黄土丘陵区边坡开挖对土壤抗蚀性影响

针对黄土高原高质量发展过程中为扩展农业等经济用地,大量边坡开挖工程对坡面土壤抗蚀能力影响等问题,以延安市羊圈沟流域内开挖坡面为对象,未开挖坡面为对照,通过野外采样与室内分析,研究了开挖坡面土壤抗蚀能力时空变化特征。结果表明:(1)在开挖率为7%的坡面,土壤团聚体平均重量直径(MWD)和有机碳含量随坡位的降低,开挖坡面呈先增大后减小趋势,对照坡面为逐渐增大趋势; 其中开挖坡面MWD在坡下区、开挖区相较于坡中区分别降低6%～8%和58%～73%; 土壤有机碳含量在坡下区0—80 cm土层内显著降低8%～41%,开挖区0—40 cm内显著降低10%～39%;(2)土壤可蚀性K_S值随坡位的降低,开挖坡面呈先减小后增大趋势,对照坡面为逐渐减小趋势,坡下区和开挖区相较于坡中区分别增大4.8%～5.0%,65.0%～109.7%;(3)坡面土壤可蚀性K_S值随开挖率的增大而增大,与有机碳含量相关性随开挖率增加而降低,开挖率为7%的坡面,坡下区土壤抗蚀能力年变化呈显著降低趋势。因此开挖坡面在后期边坡防护过程中不仅应加强开挖区稳定性的防护,还应注重坡面开挖区上部各坡位土壤侵蚀风险的降低。研究结果为边坡开挖工程设计及安全防护提供了科学指导和理论支撑。

Effect of Slope Excavation on Anti-Erosion of Soil in Loess Hilly Region

In order to expand agricultural and other economic land in the process of high-quality development of the Loess Plateau,a large number of slope excavation works affect the erosion resistance of soil on the slope,the excavated slope surface in the Yangjuangou watershed in Yan′an City was used as the object,and the unexcavated slope surface was used as a control,changes in time and space characteristics of soil erosion resistance of excavated slope were examined by field sampling and indoor sample measures.The results show that:(1)on the slope with excavation rate of 7%,as the slope position declines,the average weight diameter(MWD)of the soil aggregates and the organic carbon content of the excavated slope first increase and then decrease,and show the gradual increase trend on the control slope;the MWDs of the excavation slope in the downslope area and the excavation area reduceby 6%~8%and 58%~73%,respectively,compared with that in the middle slope area;the content of soil organic carbon significantly reduces by 8%~41%in the 0—80 cm soil layer in the downslope area,and by 10%~39%in 0—40 cm layer in the excavation area,respectively;(2)the K_S value of soil erodibility decreases with the slope position,first decreases and then increases on the excavated slope,and gradually decreases on the control slope;compared with the middle slope area,the K_S values of the downslope area and the excavation area increases by 4.8%~5%and 65%~109.7%,respectively;(3)the K_S value of slope soil erodibility increases with the increase of the excavation rate,and the correlation of K_S value with the organic carbon content decreases with the increase of the excavation rate;on the slope with an excavation rate of 7%,the annual change of the soil erosion resistance of the downslope area shows the significant decreasing trend.Therefore,in the later slope protection process of the excavated slope,not only should the protection of the stability of the excavation area be strengthened,but also attention to the reduction of soil erosion risk at the upper slope of the excavation area should be paid.These research results can provide scientific guidance and theoretical support for slope excavation engineering design and safety protection.