| Since its invention and gradual use and development in the Neolithic Age,pile foundation has become one of the common forms of deep foundation to this day.When buried in soil as a load-bearing component of the upper structure,the pile foundation can share most of the upper load with the soil on the side of the pile and the soil or rock at the end of the pile with good bearing capacity through its own advantages of high stiffness,thereby reducing its settlement and meeting the basic requirements of the technical specifications for building pile foundations.Unlike other deep foundation forms such as caissons,caissons,and underground continuous walls,pile foundations can be used in various complex geological conditions and meet engineering requirements under different working conditions.They have incomparable applicability and have been widely used in industrial and civil buildings such as high-rise buildings,roadbed engineering,bridge engineering,as well as large-scale foundation projects such as offshore docks,offshore drilling and mining platforms,and nuclear power plants.With the frequent occurrence of earthquakes in recent years,in order to minimize earthquake losses and improve the seismic resistance of buildings,studying the response law of single piles under earthquake action has become the most urgent topic at present.Therefore,this paper uses the DCIEM centrifuge shaking table equipment of the Engineering Mechanics Research Institute of the China Earthquake Administration to carry out centrifuge shaking table model tests of the pile soil superstructure system in the horizontal dry sand site,study the basic law of the dynamic response of the pile foundation under the action of 0.1g constant amplitude sine wave,and then use Open Sees PL and Open Sees finite element platforms to conduct finite element simulation,and analyze and compare the simulation results with the test data obtained from the model test,To verify the reliability and accuracy of finite element simulation.The main research content is as follows:(1)Centrifuge shaking table model test of pile soil superstructure system on a horizontal dry sand site.A pile soil superstructure system model was made using a single pile made of aluminum alloy material and a 2.5 kg mass block.A 0.1g constant amplitude sine wave was input,and the centrifuge shaking table model test was successfully conducted using the DCIEM large-scale centrifuge shaking table equipment.(2)Conduct research and analysis on the final results obtained from the centrifuge shaking table model test of the pile soil superstructure system in a horizontal dry sand site.The acceleration time history curve,pile bending moment time history curve,and pile top displacement time history curve were plotted for the data obtained under the condition of inputting 0.1g constant amplitude sine wave.Research has found that when a 0.1g sine wave is input,as the burial depth decreases,the waveform at different depths remains basically unchanged,and the peak value of acceleration continues to increase,reaching its maximum value at the surface of the soil layer,about twice the amplitude of the input wave,revealing the amplification effect of soil acceleration in dry sand sites;The magnitude of the pile bending moment inside the soil varies with the depth of the soil,reaching its maximum value at the surface of the soil,and the pile bending moment above the surface of the soil is smaller than the pile bending moment at the surface of the soil;After inputting a 0.1g sine wave,there will be a small residual displacement at the top of the pile after the vibration ends.(3)Finite element simulation analysis of the pile soil superstructure system in a horizontal dry sand site.This article uses Open Sees PL finite element simulation software to conduct finite element simulation of centrifuge shaking table model tests.Introduced the process of establishing a finite element model,including parameter settings such as sand constitutive model,shear modulus,internal friction angle,various parameters of the pile,elastic beam column elements used for the pile foundation,hexahedral solid elements used for the soil,and grid boundary conditions;And the reliability of the finite element model was demonstrated by comparing the data obtained from model experiments with various simulated data,including comparison of acceleration results,comparison of final pile bending moment results,and comparison of pile top displacement results.(4)Research on the dynamic p-y curve.This article uses the Open Sees finite element platform to construct a dynamic p-y curve analysis model.By analyzing the p-y element of sandy soil,the load-displacement curves of soil at different depths under seismic action are plotted.By observing the patterns exhibited by the load-displacement curves of soil at different depths,the study analyzes and studies the effects of seismic wave input,The soil at different depths exhibits different characteristics: the load displacement curve of the soil at the surface exhibits strong nonlinear characteristics,mainly due to the low ultimate soil resistance of the soil at the surface;In addition,from the load displacement curve,it can be seen that the curve exhibits significant slip,indicating a significant displacement at the pile soil interface at the soil surface;As the depth increases,the load displacement curve of the soil becomes more linear and the soil becomes closer to an elastic state.In addition,through parameter sensitivity analysis,it was found that the internal friction angle of sand has a significant impact on the p-y element.As the internal friction angle increases,the bending moment of the pile body will increase,while the displacement of the pile body will decrease;The influence of soil weight on the p-y element of sandy soil is relatively small and can be ignored. |
