黄河中游陕北煤矿区黄土坡面沉陷形变叠加冻融作用的土壤侵蚀效应

Soil erosion effect of subsidence deformation superimposed freeze-thaw action on loess slope in coal mining area of northern Shaanxi in the middle reaches of the Yellow River

  • 摘要: 深刻认识和科学化解煤炭开采与土壤侵蚀之间的矛盾是实现黄河中游生态保护与高质量发展的重要基石。以陕北黄土采煤沉陷区为研究区,从“采煤沉陷+冻融作用”耦合的角度,以采高、地表黄土坡面自然形态、冻融作用为研究变量,通过数值模拟试验、冻融循环试验、土壤流失模型计算等方法,揭示冻融作用对土壤机械组成、有机质质量分数以及土壤可蚀性K值的影响规律,阐明“坡面沉陷形变+冻融作用”的土壤侵蚀效应。结果表明:在任意土壤含水率和冻融作用下,坡面土壤的质地类型均不会发生改变,但土壤黏粒、砂粒、有机质质量分数与土壤初始含水率、冻融次数呈负相关,降幅分别介于3.72%~31.69%、1.05%~16.52%、4.62%~13.06%;坡面土壤的可蚀性K值与初始含水率和冻融次数呈正相关,增幅介于1.19%~8.03%,在既定土壤初始含水率的条件下,冻融循环9次后坡面土壤可蚀性K值的增幅达到最大并保持稳定;土壤初始含水率每增加1%,可蚀性K值的增幅就增加2.917%~12.187%。相较于自然坡面,在相同初始含水率及冻融循环次数下,“沉陷+冻融”作用具有增大土壤侵蚀模数(M1*)的作用,土壤侵蚀模数(M1*)的增幅介于4.17%~31.93%。采高与土壤侵蚀模数(M1*)的增幅呈正相关;在任意采高及坡形下,自然坡度为5°~15°时,土壤侵蚀模数(M1*)的增幅变化明显;当“采高为7~9 m+任意自然坡度的凹形坡”时,土壤侵蚀模数(M1*)的增幅最为显著。土壤侵蚀模数(M1*)的增幅与土壤初始含水率和冻融循环次数呈正相关,其中土壤侵蚀模数(M1*)的增幅在冻融循环9次后达到最大并保持稳定。在既定冻融循环次数下,土壤初始含水率每增加1%,土壤侵蚀模数(M1*)增幅就增加3.00%~62.50%。“沉陷+冻融”会放大地表沉陷坡面的土壤侵蚀模数(M1*)增幅,增幅放大倍数介于1.06~3.79倍。土壤侵蚀模数(M1*)增幅的放大倍数与采高呈负相关;当“采高为5 ~9 m+自然坡度为45°的任意坡形”下,土壤侵蚀模数(M1*)增幅的放大效应最为明显。土壤侵蚀模数(M1*)增幅的放大倍数与初始含水率及冻融次数呈正相关;其中土壤侵蚀模数(M1*)增幅的放大倍数在冻融循环9次后达到最大并保持稳定。在既定冻融循环次数下,土壤初始含水率每增加1%,土壤侵蚀模数(M1*)增幅的放大倍数就增加0.25%~3.21%。研究结果可为黄河中游陕北采煤沉陷区的水土流失精准防控提供科学依据。

     

    Abstract: Deeply understanding and scientifically resolving the contradiction between coal mining and soil erosion is an important cornerstone for achieving ecological protection and high-quality development in the middle reaches of the Yellow River. Taking the loess mining subsidence area in northern Shaanxi as the research area, from the perspective of “coal mining subsidence + freeze-thaw action” coupling, taking mining thickness, natural morphology of surface loess slope and freeze-thaw action as research variables, through numerical simulation test, freeze-thaw cycle test, soil loss model calculation and other methods, the influence of freeze-thaw action on soil mechanical composition, organic matter mass fraction and soil erodibility K value is revealed, and the soil erosion effect of slope subsidence deformation superimposed freeze-thaw action is clarified.The results showed that: Under the condition of any initial soil moisture content and freeze-thaw times, the texture type of slope soil would not change, but the mass fraction of soil clay, sand and organic matter was negatively correlated with the initial soil moisture content and freeze-thaw times, with the decrease of 3.72%−31.69%, 1.05%−16.52% and 4.62%−13.06%, respectively. The erodibility K value of the slope soil was positively correlated with the initial water content and the number of freeze-thaw cycles, and the increase was between 1.19% and 8.03%. Under the condition of the initial water content of the soil, the increase of the erodibility K value of the slope soil reached the maximum and remained stable after 9 freeze-thaw cycles. For every 1% increase in soil initial water content, the increase of erodibility K value increased by 2.917%−12.187%. Compared with the natural slope, under the same initial water content and freeze-thaw cycles, the effect of “subsidence + freeze-thaw” has the effect of increasing the soil erosion modulus, and the increase of soil erosion modulus(M1*) is between 4.17% and 31.93%. The greater the mining thickness, the greater the increase of soil erosion modulus(M1*); under any mining thickness and slope shape, when the natural slope is 5°−15°, the increase of soil erosion modulus(M1*) is obvious. When the mining thickness is 7−9 m + concave slope of any natural slope, the increase of soil erosion modulus(M1*) is the most significant. The increase of soil erosion modulus(M1*) was positively correlated with the initial soil moisture content and the number of freeze-thaw cycles. Among them, the increase of soil erosion modulus(M1*) reached the maximum and remained stable after 9 freeze-thaw cycles. Under the given number of freeze-thaw cycles, the increase of soil erosion modulus(M1*) increased by 3.00%−62.50% for every 1% increase of initial soil moisture content. The ' subsidence + freeze-thaw ' will amplify the soil erosion modulus(M1*) increase of the surface subsidence slope, and the increase magnification is between 1.06 and 3.79 times. The magnification of the soil erosion modulus(M1*) increase is negatively correlated with the mining thickness. When the mining thickness is 5−9 m + natural slope is 45°, the amplification effect of soil erosion modulus(M1*) is the most obvious. The magnification of soil erosion modulus(M1*) increase was positively correlated with the initial moisture content and the number of freeze-thaw cycles. Among them, the magnification of soil erosion modulus(M1*) increase reached the maximum and remained stable after 9 freeze-thaw cycles. Under the given number of freeze-thaw cycles, for every 1% increase in the initial soil moisture content, the magnification of soil erosion modulus(M1*) increases by 0.25% to 3.21%. It can provide scientific basis for the precise prevention and control of soil erosion in the coal mining subsidence area of northern Shaanxi in the middle reaches of the Yellow River.

     

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