Analysis On The Bearing Characteristics Of Steel Pipe Screw Pile And Of Pile-soil Interaction

Some temporary underground foundations will inevitably be used for the construction,fixing and repairing of the transmission line tower,or in the construction process of the UHV/EHV overhead transmission line.Nowadays,the underground foundation is dominated by reinforced concrete structure with complex construction procedure.However,there are many disadvantages for this kind of foundation,such as long construction period,damage to the environment,non-recyclability,and the vulnerability to the seasons or weather.Due to its simple structure,prompt construction,friendliness to environment and applicability to construction under various climate and geological conditions,the screw pile foundation is widely applied to a wide range of soil conditions.Nonetheless,the current research on screw pile foundation has been mainly focused on the axial bearing properties and failure mechanism of the screw pile.How to improve the structure of the screw pile and realize the multi-function of the screw pile on the premise of not reducing its bearing capacity the design of the structure and needs to be further investigated.Taking the screw pile foundation as the research object,the bearing capacity of the screw pile structure and the pile-soil interaction rules are explored by combining theoretical analysis,finite element simulation and experimental research.The main research contents include:?1?In accordance with the theory of plastic slip failure,the calculation method of axial bearing capacity of the screw pile structure under uplift and downward loading is presented.Meanwhile,the calculation method of screw pitch in the design of pile type parameters is also given.From the point of view of the microelement,the relationship between the geometric structure and the mechanics of the spiral blade is clarified,and the strength requirements of the structure of the screw pile at compression and tension are obtained.?In Chapter 2??2?The model of screw pile was made.A test device for loading the structure of the screw pile with a fast loading method was designed in the research,which can measure the bearing capacity.The influence of the ratio of helix-to-shaft diameter?D/d?,the blade number,the blade form and the loading forms on the bearing capacity of screw piles were experimentally investigated by model loading tests.In addition,the soil pressure box was buried in the sand box,and the stress distribution of the soil around the pile was collected by the TST3822 static strain test and analysis system.Moreover,the interaction rules between the screw pile structure and soil under the different loadings are also elaborated by analyzing the stress diffusion of the soil retractable blade.?In Chapter 3??3?Bearing characteristics of the screw piles and the pile-soil interaction are studied by means of the nonlinear finite element?FE?analysis with ABAQUS.At the same time,the influence of pile geometry and loading methods on axial and oblique bearing capacity of steel pipe screw pile is discussed in detail.?In Chapter 4??4?Based on the above research results and taking into account the deficiencies of the existing screw pile structures,a kind of novel steel screw pile structure with telescopic blades is proposed in this thesis.Through the FE simulation and experimental research,the effects of blade expansion ratio(h/h_max)and blade arrangements on the bearing characteristics of steel pipe screw piles are investigated,and the stress diffusion rules of soil around pile are also given.The research will provide theoretical guidance on the multifunctional design and engineering application of the screw pile foundations.?In Chapter 5?...