Study On Water Transfer And Mechanical Properties Of Root Soil Considering The Effects Of Rainfall And Growth Age Of Herbs

Aiming at the problems of vegetation on slope soil consolidation mechanism and water regulation mechanism under extreme climate change conditions in the fragile ecological environment of loess,this paper selected ryegrass plants and loess planting soil,developed a planting box for root soil mechanics test partition sampling,and carried out root soil and plain soil water migration and mechanical tests.The water migration law and mechanical properties of ryegrass root soil and plain soil under different rainfall climates and growth ages were studied.The mechanical mechanism of root soil consolidation under different rainfall climates and herb growth ages was revealed,and the shear strength model of root soil considering vegetation growth age and water regulation was established.The main research results are as follows:(1)The root morphology of ryegrass belongs to uniform distribution.The dynamic growth and development characteristics of root diameter,root length,root surface area and root volume of ryegrass at three growth stages were studied by root scanning technique.In the process of its development,the increase of root diameter is small,the root length,root volume and root surface area increase significantly,and the tensile strength and pull-out resistance of root increase greatly in the later stage of growth.(2)The planting box for mechanical test of root soil was developed,and the water migration and mechanical tests of root soil and plain soil were carried out to analyze the water migration law and mechanical properties of ryegrass root soil and plain soil under the same growth environment.In the process of precipitation infiltration,the water migration law of root soil and plain soil can be divided into three stages:jump,decline and stability.The jump of shallow plain soil relative to root soil is faster.The surface cracks of plain soil have a promoting effect on infiltration.The root system has a crusting effect on the surface of the soil layer.The permeability coefficient of root soil is greater than that of plain soil.The infiltration depth of root soil is deeper under the action of root water conduction.(3)Through the water migration and mechanical test of root soil,the water migration law and mechanical properties of root soil under different precipitation and different growth ages were studied.With the increase of growth age,the root volume increases,the ability of root to regulate water in root soil increases,the cohesion of root soil increases obviously,the friction angle changes little,and the permeability coefficient increases gradually.The volume change of root is the main factor affecting the shear strength and permeability of root soil.(4)Based on the flexible model of root soil reinforcement,the root volume ratio parameter is introduced,and the variation law of root volume ratio parameter under different growth age conditions is analyzed.A flexible model of root soil reinforcement considering growth age is proposed.The effects of three weight factors,such as plant shape function,soil water stress correction coefficient and plant potential transpiration rate,on the strength increment caused by root regulation water are studied.The shear strength model of root soil considering vegetation growth age and water regulation is established by superimposing the four parts of saturated soil strength,matrix suction caused strength increment,root reinforcement caused strength increment and root regulation water caused strength increment.