Research On Mechanical Characteristic Of Bridge Bored Piles Using Pile-end Post-grouting In Typical Loess Region

Currently, the bored pile technology has been widely used in high-rise buildings andlarge bearing capacity foundation, due to the influence of pile soft soil layer, weaken the pilebearing capacity and stability greatly, and because of the special structural of loess, producinga series of disease to bridge pile foundation, using pile by base post grouting technology cansolve the lack of weak intercalation，but the study only based on the basis of half experienceand half theory at present, therefore, determining loess area foundation bearing capacity ofpile by base post grouting is the key problems to be solved in design of pile foundation. Basedon The field static load test of t bored pile in xi’an--xianyang airport officially dedicated thehighway, taking studying the loading mechanism of grouting pile as the main line, takingdetermining the pile bearing capacity and the optimization design as the goal, on the basis ofsummarizing the research status at home and abroad, using the combination method of fieldtest, theoretical analysis and numerical simulation, studying the load-bearing characteristics ofpile end grouting pile in loess area systemically, expect filling the blank of pile stress of pileby base post grouting in loess area, provide meaningful theoretical basis, the main researchresults are as follows:1. Analyzing post-grouting pile foundation using the Vesic spherical expansion theory,modifying the rigidity coefficient index of the Vesic method, overcoming the impact of theoriginal formula can’t consider bottom sediment and soil voids the construction process,concluding that post-grouting pile foundation in the construction process, determining thecement solidification radius and pile end plastic zone before the soil shear failure.2. Base on pile-end post-grouting mechanical characteristic, summarized the maininfluence factors of load transfer and the factors should be considered for calculating, anddetermined grouting body diameter, grouting body height and the control range of diameterheight ratio, providing reasonable technical indicators for design and construction ofpost-grouting bored piles.3. Considering the collapsible deformation be influenced by soil modulus, collapsibilitythickness and collapsibility coefficient, based on the elastic theory, combined the load transfermechanism of post-grouting pile, putting forward the calculation formula of bearing capacityand settlement characteristics of bored piles in loess area, compared the results with themeasured engineering date, verifying the theory the engineering applicability of formula.4. Conducting field test of post-grouting and non-grouting respectively, testing pile axial force, distribution of resistance on pile side and pile end under different load, and analysis theprocess test data, discusses the load transfer law of pile foundation of post pressure groutingpile, studying the working mechanism of bored pile used post grouting systemically providereasonable technical indicators for bridge design and construction in loess area.5. Combined with the field test, conducting numerical analysis of bearing capacity ofpost-grouting pile foundation using nonlinear finite element analysis software, according tothe simulation results and field test, study the load-settlement mechanism in the design loadsof post-grouting bored pile in loess area, and on this basis, study influence of pile endpost-grouting, pile side grouting, pile end and pile side grouting at the same time to thebearing performance of bored piles, analyzing the influence of the pile endpoint soildeformation modulus increase and different level’s of grout along the pile side to thesettlement of pile foundation.