沟谷地形下煤炭开采对地表径流的影响

Influence of longwall mining on surface runoffs in gully terrain area

以西部矿区沟谷地形开采条件为背景,采用理论分析和模拟试验的方法,建立岩层移动与潜水位下降的关系,就沟谷地形下煤炭开采对地表径流的影响进行了探讨。结果表明:在采动裂隙未破坏潜水含水层的条件下,其储水盆地形态和汇水面积将受开采沉陷影响而发生改变,从而影响到地表径流分布和区域水系环境。随着地下开采强度的不断增大,沟谷地形下开采引起的地表径流分布将出现"稳定"、"衍生"、"转移"、"恶化"4种类型。当采高和开采面积均较小时,潜水位及地表径流水位下降不明显,故整个区域水系环境变化不大;当采高较大而开采面积相对含水层面积较小时,采煤不会造成潜水位明显下降,但会引起地表沉陷,从而造成开采区域潜水位埋深变浅,当开采区域存在沟谷地形时,由于地势较低潜水易出露地表,从而衍生出新的地表径流;随着开采面积相对含水层面积逐渐增大,采煤会造成潜水位明显下降,进而开采区域之外原有地表径流流量减小甚至消失,而开采区域存在沟谷地形且地表沉陷足够大时潜水出露,地表径流转移至开采区域;最后,采高和开采面积进一步增大时,潜水位大幅下降,直至地表径流全部消失,转移至地下储存,区域生态环境趋于恶化。研究结果可为西部干旱半干旱地区的保水采煤实践提供理论依据。

Based on the exploitation background of gully terrain area in western China,the relationship between stratamovement and groundwater level decline was established by adopting theoretical analysis and simulation methods,andthen the influence of longwall mining on surface runoffs in gully terrain area was discussed. The results show that if theaquifer is not damaged by mining-induced fractures,the basin morphology and catchment area will vary due to miningsubsidence,which would subsequently affect the distribution of surface runoffs and water environment. With the in-creasing intensity of underground mining,four types of surface runoffs distribution caused by mining in gully terrain ar-ea will appear including ＂ stable＂ type,＂ derivative＂ type,＂ transfer＂ type and ＂ deterioration＂ type. When miningheight and mining area are relatively small,groundwater and surface water level decline is not obvious and regional wa-ter environment has minor changes. When mining height is large but mining area is small comparing to the basin area,groundwater level decline is not obvious but surface subsidence is considerable. Hence,the buried depth of groundwa-ter level is shallower than before in mining area. When there are gullies overlaying on the surface of the mining area,groundwater may outcrop in the gully as its low elevation,from which new surface runoff would derive. As the miningarea enlarges comparing to the basin area,groundwater level in the whole area obviously declines;thus the original sur-face runoffs outside the mining area disappear and are transferred to the mining area because of its large surface sub-sidence. Finally,groundwater level declines rapidly due to larger mining height and mining area. Eventually,all thesurface runoffs disappear and are converted into groundwater,causing regional ecological environment deterioration.This research provides a theoretical basis for water-preserved mining practice in arid and semi-arid areas of westernChina.