Experimental Study On Vertical Bearing Capacity Of Post Grouting Bored Pile

Bored piles are the most common foundation form used in buildings at present.Due to the influence of traditional bored pile construction technology level,construction equipment,construction technology and other factors,during the construction of bored piles,there will be pile end sediment,pile side mud,stress relaxation around the pile during the hole forming process,and pile body.Concrete quality and other problems,the bearing capacity of the pile foundation is difficult to effectively exert.Post-grouting technology can increase the strength of the soil at the pile end and improve the characteristics of the pile-soil interface,thereby increasing the bearing capacity of the pile foundation and reducing settlement.In this paper,starting from the bearing characteristics of post-grouting bored-insitu piles and the action mechanism of grout,and relying on the pile foundation engineering of a museum project in Henan Province,the post-grouting bored-in-situ piles are analyzed by means of theoretical analysis,field tests and finite element numerical simulation.In-depth study of the load-bearing properties under vertical loading.The main work and research results of this paper are as follows:(1)By analyzing the vertical load transfer mechanism and slurry action mechanism of post grouting pile,the influencing factors of post grouting single pile bearing capacity and the enhancement effect of slurry on pile end and pile side resistance are summarized,and the influence law of post grouting on single pile bearing characteristics is revealed.(2)Through the field static load test,the bearing properties of the post-grouting pile and the non-grouting pile with two different pile diameters and pile lengths were compared."Steep drop type" becomes "slow change type",and the bearing performance of single pile is greatly improved.(3)Post grouting improves the strength of soil at the pile end,effectively improves the characteristics of pile-soil interface,and greatly improves the exertion level of pile end resistance and pile side resistance.After processing and analyzing the data collected from the field static load test,it is obtained that the percentage of load borne by the pile end and pile side resistance changes before and after grouting.Compared with the non grouting pile,the percentage of pile end resistance in the pile top load is increased by about 10%,and the asynchronous performance of pile end resistance and pile side resistance is improved.(4)The finite element software is used to construct the test pile model for numerical simulation,and the simulation results are compared with the measured results of field static load test to verify the correctness of the modeling.Then the finite element numerical simulation of pile foundations at different grouting parts is carried out.The simulation results show that the ultimate bearing capacity of single pile of pile end grouting,pile side grouting and pile end pile side combined grouting is 37.4%,48.9% and 65.7% higher than that of non grouting pile respectively.(5)The finite element numerical simulation of the bearing behavior of post grouting pile is carried out by changing the parameters such as pile length,pile end consolidated body diameter and grouting volume.The simulation results show that when the pile length is 35 m,the post grouting has the best effect on improving the bearing capacity of pile foundation;The increase of the diameter of the consolidated body at the pile end or the amount of grouting can effectively improve the bearing capacity of a single pile within a certain range.When it exceeds this range,the effect of improving the bearing capacity will be significantly weakened.