Study On The Stability Of Ecological Slope Considering The Effect Of Water Transfer Of Plant Root System

Vegetation protection technology is one of the important measures to prevent slope,improve soil stabilization and restore ecology.The reinforcement of plants contributes to not only the mechanical reinforcement effect of root system,but also its hydrological effect.Therefore,it is of great theoretical significance to reveal the mechanism of the influence of plant root hydrological effect on the stability of slope as well as the mechanical reinforcement effect.Supported by the National Natural Science Youth Fund Project " Roots Configuration Directional Regulation-Based Study on the Mechanism of Soil Reinforcement of Plant Slope "(Project No.51608545),in view of the effect of plant roots on water movement in slope soil the study on the mechanism of root-fixing soil and slope protection was further carried out by means of theoretical analysis,indoor and outdoor experiments and numerical simulation.The main research contents and conclusions were made as follows:1.Research on root morphology of vetiverThe morphological parameters of vetiver root system in one year growth period were obtained.It was found that the growth morphology root system of vetiver was triangular distribution.The number,surface area and ratios of roots,all decreased with the depth of soil layer by Logistic function.2.Experimental study on soil-water characteristic curve(1)According to the field soil-water characteristic curve tests,the relationships between volumetric water content and matric suction were obtained.The results show that there is a negative correlation between soil volumetric water content and matric suction,which can be well fitted by Gardner soil-water characteristic curve equation.Compared to the slope with no roots,the air intake value and water holding capacity of the soil in slope with vetiver roots could be effectively increased.According to the analysis of volume water content and matric suction at different slope positions,the volume water contents of two types of slopes decrease and matric suctions increases with the continuous hot weather.Compared to the plain soil,both of the volume water content and matric suction in plant slope soil are larger.The difference of the volume water content between the uphill and downhill becomes decreased,which leads to the water migration and secondary distribution of matric suction,the velocity of the wetting front moving down is slowed down.(2)Based on the saturated permeability coefficients measured and soil water characteristic curve,the relationship equation between permeability coefficient and matric suction is obtained by using the simplified Gardner soil-water characteristic curve formula.It is found that the permeability coefficient of vetiver slope is always less than that of plain soil slope.But the difference between them decreases gradually with the increase of matric suction.3.Experimental study on rainfall infiltration(1)Some experiments were carried out to study on rainfall infiltration by setting different rainfall intensity and rainfall time.It was found that vetiver can reduce the erosion of shallow soil and the deformation of soil mass because the roots of vetiver could accelerate the infiltration of rainwater and reduce the runoff of slope.(2)When rainwater infiltrates,the soil infiltration lines on the uphill and downhill of the plain soil change in the same time.However,the change range of the infiltration line at the foot of vetiver slope is much larger than that at the top of slope,spreading from the downhill to uphill gradually,which changes the path of infiltration.4.Theoretical analysis and numerical analysis(1)According to the water conservation of mass equation and Richards equation,combined with the theory of vetiver root absorbing water,considering the influence of vetiver root system on the seepage of pore water in slope soil,In terms of the traditional Green-Ampt and Mein-Larson infiltration model,the distribution of pore water pressure in vetiver slope was analyzed based on soil-water characteristics of unsaturated soils.In addition,the depth solutions of wetting front were obtained under the conditions of non-water infiltration and water infiltration.(2)Base on the Wu-Waldron model and Fredlund formula for shear strength,combined with the analytical solution of pore water pressure and wetting front depth under root distribution,the calculation formulas of the safety factor of vetiver slope stability under the conditions of non-seeping infiltration and seeping infiltration were deduced.(3)The numerical model of vetiver slope was established.Consequently,the changes of soil stress field,displacement field and pore water pressure before and after rainfall were obtained.And influence of water-absorbing and transpiration of vetiver root on the slope stability was analyzed.From the above research,it is analyzed the influence of the hydrologic function of the plant root system on the shallow stability of the slope.It provides some ideas to further researchon ecological slope protection.It also contributes to develop the new technology of slope protection with plants.