Study On Slope Reinforcement Mechanism Of Roots In Zheng-Xin Section Of Beijing-Hong Kong-Macao Highway

The development of highways has promoted economic growth,but also damaged the ecological environment.The excavation of the slope has damaged the origin 2021 al vegetation layer,leading to problems such as secondary bare land and soil erosion.The above geological disasters can be effectively prevented and controlled by using the method of soil fixation and slope protection with plants.Ecological protection projects based on plants are increasingly applied to highway slope protection.Many experimental studies have shown that the different material characteristics of soil and roots make plant roots strengthen the soil matrix,and plant roots can stabilize the slope.At the same time,plant roots strengthen the soil by producing additional cohesion to the soil,absorb the water in the soil to reduce the pore water pressure,thus enhancing the ability of the soil to resist damage,and play a significant role in stabilizing the soil structure,improving the soil anti-scourability,and preventing soil erosion.This paper selects the typical slope protection herbs in the shallow landslide area of the Zheng-Xin section of the Beijing-Hong Kong-Macao Highway: Artemisia argyi,Artemisia annua,Oxalis corniculata L.,Gaura parviflora Dougl.,and the shrub plant Amorpha fruticosa to systematically analyze the mechanical properties of the root material through the indoor single root tensile test and the remolded root-soil composite direct shear test.Comparing the differences in soil fixation effects of different plant roots is of great significance for promoting the practical application of ecological slope protection engineering.The main research conclusions are as follows:(1)Research on root morphology shows that the roots of the tested herbaceous plants are mostly distributed in shallow soil layers of 0-20 cm.The number of root systems gradually decreases with the depth of the soil layer.When the length of the root system exceeds the depth of the soil layer of 20 cm,the number of root systems significantly decreases.Artemisia annua has better performance in root length,root surface area,root volume,and root length density characteristics,and is more effective in reinforcing shallow soil on slopes.(2)The results of tensile test showed that the peak tension of root system was a positive power function with root diameter,and the tensile strength was a negative power function with root diameter.The tensile strength of different plant roots is as follows: Amorpha fruticose > Artemisia annua > Artemisia argyi >Oxalis corniculata L.> Gaura parviflora Dougl.,and the tensile strength of Oxalis corniculata L.is significantly improved within the diameter range of 0.75 mm.Within a certain range,the tensile strength of a single root decreases with the increase in root fiber length,and air dried roots have greater tensile strength than fresh and soaked roots.(3)The direct shear test results show that the shear strength of the root-soil composite is linearly and positively correlated with the vertical load,which conforms to Coulomb’s law.The shear strength of different plant root-soil complexes was as follows: Amorpha fruticose > Artemisia annua > Artemisia argyi >Oxalis corniculata L..The cohesion of composite soil increased by 132.8%,76.3%,24.3% and 20.9%compared with that of plain soil.Under the same test influence factors,the lower the soil moisture content,the larger the root diameter,and the more the root content,the greater the cohesion of the composite soil,and the higher the shear resistance.The increase of cohesion has a significant effect on the shear strength of the composite,and the effect of internal friction angle is small.According to the research results,the contribution of the shrub Amorpha fruticose to slope protection is greater than that of the herb.Artemisia annua has the best soil fixation effect in the herb.The mechanical properties of Artemisia argyi and Oxalis corniculata L.are similar,and can be replaced as the slope protection plant of the same grade.The results of this study provide a theoretical basis for the ecological construction of slope vegetation in Zheng-Xin section of Beijing-Hong Kong-Macao Highway.