The Soil Plug Effect And Single Bearing Capacity Analysis Of Open-ended Variable Section Pipe Pile

Construction of precast pile is widely used in engineering for reliable technique, simple construction, low cost of the precast pile.Variable section pipe pile is a pile presented on the basis of the equal diameter pipe pile, which can give full play to the advantages of pipe pile in construction and also take the actual characteristics of the strata and the actual force of pile into account. This paper combines the model test and theoretical analysis method, further clarifies the load-bearing mechanism of variable section pipe pile.Firstly, get the latest research results of pipe pile referring to the recent relevant archives, put forward the research method and content in this topic.Secondly, Conduct Indoor model contrast tests of equal diameter pipe piles and variable section pipe piles, obtain the relationships between buried depth and pile penetration resistance and the changes of the height of soil plug along with the buried depth, summary the differences of variable section pipe pile and equal diameter pipe pile.Thirdly, based on Vesic cavity expansion theory, analyses pile sinking effect of variable section pipe pile by considering the depth of pile and soil plugging effect, and obtains the theoretical derivation calculation formulas of variable section pipe pile resistance and penetration resistance, analysis the test data and the calculated values to verify the derived formulas’ correction, improves the design theory of segmentally variable section pile.Finally, the bearing capacity under vertical load of the two kinds of piles including the stress of pile, the load settlement, pile tip resistance and side friction are compared based on the indoor large scale model test. The results of the study show that: pile bearing capacity of segmental variable section pipe piles are better than the equal diameter pipe piles when the mean diameter is same. The higher average diameter and higher the variable diameter ratio are, the single pile bearing capacity, unitvolume bearing capacity and the material use rate of pile body are higher;The axial force of segmental variable section pipe pile mutates in variable cross section, and pile axial force attenuation speed in the lower part of variable cross-section.