Rock-socketed Piles Balance Test And Analysis

With the construction of long-span bridges, high-rise buildings and heavy factory buildings, the piles whose capacities are more than 1,0000 kN is used more and more. The conventional static loading test faces great challenges, and sometimes the site is not fit to the conventional static loading test. The O-cell loading test for pile capacity has unique advantages where the conventional static loading test can not be carried out. However, the method is a new testing technology, and some key technical problems need solutions. In this paper, the problems of the method in engineering application have been studied and discussed. The main results are as fallows:(1) The domestic and the foreign researches of O-cell test are systematically presented. The existing theoretical analysis methods of the load-movement relationship of the pile are summarized. Hot research issues of O-cell test are discussed.(2) The field O-cell test of a rock-socketed pile are carried out and the first-hand data about the load transfer mechanism of the pile are obtained. The shaft resistance of the pile, especially the part of the pile above the O-cell box are analyzed. The relationship of the shaft resistance and the relative displacement between pile and soil is studied.(3) The difference of the pile load transfer mechanism among O-cell test and the conventional compressing pile test and the uplift pile test are analyzed. The impact of various loading position and loading direction, distribution and development of shaft resistance of pile is analyzed in theory.(4) According to defects of the existing equivalent conversion method for O-cell test, The original equivalent conversion method using the elastic theory is modified. The shaft resistance of pile are modified using the Mindlin's solution. The whole calculation process with FORTRAN programming language are done. Based on the above analysis and calculation, a new method of equivalent conversion method for O-cell test is put forward.(5) The O-cell loading test of rock-socketed pile is numerically simulated by ADINA finite element software. The rationality of the finite element model comparing the in-situ measured values are verified, then The conventional static loading test of the pile on the same site under the same conditions is modelled. The load-movement curve of the conventional static loading test and the previous equivalent-transformed curve are compared and draw some useful conclusions.