ISSN 1003-8035 CN 11-2852/P

    青藏高原东北部黄土区柠条锦鸡儿根系的锚固效应

    The root anchorage effect of shrub species Caragana Korshinskii Kom. in the loess area of northeastern Qinghai–Tibet Plateau

    • 摘要: 柠条锦鸡儿是青藏高原东北部黄土区主要的护坡和水土保持灌木,然而对该灌木根系锚固作用机理及其固土护坡效应方面仍缺乏系统性认识。鉴于此,该项研究在阐明柠条锦鸡儿根系锚固机理的基础上,提出了根系对黄土斜(边)坡浅层土体稳定性贡献计算模型。在此基础上,以研究区内生长期为11 a的柠条锦鸡儿为主要研究对象,通过现场根系挖掘试验、原位拉拔试验和理论分析,明确了假定滑动面条件下根系锚固力取值,并进一步定量评价了柠条锦鸡儿根系对黄土浅层滑坡稳定性的增强作用。结果表明:由于根系在地表没有“锚头”结构,故在确定滑动面几何特征的情况下,柠条锦鸡儿根系所能提供的实际锚固力大小取滑动面以下锚固段根系最大抗拔出力和滑动面以上根系锚固反力之间的最小值较为合理;生长期为11 a的单株柠条锦鸡儿根系锚固于最大厚度为2 m的圆弧形滑动面不同条块上时,潜在滑动面稳定性系数增幅为0.018%~0.427%,当单株根系锚固力作用于潜在滑动面中上部条块时,潜在滑动面稳定性系数相对高于根系锚固力作用于最顶部和下部条块;当4株柠条锦鸡儿根系以2块条块的间距(约3 m)作用于潜在滑动面时,潜在滑动面稳定性系数可提高1.035%~1.111%,显著高于(P<0.05,ANOVA)单株根系作用时的稳定性系数。试验株根系锚固作用能够提高降雨入渗条件下黄土斜(边)坡浅层土体稳定性,但是作用效果有限。

       

      Abstract: Shrub species Caragana korshinskii Kom. dominates slope protection and soil and water conservation in the loess area of the northeastern Qinghai–Tibet Plateau. However, the root anchoring mechanism and the effects of soil consolidation and slope protection of this shrub species remain unclear. This study aimed to elucidate the anchoring mechanism of roots of the C. korshinskii roots and establish a calculation model to evaluate their contribution to the stability of shallow loess slopes. C. korshinskii plants with an 11-year growth period were selected as the study subject. The anchoring force of C. korshinskii roots was determined through in-situ excavation tests, in-situ root pullout tests, and theoretical analysis, along with their impact on the stability of shallow loess soil slopes. The results showed that, due to the absence of a “bolt head” structure on the root surface, it was reasonable to consider the anchoring force provided by the roots as the minimum value between the maximum pullout resistance of the roots below the sliding surface and the anchoring reaction force of the roots above the sliding surface, based on the geometric characteristics of the sliding surface. When the roots of an 11-year-old C. korshinskii roots were anchored on different sliding blocks of a shallow landslide with a maximum thickness of 2 meters, the stability coefficient of the potential sliding surface increased by 0.020% to 0.408%. When the roots of a single plant were anchored in the middle and upper parts of the potential sliding surface, the stability coefficient of the potential sliding surface was relatively higher than when the plant roots were anchored at the top and bottom positions. Moreover, when four C. korshinskii roots were anchored to the shallow landslide with a row spacing of two sliding blocks (approximately 3 m), the stability coefficient of the potential sliding surface increased by 1.035% to 1.111%, which was significantly higher than when a single C. korshinskii root was anchored (P<0.05, ANOVA). The anchorage effect of the root systems could enhance the stability of shallow soil on loess slopes under rainfall infiltration conditions, but the effectiveness was limited.

       

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