Stability Assessment of Ground Surface along Tunnels in Karst Terrain Using Improved Fuzzy Comprehensive Evaluation

The stability of ground surface along tunnels in karst terrain is influenced by complex factors, among which the karst features are the significant ones. Under the influence of karst, the ground surface along tunnels is very easy to collapse, thus causing great casualties and economic losses. To provide guidance for maintaining the stability of ground surface along tunnels, an analysis system is proposed for assessing the stability of ground surface along tunnels in karst terrain based on an improved fuzzy comprehensive evaluation. Based on the case analysis of ground collapse along tunnels in karst terrain and the review of the related researches, the evaluation index system for ground surface stability assessment was established. The ridge-shaped membership functions were constructed to calculate the membership degree for the evaluation indices. The comprehensive weighting method combining the Fuzzy Analytical Hierarchy Process and correlation analysis was applied to determine weights for evaluation indices. And the ground surface stability level was recognized based on the maximum membership principle. The proposed assessment system was applied to assess the ground surface stability along the tunnels of Guiyang Metro Line 1, and the assessment results agreed well with the regional ground collapse history, verifying the effectiveness and reliability of the assessment system. Combining with the assessment results, a series of measures were conducted to promote the ground surface stability before tunnel excavation. This system provides a valuable tool for assessing and guiding to improve stability of the ground surface along tunnels in karst terrain.

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