Model Testing And Numerical Analysis On Anti-overturning Performances Of Plant Roots

China is among the countries mostly affected by typhoon.Urban road blockages and damage to vehicles and public infrastructure caused by severe storms and rains occur frequently,which poses a great threat to people's lives and property.However,the tree root system composition and morphology are complex in nature,and the difference in anti-overturning performance of different types of forest trees is significant.Therefore,it is of particular importance to study the overturn process as well as the key influential attributes of different tree roots.Previously,researchers mainly focused on the in-situ pull-out test,single root tensile strength test or finite element simulation of single root type.There are few studies on flatrate lateral loading tests and comparisons of different root types.Based on the model test on the root system and a series of three-dimensional numerical simulation,the main research contents and conclusions of this study are as follows:(1)The shear strength of natural soil was studied by direct shear test of soil samples,and the change trend of c,? value and shear strength with moisture content was analyzed by changing the moisture content.The results showed that in the test range with moisture content ranging from 7% to 22%,the shear strength of soil increases first and then decreases with the increase of moisture content.The peak of shear strength is obtained when the moisture content is equal to 13.0%.In addition,with the increase of moisture content,the soil cohesive first increases and then decreases,which produces little effect on the internal friction angle.(2)A self-designed lateral loading device was used to apply a constant rate lateral loading test to the ginkgo seedlings.The effects of soil moisture content and root depth on the pull-out resistance of the roots during the extraction process were analyzed.The change of the anti-overturning force in the root displacement-drawing force curve can be summarized as a gentle rise and a steep rise.And the three stages of slowly rising to reach the peak,corresponding to the elastic deformation of the trunk in the model test,the root soil began to shift and most of the soil sheared to reach the peak of the anti-overturning force.The maximum anti-overturning force of the roots showed an overall trend of increasing first and then decreasing with the change of water content.The maximum antioverturning of the roots was the most significant when the measured near-saturated moisture content was measured.The maximum anti-overturning force of the roots showed an overall trend of increasing first and then decreasing with the change of moisture content.The maximum anti-overturning of the roots was the most significant when the measured near-saturated water content was measured.The increase of root depth can effectively increase the maximum anti-overturning force of forest roots,and is exponentially correlated in the depth range of the experiment.(3)The finite element model of vertical root system,horizontal root system and scattered root system considering size effect was established.PLAXIS 3D finite element software was used to simulate the lateral loading of three common root types: vertical root,horizontal root and scattered root.The failure process outputs a displacement-load curve of the root failure process.Through the root-free simulation method,the antioverturning force and loading displacement peaks of different root types and lateral roots were obtained,and the effects of different root types and their lateral roots on the overall anti-overturning strength and stiffness of the trees were revealed.