Effect Of Arbors Root Systems To Stabilze Slope In A Geological Hazard-Prone Region

Vegetation root plays an important role in preventing soil erosion and shallow landslides.Roots prevent mass movement by anchoring a soil layer and by forming a binding network within the layer.In order to reveal the affection of ecological restoration plant roots on the reinforcement of slope stabilization,the study focused on the four typical arbors roots(Populus tomentosa,Robinia pseudoacacia,Olea europaea and Zanthoxy lumbungeanum)on soil reinforcement effect.Field investigations were conducted to estimate the root area ratio(RAR)in vertical soil profile.Laboratory tests were performed to measure root tensile properties and the characteristics of soil shear strength.The root additional cohesion was calculated by Wu-Waldron model(WWM)and Fiber Bundle model(FBM).The finite element method to simulate the stress concentration area of the 30oslope and compare the effect of four plant roots on the slope stability.In additional,physical and chemical characteristics and root distribution in the vertical soil layer were investigated to explore the mechanisms by which these three factors influence root tensile properties.The main results are as below:(1)The density and distribution of different plants root showed decreased trend with the increase soil depth.In the vertical soil,the characteristics of the four plant roots were mainly hair root,the distribution of diameters classes were significant for Populus tomentosa and Robinia pseudoacacia however insignificant for Olea europaea and Zanthoxylum bungeanum.(2)The RAR of the four plants was P.tomentosa(0.163%)> R.pseudoacacia(0.162%)> O.europaea(0.049%)> Z.bungeanum(0.031%),while the RAR of P.tomentosa and R.pseudoacacia were greater than the limitation of slope reinforcement(0.1%).Distribution was strongly related to soil depth and spatial distribution for P.tomentosa and R.pseudoacacia but not similar trend for O.europaea and Z.bungeanum.For P.tomentosa and O.europaea,physical and chemical characteristics of soil were differed significantly with distribution of root diameter classes,for R.pseudoacacia and Z.bungeanum showed insignificant.(3)For the four plants,the peak tensile force and tensile strength showed significantly increased with the increase of root diameter.Peak tensile force for P.tomentosa and R.pseudoacacia showed power function with the increasing of root diameter,and linear relationship for O.europaea and Z.bungeanum.The tensile strength showed decreased power function with increasing root diameter for the four plants and strong significant on species root tensile properties.(4)The additional cohesion calculated by two models were found that the FBM was lower than the WWM,with R.pseudoacacia> P.tomentosa> O.europaea> Z.bungeanum,and it can be assumed with the distribution of root diameter classes in the vertical profile.The factor of stability for 30o slope with four plant roots were higher than bare slope without roots and ANSYS finite element simulation also proved the slope with the four plant roots improve the slope stability and reduce the risk of landslides.