cloud. Monitoring data related to ground subsidence, building settlement, embankment settlement, pipeline settlement, and segment deformation are selected as evaluation indices to develop a comprehensive extension cloud evaluation model for shield tunneling safety. The model is validated using real-world engineering cases. The results show that according to the combined weight results obtained by the game theory, analytic hierarchy process, and entropy weighting method, the safety and stability evaluation indexes of the shield tunnel interval in this case are building settlement, segment deformation, ground settlement, pipeline settlement, and embankment settlement in order of importance. The safety and stability of nineteen monitoring groups are evaluated using the comprehensive extension cloud model, including eight Level Ⅲ, four Level Ⅱ, and seven Level Ⅰ. Among them, monitoring groups at Level Ⅱ and Level Ⅰ nearby need to adopt corresponding preventive measures. The comprehensive evaluation model developed in this study, based on game theory and extension cloud, can reflect the uncertain relationships among various indicators. It helps to avoid the one-sidedness of single weighting. Compared with fuzzy comprehensive evaluation, the calculation results are more aligned with objective reality. Based on the aforementioned research, a comprehensive evaluation method is proposed, which combines game theory and extension cloud model. This method offers a novel approach and concept for safety evaluation in shield construction. The research can provide scientific references for the safety and stability evaluation of shield tunneling in sandy and pebble strata in the Chengdu area.