Experimental Study On Strength Of Shallow Loess Under The Action Of Herbaceous Roots

In order to study the strength of shallow loess under the action of herb root,this paper designs the test scheme of shear strength of loess with alfalfa root,considers the state of low confining pressure/vertical pressure,and artificially cultivates loess samples with root through triaxial test The strength characteristics and root pullout resistance of loess with roots were studied by direct shear test and root pullout test;Then the WwM model was optimized by root pull-out force;The effect of vegetation root growth on the stability of loess slope with alfalfa root system was studied.The main conclusions of this study are as follows:(1)Under the condition of low confining pressure,the stress-strain curve of the sample is strain softening type,while under the condition of high confining pressure,the stress-strain curve of the sample is strain hardening type.The fitting results of shear strength index show that the cohesion of soil with roots is obviously greater than that of soil without roots,and the internal friction Angle has no obvious change.(2)The diameter of the fracture has no influence on the pull-out force,while the pull-out length and the diameter of the surface have significant influence on the pull-out force.The correction coefficient of the WWM model k" can be expressed as a time-related function.With the growth of time,k" firstly increases and then decreases,and the decreasing trend of k"decreases monotonically with the growth time.(3)When the sliding surface depth is 0?1m,the slope safety factor always shows a monotonically decreasing trend with the increase of the sliding surface depth.With the increase of the slope angle,the slope safety factor firstly decreases and then increases.The slope safety factor calculated by the theoretical value is obviously larger than that calculated by the test value.(4)The existence of vegetation can significantly improve the distribution of slope stress,displacement and plastic zone,which indicates that vegetation can effectively inhibit shallow slope landslide under rainfall conditions,and the effect of vegetation enhancing slope stability is more significant with the growth of vegetation.