Study On Mechanical Properties Of Root System Of Three Soil And Water Conservation Plants

The climate conditions and landform types in the central and western regions of Inner Mongolia are complex and diverse,thus forming a sensitive fragile ecological environment.For many years,it has been committed to repairing the damaged ecological environment through plant measures.Because plant roots intersect,entangle and interact with the soil,they form similar "reinforcement" and "anchor" effects on the soil,so as to improve the resistance of the soil to various erosion forces from the outside,and become the main manifestation of plant soil-fixing ability.In this thesis,three typical soil and water conservation plants in the semi-arid area of Inner Mongolia: Caragana(Caragana korshinskii Kom.),seabuckthorn(Hippophae rhamnoides Linn.),and alfalfa(Medicago sativa L.)as the object,through field test and Indoor simulation experiments are combined to study the ultimate tensile strength,bending strength and breaking-resistant strength mechanical properties of three plant single roots,and the mechanical properties of self-repairing roots after shear damage;indoor root-soil complexes Study on shear characteristics,and analyze the vertical load,the number of roots and other influencing factors,and the research on the friction characteristics of the root-soil interface.The main research conclusions are as follows:(1)The in-situ instantaneous ultimate tensile strength,flexural strength,tensile strength and flexural strength of the three plants were significantly different among species,which were Caragana > seabuckthorn > alfalfa,while the flexural strength and flexural strength were Caragana > alfalfa > seabuckthorn.The magnitude of damage resistance of the three plants was as follows : tensile strength > breaking-resistant strength > bending strength.(2)Under the same conditions,the shear strength of root-soil composite was :Caragana(15.96±3.13)KPa > seabuckthorn(13.57±2.31)KPa > alfalfa(8.44±2.85)KPa > Plain soil(6.17±0.91)KPa,and the residual strength was : Caragana(9.84±2.18)KPa > seabuckthorn(7.67±1.63)KPa > alfalfa(4.14±1.58)KPa > Plain soil(3.68±0.85)KPa.It shows that the root system can effectively improve the shear strength and residual strength of soil,and the stability of soil is also significantly enhanced.(3)The degree of damage significantly affects root growth and the self-repairing ability of ultimate shear resistance.Severe damage(degree C: 75% of the average ultimate shear force)has a significantly greater impact on the survival rate and shear resistance of the three plants than mild(A degree: 35% of the average ultimate shear force)and moderate(degree B: 55% of the average ultimate shear force)damage,which can easily cause root death and thus plant death.After 1 month of self-repairing of the three plants under the shearing damage forces of A,B,C,the overall survival rates of the plants were76.67%,70%,and 53.33%,respectively,and the survival rates after 3 months of self-repairing were 100%.,93.33%,80%,plant roots can repair themselves after being damaged by shearing force.The smaller the damage force,the higher the overall survival rate.After 1 month and 3 months of self-repair for the three plants,the shear strength values of the damaged root-soil complexes were all greater than those of the plain soil and less than the undamaged parallel control.Comparing the three plants,Caragana had stronger self-repairing ability after being damaged by shearing,followed by seabuckthorn,and alfalfa had the weakest resilience.(4)The shear strength of plain soil and three plant root-soil complexes increased with the increase of vertical load,and the two showed a linear positive correlation,and the correlation coefficients were all greater than 0.9.Under the same vertical load,the shear strength of the three plant root-soil complexes increased first and then decreased with the increase in the number of roots,and reached a peak when the number of roots was 4;the three plant root-soil composites With the increase of the number of cloth roots,the friction coefficient of the body generally shows a trend of first increasing and then decreasing;the internal friction angle does not change significantly with the increase of the number of cloth roots.(5)The average tensile strength of the root-soil interface of the three plants increases linearly with the increase of root diameter,and the pull-out shear strength of the root-soil interface decreases with the increase of root diameter in a power function;The shear strength of the root-soil interface increases first and then decreases with the continuous increase of the water content in the soil;the loading speed of the instrument has no obvious effect on the pull-out shear strength of the root-soil interface;the root-soil interface pulls out With the increase of soil moisture content,the change trend of shear strength in sandy soil and loess shows a trend of first increase and then decrease,and the shear strength of loess is higher than that of sandy soil,indicating that soil type has an effect on root-soil interface tensile shear strength The impact is significant.