Osterberg-cell Method Test Pile Foundation Bearing Capacity Reliability Research

With the rapid development of Chinese economy, many bridges became larger and larger. Structures of the bridge became more complex. The ultimate bearing capacity of the pile and pile testing techniques have become more sophisticated, in order to adapt to this development, self-balancing law came into being.Industry experts believe that the traditional method of data obtained test results have high credibility, reliability, but self-balancing method applied late in the Chinese project, the results of this test method has not been widely recognized, therefore, this paper will study the reliability of self-balancing test for pile bearing capacity. This paper conducted nine test pile vertical bearing capacity tests by traditional method and self-balancing method, testing the lateral friction, pile end reaction force variation with load and load-displacement curve. This paper used statistical theory to systemically study. The main contents of this paper are as follows:We carried out the vertical bearing capacity test of the Mulan Songhua River Bridge’s one test pile, Yanji Buerhatong River Juzi Street Bridge’s one test pile and Nen River Bridge’s one test pile, and measured limit lateral friction, the reaction force of pile end and the carrying capacity of the pile;We carried out the self-balancing test of the north shore line Songhua River Bridge’s three test piles, Mulan Songhua River Bridge’one test pile Yanji Buerhatong River Juzi Street Bridge’s one test pile and Nen River Bridge’s one test pile, and measured limit lateral friction, the reaction force of pile end and the carrying capacity of the pile; We used the chauvenet criterion to remove the error test data, and used the statistical theory to analyze the extreme side friction and pile bearing capacity which tested out by self-balancing method, and analysed the reliability of the method.Through the research, the following conclusions are made:(1) The actual test of three traditional static pressure method, five root self balancing method, the limit of the test pile side friction and the vertical bearing capacity.(2) By x1 test inspection known for limit of the static load test of pile side friction values with the self-balancing method measured the ultimate side friction of pile foundation test measured values of the ratio of the statistical distribution is normal distribution, namely～(0.95, 0.95) of the normal distribution function. Assurance rate was 95%, the value of 1.27.(3) When the confidence level of 0.95, static load test and pile foundation bearing capacity value obtained from the equilibrium method test pile foundation bearing capacity the ratio of the measured values, the confidence level for the confidence interval of 1-α is (0.782,0.977).