黄土高原山地采煤沉陷对土壤侵蚀的影响

Effect of mining subsidence on soil erosion in mountainous area of the Loess Plateau

为了测度山地井工采煤区地表沉陷引起的土壤侵蚀因子在空间和数量上的变化,该文以开采沉陷规律和模型为基础,运用数字地形分析、遥感影像融合等技术,揭示了黄土高原煤矿区山地开采沉陷引起的地表坡度、坡长、植被覆盖3大因子在空间上的改变量以及由此导致的土壤侵蚀变化量,并分析了土壤侵蚀的变化机制。研究结果表明:2001-2010年,研究区因开采沉陷导致地表平均坡度减少0.025°,平均坡长因子减少0.139;沉陷区内土壤侵蚀量不变、减小和增大的土地面积分别为3.083、3.412和4.707 km2,沉陷区外土壤侵蚀量减小和增大的土地面积分别为0.143和0.023 km2,土壤侵蚀总量减少78426.95 t,平均减小689.892t/(km2·a);开采沉陷导致坡长因子变化,对土壤侵蚀的影响波及到沉陷区以外的部分地区;山地开采沉陷对土壤侵蚀的影响与平地差异明显,不存在绝对的正向或负向影响,并且在沉陷区内外均可能为正向或负向,其结果与原地貌及沉陷幅度、区位密切相关;沉陷可能导致坡面下游区域的汇水面积和坡长因子变化。该研究结论为山地矿区土壤侵蚀区位、侵蚀量预测提供依据。

Mining subsidence reshapes the surface structure and morphology in a mountainous area. However, surface deformation and movement rules in a mountainous area influenced by mining subsidence are quite different from rhose in a flat area, which result mainly from the superposition of ground subsidence and surface moving caused by slippage. Research about change of the soil erosion caused by the above phenomenon is very necessary. In this paper, based on mining subsidence rules and models, a DEM of the subsidence area was constructed referring to the subsidence parameters in the research area. On this basis, the soil erosion changes of three major factors-slope, slope length factor, and vegetation coverage factor caused by mining subsidence in a revised universal soil loss equation in mountainous area were measured for the first time, and the other three parameters that were not disturbed by mining in a revised universal soil loss equation were calculated according to relevant research studies. Finally, soil erosion quantity in the research area was calculated. The results showed that：From 2001-2010, the average slope decreased by 0.025°, caused by mining in the study area, average slope length factor decreased by 0.139, the area that soil erosion unchanged,reduced and increased in subsidence area was respectively3.083,3.412 and 4.707km2, and the area in which soil erosion reduced and increased out of the subsidence area was respectively 0.143 and 0.023km2, the totally soil erosion amount decreased by 78426.95t, 689.892t/km2 in average per year, which was mainly caused by the decrease of slope length and slope. The impact on soil erosion affected by mining subsidence in the upstream area will influence in part the area of the watershed where outside the mining area, and ending in the position where the slope length is ended, because mining subsidence changes the flow direction, and furthermore, flow length is changed as a result. In the basin of the subsidence area, the subsidence value was basically the same, slope and flow direction doesn’t change. Nevertheless, the physical and chemical properties of the soil are changed, the vegetation was injured, and the vegetation cover factor became the main factor influencing soil erosion in this region. Soil erosion affected by mining subsidence in a mountainous area is quite different from flat ground. On flat ground, mining subsidence will absolutely intensify soil erosion except in the subsidence basin, because the slope and slope length are increased, but in a mountainous area, there is no absolute positive or negative influence, and the result is closely related to the original landform, subsidence magnitude, and location. The research conclusions can provide a scientific basis for soil erosion predictions in a mountainous mining area.