Technical standards and commentaries for port and harbor structures in Japan notes that in-situ load test is one of the estimation method of axial capacity of piles. The in-situ load test could provide more precise estimation of the axial capacity of piles at the site than various estimation equations. However, the technical standards and commentaries dose not clearly specify a procedure to derive a characteristic value of the axial capacity from the load test result. It dose not expose the partial factor for the characteristic value, either.
The authors analyzed the data of load tests not only reported in previous studies but also conducted at many ports in recent years, and evaluate variability of the test results. The load test were classified in three categories of test condition: identical condition, similar condition and the others. For each condition, the procedure was suggested to derive the characteristic value from the test results and to decide the partial factor for it.
In the suggested procedures, the characteristic value was calculated as the lower limit of 75% confidence interval of the mean value. The procedure covered the case with only one test data. It was revealed that the partial factor should be increased from the traditional value in the case that the load test was conducted under the identical condition. Even in the case of the similar condition, the possibility was indicated to increase of the partial factor with expert judgments.