5. Analysis of Vulnerability Index Method Based on Variable Weight Theory in Engineering Application

A case study on engineering application of the new approach for evaluating the risk of coal seam floor water inrush is conducted and described in this chapter. For different types of karst water system and geological structure models of coal strata, an application research on water inrush from the underlying Ordovician has been carried out through applying vulnerability index method based on zoning variable weight, combined with specific coalfields, "monoclinic Shun set type" of Xiandewang Mine #9 and "monoclinic Retrograde" of Wangjialing Mine #10. From all the evaluation results, we can draw conclusions as follows: Because water inrush coefficient method only considers two factors--aquifer water filling pressure and thickness of impermeable layer, and there are only two results--danger zones and security zones, the water inrush coefficient method has poorer evaluation accuracy. For the traditional vulnerability index method, the weight of the same main controlling factor is a constant in the evaluation process, and does not vary with different values of the same main factor, therefore it is not suitable for practical work. Compared with traditional water inrush coefficient method and vulnerable index method based on constant weight, vulnerability index method based on zoning variable weight realizes the multi-level zoning of water bursting risks, and has higher evaluation accuracy, and the evaluation result is consistent with reality.