The Experimental Study On The Mechanical Properties Of Soil Reinforcement By Plant In Freeway Slope

The construction of the highway during the excavation of large filling,serious damage to the local ecological environment,easy to cause soil erosion,landslides,mudslides and other common geological disasters,a great threat to personal safety.The traditional engineering slope protection technology is not only a large amount of engineering,more supplies,high cost,relatively simple form,but also permanently destroy the ecological environment Therefore,the highway slope treatment is a problem to be solved urgently in highway engineering construction.This paper mainly based on the 948 project of the State Forestry Administration,"The introduction of key technologies for deep slope cutting slope restoration"(project number 101-9968)and the slope solid project of Da Yue high speed eighth contract section.In this paper,two species of shrubs planted by Magnolia multiflora and Robinia pseudoacacia were selected as the research object.The distribution regularity and mechanical properties of the two root systems were studied by investigation on distribution Characteristics of Plant Roots,root-soil complex shear and root-soil composite drawing test.The main innovation conclusions are as follows.1.There were some differences in the root morphology of the two shrubs of Magnolia multiflora and Robinia pseudoacacia Through the study of plant root morphology distribution.The main root system of Robinia pseudoacacia is not obvious,but its horizontal roots and oblique roots are more and Intertwined into a network,which is conducive to enhancing the integrity of the slope soil.The main root system and the secondary root system of Magnolia multiflora are more developed,and the anchor rod is used in the slope protection to maintain the stability of the slope.2.Through the shear test of root soil complex of Magnolia multiflora and Robinia pseudoacacia,it was found that the plant root system can effectively improve the shear strength of soil.It is found that the shear strength of the root soil composite is consistent with Coulomb’s law and we can derive the cohesive force C and the internal friction angle of Magnolia multiflora and Robinia pseudoacacia according to Coulomb’s law through the analysis and processing of test data.The shear strength of the Magnolia multiflora-soil complex is slightly larger than that of the Robinia pseudoacacia-soil complex under the same condition.3.Under the same conditions mixed layout of shear strength is the highest;and the shear strength is the second when the roots are laid Oblique,When the roots are all laid vertically,the shear strength is minimal;Under the same root number and the same root condition,the shear strength of the root-soil complex increases and then decreases with the increase of the root diameter,When the root diameter is about 1.0～1.2mm,the shear strength of the root-soil complex reaches the maximum value.4.The stress-strain curves of plain soil and root soil complex under different conditions were obtained through the triaxial test of the root soil complex carried out by Magnolia multiflora and Robinia pseudoacacia.There was a linear trend of stress-strain curves of the non-root soil and root soil composite when the axial strain is less than or equal to 2%In a variety of confining pressure and moisture content conditions,when the axial strain is greater than 2%,the deviator stress difference increases slowly,The specimen was hardened and the curve became stable while the deviator stress reached the maximum at the end.5.Through the experimental research on the single line of two plants of Magnolia multiflora and Robinia pseudoacacia we can see that under the condition of the same density and different soil water content,the maximum pullout force of Magnolia multiflora and Robinia pseudoacacia root increased first and then decreased with the increase of soil water content.When the water content was 21.4%,the root pulling force was the largest;The maximum pullout force of roots of Magnolia multiflora and Robinia pseudoacacia increased with the increase of soil sample density,and increased with the increase of effective root system under the same conditions.The above research is to explore the soil mechanics characteristics of two shrubs and root soil complex of Magnolia multiflora and Robinia pseudoacacia.It is an important reference value for the application of these two kinds of plants to the comprehensive prevention and control of expressway slopes.