Research And Application Of Pile-end And Pile-side Post-Grouting Technology Of The West Control Tower In Beijing New Airport

The Pile-end and Pile-side Post-Grouting Technology in geotechnical engineering is a new achievement in recent years.The technology has been developing in practice,and it has overcome the influence of traditional bored pile construction technology.The bearing capacity of foundation piles that use this new technology will not be reduced due to mud and sediment,and the Post-Grouting-Pile is widely popularized and applied because of its excellent mechanical stability.Therefore,this technology has great research value and engineering significance.Based on the West Tower Project of Beijing new airport,the design of post-grouting scheme and static load test of post-grouting pile are introduced in detail.According to the concrete engineering practice and the mechanism analysis of the post-grouting,through the static load test of the site test pile and the finite difference simulation method,the technology is studied in depth and concretely.The following conclusions are obtained:The Pile-end and Pile-side Post-Grouting Technology can reinforce the base pile.Under the action of high pressure grouting pump,the cement slurry permeates,presses and cleavages the soil of the pile side pile,and the cement slurry will also have physical and chemical reaction with the soil around the pile.Therefore,the post grouting reinforced the pile side and the pile end soil,improving the lateral friction resistance and the end resistance of the foundation pile,thus enhancing the overall bearing capacity of the foundation pile.The static load test of the post grouting pile shows that the ultimate bearing capacity of the pile satisfies the design requirements.Due to the limitation of field test piles,the test piles do not have no-grouting piles as contrast.The ultimate bearing capacity of the non-grouting pile is estimated by the method provided by the "technical specification for building pile foundation"(JGJ 94-2008),which is comparable with the field test.After grouting,the total side resistance of the pile is 0.99 times higher,the end resistance is 0.33 times higher,the ultimate bearing capacity is increased by 0.9 times,and the ultimate bearing capacity of the non-grouting pile is less than the design value,which shows that the design of the pile test is reasonable.Through FLAC3 D numerical simulation,it is found that the displacement field of pile and soil is obviously different before and after grouting,and the displacement field of grouting pile is better than that of non-grouting pile.Because the post grouting effect of grouting and solids around the pile can transfer the load of pile top to the deeper extent of the soil.Under the same load,the settlement of grouting piles is smaller than that of non-grouting piles,and the lateral resistance of piles is also very large.The grouting pile and the non-grouting pile are all friction piles.Although the simulation results have error with the field measurement,the reason lies in the idealization of numerical simulation and the discreteness of geotechnical engineering,but the general trend of numerical simulation is close to the measured data,which can be used as a reference for the engineering practice.