Research On Pullout Behavior Of Aeolian Sand Shallow Foundation Reinforced By Geogrids

With the in-depth development of energy development strategies in the northwestern region of China,it is necessary to build a large number of transmission towers in the desert area and improve the power grid structure to meet energy development requirements.The desert aeolian sand has loose soil,low shear strength and insufficient bearing capacity.For the construction of transmission lines in such a wind and sand environment,the stability of the tower foundation is particularly important.If the geogrid is embedded in the aeolian sand foundation to form a composite soil reinforcement layer,the tensile strength of the geogrid and its friction with the soil can improve the bearing capacity of the foundation and enhance the integrity and the stability of the sand..Based on the above situation,this paper conducts finite element numerical analysis and indoor model test on the pullout performance of anchor plates in sand under reinforced and unreinforced conditions.Firstly,the pull-out model test of indoor reinforced foundation anchor plates with different geogrid layers,grid layer spacing and reinforcement dimensions was carried out.The load-displacement data obtained from the test were collated to analyze the uplift resistance of different reinforced foundations and the Pull out the change in performance,and explore its reinforcement effect.Then,using MIDAS-GTS/NX finite element analysis software,the numerical model of the shallow-buried anchor plate pull-out test of the reinforced foundation is established,and the test results are compared with the numerical model calculation results.The two methods are in good agreement with the deformation resistance of the foundation and the surface deformation of the foundation.The validity and accuracy of the numerical simulation are verified.On this basis,the basic depth of the foundation is changed,the number of geogrid layers and the layer spacing are changed,and the interaction between soil and geogrid is discussed based on the development of displacement and stress in the numerical results.The effects of foundation burial depth and geogrid laying method on foundation failure mechanism and uplift capacity of reinforced foundation are analyzed,and the best scheme for shallow foundation reinforced foundation treatment in sand is proposed.Both the test and the finite element calculations show that the tensile strength of the geogrid effectively inhibits the expansion of the plastic zone of the soil,delays the appearance of the failure surface,and limits the lateral displacement of the soil near the grid,increasing the surface damage.Scope,thereby enhancing the integrity of the foundation and the uplift capacity.Through the finite element numerical calculation,with the burying depth is certain,as the number of geogrid layers increases,the ultimate drawing resistance at the time of failureincreases nonlinearly.At the same time,the increase in the buried depth ratio also leads to an increase in the uplift load.Considering the cost performance,in actual engineering,the number of layers of the grid should be 1-2 layers.When laying two layers of geogrid,the layer spacing should not be too close,and the length of the geogrid layer is preferably 3 times of the base width..In this paper,the uplift bearing characteristics of shallow foundation of sandy soil foundation are studied by using model test and finite element analysis.The pullout mechanism of reinforced soil and the influence of different reinforcement conditions on the uplift bearing characteristics are analyzed.It provides an effective reference for the theoretical basis of geogrid-reinforced foundation design for transmission lines.