| It's a important significance subject for studying the test of bearing behavior of the super-longhole bored pile in losse subgrade. This thesis use the fourteen piles site testing data of seven super long bridges of Zhengzhou—Xi'an passenger dedicated line for studying bearing behavior & deformed mechanism of the super-long pile in losse foundation, and analyzing the mudecake effect which influencing bearing behavior of the super-long pile, and also proposed deformation design theory of the super-long pile under considering the mudecake effect. This thesis try to use above theory for practice which provide basis for engineering design, especially hope can provide the new thought and effective method for method selction of foundation piles and ensuring bearing capacity of super-long pile.1. In normal situation, the bearing capacity characters of super-long pile in losse subgrade appeared same as in clay. But when losse subgrade encountering water, the above situation will be different as there's pile side negative frictional resistance.2. The L/D and pile-soild modular ratio are same, the pile-soil relative dispalacement of same pile section is bigger when considering sediment than non-considering. The influence of sediment on pile side friction character increases gradually with decrease of L/D. The transfer rate of pile axial force is faster when considering sediment, than non-considering, and the sediment influence the founction of pile tip resistance. No matter what L/D is changing, the sediment influence on pile tip resistance is great. At the same L/D situation, the sediment influence on pile tip resistance is greater than upper pile axial force.3. The thickness of mudcake has a big influence on pile force character, at the same loading founction, the settlement of mudcake pile is stronger than non-mudcake pile, and the the settlement increase with mudcake thickness increasing. Because of the founction of mudcake, pile side friction is decrease. The mudcake is more thickness, the pile side friction derecease more. So controlling the thickness of mudcake can provide bearing capacity of super-longhole bored pile.4. Each super-long pile has difference in decay rate of axial force of pile body along pile depth. The pile is more depth, the decay of axial force at pile body middle-upper part is more faster. Each super-long pile body middle and lower part is the main part for bearing loading of pile top, the middle and lower part only take 3/5 long in total length but bearing about 80% loading undering ultimate load. The middle-upper of pile side resistance is bigger but lower is smaller along pile depth with loading curve, and there's no "R" showing, peak increase along with pile top loading. The rult for pile side friction by tested is larger than value of National Code of Pile Foundation Design and reconnaissance report, which prove the pile foundation in this project have great bearing capacity. The pile tip resistance along the settlement of pile end increase apprear linear model of work-hardening, that means the pile tip resistance along the settlement of pile end increase will keep increasing and no peak apprear under biggest loading of pile top.5. When finite element analysis parameters and test parameters are same, the result of mudcake effect, pile length,pile diameter by finite element influence on super-long pile bearing capacity are as same as the result of field test. But, the finite element could not simulate each parameters of real soil during analysis, so the curve of pile side friction along depth has big difference with field test.
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