Single Pile Formation Mechanism And The Simplified Model Of Negative Skin Friction

This article describes different methods of determining single pile's negative friction .The advantages and disadvantages of these methods are discussed. So it is necessary for us to research simple model to determine negative friction.The factors that cause negative friction are discussed. The mechanism of negative friction and the methods decreasing it are also studied. The neutral point and negative friction are determined according technical code for building pile foundation. Load transferring equation is deduced.Based on load transferring concept, the author puts up with a new method which uses double broken line model to calculate negative friction. The author utilizes double broken line model to show relation between friction and displacement around the pile. The article establishes equation about friction and relative displacement according to elastic or plastic condition that soil around or in the tip of the pile lies in. Then we use continuous and border conditions to determine relative displacement. The negative friction and axel force of single pile can be defined based on relative displacement. In the same time we let the relative displacement be zero. The neutral point can also be determined.If the soil around the pile includes several layers, we suppose each layer is well distributed. And we build equation for each layer. Then we get all equations together. Using continuous and border conditions of each layer, the negative friction will be attained. The character of soil which is around an in the tip of the pile varied greatly. We must select different hardening or soft model.Combined with the two actual projects, the author tests the precision of the method. The examples prove that it is accepted, so this way can be tried to use in the actual project.