Subsidence Features And Risk Prediction In Coalmine Goafs

This thesis applies the extension theory, AHP and GIS system to the research of goaf subsidence of the coalmine in the Xishan (western mountainous) area of Beijing. The probability integral method and numerical simulation method were used for the prediction of goaf collapses. The main idea is to reduce the artificial disturbance in the risk zonation and provide basic data in the early warning forecast of geological disaster.The Xishan area of Beijing has a long history of exploitation of coal deposits. Mining of the coal deposits has caused many geological environment problems, such as goafs, destruction of groundwater and ecological landscape. These problems have made a serious influence on the environment of this area, and affect the development of the economy.There are many problems in the research of risk zonation of mining subsidence. For example, the stratum structure and geological background are often excluded; the artificial factors are magnified; the method of risk factors zoning needs improvement and the GIS method is rarely used in the research.The risk factors zoning of mining subsidence plays a vital role in the preventing and curing of geological disaster. Analysis and risk factors zoning of mining subsidence in the Xishan area of Beijing is the main part of this thesis. Based on the investigation and analysis of the available data, the present situation of mining subsidence in the Xishan area, the history of exploitation of coal, the characteristic and influence factors of the mining subsidence are reviewed. And the present research condition of the mining subsidence is also analyzed. Then, a new model for goaf subsidence prediction is proposed by using the extention theory, GIS system and AHP analysis. The conclusions as follows:1) The characteristics, type and distribution of the mining subsidence in the Xishan area of Beijing are discussed. The overlying strata, rock structure, size of mining subsidence area, the seam angle, thickness of the strata, repeated mining, hydrology, topography of the terrain, unconsolidated sediments cover, tectonic stress field, discontinuous surface traits are also analyzed. 2) Based on the extension theory, AHP and G1S system, the model of mining subsidence risk factors zoning is constructed. The risk factors zoning of the Xishan area is made by using this model. with the GIS software, the risk of goaf subsidence is divided into five grades.The fourth-grade risk area is 9.81 km², the third-grade risk area is 20.19 km², the second-grade risk area is 42.18 km², the first-grade risk area is 27.28 km², and the other area is the zero-grade risk area. Besides the research of risk of mining goaf subsidence, this work has also predicted the mining subsidence in the typical region through the probability integral method and FLAC program.3) Besides the research of risk of mining goaf subsidence, this thesis has also predicted the mining subsidence in the typical region through probability integral method and FLAC program. The future mining subsidence is predicted in the K125+400-K125+800 section of the 108 national road and Nangang area in Mengtougou.According to the simulation results, the surface subsidence in the 108 national road can be 4.5m, the horizontal displacement can be 1.50m under the condition of the vehicle dynamic load and rainfall. And the surface subsidence would cause the road slope crack, and even lead to damage of the road.The ground deformation in the mine sections I and II in Magezhuang is lager than in other areas. And the surface subsidence is expected from 1.7 to 2.3m; curvature of 0.3～0.7×10^-3/m, the horizontal movement of 10.0～23.0 mm/m , inclination of 10²4mm/m. the surface subsidence in south-east area of Nangang is expected from 0.6 to 1.4m, curvature of 0.15～0.3×10^-3/m, the horizontal movement of 1.0～6.0 mm/m , and inclination of 4～10mm/m.This research contains some exploration work and innovation in theory. The result of this research can be used in the preventing and curing of geological disaster, programming of disaster prevention, and the development of economy in the Xishan area in Beijing.