Test And Application Research On Pullout Resistance Of Uplift Piles In Complex Sites

On the basis of summarizing the research results of the predecessors,after the theoretical analysis of the bearing mechanism of the piles,combined with the test results of the uplift bearing capacity of a single pile in the Zhengzhou project,the pullout resistance of the uplift piles under the complex site is insufficient.In the case of the construction of the pile end pile side,the post-grouting and other grouting techniques are used to improve the pullout resistance of the single pile.The finite element simulation software was used to analyze the bearing characteristics of unpracked and post-grouted uplift piles,mainly in the following aspects:(1)Taking the engineering example as the background,the complexity of the site soil and the application of the uplift pile in the complex site are explained.Summarize the research status of uplift piles,and briefly introduce the application,design and construction points of uplift piles.The bearing capacity characteristics and failure modes of uplift piles under vertical load are analyzed theoretically.The calculation formulas of ultimate bearing capacity of single piles are analyzed to study various factors affecting the bearing capacity of uplift piles.Calculation method of bearing behavior and bearing capacity of piles and compression piles.(2)Based on the test results of the uplift bearing capacity of single piles in a project in Zhengzhou,through the research and test data,the reasons for the insufficient pullout resistance of the uplift piles are analyzed.(3)In view of the insufficient pullout resistance of the uplift piles,the measures to improve the pullout resistance of the uplift piles are analyzed from the aspects of design angle,reduction of mud thickness and post-grouting.This paper introduces the grouting test after the uplift pile,analyzes the curve fitting of the post grouting pile,and analyzes the empirical formula of the post grouting test result,which shows that reducing the grouting amount can also make the bearing capacity of the uplift pile meet the requirements.The formula shows the reduction of pile side frictional resistance and pile anchoring force and the reinforcement after grouting in the presence of mud and sediment.It also shows that the effect of post-grouting on the pile end is obvious.(4)The finite element software ABAQUS was used to simulate the un-grouted and post-grouted uplift piles,and the simulation results were compared with the actual test results.The variation of the bearing capacity of uplift piles under different grouting parameters is simulated and analyzed,which proves that the post grouting,especially the post-grouting of the pile end,can significantly improve the bearing capacity of the pile.