Study On Vertical Bearing Capacity Test And Stress Characteristics Of Composite Dredged Pile Foundation With Expanded Bottom Pile-cap

Based on the belled pile foundation with advantages of high bearing capacity,large rigidity of pile body,able to withstand large vertical loads and the small settlement,this paper,by the application it to the theory of reducing-subsidence,integrates their characteristics.Thus,the advantages of the belled pile foundation can be fully utilized,and the reducing-subsidence foundation can be effectively played in the leading role,in order to rationally control the reducing-subsidence of buildings.In this paper,as the research background of the theory of reducing subsidence pile foundation,through the laboratory model experiments,and combined with the finite element numerical simulation analysis,the vertical bearing capacity of the belled pile-pile cap is preliminarily studied.This paper mainly researches,as followings:1.The laboratory model experiments are employed to establish a variety of analysis working condition,make the single pile cap,three pile caps,four pile caps and six pile caps composed of the straight pile and belled pile,respectively,and simulates deformation by force process of all the work condition foundation under vertical load.Through the analysis of the test data,the vertical bearing capacity performance and influence law of the belled pile-pile cap are studied.2.Through the finite element software,a variety of analysis conditions are stimulated,the single pile cap,three pile caps and four pile caps composed of straight pile and belled pile are respectively established and the deformation by force process of all the work condition foundation under vertical load is stimulated.Through the analysis of the numerical simulation results,the vertical bearing capacity performance and influence law of the belled pile-pile cap are studied..3.Summarize the calculation methods of pile foundation settlement and the influence factors of its settlement.Combined with the specific engineering case,the settlement calculation method of the belled pile group is analyzed and researched.Based on laboratory model tests and numerical simulation analysis,it can be known that:1.For the load-bearing deformation of a single pile under different working conditions,the settlement of the pile tip of the expanded bottom pile is smaller than that of the straight pile,and the load holding performance is higher;The bearing capacity of extended bottom pile cap foundation is higher than that of straight pile foundation.Due to the presence of enlarged head,the size of pile tip is larger than that of straight pile,so the compression range of expanded bottom pile on the foundation soil under the pile is also larger than that of straight pile.2.For the load-bearing deformation process of pile group bearing platform under different working conditions,with the increase of external load,the bearing performance of expanded bottom pile is obviously better than that of straight pile,and the expanded bottom pile has more bearing performance safety reserves than the straight pile.With the increase of external load,the pile subsoil is continuously compressed and compacted,and the stress at the pile tip is better dispersed due to the existence of the expanded head,so the pile tip resistance of the expanded bottom pile is slightly smaller than that of the straight pile.