Research On Load Transfer Mechanism Of Prestress Concrete Pipe Pile

Based on theoretical research and developing investigation on load transfer testing on single pile, this paper carries on a serial of full-scall load transfer test on static pressure pre-stressed steel pipe pile. The piles were instrumented with strain gages which were installed on the surface of pile's concrete outer wall and were protected by the epoxy and the steel disk. According to the results of static loading test, we have the load-settlement cures, the data of strain in the pile shaft and the axial force distribution curves of the test piles. At the same time we can get the relation curve between the shaft resistance and the relativc displacement. The results are basic data for the analysis static pressure pre-stressed steel pipe piles.Analyzed the behavior of shaft resistance on pre-stressed steel pipe pile, the range of the ultimate value of shaft resistance in every soil layer is presented, the relative displacements to mobilize the ultimate resistance is different when soil is different, generally, it is not larger than 10 mm. The significant strains soften happened after the ultimate resistance were mobilized.Because of the squeeze efect the shaft resistance at the shallow depth is constant. The deeper the depth, the greater the shaft resistance is. Analyzed the behavior of end resistance of piles, the range of the ultimate value of end resistance is presented. Compared to the other types of piles, the settlement of the pile to mobilize end resistance is very litle. Generally, it is 5%~10% of the end diameter for the ultimate end resistance. The existing of residual stress near pile end increases end resistance and shaft resistance near pile end.This paper researched the load-settlement characteristic, anlysized the settlement influence factor and load transmission characteristic. Through the pre-stressed aperture pipe piles and the blind pipe piles'load - settlement test, contrasted their Q-S curve shape, analyzed their settling qualities, and obtained that under the same condition the blind pipe piles are more superior than aperture pipe piles in controlling settlement.At the same time, this paper contrasted the difference between the actual result and the predicted value and supposed a formula revision, and confirmed the correlation formula practical significance.