Ground Surface Subsidence And Ecological Disturbance In The Mining Area Of Loess Plateau With Complex Environments

China is at the stage of rapid development of modernization.In the future,coal will remain the dominant source.Coal mining promotes regional economic and social development,but also has serious negative impacts on local ecological environment.The most prominent problems are ground surface subsidence and ecological disturbance.The primary objective of ground surface subsidence researches is to monitor ground surface subsidence with high precision,high efficiency and periodicity to obtain the "real" ground surface subsidence law as much as possible.Compared with traditional methods,the In SAR(Interferometry Synthetic Aperture Radar)estimates the ground surface subsidence using phase difference of SAR images in two times with the advantages of all-weather,large-scale,low cost,and high precision.Then,various differential radar interference and multi-phase In SAR technologies have been developed,and their application fields have been gradually expanded to earthquake,volcano,landslide,and so on.Due to complicated geological and mining conditions,the formation mechanism of ground surface subsidence in the mining area of Loess Plateau is very complex.It is difficult to achieve ideal estimation and prediction of ground surface subsidence by traditional technical methods and prediction models.At the same time,Loess Plateau is an ecologically sensitive area,and the ecological disturbance caused by coal mining is more profound and irreversible.There is no model to follow for the time series variation of ecological disturbance and ecological restoration in the mining area of Loess Plateau.Using remote sensing,ecology,geology,and mining subsidence,the study takes Xuangang mining subsidence area as experimental area to study ground surface subsidence and ecological disturbance under complex mining conditions in the mining area of Loess Plateau.The main achievements and conclusions are as follows:(1)Our study profoundly reveals the spatio-temporal variations of ground surface subsidence under complex geological formations and mining conditions in the mining area of Loess Plateau.The SBAS-In SAR(Small Baseline Subsets In SAR)method is a reliable method for groundsurface subsidence estimation in the mining area of Loess Plateau.The ground surface subsidence caused by coal mining shows time accumulation effect.The ground surface subsidence curve on the side of stop line is relatively flat.The ground surface subsidence shows significant relationship with the advancing direction and distance of coal face.The disturbance coefficient of mining face in the Xuangang mining subsidence area is about 24.55.The acceleration and decline period of settlement account for 58.62% and 75.95% of the total settlement.The geological structure and repeated mining are the important factors that affect the ground surface subsidence in the coal mining area of Loess Plateau.(2)Our study establishes improved Knothe time function models by coupling with ground surface subsidence value derived from SBAS-In SAR method.The models are used to estimate ground surface subsidence that has occurred and to predict ground surface subsidence that has not yet occurred.Compared with Knothe time function model,the modified Knothe time function model greatly improves the estimation accuracy of ground surface subsidence value at any time during monitoring period.The predicted trend of ground surface subsidence based on improved Knothe time function model is consistent with that based on SBAS-In SAR.(3)In the study,vegetation quantity and quality,spatial distribution,and ecosystem service value are selected to quantitatively analyze the temporal variations of ecological disturbance in coal mining subsidence area.From 1986 to 2018,the area of vegetation coverage in Xuangang mining subsidence area decreased,the area of industrial and mining land increased,and the vegetation quality decreased first and then increased.The spatial correlation index of vegetation shows a trend of rapid decline,slow decline,and fluctuation rise with time lag effect.The fluctuation of ecosystem service value is decreasing,and the speed is positively related to the scale of coal mining.From 1986 to 2018,the ecological service value of Xuangang coal mining subsidence area fluctuated between 112 million yuan and 135 million yuan with a general decreasing trend.The ecological service value in the Xuangang mining subsidence area rapidlydecreased after 2006.The large-scale coal mining is the main reason for the sharp decline of ecological service value in the mining subsidence area.(4)Our study proposes the whole process and closed-loop ecological restoration analysis framework of coal mining face in mining subsidence area.The ecological restoration is defined for coal mining subsidence.The major principles of ecological restoration are fully explored for coal mining subsidence area.The estimation methods of ecological benefits from soil and water conservation are established for ecological restoration in the coal mining subsidence.Then,based on the analyses of spatial distribution and land types,the potential planting regions of Hippophae are defined,the ecological and economic benefits are estimated in the Xuangang mining subsidence area.Our study provides basic theory and technical support for the selection of ecological restoration modes in the mining subsidence of Loess Plateau.