Relationship Analysis Between Soil Shearing Strength And Its Impact Factors Of Different Land Utilization Types

As one of the facing ecological and environmental problems in today's world,water and soil loss not only seriously restricts the sustainable development of environment,but intensifies environmental degradation as it brings economic loss to mankind as well.Water and soil loss in slopes can cause the degeneration of soil quality and the decline of slope productivity,in which the gradient acting as one of the important factors of determining the happen of it.Soil shearing strength,a index that expressing the characteristics of soil and often determining soil anti-erodibility,is often applied to the evaluation of regional water and soil loss.Five kinds of land utilization types located in Tian Zhu mountain of Shenyang,including conifer and broad-leaved mixed forest,shrubwood,field,sloping farmland and wasteland,which were divided into three slope positons in this experiment as upper,middle and lower so as to take samples,under different gradient as 10 °,15 ° and 20 °,had been taken into consideration in order to determine some numerical values,including soil shearing strength indexes,soil structure,moisture content,bulk density,dry density,total porosity and organic matter,and after that the soil shearing strength of different land use types,with the variation rules of the relevant factors under different gradient and slope positions,were analyzed.Besides,the impact factors of soil shearing strength,and the main influencing factors on each land use type were analyzed via data analysis methods at the same time.The main conclusions were as follow:(1)Describe the characteristics of soil physical and chemical properties of different land use typesIn conifer and broad-leaved mixed forest,shrubwood,field and wasteland,the content of Sand was relatively low,but the content of Powder and Clay were high,while in sloping farmland,the relevant content presented as the opposite.Besides,along with slope positions and gradients,the variation rule was not obvious.In the case of different land use types,the dry-screening MWD increased firstly then decreased with gradient increasing gradually.Along with the increasing of gradient,the aggregate wet-screening MWD value of different land use types was increased.In the case of different land use types,soil moisture content and total porosity increased continuously from the upper slope position to the lower ones,and the variation degree was relatively obvious.Soil moisture content and total porosity changed unapparently with the variation of gradient;under the different land use types,soli bulk density and dry density presented the tendency of decreasing basically from upper slope position to lower;among all the gradients being considered,the sloping farmland had higher soil bulk density;soil bulk density and its dry density varied unapparently with the change of gradient;with the changing of gradients and slope positions,the variation of organic matter was inconsistent.(2)Analysis soil shearing strength under different land use typesIn the case of the same used land,the soil cohesion gradually decreases from upper slope position to lower,meanwhile,it increased firstly then decreased with gradient increasing gradually.In the case of different land use types,soil shearing strength followed the order as sloping farmland>field>conifer and broad-leaved mixed forest>wasteland>shrubwood.(3)The main influencing factors of soil shear strength under different land use types were obtainedThen the influential factors were analyzed with the method of the grey correlation,The order of correlation between cohesion force C and influencing factors is:bulk density>dry density>total porosity>water content>organic matter content>powder clay ratio>dry wire MWD value>wet filter MWD value.The order of correlation between the friction angle ? and the influencing factors is:bulk density>dry density>total porosity>water content>organic matter content>dry screen MWD value>powder clay ratio>wet screen MWD value in conifer and broad-leaved mixed forest,wet-screening MWD value has the greatest close degree with soil cohesion,and in the case of wasteland,it was organic matter,while under the case of other three used land,soil bulk density and dry density has comparatively greater close degree with soil cohesion.In conifer and broad-leaved mixed forest,shrubwood and wasteland,after calculating by four kinds of close degree methods,the total porosity had an relatively greater effect on soil internal friction angle,besides,soil bulk density and dry density being significant impact factors on field and sloping farmland.The main factors affecting soil shear strength were obtained,and the dry density,bulk density,total porosity,wetland MWD value and dry root MWD value were used in coniferous and broad-leaved mixed forest.The main influencing factors were density,dry density,organic matter,total porosity and water content in other land use types.The results showed that the main factors were bulk density,dry density,dry root MWD value,total porosity and water content.(4)The relationship between soil shear strength and main influencing factors was obtainedThe equations of soil shear strength based on dry density and bulk density were established(R~2=0.865).In sloping farmland,the predicting model,which was based on dry density,bulk density and dry-screening MWD value,was established(R~2=0.865).In shrubbery,a linear model of soil shear strength based on dry density was established(R~2 = 0.919).In the garden,a linear model of soil shear strength based on the MWD value of the aggregated dry sieve was established(R~2 = 0.874).In the garden,a linear model of soil shear strength and bulk density was established(R~2= 0.864).