典型荒漠植被根系对塔里木河岸坡冲刷过程影响试验研究

为探讨植被根系对河岸冲刷过程的影响作用,取新疆塔里木河岸坡原状土,选取当地优势灌木红柳、乔木胡杨根系,通过室内水槽试验,分析不同植被根系对河岸冲刷起防护作用的贡献率。结果表明:①无根系河岸水下淘刷形式主要为圆弧状,下部抗冲能力差;有根系河岸的淘刷形式主要为三角形,下部抗冲能力强,上部悬空层的稳定性好。②根系的网络固土作用使河岸的抗冲能力提高12%~42%;相同植被根系河岸,根系的布置方式对河岸的固土能力有显著差异,V型根系的固土作用优于竖直型;不同植被根系河岸,红柳根系的固土能力大于胡杨根系,平均提高27%。③根土胶结崩塌体堆积形式主要为三角形,且堆积体的占比大于无根系崩塌体;红柳根系胶结崩塌体的分解速率最慢;根系牵拉系数可作为反应根系对河床防护作用贡献的参数,实际计算中可按1.15~2.52进行估算。研究结果可为塔里木河河道岸坡防护提供理论参考。

Experimental Study on the Influence of Typical Desert Vegetation Roots on Erosion Process of Tarim River Bank Slope

In the purpose of exploring the effect of vegetation roots on riverbank erosion process, the contribution rate of different vegetation roots to riverbank erosion protection was examined via indoor flume experiments. The undisturbed soil samples were taken from the banks of the Tarim River in Xinjiang, and the roots of local dominant shrubs Tamarix ramosissima and Populus arbores were selected as research objects. Results demonstrated that: (1) Rootless river bank mainly suffered from arc-shaped erosion with insufficient anti-scouring ability in the lower part, while rooted river bank mainly saw triangular erosion with strong anti-scouring ability in the lower part and good stability in the upper suspended layer. (2) The soil-fixing effect of the root system enhanced the impact resistance of river bank by 12%-42%. Given the root system of the same vegetation, the soil-fixing ability of the river bank differed remarkably with the arrangement of the root system: V-shaped root system had a superior soil-fixing effect than vertical system. Tamarix ramosissima root system had a better soil-fixing ability than Populus euphratica by 27% on average. (3) Root-soil cemented collapse body accumulated mainly in a triangular shape, and the proportion of accumulation is larger than that of non-rooted collapse; Tamarix ramosissima root cement collapse decomposed in a smallest rate. In addition, the root traction coefficient can be used to reflect the contribution of roots to riverbed protection, and can be estimated as 1.15~2.52 in calculation. The research findings offer theoretical basis for the slope protection of the Tarim River.