黄河源河岸高寒草甸含根土体抗拉、抗剪特性及其影响因素

Tensile and Shear Characteristics and Influencing Factors of Root-bearing Soil in Alpine Meadow on Bank of Yellow River Source

[目的]研究黄河源区河岸带高寒草甸含根土体抗拉、抗剪特性及其影响因素,为源区河岸保护和河流崩岸力学机制研究提供数据支撑。[方法]以青海省河南县兰木措曲弯曲河流为研究区,以不同退化程度的河岸高寒草甸含根土体为研究对象,分析含水率、含根量、根系组成以及冻融循环次数对含根土体抗拉、抗剪强度的影响,并探讨含根土体抗拉强度与抗剪强度之间的关系。[结果]含根土体的抗拉、抗剪强度随含水率从30%增加至55%逐渐减小,且抗剪强度是抗拉强度5倍左右;植物根系的加入能有效提高土体的抗拉、抗剪强度,当根系含量由0%增加至0.25%,抗拉、抗剪强度增幅分别为45%和107%,且根土体抗拉、抗剪强度在禾本科植物比例为100%时达到最大值,分别为4.38和19.98 kPa;经多次冻融循环之后含根土体冰融循环次数与抗拉强度拟合曲线呈双峰式变化,随冻融循环次数增加土体原网状结构首先破坏然后重新达到平衡;含根土体抗拉强度与抗剪强度之间呈线性相关性。[结论]黄河源区高寒草甸退化加剧使根量与根系形态发生了明显的变化,表现为含根土体的抗拉、抗剪强度逐渐降低。因此,应尽可能减少过度放牧及人为干扰,保护河岸原生高寒草甸植被,以保持源区河岸稳定。

[Objective]The tensile and shear resistance characteristics of the riparian alpine meadow rooted soil and the influencing factors along the riverbanks of the Yellow River source area were analyzed to provide data support for research on riverbank protection and the mechanical mechanisms of riverbank failure in the source area.[Methods]Taking the meandering river Lanmucuoqu in Henan County,Qinghai Province,as the study area and the rooted soil of alpine meadows with varying degrees of degradation along riverbanks as the research object.The effects of water content,root content,root system composition,and the number of freeze-thaw cycles on the tensile and shear strength of root-bearing soil were analyzed.The relationship between the tensile and shear strengths of the root-bearing soil was also explored.[Results]The tensile and shear strengths of the rooted soil gradually decreased as the water content increased from 30%to 55%,and the shear strength was approximately five times than that of the tensile strength.The addition of plant roots effectively improved the tensile and shear strength of the soil.As the root content increased from 0%to 0.25%,the tensile and shear strengths increased by 45%and 107%,reaching maximum values of 4.38 and 19.98 kPa,respectively,when the proportion of gramineous plants was 100%.After multiple freeze-thaw cycles,the fitting curve of the root-bearing soil showed a bimodal pattern,with the original network structure of the soil first being destroyed and then reaching a new equilibrium as the number of freeze-thaw cycles increased.A linear correlation was observed between the tensile and shear strengths of root-bearing soil.[Conclusion]The degradation of alpine meadows in the Yellow River source area has led to significant changes in root quantity and root system morphology,resulting in a gradual decrease in the tensile and shear strengths of the rooted soil.Therefore,it is necessary to minimize overgrazing and human interference to protect the native alpine meadow vegetation along riverbanks and maintain the stability of riverbanks in the source area.