Study On The Seismic Behavior Of Single Pile Foundation Considering The Influence Of Pile-soil Gap

In recent years,the frequent occurrence of big earthquakes in the word has brought huge losses to people.However,with the development of today's society,the population is becoming more and more concentrated,and the building structure is getting larger and larger.Once the earthquake disaster occurs,it will bring more damage.After the investigation and analysis of the earthquake disaster accident,it is found that the damage of the building structure foundation cannot be ignored,and the research on the seismic performance of pile foundation,as the most widely used foundation form,is of great significance to the research on the seismic design and failure mechanism of the structure.In the process of strong earthquake,due to the stress concentration,the soil around the pile will produce a large nonlinear stress field and displacement field,resulting in the separation of the pile-soil interface,and the dynamic response of the pile foundation will also show strong nonlinear.At this point,the linear elastic assumption of pile foundation,soil and pile-soil contact can no longer meet the seismic demand.Therefore,this paper focuses on the study of the working state of the underground part of the pile foundation,the response of the soil around the pile and the site effect.The main contents of this paper are as follows:(1)The research status and development of pile-soil interaction at home and abroad are briefly summarized,and the characteristics of each pile-soil interaction model are reviewed.(2)The part of pile-soil interaction in the OpenSees calculation platform is introduced in detail,including the nonlinear Winkler foundation beam model,the realization method of the dynamic p-y curve model,and the material constitutive relationship involved in the model.The results show that the two pile-soil interaction models can be well implemented on the OpenSees calculation platform.(3)Based on the OpenSees calculation platform,the numerical analysis model of nonlinear clearance between single pile and soil was established,and the accuracy of the model was verified by comparing with the experimental results in literature.On this basis,the interaction between single pile and soil with different soil constraints is considered,and the seismic performance of single pile foundation considering the pile-soil clearance is explored based on the development of pile-soil gap,the main indexes of pile displacement,shear force and plastic hinge length.(4)Numerical analysis was used to construct the pile-soil dynamic interaction model with consideration of pile-soil nonlinear contact single pile-soil dynamic interaction model and the pile-soil nonlinear contact single pile-soil dynamic interaction model without consideration of pile-soil nonlinear contact single pile-soil dynamic interaction model,and to compare and study the working state of pile foundation,free field field effect and soil deformation around piles in seismic action of the two models.It is found that considering the non-linear contact between pile and soil,the stiffness of the model decreases and the displacement of pile increases.