Study On Unsaturated Infiltration Model And Ecological Reinforcement Mechanism Of Slope Under Rainfall Condition

In recent years,landslide caused by rainfall frequently occurs.The law of soil rainfall infiltration and the ecological reinforcement mechanism of plant root system are very important to the analysis of slope stability.The methods of theoretical analysis,model test and numerical simulation were adopted in this study.The unsaturated rainfall infiltration model which is more consistent with the distribution of water content in the wet zone was derived.In addition,the influence mechanism of water absorption and reinforcement of plant roots on slope reinforcement under rainfall infiltration conditions was studied.The main results are as follows:(1)The wet zone is typically assumed to be divided into a saturated zone and a transient unsaturated zone during infiltration.Here,variations in the depths of the saturated zone and the transient unsaturated zone during the infiltration process were studied using Seep/W software.The Wet Zone Partition Function R(t)and its fitting parameters were presented,the function is in the form of a three-parameter exponential.This function can characterize variations in the ratio of the saturated zone depth to the wetting front depth over time.The fitting parameters were predicted by a back propagation(BP)neural network constructed by MATLAB software.(2)The equivalent hydraulic conductivity(k_s')was presented to characterize the permeability of the entire wet zone,and equivalent hydraulic conductivity coupled with the ratio R was derived.An improved Green-Ampt(GA)infiltration model was established based on the Wet Zone Partition Function and the equivalent hydraulic conductivity.The infiltration results simulated by the improved Green-Ampt model,Seep/W and the traditional Green-Ampt model were compared with the measured values.The results show that the inproved Green-Ampt model can accurately simulate the infiltration process.(3)A slope rainfall model test platform was built.A rainfall contrast test between bare slope and ecologically reinforced slope was carried out.The slope reinforcement mechanism under roots water absorption of the Hybrida Vicary Privet was studied.The results show that the roots water absorption can increase the soil suction of the slope.When the depth is greater than the length of the root system,as the depth increases,the suction of the slope is less affected by the roots water absorption.When the soil saturation of the slope is higher,the impact of root water absorption root is less obvious.In addition,the analysis results of soil water characteristic curve show that role of root water absorption improves the water holding ability of slope soil,and then affects the slope stability.(4)The laboratory test was carried out to study the reinforcement mechanism of root reinforcement on the slope.It was concluded that the tensile strength and elastic modulus of the roots of Hybrida Vicary Privet were negatively correlated with the diameter.The role of root reinforcement can effectively improve the soil strength.The soil cohesion is more significantly affected by root reinforcement,and the internal friction angle is less affected.When the other variables of the root system are kept the same,the larger the root diameter,the root distribution density,and the single root length are,the greater the shear strength of the root reinforced soil is.The root distribution angle can also affect the root reinforcement effect,and the root reinforced soil which is horizontally placed has the highest shear strength.(5)The influence of root characteristics on the reinforcement effect of slope is obtained based on the numerical analysis of ecological slope under rainfall conditions.With the increase of the bond strength of the roots,the safety factor of the ecological slope increases gradually,and then gradually stabilizes.The larger the root diameter,the denser the distribution,and the longer the root system,the smaller the horizontal displacement of the ecologically reinforced slope.In addition,as the length of the root system increases,the potential slip surface of the slope gradually moves toward the deep layer.