Deformation Characteristics Of Multi-story Building Pile-raft Foundation In Dredger Fill Area

The dredger soil has the characteristics of high compressibility,large natural water content,small permeability coefficient and large void ratio.Therefore,when constructing multi-story buildings on dredger soil,various engineering problems such as insufficient bearing capacity and excessive building settlement may occur.This article takes the pile-raft foundation of a multi-storey building in the Caofeidian blow-filled land area as the research object.Through the combination of on-site monitoring,numerical simulation and theoretical analysis,the law of settlement and deformation of the multi-story building pile-raft foundation during construction is studied.Firstly,the domestic and international researches about piled raft foundation and dredger ground treatment methods are summarized.And the bearing mechanism,settlement calculation method,pile-soil interaction and raft analysis of piled raft foundation are also summarized.Based on the existing mechanism,the pile-raft foundation of a multi-story building in the Caofeidian landfill area was used as the test site.The settlement of piles,pore water pressure and horizontal displacement were monitored on site,and the deformation characteristics of piled raft foundation of multi-story building was summarized.Secondly,the PLAXIS 3D finite element software was used to simulate the test project.The simulated results were compared with the monitored values to verify the effectiveness of the numerical simulation.The deformation mechanism of the two different types of foundations,raft foundation and pile-raft foundation are studied,and the role of the pile is further explored.Finally,the influence of pile length,pile diameter,pile body inclination angle,raft thickness,loading rate,and long and short piles on the settlement of pile-raft foundation was studied by numerical simulation.The results show that the numerical simulation results are in good agreement with the monitoring values.PLAXIS 3D finite element software is proved to be able to well simulate the construction process of multi-story building pile-raft foundation.The settlement of pileraft foundation is much smaller than that of raft foundation.Therefore,by using the piled raft foundation,the settlement of the building during construction can be effectively controlled.From the simulation results,95% of the load is born by the pile body in the pile raft foundation,and the load is transmitted to the bearing layer which has higher load capacity and lower compressibility.Consequently,the total settlement of the foundation is significantly reduced.Within a reasonable length,the increase in pile length can significantly reduce the deformation of the foundation,and the settlement will not increase when the pile is inclined at a small angle.Reasonable arrangement of long and short piles can effectively reduce the differential settlement of buildings.