Study On Liquefaction Of High-piled Wharf Foundation Under Earthquake Action And Its Influence On Structural Safety Performance

The impact of site liquefaction under earthquakes on buildings supported by pile foundations cannot be ignored.However,due to the irregularity and discontinuous nature of the soil itself and the complexity of the dynamic interaction mechanism between piles and soils,the current liquefaction discriminating methods of different national standards are mainly empirical methods and consider the influencing factors of liquefaction incompletly or in different ways,so the discrimination results judged by different standards are different,and even very different.Accurately judging the liquefaction of soil is very important for the dock slope and structural stability.Therefore,the main research work and conclusions of this paper are as follows:(1)Summarize the typical cases and related research results of the pile foundation damages caused by earthquakes and liquefaction at home and abroad in recent years.Summarize the stress modes and common damage forms of the high piled piers under earthquakes.One of the most important and most damaging damage methods is that the large displacement of the foundation caused by liquefaction produces a large horizontal load on the pile foundation,which can easily cause the bending or shear failure of the pile foundation.(2)A numerical model for the joint action of the wharf structure and bank slope was established.After analyzing and verifying the reliability of the model,the numerical calculation with a large number of variable parameters shows that the liquefaction of the high-piled wharf foundation affects the structural safety performance.The main failure mode is the failure of pile foundation caused by lateral deformation of loose foundation soil.(3)The methods of judging the liquefaction of foundation and the factors considered in seismic design standards of China,the United States,and Europe are analyzed and compared.Based on the comparison and analysis of numerical models for determining the liquefaction criterion based on whether the excess pore water pressure ratio of the foundation soil exceeds 1 or not,the liquefaction calculation differences in the seismic design standards in countries such as China,the United States,and Europe are systematically studied.(4)The actual liquefaction failure pattern and its influence on the structure were obtained through actual engineering case analysis.It was found that the maximum bending moment on the pile was found at the pile head with the elastic constitutive soil model,but the calculation of the liquefaction effect and with the elasto-plastic soil constitutive model showed that the maximum bending moment of the pile may appears under the soil.Comparing the plastic constitutive model of soil with the liquefied constitutive model of soil,the results show that compared with the elasto-plastic model,restrain of the soil in the liquefied constitutive model is more weak.The horizontal shear force of the body is increased,so the internal force of the pile considering liquefaction is greater,and the position of the restraining point is lower.Under the same conditions,the same diameter of the pile foundation structure after the liquefaction of the foundation occurs,the displacement of the full-straight piles structure is relatively large,but the displacement of the fork pile structure is relatively small.