Study On The Characteristics And Forming Mechanism Of Land Collapse In Binchang Mining Area

Binchang mining area lies in the joint-part between theandeloess plateau in north shaanxi province and loess plateau in east gansu, and the coal resources reached to 6.9 billion ton. After excavating the coal seam from underground, land resources, ecological environment, water resources, building, and transportation would be destroyed seriously. So study the characteristics and forming mechanism is important to the protection of mine, ecological environment, buildings, land resources and Government's Policy-Making in Binchang mining area.Based on the survey and analyse of the land collapse (discontinuous deformation), there are 4 land collapse (discontinuous deformation) types that are collapse basin, crack, collapse slot, and loess landfalls cave dwelling collapse are summarized. The paper conclude that main factors influenced the land collapse (discontinuous deformation) are the mining depth and the thickness of bedrock, the width of working face and the mining height, overlying rock and the thickness of key strata(the sandstone in luohe formation) and topography et al.This paper using formulas from the regulations (Regulations for setting coal pillar and mining under buildings, water bodies, railways and main roadways) and norms (National Exploration norms for hydrogeology and engineering geology of coal mine), empirical data, numerical simulation, similar material simulation, and the measured data to analyze the development law for "two zones" of overburden rock in Binchang mining area. Comparing the corresponding ratio of the fractured zone height to the mining height based on the development height for "two zones" of overburden rock, the results show the ratio calculated by formula of regulations is much less than the measured value when little larger by formula of norms; the data obtained by numerical simulation, similar material simulation and experience are very close to the measured value, the ratio of the fractured zone height to the mining height range from 11.5 to 13.4. After comprehensive analyzing, it is feasible to predict the development height for "two zones" of overburden rock in Binchang mining area using the ratio 13.3. At last, based on the analysis above, water-disaster prediction figure in Binchang mining area is made and the area in the middle and northwest of Binchang mining area have a serious water disaster.Through numerical simulation, similar material simulation and field survey and analysis, we summarize the model of overlying strata failure with the land collapse (discontinuous deformation) developed in Binchang mining area, which is cavied zone, fractured zone, continuous deformation zone, the local tensile failure areas of the key strata, and the failure of the loose strata. There are large free space between continuous deformation zone and fractured zone. The local tensile failure area of the key strata is only the weakening of rockmass strength. Based on the analysis above, mathematical model of land collapse (discontinuous deformation) prediction is set up.