Experimental Investigation Of Slope Reinforcement By Herbaceous Plants

The tensile and shear tests of fresh,dry,reclaimed water,inactivated roots and root soil complexes of tall fescue of herbaceous plants were carried out,and their mechanical properties were compared.Based on the experimental results and existing theories,the hydrological effects of transpiration and water absorption of plants were theoretically analyzed.Finally,the effects of rainfall intensity and coverage factors on the ecological effects of plant ecological reinforcement were studied by simulating artificial rainfall,the main conclusions are as follows:1.Mechanical effect:the larger the diameter of the herbaceous plant,the shorter the root,the better the tensile properties,the greater the external load that the root soil composite can bear,the root system is less easily cut off in the shear,and the wind dry root system has the best resistance and shear resistance.The higher the root content,the greater the shear strength of the root soil complex;when the moisture content is 17.64%-24.77%,the higher the moisture content of the root soil complex,the greater the shear strength.The accurate value of shear strength of root soil composite can not be simply expressed by the shear plane RAR.The Wu and Waldron models can be easily evaluated by multiplying the reduction factor.2.Hydrology effect:plant root water absorption and transpiration can change the shear strength of soil and change the soil moisture content.On this basis,the concept of plant suction is proposed.Based on the theory of moisture absorption and capillary pressure,the expression of plant suction in the most loosely packed and closely packed soil particles is obtained from the microscopic perspective.Plant roots occupy the pores of soil and affect the infiltration of wetting front.Based on this,the Green-Ampt model is improved and the improved formula for wetting front depth is obtained:zf*=(e0+1)Rt/[e0-RV(e0+1)](?s-?0)cos?,combined with the additional skid resistance provided by the tensile properties of the roots,the formula of safety factor for unsaturated vegetation infiltration under rainfall conditions is obtained.3.Ecological effect:The falling rain can affect the vertical and horizontal displacement of soil particles by transforming into two parts:infiltration soil and surface runoff.When rainfall intensity>soil permeability coefficient,the smaller the rainfall intensity,the higher the vegetation coverage,the longer the flow time of the slope,the less sediment in the slope runoff caused by rainfall,the sediment content of the slope with 100%vegetation coverage is only 0.08%and 0.06%,and the slope is stable,the reason is that the interception of the vegetation ground stems and leaves makes rain impact.The velocity of the soil on the slope becomes smaller,the impact force decreases,and the wetting front moves slower.At the same time,vegetation roots can also network,intercept soil particles,and maintain the stability of soil particles.Through experiments and theoretical derivation,the mechanical effect,hydrologic effect and ecological effect of herbaceous plants have played a very good role in the reinforcement and stability of the soil,and the quantitative study of its effect can be used to guide the ecological management and evaluation of the vegetation slope.