| As the main foundation form of high-rise building under specific environment conditions,high-strength concrete pile foundation has been widely used in foundation works with the continuous progress of concrete material technology for engineering.The common driven piles and drilling piles have been widely used in the mid-20th century.Due to the rapid development of the construction industry,coastal and offshore structural works have put forward higher requirements for the uplift resistance property of pile foundation,and some design of uplift pile,such as screw pile,rod pile,supporting pile,etc.,has been compiled into specifications.Engineering practice shows that there are some problems in the construction implementation and working methods of uplift piles,such as complicated construction procedures,time-consuming and labor-consuming,and great environmental impact.In order to improve the function and benefit of the uplift pile foundation,a new type of uplift pile foundation is studied in view of the deficiency of the existing uplift pile.This paper is a constituent part of the invention patent"Design Method of Bidirectional Press-spinning Uplift Pile"(Patent No.:ZL 2013 1 0007835.5).Bidirectional press-spinning uplift piles are two piles with spiral outer surface in the opposite direction.After the static pile loading,it is fixed on reinforced concrete caps.When there is a subsequent load,the pile shows better uplift resistance property because the rotation is locked.This paper studies the uplift resistance property of bidirectional press-spinning uplift pile by finite element simulation analysis.The main research contents are as follows:The bearing characteristics of bidirectional press-spinning uplift pile are analyzed by consulting data and drawing on the existing research results.Considering the different form of spiral surface,finite element analysis is carried out to compare the uplift displacement of bidirectional press-spinning uplift pile,supporting pile and ordinary concrete square pile with the relative displacement of pile soil.The transfer law of axial force of bidirectional press-spinning uplift pile is investigated;According to the conventional design method,the uplift resistance bearing capacity of bidirectional press-spinning uplift pile is estimated theoretically.In the application of the existing theory and research methods,the bearing capacity of this new pile foundation is studied.In order to verify the function and effectiveness of the bidirectional press-spinning uplift pile,the finite element simulation is carried out on the premise of ensuring the same amount and load of concrete.The main conclusions of this paper are:The analysis of uplift displacement and relative displacement shows that the uplift resistance property of bidirectional press-spinning uplift pile is larger than that of supporting pile and far larger than that of common concrete square pile;Under the condition of commonly used soil,the transfer law of axial force of bidirectional press-spinning uplift pile is studied.It is concluded that the axial force is the largest at the top of the pile,decreases gradually along the pile buried depth.The axial force at the bottom of the pile is the smallest,and the nonlinear trend of axial force change is not obvious.The law of axial force transfer has nothing to do with cohesion,internal friction angle and density of soil;By comparing with the law of axial force transfer of grouting-formed threaded pile,it is concluded that the lateral resistance of the middle part of the bidirectional press-spinning uplift pile is effectively utilized;It is concluded through theoretical estimation that the uplift bearing capacity of the bidirectional press-spinning uplift pile is 77%higher than that of the supporting pile and 172%higher than that of the ordinary concrete square pile.The analysis shows that the bidirectional press-spinning uplift pile has obvious advantages in its function,environment effect and comprehensive evaluation because of its unique structure. |
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