Experimental Study On Soil And Water Characteristic Curve Of Slope Soil Considering Root Morphology

Vegetation slope protection can not only improve the stability of the slope,but also repair the damaged ecological environment.Plant soil consolidation and slope protection technology is not only reflected in the mechanical reinforcement effect of roots on soil,but also its hydrological influence can not be ignored.Therefore,studying the hydrological effect of plant roots on slope soil has important theoretical significance for engineering construction.Based on the National Natural Science Youth Fund Project "Research on soil consolidation mechanism of plant slope based on directional regulation of root configuration"(Project No.:51608545),this thesis further explores the mechanism of root soil consolidation and slope protection by taking the soil-water characteristic curve of vegetation soil mass as the research direction through a large number of search research literature,theoretical analysis and indoor and outdoor tests.The main research contents and conclusions are as follows:(1)Three Vetiver root systems with growth periods of one month,three months and half a year were obtained by full section excavation method,and the relevant root growth morphological parameters such as root number,root diameter,root length,root area index and root volume ratio were counted and analyzed.It was found that the growth rate of primary root number,root diameter and root length of vetiver root system was relatively slow in the early growth stage,The root system mainly splits more secondary and tertiary roots through the derivation of primary roots,so as to achieve the growth conditions of expanding around the soil and absorbing more water and nutrients.The number of first-order roots in the soil section decreases with the increase of soil depth,and the number of second and third-order roots presents a change law similar to parabola and ellipse with the increase of soil depth;Through the fitting analysis of the data,it is found that the variation laws of root surface area coefficient(RAI)and root volume ratio(RV)of each soil layer section of vetiver root system with the decrease of depth accord with the Gaussian function distribution.(2)The change data of matrix suction and moisture content of vegetation soil and bare soil are monitored and collected through field test.Through research and analysis,the main conclusions are as follows:1)under the interception of plant leaves and the water absorption of plant roots,the moisture content of vegetation slope soil is slightly smaller than that of bare slope soil.2)There are differences in the volume moisture content of soil layers at different depths and the change range affected by rainfall.The response of deep soil to rainfall is not as sensitive as that of surface soil.In addition,there are fewer roots distributed in the soil layer and the absorption of soil moisture is low,resulting in the change of water content of deep soil is more stable than that of surface soil.3)The magnitude and variation range of matrix suction of vegetation soil are greater than that of bare soil in the same soil layer;Because the roots distributed near the surface soil are more dense and subject to stronger light radiation,the closer the slope soil to the surface,the greater the change range of matrix suction.On the contrary,the deeper the soil layer,the smaller the change range of matrix suction.(3)The results show that the V-G model fits the discrete data points of matrix suction and moisture content of bare soil and vetiver vegetation soil obtained from the test well.Through comparative analysis,it is found that the soil water characteristic curve of vegetation soil is more gentle than that of bare soil;The larger the root volume ratio of soil,the more parameters of soil water characteristic curve.The smaller the value is,the larger the air intake value is,which means that the matrix suction of vegetation soil is higher than that of bare soil at the same moisture content,which improves the water holding capacity of soil.It is also found that the existence of roots also has an impact on the saturated water content,inflection point and slope of soil.Through the root volume ratio RV,the soil water characteristic curve of vegetation soil is predicted.It is found that the prediction curve is in good agreement with the measured value of the test.It explains that the plant root system reduces the pores between soil particles by filling the pores between soil particles,improves the air intake value of soil,and improves the water holding capacity of soil.Secondly,it also verifies the feasibility and effectiveness of the Gallipoli model,that is,by combining the bare soil water characteristic curve and the root volume ratio Rv,it can effectively predict the soil water characteristic curve of vegetation soil,and can effectively simplify the steps of predicting the soil water characteristic curve of vegetation.