Pile-soil-complex Structure Shaking Table Test And Numerical Simulation And Study On Related Parameter Of Pile-soil

The urban traffic congestion promotes the underground space development andutilization, transport junction projects are developed rapidly. The seismic behavior andsecurity of these projects attract more and more attention both in academic andengineering circles.A shaking table model test of large-scale pile-soil-structure interaction isaccomplished on the transport junction of Tianjin station, and the soil-structuredynamic interaction regulation is revealed. Furthermore, dynamic P-Y curve is studiedwhich based on the shaking table test. The rational value range of contact stiffnessfactor between pile and soil is explored, and numerical simulation of the shaking tabletest is carried out which reproduces the process of the test, comparative analysis isperformed between simulation data and testing data, the rationality of the numericalsimulation and test are verified by each other. The major work and conclusions of thisdissertation are as follows.（1）Typical seven transverse frames of Tianjin transport junction are selected asthe object of the test, which contain two layers above-ground structures, three layersunderground structures, and group piles foundation. The seismic behavior underuniaxial seismic load is studied. Micro-concrete is adopted to make the station model;the model soil is designed according to the dominant period; three kinds of boundaryare designed in the rigid soil box and respective good effect is verified, Taft wave,Tianjin wave and artificial seismic wave are selected to conduct several loadingconditions from small earthquake to large earthquake. The results show that: theacceleration amplification coefficient of pile and soil is more than one under smallearthquake, while it reduces obviously in the big quake, and the existence of pilesreduces the amplification coefficient. The maximum displacement and strainamplitude of the pile, also the contact pressure between pile and soil increase as theseismic magnitude increases. The deformation becomes bigger as the pile’s heightincreases, and the strain of the pile in the middle part is larger than the two tips, whilethe contact pressure of the middle part increases significantly comparing with the twoends of the pile. The maximum story drift angles of the aboveground and undergroundstructures meet the code requirement after large earthquake. （2）According to the data of the shaking table test, the dynamic P-Y curves ofpile-soil under sine wave are obtained through the theory of elastic foundation.Furthermore, the distribution rules of damping and spring stiffness coefficient atdifferent depths during different periods are calculated. It is shown that both thedamping and the spring coefficient increase with the increase of the pile depth, theincreasing amplitude is more obviously at the lower part of the pile. Due to theinfluence of bottom raft, damping and spring stiffness coefficient distribution alongthe pile can approximately be taken as piecewise linearization, and the turning point isat about the1/3length from the top of the pile. And with the continuous vibration,damping is stable along the pile except slight increase at the bottom of the pile whilethe spring stiffness coefficient decreases continuously, and the decrease magnitude isexpanded as the depth increases.（3）The interface contact problems of pile-soil interaction are studied. Considerthe prototype (also model) single pile of the Tianjin transport junction and soil intoplane strain problem, the rational value range of contact stiffness factor between pileand soil based on penalty function is explored. The study shows that when adoptlinear elastic model to simulate soil, the depth of the underlying element decreasesand soil stiffness increases cause the contact stiffness increase, then rational valuerange of contact stiffness factor (FKN) decreases. The overall value is within the frontone-third of the suggestion range (0.01-10) by the program. If choose elastic-plasticmodel to simulate soil, the stiffness factor should be magnify100times compares tothe elastic model when the soil still in elastic deformation stage. When the soil bearsbig force and into plastic deformation stage，the value range of stiffness factor relatesto the plastic strain range of the soil, and reduces as the horizontal load increases.（4）2D finite element contact model is established and acceleration resultsbetween numerical simulation and test are compared under different waves anddifferent magnitude. The results show that: the waveform of acceleration timehistories curve perform similarity between simulation and test. The peak accelerationof the measuring points shows the same rules as the magnitude and height changes.Compare with the pile, the2D contact model can be better reflects the accelerationresponse of the underground structure. The simulative results agree well with theexperimental ones under small earthquake, but the deviation increases when it suffersmedium earthquake.