| Shulan is one of the important coal production bases in northeast China,and has a hundred year of coal mining history.A large number of mining exploitation of coal resources forms a large area of goaf.The goaf cause serious ground subsidence and ground fissures,as well as induced disaster such as the destruction of buildings and cultivated land etc.Fifth Mine is located in the southwest of Shulan coalfield,the problem of ground collapse is particularly prominent.Therefore,in this paper,Fifth Mine is selected as the research object。The main job of this paper is as following:(1)Collect the data of the study area,and gather the basic conditions of the natural geographical conditions,regional geological conditions,hydrogeological conditions,etc.Moreover,according to the data of mining area,determine the basic situation of mining and the basic characteristics of the deposit and coal seam,and count the scale,spatial distribution,stop time of the existing 96 mined out area.(2)The remote sensing interpretation and field investigation are carried out to study the ground subsidence in the study area.First of all,the remote sensing image of the study area is corrected,and then the remote sensing interpretation of the ground subsidence was carried out in combination with the regional topographic maps and GoogleEarth images.After the interpretation is completed,the field investigation of ground collapse is confirmed by referring to the interpretation results.Finally,a total of 7 ground subsidence and ground fissures in the study area were identified in the study area.(3)According to the investigation results of ground collapse in the study area,the distribution characteristics of ground collapse are analyzed:The ground collapse pit shape are irregular and ellipse;The location of the ground collapse is zonal distribution along the northeast;According to the study area lithology and roof management methods,the roof caving of goaf is considered to be the main cause of ground collapse.At the same time,according to the actual situation of the mining area,the main influencing factors of the ground subsidence in the area are as follows: topography,rock mass structure and structural features,the influence of surface water and groundwater,the influence of coal seam characteristics,the influence of mining methods and roof management methods.(4)Determine the relative risk level of 96 mined out areas in the study area.According to the characteristics of mined out area,the following 7 factors are selected as evaluation indexes:geological structure,compressive strength of rock mass,tensile strength of rock mass,buried depth,dip angle of coal seam,the influence of surrounding underground goaf,existence time of mined out area.Then use AHP to determine the weight of evaluation index.Finally,the risk level of all mined out areas is determined by the extension theory:the number of level Ⅳ:0,the number of level Ⅲ:4,the number of level Ⅱ:77,the number of level Ⅰ:15.According to the results of the classification,the high risk area of ground subsidence in the study area is roughly defined,which provides a reference for the hazard assessment of the ground collapse(5)Hazard assessment and zoning of ground collapse in the study area are carried out.According to the investigation results of ground collapse in the study area,the following 7 evaluation indexes were determined:influence degree of structure,development degree of surface water,coal seam dip angle,mining depth,mining thickness,the number of space in the goaf,the time of stopping mining.Finally,based on the rough set theory and ArcGIS software,the hazard level of the ground subsidence in the study area are determined.The results show that the high risk area of the ground subsidence is located in the northwest of the study area,which is in good agreement with the results of the fifth chapter.Therefore,the research results of ground collapse hazard can provide some reference for the prevention and control of ground subsidence in study area. |
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