Study On Uplift Mechanism Of Composite Foundation Of Plate And Anchor Cable In Loess Ground

Because of the inherent defects of the existing transmission line foundation,the sinking and destruction of the tower foundation occurred frequently in loess ground.In order to improve the stability and safety of transmission line foundation in loess ground,this paper constructed a joint board cable foundation for transmission lines in loess ground,and obtained the patent of invention,the foundation can give full play to the mechanical characteristics of loess,anchor cable and anchor plate,and can greatly reduce the basic cost.To verify the reliability and rationality of the foundation,in this paper,the anti uplift mechanism and ultimate uplift capacity of joint board cable foundation in loess ground are systematically studied.The innovative research and main conclusions are as follows:(1)A three-dimensional mechanical model for calculating uplift ultimate bearing capacity of anchor plate in loess ground is established,the uplift ultimate bearing capacity of anchor plate in Loess under different buried depth is deduced,and the calculation formula is simplified.The calculation program of Dimensionless coefficient is compiled,the results of the dimensionless coefficient calculated by the program are compared with the results of the dimensionless coefficient of the expanded pile.It is preliminarily concluded that the formula for calculating the uplift capacity of the joint board cable foundation is reasonable.Meanwhile,in the physical and mechanical properties of anchored soil,the cohesive C has the greatest influence on the bearing capacity of the joint board cable foundation.(2)The numerical simulation model for uplift of joint board cable foundation is establied by using FLAC3 D finite difference numerical simulation analysis software.The model simulates and analyzes the uplift mechanism of the joint board cable foundation in shallow and deep buried depth loess ground and the formation and evolution of the fracture surface in the loess ground.It is found that the developmentof plastic failure zone in loess ground is directly controllfed by shear strain,and the influence factors of ultimate uplift bearing capacity of joint board cable foundation are studied,the equivalent relation between square and circular anchor plate is analyzed,it is concluded that the equivalent method for the diameter of the side length is a safer method for the design of the square anchor plate,which provide a basis for equivalent calculation of uplift capacity of anchor plate,the uplift process of anchored soil under deep and shallow buried state is calculated and analyzed,the law of stress and strain and the failure condition of anchored soil under deep and shallow burying are obtained,at the same time,the critical depth ratio of anchored soil is calculated to be around 2.5,which provides an important reference value for the critical depth ratio for the design of the anchorage plate,and the value calculated by the oil pressure meter method can better reflect the anti-pulling capacity of the anchored soil.By using the backstepping cohesive force method,the numerical and theoretical results are corrected.(3)A field experiment device for anchor plate resistance is designed,through field test,displacement with time curve of uplift of anchor plate in loess ground,load with displacement curve,ultimate uplift bearing capacity with buried depth ratio curve,uplift bearing capacity coefficient with buried depth ratio curve,radius of ground rupture surface with buried depth ratio curve are obtained.The anti uplift mechanism of anchor plate is systematically studied,and it is confirmed that the depth ratio has the most important influence on the uplift capacity of anchor plate,which provides the real and accurate data for theoretical calculation,numerical simulation analysis and design and construction of joint board cable foundation in loess ground.The advantages and disadvantages of the oil pressure meter method and the tangent method to calculate the ultimate uplift bearing capacity are analyzed in field anchorage resistance test.It is found that the value of the bearing capacity calculated by the tangent method is quite different from the value measured by the oil pressure meter under the deep buried state.The reasons that affect the deviation of the experimental results are analyzed,it is concluded that the stratified compaction,the measurement error,the discontinuous loading of the load,and the error of theexperiment of the soil sample will cause the inaccuracy of the test results,meanwhile,it is concluded that stratified compaction is the main reason that affects the error of the test results.(4)The theoretical research,numerical simulation and field test results for anchor plate pulling resistance of joint board cable foundation are compared and analyzed,the cause of the error is obtained,the value of uplift bearing capacity calculated by three modified methods respectively are very close,and the error is small,it is proved that the three methods are correct.Achieved the mutual corroboration of the theoretical study,numerical simulation and field test study on uplift of joint board cable foundation anchor plate,the uplift mechanism of joint board cable foundation anchor plate in loess ground is revealed,the uplift ultimate bearing capacity of the anchor plate and formation and evolution law of fracture surface in loess ground are obtained,which provide theoretical support for the design and construction of joint board cable foundation in loess ground.