Evolution, Water And Soil Response And Optimization Of Landform Construction In Giant Open-pit Coal Mine On Loess Area

This paper summarized and classified the morphologic characteristics of open-pit coal mine in loess area through the research about the extremely fragile ecological en vironment, the huge human disturbance, and the seriously damaged land in the giantc oal mine, analyzed the mechanism and process of landform evolution in the integrated project, which consists of peeling, mining, transportation, dumping and reclamation, selected topographic index, quantificationally analyzed the space-time evolution laws about topography rebuilding, and then analyzed the impact on spatial variation of soil, site conditions of vegetations, variation of river channels and the corresponding hazar d through field survey sampling, laboratory analysis, remote sensing interpretation an d literature and related data collection, analysis remodeling spatial variation of soil to pography, vegetation site conditions, at last, put forward topography optimization rem odeling and suggestions for loess landform reshaping large surface area as the referen ce of loess landform rebuilding, soil reconstruction, revegetation and ecological establ ishment in the future, and got the following results:Macroscopic results were that open-pit coal mining landform is classified into dynamic mining landform, which consists of the stripping topography, the marching pit topography and the dumping topography, and recontruced landform becoming steady, which consists of the remaining pit topography, waste-dump topography and inner spoil dump topography, through analyzing the characteristics of disturbed topography on the loess area, and analyzed the longitudinal process of peeling and mining, transverse process of transportation and dumping, methods of reclamation and technology of landform reconstruction on open-pit coal mine in the Pingshuo mining area, through summarized the integration process, which consists of peeling, mining, transportation, dump, shaping and reclamation in the open-pit mines in loess area.The results of quantitative analysis of morphological evolution shows, that the process of mining, casting, reclamation in the large opencast mine on loess hilly region presents five kinds of trends; that there are two new single indicators of terrain evolution, fluctuation factors and distortion factors, whose contribution rate is93.94%, and their principal component values has been calculated; and that the opencast mining area landform evolution has been divided into four stages:mine pit and external dump forming, pit advancing and inner dump forming, pit disappearing and inner dump advancing and inner dump stabilizing, which reveals the terrain indicators’difference of different stages and phased ecological risk.The impact of remodeling topography:Reshaped landform, which is an important factor for reclaimed soil properties in large opencast coal mine in loess area, affects development characteristics and spatial variability of reclaimed soil;the characteristics of reclaimed soil in different slope positions, or different slope gradients, or different slope aspects, or different vegetation restoration patterns were significantly different; soil moisture content’s and total nitrogen’s correlations with vegetation restoration patterns, reshaped landform and remote sensing indexes are good, but volume weight of soil’s, organic matter’s, total phosphorus’s, total potassium’s are poor; through regression Kriging method,resuits of regression prediction of soil moisture content, organic matter, total nitrogen and total phosphorus are good, and then the results’residual errors are reduced.Reshaped landform has a strong impact on vegetation site conditions, restoration and development. Different site types determines the difficulty of vegetation restoration, vegetation configuration type and succession law. Among them, a thick layer of loess platform type, slope soil medium/lower part of the slope type have good site conditions to vegetation restoration; The study area was eventually divided into2site area:platform and slope; platform area was classified into9site type groups and13site types, while slope area into9site type groups and20site types. This provided basis for the improvement of mine site conditions, vegetation restoration and maintenance as well as the local ecosystem recovery.When getting the channels in the open-pit coal mines on loess area through DEM,the appropriate resolution ratio and threshold value of catchment are respectively5m and5000. Through comparing the hydrological landform in1990 with that in2013, results that after severe disturbance in mining area, hydrological characteristics changed greatly, which leads channels’ self-similarity disappear, and the landform integrally has a simplification trend, which is that density and complexity of catchment lines reduced, and elevation difference and slope of drainage basin increased.Flood index has obvious hierarchy before mining disturbance, and humidity index and intercept index both have homogeneous distribution, but all three changed greatly after disturbance, which shows that flood index has no hierarchy, humidity index has uneven distribution and intercept index reduce integrally, and the flood risk index increases.Through planning and design of drainage basins and channels, extraction of original geomorphic parameters and optimizing parameters of constructing model, GeoFluvTM constructed a model imitated the natural landform. The design of the model is a constructing process of from points, lines to surface, traditional design of platform-slope-platform is replaced by concave gentle slope, traditional landform, which has ladders, is replaced by deviously gentle slople, landform changed from single to multiple, and the dump that is inharmonious with surrounding is replaced by imitated-nature landform which is connected with surrounding. Through construction of landform in GeoFluvTM, the drainage basins, channels and hillslopes would be tending towards stability, and the channels would become wriggle, which slow down the speed of stream, and incease stability of channels.