Model Test Study On Vibration Response Characteristics Of Screw Pile

As a complex pile foundation with complicated structure,screw pile has the advantages of less construction land,faster construction speed,effective shortening of construction period,pollution-free environment and flexible construction mode.It has been widely used in civil engineering at present,such as photovoltaic support foundation,pit wall and slope support,offshore structure cable and transmission line tower foundation.The state has strict restrictions on the vibration frequency and displacement of foundations in some major projects,and there is still lack of relevant experiments and related theoretical studies.Therefore,it is of great practical significance to study the vibration response characteristics of screw pile foundation under dynamic loading.In this thesis,the screw pile foundation is taken as the research object,and the dynamic response characteristics of screw piles are investigated using the combination of theoretical analysis and model experiments,the specific contents are as follows:1.Through the equivalent treatment of the pile model,the screw pile is simplified into a variable cross-section pile,and both the pile and the soil are regarded as viscoelastic.A differential vibration equation of screw pile-soil interaction is established,and a semi-analytical solution is obtained.Then,the influence of the geometric parameters of the screw pile and the changes of the pile damping on the longitudinal vibration response characteristics of the screw pile is analyzed using the given equations.2.Using the sand box model test method,the self-made model test system of pile-soil dynamic interaction is made of three parts:the horizontal excitation system,the data acquisition and analysis system,sandbox.The nonlinear vibration response characteristics of steel pipe screw single pile and straight pile in sand are studied under longitudinal excitation.Then the effects of length-to-diameter ratio?L/D?,blade spacing-width ratio?S/D?,blade extension ratio?D₀/D?,excitation load amplitude?F₀?on the horizontal vibration response of single pile model are analyzed.3.The transverse dynamic response of screw piles will be affected by the geometry of the pile and the properties of the soil,using a self-made transverse vibration model test platform,the transverse vibration response characteristics of screw pile models with different materials and geometric structures in two soils are studied.The effects of the geometric parameters of the pile body?such as the blade spacing-width ratio S/D,blade extension ratio D₀/D?,the load amplitude?F₀?and the vibration frequency?f?on the transverse dynamic response of the pile model are analyzed.For comparison,the transverse dynamic response characteristics of the straight pile are also analyzed.