Foundation Of Theoretical Analysis Of The Balance Test Piles And Engineering Research

As high-rise buildings and large span bridges are built, more and more large-diameter, large-tonnage, super-long piles have been applied, but the test relied on the traditional static load apparently cannot have satisfied the requirements. In view of this situation, the developed countries proposed the test method of burying load the box in the pile body, which is called the O-cell method or self-balanced method. As a new kind of single pile bearing capacity test technology, the superiority of the pile trialing the balance and the huge potential in the economy has been showed. Presently, it is the preferred method of pile static load test in North America, and this method is also in the trial in many parts of our country. The thesis bases on Ningbo hub station building renovation project of large-diameter, large-tonnage, super long-piles engineering, makes a systematical and in-depth research on the technology of self-balance pile load test. The study includes the following parts:(1) The theory of self-balancing pile trailing, test equipment and test process, expounding its key technical points and the difference between it and the method of traditional static load pile trialing.(2) Discussing the burial position of the load cell and how to determine the "balanced point position", and analyzing and calculating the position with the help of practical engineering projects.(3) Through comparison with traditional static load pile trialing, analyzing self-balancing upper and lower section of pile load transfer mechanism, exploring the theory of equivalent conversion method from Q-s curve of self-balancing to traditional static load pile trialing(simplified conversion and specific conversion) and simplifying Coefficient K in the conversion method that can be used in engineering application conclusion.(4) Based on ABAQUS finite element software, establishing self-balance pile model which simulate loading process on the upper and lower section of pile, and exploring the mutual influence between the stiffness ratio of soil pile to that of pile and pile aspect ratio and upper and lower section of pile. (5) Applying the theory of self-balancing pile trailing to the specific projects with the experience gained in Hub Housing Reconstruction Project in Ningbo, conducting theoretical simulation of self-balanced loading and making a comparative analysis between theoretical displacement and practical displacement.Finally, based on the comprehensive summation, the further topics are put forward. It mainly includes the question of determining the "balanced of position", and the question of selecting transform coefficient K in the simplified conversion.