The Analysis For The Negative Frictional Force And Bearing Capacity Of Pile Foundations In A Dredging Site With Consideration Of Self-weight Consolidation

With the rapid economy development,there are more and more hydraulic fill projects in coastal areas.However,due to the characteristics of high compression and low permeability,there will be a large settlement after the completion of the hydraulic fill project,which leads a great threat to the safety and reliability of the project.Because of its low permeability,it always takes a long time for its consolidation under the self-weight and external load in the hydraulic fill site.And it will certainly have a great impact on the bearing capacity,especially the negative friction of pile foundation in the site.For the negative friction of pile foundation in this site,scholars have made great efforts to research by various methods and obtain some numerical and analytical solutions,which change with the depth.However,the frictional resistance is actually a variable which changes with time and depth at the same time.At present,there are few analytical solutions which can take the change with time and depth into consideration at the same time.In this paper,the interaction model of pile and soil is established by combining the solution of double-layer foundation and layered foundation with the stress analysis of pile.The analytical solutions of the negative frictional resistance in double-layer foundation and layered foundation with the change of depth and time under different conditions are obtained.This paper analysis the factors which influence the negative frictional resistance of the pile foundation,and the significant conclusions for the project are obtained.The main research contents and innovations are summarized as:(1)For the method of negative frictional resistance calculation of pile foundation,this paper has summarized and analyzed.And the method of load transfer analysis is adopted.The load transfer function is an improved bilinear function,which uses the relative displacement between pile and soil to connect the consolidation process of the foundation with the development process of bearing capacity of the pile.Based on the element stress analysis,the process of pile and soil interaction is simulated,and the governing equation of the negative friction of pile foundation is established.(2)Due to the influence of self-weight stress,there is still consolidation settlement after construction,which will have a negative impaction on the bearing capacity of pile foundation.Based on the one-dimensional consolidation solution in double-layered foundation,the consolidation settlement solution of self-weight stress of hydraulic fill on double-layer ground is solved in this paper.The interaction model and governing equation of pile and soil under the double-layered foundation are established.According to the analysis of the possible conditions in the actual project,the analytical solutions of the relative displacement between pile and soil,the frictional resistance and the axial force of pile under different conditions are obtained,and the calculation method of the neutral point at different times is given.(3)Double-layered foundation is a simplistically equivalent form of actual foundation,which is distributed in layers.In this paper,the settlement solution of layered ground under the influence of hydraulic fill self-weight stress is solved on the basis of one-dimensional consolidation solution of any layer foundation under variable load.The interaction model and governing equation of pile and soil on layered foundation are established.Finally,the analytical solutions of the relative displacement between pile and soil,the frictional force and the axial force are obtained,and the determination method of the neutral point position at different times is given.(4)In order to verify the correctness of the solution,this paper compares the analytical solution of double-layered foundation and layered foundation with the measured data.(5)The bearing capacity of pile foundation in hydraulic fill site will be affected by many factors.This paper analyzes the time factor,the load on the top of the pile,the diameter of the pile and the degree of consolidation,and the influence rules of different factors on the bearing capacity of piles are obtained.