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

The determination of the vertical bearing capacity of the prestressed concrete pipe piles is hot topic, but it is difficult and important, however, there are only a few empirical formulas about the calculation of the vertical bearing capacity of the prestressed concrete pipe piles and there is no leading method in china. If the results of the bearing capacity of the singe pile are determined based on the empirical formulas of the current design code, generally, it will be much lower than that based on the static load test. In the paper, based on the new schoolhouse base construction of Yangzhou university , the soil plugging effect and soil compaction effect, the author analyzed the behavior of stress and its mechanism of bearing in details. It also illustrates that the soil Plugging effect and soil compaction effect are the main reasons for the enhancement of the vertical bearing capacity of a single prestressed pipe piles.Based on theoretical analysis, this paper conclude 15 cases of the static load test result in Yangzhou. Firstly, based on the geological information and《Tehchnical Code for Pile Foundation》(JGJ94-94), the paper calculates the bearing capacity of the single pile. Secondly, the paper analyzes the difference between the practical bearing capacity and the design bearing capacity. And the paper discover some factors which included the soil plugging effect and soil compaction effect, pile diameter, pile length, the characteristics of density of the soil can influence the vertical bearing capacity of pipe pile. At last, the paper also modifies the standard value of friction resistance at pile shaft and friction resistance at pipe tip. The paper get the result of vertical bearing capacity by means of formula in code that the coefficient has been revised. Comparisons are made between the calculated values and the measurements and the modified value proved to be appropriated.By using the software FLAC-3D the mechanism of load transfer form is studied and the vertical bearing capacity as well. Different soil modulus along the pile and underneath the pile are considered. Length, diameter and the thickness of pile wall are also studied in order to grasp the main effects on pile bearing capacity and guide practical design.