Research Of Uplift Mechanism And Durability Of Bored Pile With Enlarged Bottom

Bored pile with enlarged bottom is a new type of pile used in engineering, which has a higher capacity compared to traditional piles. It has been widely used in the large municipal facilities, large span bridges, high-rise buildings and other structure in recent years.Up to now, the researches of Piles with enlarged bottom can’tcatch the level of application. The tradition measures of ensuring vertical bearing capacity of piles with enlarged bottom are the field loading tests. But it costs too much time and funds, and also difficult to gain the whole Q-S curve. So it is necessary to discuss the bearing character of the enlarged bottom piles and find out a more reasonable method of numerical simulation to ensure vertical bearing capacity of the pile. In this paper the FEM software ANSYS is used to model the pile-soil interaction and in-depth analyze bearing character of the enlarged bottom pile. The main research contents in this paper are as follows:(1) With the plane element, the axisymmetric model is established by ANSYS software, in witch, the contact elements are set between the pile and soil to simulate the separation and sliding. And then simulate the working mechanism of the pile under uplifting load.(2) The mechanism of enlarged bottom piles, the load transmission behavior and the failure mechanism of soil are analyzed. Then main factors affecting the bearing capacity and the uplift mechanism of pile in different kinds of soil are discussed.(3) The chloride-induced corrosion mechanism of bored pile under coastal environment was pointed out, a model of chloride ions transport in the reamed bored pile was established and the corresponding durability limit states was also proposed, according to the parameter in project, life prediction methods for different water-cement ratio, the thickness of the protective layer, the exposed region of the concrete failure probability is analyzed and calculated. some concrete resistance to chloride ion penetration enhancing measures was then put forward.(4) Finally, the mechanism of piles exposed to freeze-thaw cycles was discussed, which contains its failure mechanism and failure modes. Some measures were also proposed to prevent its damage.