Evaluation of land damage degree in coal mining area with high groundwater level based on matter element extension method

The underground mining in the coal mining area with high groundwater water level has inevitably caused the ground collapse and the reduction of farmland production, but the damage degree and damage range are difficult to obtain. The mining subsidence land in coal mining area with high groundwater level has typical uncertainty and fuzziness. The evaluation of land damage degree is the theoretical basis for the formulation of land reclamation plan and compensation standard for damaged farmers in mining area. The entropy weight method is used to determine the weight of ten indexes, including water accumulation time, subsidence depth, tilt deformation（east-west direction, north-south direction）, curvature（east-west direction, north-south direction）, horizontal deformation（east-west direction, north-south direction）and horizontal movement（east-west direction, north-south direction）. The limit condition method and extension evaluation method are combined to evaluate the land damage degree of 34 evaluation units, including gorgon field, rice corn field and lotus root pond. The results show that the total area of gorgonian land is 444.7 hm², and the moderately damaged area is 135.7 hm², accounting for 30.51%. The whole rice and corn field is in a state of mild damage, with a total area of 747.2 hm². The total damaged area of lotus root pond is 562.6 hm², and the moderately damaged area is 151.8 hm², accounting for 26.98%. The overall land damage in the study area is good. The conclusions could provide theoretical support for scientifically determining the degree and scope of land damage, and are of great significance for the preparation of land reclamation plans and the formulation of damage compensation standards.