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Date of Publication:2022-10-07

Journal:铁道科学与工程学报

Issue:5

Page Number:821-826

ISSN No.:1672-7029

Abstract:The determination of neutral point position is one of the most important aspects in dragload,downdrag, and total bearing capacity of pile foundation design and calculation,in which pile foundation is influenced by negative skin friction.The empirical methods for determining neutral position specified by current design codes often result in values different than practical ones.Visual model tests on neutral point position of pipe pile under negative skin friction using non -intrusive testing methods were carried out on transparent soil.The displace-ments of pile and soil were measured,and the relative displacement of pile-soil and the position of neutral point were analyzed and discussed.In order to make a comparative analysis,model tests on pipe pile with different di-ameters under negative skin friction were also performed.The curves of neutral point position versus surcharge between pipe piles with different diameters were analyzed.The test results show that,in this model test condi-tion,the neutral point of pipe piles located approximately at 0.7 H -0.9 H (where H is the pile length),slight-ly lower than the values suggested by the Chinese Code (0.7 H -0.8 H ),and that the downdrag of pile is near-ly increases linearly with increasing surcharge load.

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