| Transmission Tower foundation is the most important load-bearing structure in transmission line engineering.The selection and design optimization of foundation type is the premise to ensure the safety and economy of transmission line operation,and is also one of the important research directions in the field of transmission engineering.For transmission line engineering crossing frozen soil geology,there are many complexities in tower foundation design.The difficulty of tower foundation design lies in ensuring the stability of frozen soil foundation.Frozen soil has great frost heaving effect and obvious frost heaving damage to buildings.Tower foundation is prone to generate large tangential frost heaving force in frozen soil,which will produce freezing and pulling effect on the foundation,thus affecting the stability of the foundation.For transmission tower foundations in seasonally frozen soil areas,frost heaving and thawing of surrounding soil will lead to freezing of transmission line foundations,which will seriously affect the safe operation of transmission lines.Therefore,the selection and optimal design of seasonal frozen soil foundation have important engineering significance and application value for ensuring the safe operation of transmission lines.Based on the 220kV transmission line of Huolinhe River in Inner Mongolia,according to the geological data of frost heaving tower in the geological survey data,the finite element model of the interaction between the straight column expansion plate foundation and the cone column expansion plate foundation of the transmission tower and the surrounding frost heaving soil is established by ABAQUS finite element software,and the frost heaving resistance of the two types of expansion plate foundations is analyzed and compared.Firstly,according to the characteristics of seasonal frozen soil,the paper comprehensively considers the heat conduction in soil and the actual temperature field distribution of tower foundation,calculates and analyzes the temperature field around the foundation,and verifies the correctness of the temperature field.According to the analysis of temperature field,the section size and height of tower foundation column are determined.Then,the temperature field calculated by temperature simulation is applied to the structural model as a predefined field.Through the relationship between temperature and frost heaving coefficient of soil,the coupling field of temperature,stress and deformation under frost heaving condition is established.Through frost heaving coupling field,comparative analysis of frozen pullout of straight column foundation and cone column foundation with different radius expansion plates is carried out.The results show that the frost heaving performance of soil is closely related to temperature,the frost heaving displacement of soil decreases continuously along the depth of soil,and the frost heaving stress is positively related to the frost heaving displacement of soil.The frost heaving resistance of cone column foundation is obviously better than that of straight column foundation.When the column height of straight column foundation is 2.4m,the expansion plate radius is at least 2m,which can offset the frost heaving force.At this time,cone column expansion plate foundation can completely offset the frost heaving force at 1.5m.Finally,the uplift bearing capacity of the foundation is simulated and the displacement load curves of each model are obtained.The uplift bearing capacity differences of different sizes and types are analyzed and compared to verify that the foundation meets the uplift bearing capacity requirements.The research results of this paper will provide reference for the design of straight column expansion plate foundation and cone column expansion plate foundation under the frost heaving tower position of the project. |
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