Comparison Of Solid Mechanical Character Of Two Herbs

In order to reveal the mechanism of soil erosion resistance of root system,it provides some basic mechanical data for selecting excellent soil and water conservation plant species in vegetation restoration and reconstruction.Taking two typical soil and water conservation herbs Astragalus adsurgens and Medicago sativa as the research objects,field in situ and laboratory tests were carried out to study the tensile mechanical properties,shear mechanical properties and root-soil interface friction characteristics of the two plant roots.The effects of different influencing factors on them were studied.Studies have shown that:(1)Within 1-4 mm of root diameter of two plants,tensile strength of Medicago sativa(182.98 ± 95.94;50.54 ± 15.99)< Astragalus adsurgens(219.13 ± 115.48;60.72 ± 15.90);Compared with the species,the instantaneous ultimate tensile coarse root is large and the tensile strength is small.The ultimate tensile mechanical properties of Astragalus adsurgens and Medicago sativa under parallel control and callus self-repair were consistent with the instantaneous ultimate tensile mechanical properties.(2)Within 1-4 mm of root diameter of two plants,the survival rate of Medicago sativa was(89.80 ± 0.05Ba;78.43 ± 0.05Bb)compared with that of interspecific Medicago sativa(91.67 ± 0.03Aa;82.00 ± 0.06Ab);The survival rates of Astragalus adsurgens and Medicago sativa were self-healing(82.00±0.06 Ab;78.43 ± 0.05 Bb)< parallel control(91.67 ± 0.03Aa;89.80 ± 0.05Ba).The activity values were consistent with the survival rate: the activity values of Medicago sativa after parallel control and self-healing(4.20±0.54 Ab;3.52± 0.76 Bb)< Astragalus adsurgens(4.43 ± 0.52Aa;3.78 ± 0.46Ba),and the activity values of Astragalus adsurgens and Medicago sativa were self-healing(3.78 ± 0.46 Ba;3.52 ± 0.76 Bb)and parallel control(4.43 ± 0.52Aa;4.20 ±0.54Ab).(3)Within plant root diameter within 1-2.5mm,at 12.5 KPa,the stress-strain relationship of the root soil complex shows obvious characteristics of elastoplastic materials,and the shear strength of the root soil complex increases first and then decreases.At the main distribution layer of Astragalus adsurgens and Medicago sativa,the soil moisture content is10.86%-16.5%,the root number is 4,and the root diameter is 1-2 mm.The cohesion is the main reason to increase the shear strength of the root soil composite.(4)The friction coefficient and cohesive force at the root soil can be deduced by Moll Coulomb theory.At 12.5 KPa,the shear strength and resistance of the relative displacement were greater than the plain soil.The improvement of the shear strength of the root soil interface is achieved by increasing the friction force of the root soil interface.The soil water content increases,the cohesion of the root soil interface increases and then decreases,the internal friction angle and friction coefficient of the interface are 8.5%,the soil water content of the soil reaches peak(7.67KPa),the soil water content of 16.5%,the viscosity of alfalfa root soil is 9.99 KPa.(5)Within the root diameter of both plants of 1-4mm,the tensile force of the coarse root soil interface is large,small tensile strength,large friction resistance and small friction resistance per unit surface area.The tensile force at the root soil interface is Shadawang(38.74±10.06)<alfalfa(31.93±6.87).When the soil moisture content is 10.86%,the tensile shear strength of the root soil interface between two plants reaches peak,and alfalfa is 1.02 times that of sand;the shear strength of sandy soil interface is <loess;the peak shear strength of alfalfa soil interface is 3.39 times the tensile strength of sandy soil The peak loess is 4.09 times the sand.