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| Mechanism of riverbank protection by desert riparian vegetation roots in Tarim River basin |
| ZONG Quanli1，2，FENG Bo2，CAI Hangbing2，CHEN Zhikang2，WANG Jianxin2 |
(1. Key Laboratory of Yellow River Sediment，Ministry of Water Resources，Zhengzhou，Henan 450003，China；
2. College of Water Conservancy and Civil Engineering，Shihezi University，Shihezi，Xijiang 832000，China) |
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Abstract Desert riparian vegetation with rich roots can stabilize the slope and prevent soil erosion effectively. The vegetation of the riverside of Tarim River was studied. Six typical sections in the upper and middle reaches of Tarim River were surveyed. A total of 28 soil samples were obtained，of which 17 samples are root-soil composites including Tamarix ramosissima，Phragmites australis，Glycyrrhiza sp.，Alhagi sparsifolia，Nitraria sibirica and Populus euphratica. The direct shear tests were conducted for root-soil composites of six vegetation roots and soil samples without roots respectively. The cohesion and internal friction angle were compared and the effects of different vegetation roots on shear strength were analyzed. A single root tensile test was conducted for six vegetation types to analyze the relationships between the tensile and shear strengths and the root diameter. The roots were found to enhance the shear strength of the soil through mainly the increasing of the cohesive strength，but had little effect on the internal friction angle. The root-soil composites have cohesions of 9.43 to 28.30 kPa，higher than the rootless soil with values from 3.14 to 16.51 kPa. The tensile strength of root decreases with the increasing of root diameter，while the tensile force increases with the increasing of root diameter. Based on the analysis of mechanical characteristics of root-soil interaction，two models of the root and soil interaction were proposed with the assumptions of rigid and flexible roots respectively，representing the increased maximum and minimum shear strengths. The formulas of the increased maximum and minimum shear strengths with rigid and flexible roots were deduced. The calculated results agreed with the experimental values.
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2018, Vol. 37 
