Study On Soil Moisture Change In Mining Subsidence Area Based Multi-source Monitoring Data

Underground mining leads to overburden and surface subsidence and environmental damage.The Western Loess Plateau is an important coal production base in China.The ecological environment of human settlements is fragile.Large-scale coal mining has changed the original geographical environment,and aggravated the risk of soil erosion,land degradation and geological disasters.Soil moisture is an important factor that affects the geographical and ecological environment.The researches on the change of soil moisture caused by mining subsidence is still in the exploratory stage.So this paper chooses the Dafosi coal mine,a typical loess mining area,as the research area.By using remote sensing image inversion,field monitoring,spectral data modeling and other methods,the temporal and spatial variation characteristics of soil moisture in mining subsidence area from different scales are analyzed,so as to reveal the mechanism of soil moisture change caused by mining subsidence.The main research contents and results are as follows:(1)Based on the scale of mining area,the temporal characteristics of soil moisture evolution in Dafosi coal mine in recent ten years are analyzed.Using the remote sensing images of 2010-2019 to establish the Ts-NDVI space in the mining area,calculate the temperature vegetation drought index in recent ten years,invert the time-series changes of soil moisture in the mining area,and select non-mining area with similar geographical environment around the mining area for comparative analysis.The results show that the time sequence change of soil moisture in the mining area is significantly more fluctuant than that in the non-mining area.On the season,the soil moisture in the mining area is higher than that in the non-mining area in January,and lower than that in the non-mining area in July.(2)The characteristics of soil moisture in mining subsidence area were studied on the working face scale.Taking the surface of 41209 coal area as the experimental area,the crack zone in the subsidence area and the non-mining affected area are selected for sampling.The soil moisture content of the sample was monitored,and the corresponding spectral reflectance data was collected by using a ground spectrometer.The results showed that the soil moisture content was negatively correlated with the spectral reflectance data.The fusion calculation of measured moisture content and spectral data is used to establish the soil moisture estimation model that based on spectral data inversion.By measuring soil sample spectral reflectance,the moisture content data of the soil in the subsidence area can be conveniently obtained.The results show that the soil moisture content in the fracture development area of the surface subsidence basin is higher than that in the non-mining affected area after rain or low temperature environment,and conversely,it is lower than that in the non-mining affected area.(3)The mechanism of soil moisture change in mining area is revealed from the surface deformation and the changes of soil physical properties by mining subsidence.Considering the mining geological conditions of 41209 working face.D-InSAR is used to obtain the dynamic boundary of the surface subsidence area.Based on the probability integral method model,the deformation and fracture distribution characteristics of the subsidence area are analyzed,and the quantitative relationship between the soil moisture content,the surface deformation and the soil compactness is revealed.The variation characteristics of the soil moisture content with different densities were determined by experiments in the nature environment.The comprehensive analysis results show that the subsidence of coal mining causes the surface tensile deformation and crack development,resulting in a decrease in soil compaction,which enhances the effect of water infiltration and evaporation in the soil.Due to the difference of temperature and evaporation effect in different seasons,the soil moisture in coal mining subsidence area has the above fluctuation characteristics.This paper reveals the influence mechanism of mining subsidence and deformation on surface soil moisture in loess mining areas,which has reference value for land reclamation and environmental protection in mining areas.