Application Research Of Post Grouting Technology For Bored Pile For Bridge

Since the world entered21st century, Chinese economy has been maintaining rapiddevelopment, as a result, sharp rise in traffic volume necessitates stricter requirement ofpublic traffic facilities, and the government has been intensifying infrastructure constructionin order to meet the requirement of increasing traffic volume, with more than1000km ofhigh-grade highway completed every year. High grade highways in loess sandy soil regionsare likely to bring a series of problems to pile foundation in bridge substructure due tostructural particularity (low in frictional resistance and bearing capacity, and collapsibility etc.)of loess and sandy soil, such as overlong pile length, overlarge pile diameter and inadequatebearing capacity in later stage, which give rise to huge waste in construction due to not onlyhigh difficulty but also high cost in construction. At present the bored pile technology hasbeen widely applied, however the bearing capacity and stability of pile foundation are greatlyweakened under the influence of soft soil layer on pile tip, especially the bridge in loess andsandy soil region is also likely to bring about a series of diseases in bridge pile foundation dueto its structural particularity. Adopting post grouting technology shall effectively improvecarrying capacity and side frictional resistance of pile tip, At present, the application of thetechnology is to be further generalized, the reasons for which are that although manytechnologies are mature in theory, there are fewer technical specifications and that fear offailure to achieve the desired effect in practical application of technology as a result ofimproper operation, therefore, many professionals would rather waste more material thanadopt the technology. The paper concludes that the post grouting technology is capable ofimprovement in bearing capacity at the bottom of pile and increase in frictional resistance ofthe soil around the pile tip as well as reduction in length and diameter of pile based on theanalysis of the operating principle of the post grouting technology for bored pile. The paperpresents research of the stress mechanism of the post grouted pile foundation of the bored pilebased on the bored pile subjected to post grouting under pile tip in the works for expresswayfrom Xi’an to Xianyang so as to offer theoretical basis for application and generalization ofthe post grouting technology. The paper presents research and analysis of the post groutingtechnology for pile tip of bridge in typical region adopting technical means integratingtheoretical analysis and numerical simulation and field test based on summary of the presentsituation of researches both here and aboard and the research findings of which shall serve astheoretical and technical guidance. The major researches given in the paper are as follows:First, the paper presents systematic analysis of the theory and construction process for post grouting in bored pile for bridge and concludes the practical construction and operationspecification, quality inspection standard applicable to construction of highway bridge so asto guide and regulate the application of the technology to highway bridge field.The paper, based on the numerical simulation and rational geo-mechanical model andfield static testing, also presents analysis of and comparison between post grouted bored pilewith conventional diameter and conventional bored pile for highway bridge in terms ofrelevant parameters such as ultimate bearing capacity of pile foundation and role of internalforce in pipe body so as to research the operating mechanism of the post grouting technologyfor the bored pile for highway bridge;Finally, the paper presents field testing on test pile with post grouting technology and testpile without post grouting technology so as to determine the distribution of various controlparameters for axial force on pile body and resistance on pile side and pile pit under differentloads and carry out contrastive analysis of test data to evaluate their effects in constructionand offer technical support to generalization of the post grouting technology.