Study On The Safety Influence Of Bridge Pile Foundation Based On The Shaking Table Test Of Liquefied Soil Layer

A large number of seismic damage investigation results show that the earthquake liquefaction of site soil has a great impact on the bridge pile foundation structure,which is one of the main factors causing the earthquake damage of the bridge pile foundation structure.The in-depth study on the reaction law of soil in the liquefaction process and the damage mechanism of pile foundation has an important practical engineering significance to avoid and reduce the damage of the bridge structure.In view of this,on the basis of the National Natural Science Foundation of China funded project "dynamic interaction shaking table test research of pile soil bridge structure in liquefaction site",this paper uses FLAC3 D software to carry out numerical simulation of single pile test model,and studies the dynamic response of pile soil bridge structure in liquefaction site and the impact of pile safety under different intensity of seismic wave.The main research contents and achievements are as follows:(1)A three-dimensional numerical analysis model of pile-soil-bridge structure in liquefaction site is established.By inputting 0.15 g EI Centro wave and 0.5g EI Centro wave,the dynamic response law of soil and pile in liquefaction site under earthquake is studied,and compared with shaking table model test to verify the correctness and reliability of numerical simulation.(2)The three-dimensional numerical model is established under the condition of non free field,and the change rule of the pore pressure ratio with the different buried depth of the soil is obtained through simulation analysis.The critical pore pressure ratio when the saturated sand is liquefied is proposed as one of the basis for whether the saturated sand is liquefied,which can provide the basis for the rational design and construction of similar bridge pile foundation.(3)Based on the three-dimensional numerical simulation analysis of pile-soilbridge structure,the mechanical response law of bridge pile foundation in liquefied soil site in strong earthquake area is obtained: the bending moment of pile body is the largest near the position of three times of pile diameter below the ground surface;the influence of the change of pile foundation fundamental frequency on the safety of pile foundation under different earthquake intensity is discussed.(4)Based on the results of shaking table model test and numerical simulation analysis,the bending capacity of pile foundation is calculated,and the peak bending moment of pile foundation under different working conditions is obtained,so as to evaluate the safety performance of pile foundation and reveal the key points of seismic design of bridge pile foundation in liquefied soil site.