Research On Vertical Bearing Capacity Of Prestressed Concrete Pipe Pile In Tianjin City

The key element in the design of pipe piles is the determination ofthe vertical bearing capacity of a single pile. However, till now, thereare only a few empirical formulas about the computation of the verticalbearing capacity of the prestressed concrete pipe pile in the worldwideand there is no leading method in China. If the bearing capacity of asingle pile is determined based on the empirical formula of the currentdesign code, generally it will be much lower than that by static loadtest. In the paper, based on the soil plugging effect and soilcompaction effect, the author analyzed the behavior of stress and itsunique mechanism of bearing in details. It also illustrates that thesoil plugging effect and soil compaction effect is the main reason forthe enhancement of the vertical bearing capacity of a single prestressedpipe pile. Based on theoretical analysis, this paper count and conclude thecases of the static load test results of 15 projects in several typicalregions in Tianjin and also analysis the difference between thepractical bearing capacity and the design bearing capacity. Thosefactors, which will influence the vertical bearing capacity of a singlepipe pile, are analyzed. These factors include soil plug, soilcompaction, pile diameter, pile length, the characteristics and degreeof density of the soil at the pile toe, the depth that the pile toepenetrates into the bearing layer and the thickness of the bearing layerbelow the pile toe. The paper also modifies the standard value of ultimate endresistance with silt and sandy soil as the bearing layer for precastpiles, which is specified in the .Comparisons are made between the calculated values and the measurements.Moreover, the applicability of modified standard value of ultimate endresistance to the pipe pile is verified.