Abstract: With the rapid development of China’s high-speed railway, some key lines will inevitably pass through the goaf site. Therefore, the “activation” classification of high-speed railway subgrade in goaf area needs to be solved first prior to a series of problems such as route selection of high-speed railway in goaf area. In this article, the underground goaf at the chainages DK259+135.95−DK259+710.00 of Taiyuan-Jiaozuo high-speed railway is taken as an example. A classification and evaluation model for "activation" of high-speed railway subgrade in goaf area is established using the basic principles of analytic hierarchy process and fuzzy mathematics. Firstly, five major factors and nineteen sub-factors affecting the classification of high-speed railway subgrade in goaf area are determined. On this basis, the classification standard of influence degree for “activation” classification factors of high-speed railway subgrade in goaf area is proposed, and the corresponding classification standard of “activation” of high-speed railway subgrade in goaf area is obtained by combining the influence degree of each major factor. By adopting the analytic hierarchy process, the weights of influencing factors and evaluation factors are determined, and the membership degrees of evaluation factors are obtained in combination with Delphi method, fuzzy statistics and membership function. Meanwhile, the typical characteristics of “activation” classification of high-speed railway subgrade in goaf area are preliminarily examined. Finally, the “activation” classification of the railway subgrade in goaf area is carried out using fuzzy comprehensive evaluation method, and the subgrade in this project is determined to be “necessarily activated”. The classification conclusion of the model is in line with the actual working conditions of the site, which provides a guiding significance for the later treatment of the subgrade in goaf area by grouting. After grouting treatment for the goaf area, another “activation” classification is carried out, and the subgrade in this project is determined to be “inactive”, which provides a scientific and reasonable demonstration for the safe operation of Taiyuan-Jiaozuo high-speed railway.

Key words: high-speed railway, subgrade in goaf area, “activation”classification, fuzzy comprehensive evaluation, influence degree