Numerical Simulation Of Optimization Selection In Cyclically Change Diameter Piles

With the advantage of factory prefabrication and quality assurance，pipe piles areincreasingly widely used in today’s foundations of various civil structures, and theproduct is more and more standardized and serialized, in which the prestressedconcrete pipe pile is one of the most widely used type of pile recently, and itsapplication is more and more mature. With the rise of the high-rise, in the fields offoundation engineering, the requiremnet of foundation pile characteristics isdiversified, which results in various kinds of shaped piles accordingly. In recent years,many scholars have studied shaped pile. As a new type of pile, cyclically changediameter pile is still lack of theoretical guidance and engineering practice, studyingon bearing performance and parameter optimization of cyclically change diameterpile has significance on conducting practical engineering application and optimizationdesign of cyclically change diameter pile.Through a theoretical analysis on the existing research results, combined withthe actual, taking the cyclically change diameter pile as the research object, I use thefinite element analysis software to establish the numerical analysis model of thecyclically change diameter pile, through applying vertical load on pile top to researchthe degree of side friction display on the bamboo part and the body part and normalpressure on the variable diameter part, and the contribution degree of lateral frictionin single pile vertical bearing capacity. Comparing with the bearing performance ofthe ordinary prestressed pipe pile, I summaried the vertical bearing mechanism of thecyclically change diameter pile, then analysised the degree of sensitivity of thebearing performance of the cyclically change diameter pile to the importantparameters, such as the length of the variable diameter part and the center distance ofthe bamboo part, to provide technical support for the optimization selection. Themain conclusions are as follows:（1）The cyclically change diameter pile can save material consumption, at thesame time, it can improve the vertical bearing capacity and reduce the settlementdeformation significantly. Under the vertical loads, the support function from the soil that in the area of konb A apparently impoves the contribution of the single sidefriction resistance to the vertical bearing capacity, which give expression to the kindof end resistance from the variable diameter part.（2）The center distance of the bamboo part is very important to the performanceof side friction in the area under it. The optimization of the center distance of thebamboo part should consider the construction factors, meanwhile ensure theperformance of side friction in the area on and under it.（3）The length of the bamboo part influences the pile side area and the endresistance under the knob A, so it influences the pile’s vertical bearing capacity, and ithas a apparent influence on the side resistance.（4）Under the vertical loads, interaction between pile and soil is complex. Theside resistance of the bamboo part shows a "anti C" shape and the pile body partshows S shape.