Geological safety risk assessment of underground space utilization in Xiongan New Area

The utilization of underground space is related to geological environment. Identifying the geological safety risk and their influencing factors of underground space utilization can provide scientific basis for underground space management and the safety of underground space facilities. Previous studies have utilized various methods including analytic hierarchy process (AHP), fuzzy mathematics, and neural network to analyze the geological environment conditions of urban underground space. However, their methods have limitations in terms of objective weighting. To address this, considering the data correlation, discreteness, and relativity (conflict), an improved analytic hierarchy process incorporating the criteria importance through intercriteria correlation (CRITIC) method was introduced. The CRITIC-Entropy combination weighting method, which made the weights more scientific and reasonable, was proposed to evaluate the geological safety risk of underground space utilization. In Xiongan New Area, the geological safety risks related to stress variation, bearing capacity, submergence and anti-floating, soil pressure change, and sand liquefaction were analyzed. The evaluation focused on four aspects: space, resources, environment, and disaster. Quantitative indicators, such as aquifer thickness, characteristic value of soil bearing capacity, compression modulus of soil, ground elevation, buried depth of groundwater level, land subsidence rate, and sand liquefaction index were selected to construct the geological safety risk evaluation index system for shallow (0−15 m), sub-shallow (15−30 m), sub-deep (30−50 m), and deep (50−100 m) underground spaces. The study reveals that the geological safety risk of underground space in the study area follows a pattern that deep layers have a lower risk compared to shallow layers. The areas with Ⅰ and Ⅱ risk grades are predominantly located at Baiyangdian and its surrounding areas, east of Nanzhang town, and east of Daying town. The cumulative acreage of Ⅰ and Ⅱ risk grades in shallow, sub-shallow, sub-deep, and deep underground space accounts for 54.49%, 42.51%, 41.06%, and 42.18%, respectively. Additionally, the dominant factors influencing the geological safety risk vary across different layers of underground space, while compression modulus of soil, characteristic value of soil bearing capacity, ground elevation, and buried depth of groundwater level show high weights. It is also important to consider the risk changes caused by the potential changes of land subsidence rate, buried depth of groundwater level, and different excavation ways in the future research. These findings provide a geological foundation for the scientific optimization of underground space utilization and disaster prevention and mitigation in Xiongan New Area and other similar areas.