The Tensile Properties Of Roots Of Four Plants Response To Cyclic Loading

To enrich the mechanical mechanism of soil fixation of plant roots and provide theoretical basis for vegetation construction in mining areas.In this study,four species soil and water conservation plants in arid and semi-arid areas: Caragana microphylla,Salix psammophila,Hippophae rhamnoides,Artemisia ordosica were taken as the research objects,the tensile properties of roots with diameters from 1-5mm of four plants in response to repeated loading and unloading were measured axial cyclic loads test with TY8000 servo control testing machine.The results show that:(1)Within the range of 1-5 mm root diameter,the tensile force of the roots of the four plants under three cyclic loads(low cycle loading,high cycle loading,alternating load)was enhanced compared with the monolonic load,the tensile force enhanced of roots of Salix psammophila was particularly prominent: the average tensile force of straight roots and lateral roots under alternating load increased by 50.89% and 60.86%,the average tensile force of straight roots and lateral roots under high cycle loading increased by 35.63% and 22.88%,the average tensile force of straight roots and lateral roots under low cycle loading increased by 28.33% and 10.40%;the tensile force enhanced of roots of Caragana microphylla was smallest: the average tensile force of straight roots and lateral roots under alternating load increased by 2.57% and 14.70%,the average tensile force of straight roots and lateral roots under high cycle loading increased by 11.50% and 14.69%,the average tensile force of straight roots and lateral roots under low cycle loading increased by 1.87% and 7.92%;the tensile force enhanced of roots of Hippophae rhamnoides,Artemisia ordosica was between the above two plants.The tensile strength of roots of four plants under cyclic loads was similar to that of tensile force,in other words,the tensile strength of roots of four plants under cyclic loads greater than that under monolonic load.In general,the enhancement degree of tensile force and tensile strength of roots of four plants under three cyclic loads was shown as follows: alternating load > high cycle loading > low cycle loading.(2)The tensile force of straight roots and lateral roots under monolonic load,low cycle loading,high cycle loading,alternating load were positively correlated with the diameter as a power function,the tensile strength of straight roots and lateral roots under monolonic load,low cycle loading,high cycle loading,alternating load were negatively correlated with root diameter as a power function,it is show that cyclic loading does not change the relationship between tensile force-root diameter and tensile strength-root diameter.Within the range of 1-5 mm root diameter,the tensile force and tensile strength of roots of four plants with different root types were significantly difference(P<0.05),the tensile force and tensile strength of the straight roots of the same plants were greater than that of the lateral roots.The tensile force and tensile strength of straight roots and lateral roots of four plants were different among species: Caragana microphylla > Salix psammophila > Artemisia ordosica,Hippophae rhamnoides,there was no difference in tensile properties between Artemisia ordosica and Hippophae rhamnoides.(3)In the process of low cycle loading and high cycle loading,the roots of four plants showed obvious elastoplastic characteristics.During the cycle process,the force-displacement curve changes from loose type to intensive type,the plastic deformation accumulates and the increment decreases gradually,the elastic deformation becomes s Table.and tends to be fixed,the elastic deformation and plastic deformation of roots under high cycle loading were greater than those under low cycle loading.When the root is subjected to alternating load(low cycle loading and high cycle loading are repeated in turn),the effect of high cycle loading on root deformation is greater.(4)Within the range of 1-5 mm root diameter,the elastic stress,ultimate stress and elasticity modulus were negatively correlated with root diameter after monolonic load,low cycle loading,high cycle loading and alternating load.The interspecific relationships of average elastic stress and ultimate stress were as follows: Caragana microphylla > Salix psammophila > Artemisia ordosica > Hippophae rhamnoides;The interspecific relationships of average elasticity modulus after monolonic load was Caragana microphylla > Salix psammophila > Hippophae rhamnoides > Artemisia ordosica.The interspecific relationships of average elasticity modulus after cyclic load was different from monolonic load,the interspecific relationship after cyclic load is shown as Salix psammophila > Caragana microphylla > Artemisia ordosica >Hippophae rhamnoides.Compared with the monolonic load,the elastic stress,ultimate stress and elastic strain after cyclic loading all show an increasing trend,which mainly shows high cyclic load > low load cycle > monolonic load.(5)Under the monolonic load,the stress-strain curves of roots of four plants show linear positive correlation at the beginning,when the elastic limit point is exceeded,the strain increases rapidly with the increase of stress,and the deformation transition from linear elastic deformation to nonlinear deformation.The stress-strain curve after three kinds of cyclic loading(the limit curve of applying again force to destroy after cyclic loading)were different from those of monolonic load,the initial stress-strain curve of cyclic loading was carried out along the cyclic loading path,the slope of the curve decreases rapidly when the upper limit load of the cycle process was reached,the later stress-strain curve of cyclic loading is similar to monolonic load.