Research On Shear Strength Of Different Crops Soil In Brown Soil Zone Of Liaozhong

With the continuous development of economy and society, soil erosion has become one of the serious ecological and environmental problems in the world today. In recent years, China’s problem of soil erosion is increasingly severe, and the issues of ecological balance are also facing serious challenges. Surface runoff on the soil would produce a certain shear force. When runoff shear force generated by local surface is greater than the shear strength of soil, some soil structure will be destroyed, resulting in the occurrence of soil erosion. Therefore, research on soil shear strength is vital significant on the establishment of soil erosion prediction model in physical concepts.In this study, corn field, beans, fruit trees fields and fruit tree table fields had been taken as researching regions in the watershed of Mountain Moyun, which was designated by GPS, and the cutting ring had been used to take soil samples. In laboratory, soil cohesion force, internal friction angle of soil, moisture content, soil particle composition and its bulk density had been tested. This paper analyzed the influence of slope position on soil shear force in corn field, beans, fruit trees field and fruit trees table fields, besides, SPSS regression and MATLAB response surface had been taken into account for analyzing the relation between soil shear force and it’s influencing factors. The main conclusions of this paper are as follows:(1) Results on variation rule of soil shear force and its influencing factors in different slope positionIn corn field, soil cohesion force and soil bulk density decreased with the change of slope position from upper to lower, while internal friction angle of soil, soil moisture content and clay content showed an increasing trend with slope position change. In fruit tree field, soil cohesion force and soil bulk density showed an increasing trend with slope position from upper to lower, while soil moisture content, internal friction angle of soil and clay content showed an opposite trend. In fruit table field, soil cohesion force showed an increasing trend with slope position from upper to lower, while soil internal friction angle showed an opposite trend, and soil moisture content became higher during the period of autumn and in spring lower; soil bulk density increased in spring, decreased in autumn with slope position variation; the content of clay showed an opposite tendency in these months.(2) Influencing characteristics of different crops on soil shear forceSoil cohesion force of different crops were as follows:corn field>fruit trees field>beans>fruit table fields. Soil internal friction angle of different crops were as follows: beans>corn field>fruit trees fields>fruit tree table fields. Soil moisture content of different crops were as follows:fruit tree table fields>fruit trees field>beans>corn field. Soil bulk density of different crops were as follows:fruit tree table fields>fruit trees field>beans>corn field.(3) Relations between soil shear force and its single influencing factorSoil cohesion force, c value, in fruit trees field and fruit tree table field increased at first and then decreased with the increase of soil moisture content, ω value, soil internal friction angle, (?) value, within fruit tree field and fruit tree table field had a same tendency as ω value increased, while c value within beans and fruit tree table field showed an opposite trend as the soil bulk density, p value, increased. In corn field and fruit trees field c value decreased as p value increased. In all the crop fields, c value decreased as (?) value increased. In corn field, beans and fruit trees field, soil cohesion force, internal friction angle of soil and moisture content showed significant differences (P<0.05). In all the crop fields, the changing section of soil bulk density within the tillage layer showed significant differences (P<0.05).(4) The establishment of prediction equation of the soil cohesion forceSoil cohesion prediction equation were calculated by the gradual regression analysis to analyze the relationship between soil cohesion force and other factors, which containing soil moisture content, internal friction angle of soil and soil bulk density, besides, the linear equation on soil cohesion force was established by utilizing the two factors of soil internal friction angle and soil moisture content: (c=-2.039(?)-0.791ω+101.339).