A Novel Evaluation Method for the Stability of Construction Sites on an Abandoned Goaf: A Case Study

In recent years, more and more expressways have passed through abandoned goafs. However, the surfaces above the goafs have been experiencing long-term residual deformation, which may bring risks for the construction of expressways. In order to avoid risks, it is very necessary to evaluate the operation safety of the expressway above the goaf. Thus, the precise evaluation of site stability is the key. Based on the variable weight theory and regret theory, the stability evaluation model of the construction site above the goaf was established, which had 12 evaluation indexes. The constant weight of each evaluation index was determined by the triangular fuzzy analytic hierarchy process, and modified according to the variable weight theory. Then, the attribute value matrix was established based on regret theory to evaluate the stability level of the construction site. In order to reduce the influence of subjective factors, validity coefficient and correlation coefficient were used to analyze the validity and reliability of the matrix. The built model was used for Mianluan Expressway. The results showed that the irregular goaf was unstable for the expressway construction site, and the working faces of 18101, 18041 and 21201 were basically stable. Then, the evaluation results were proved by the high-precision leveling results in the field, and the countermeasures of different stability levels were given. The model can accurately evaluate the stability of the construction site above the goaf, and provide a theoretical basis for later management and monitoring to ensure the operation safety of the expressway.