Study On Engineering Characteristics And Detection Analysis Methods Of Uplift Pile In Shenzhen City

In recent years,with the rapid development of infrastructure construction,the uplift piles have been widely used.However,the theoretical analysis and research of uplift piles are far behind the practical engineering practice.Now stage design calculation method of uplift piles is adapted from compressive piles,it is necessary to study the load transfer mechanism and design method of the uplift piles.For this reason,this paper is based on field measurement,theoretical deduction and numerical simulation to study the load transfer mechanism of uplift piles.The main research work and conclusions are as follows:(1)The uplift static lode test result of three piles in Shenzhen region were analyzed.It showed that the U-? curve is the slow variant,the axial force of pile by custom uplift test method pass down descending along the pile,and that of piles by self-balanced test method was opposite completely.The shaft friction resistance of soil around pile played a role at the first loading and increase with depth.(2)Load transfer method was used to calculate the bearing capacity and deformation of uplift pile tested by conventional method and self-balanced testing method.While in this thesis,the load transfer function was expressed by the unified tri-linear curve model which has two advantages.The first one is that the expressions are simplified and easier to use due to the load transfer models of traditional uplift pile and self-balanced pile are all unified by the tri-linear curve model.Furthermore,the tri-linear curve could fit the tested data better.The load transfer method was solved by the modified method for harmony of displacement.Different convergence criterions were adopted to solve in traditional uplift pile and self-balanced pile.The modified method for harmony of displacement could research the bearing characterizes of uplift pile under various loading levels,especially,which also can obtain enough precision when the displacement of self-balanced pile head is very small.The proposed approaches were verified by the measured data.The results indicated that the numerical and measured results were in good agreement,and the proposed unified tri-linear curve model and modified method for harmony of displacement are valid and correct.(3)The ABAQUS software was used to simulate the test uplift pile under the project conditions,the error between simulation results and experimental data was within the acceptable range,it showed that ABAQUS is feasible to simulate the pile.Then,the ABAQUS software was used to make numerical simulation to traditional uplift pile and self balance uplift pile to analyze the Q-S curve,axial force and pile friction distribution under the two test methods.Through comparative analysis,the difference of the two testing methods was the friction's order of play,axial force distribution also differ due to the loading position,using self-balanced method instead of the traditional uplift test method is feasible.In general,this thesis focused on the stress characteristics of uplift pile and studied on the calculation method of uplift pile design.The results above may provide some valuable references for the engineering design.