Study On The Frictional Resistance Of Friction Piles After Deep-filling And Strong Ramming

With the increasingly tense land resources available in the coastal areas and the central and western regions,more and more buildings and structures have been built on newly-found filling layers,soft soil layers and other foundations,resulting in the widespread use of pile foundations.In the body,because the settlement of the soil around the pile is larger than the settlement of the pile under the load,it often leads to the negative friction resistance of the pile,reduces the bearing capacity of the pile,and increases the design and construction costs,even Impact on the safety of the superstructure of the pile foundation.In the actual construction process,the treatment method for under-consolidation fill is mainly used to reduce the impact of the filling on the negative friction resistance of the pile foundation,or to convert the negative friction resistance into a positive friction resistance,thereby increasing the pile foundation.Bearing capacity,and make full use of the advantages of powerful boring to optimize the design of pile foundation and reduce the project cost.However,due to the study on the properties of piles and soils after dynamic compaction,especially the research on the negative friction resistance of the pile foundations after strong ramming,the current norm has no clear stipulations.In this paper,a deep-filling dynamic compaction test project of Liancheng Chemical Plant in Nanchong City,Sichuan Province is carried out to study the friction resistance and other factors of the piles after dynamic compaction.The main tasks of this paper are:(1)Through the study on the negative friction resistance of the pile foundation at the site,a more profound understanding of the law of the axial force of the pile body and the frictional resistance of the pile body is obtained,and the characteristics of the time effect of the position of the neutral point of the pile body are known;(2)Analyze the law of the negative friction resistance of piles with time,and obtain the calculation formula of the change of pull-down load with time.This formula can provide reference for the design of side friction resistance of the approximate engineering;(3)Using the finite element simulation software ABAQUS to establish the site model of the pile foundation,it is verified that the dynamic friction can effectively reduce the negative friction resistance of deep under-consolidated fill;(4)Through the simulation study of different pile top load,different thickness of fill layer and different pile diameters,the law of change of pile friction and pile top settlement is obtained.The calculation formula of the pile down load and the thickness of the filling treatment,the relevant conclusions can provide reference for the design and construction of the pile foundation of the approximate engineering,so as to reduce the engineering cost.