| The probability of failure of friction pile foundations in clay deposits subjected to axial loads is evaluated. The probabilistic procedure provides a consistent method for the modeling, analysis, and updating of uncertainties that are involved in the determination of pile capacity. Results are used to demonstrate a probability - based procedure for the design of pile foundation.; Factors contributing to the variability of friction capacity were identified. Detailed uncertainty analysis of each of these factors is then performed based on extensive review of literature and analysis of a large base of well-conducted pile load test data.; Random field model is used to describe inherent spatial variability of soil properties. When several soil layers are encountered, soil properties between layers are assumed to be statistically independent. The case of random occurrence of an irregular soil material is also considered. In all cases, the overall effect of the inherent variability may be conveniently treated by defining an equivalent soil deposit consisting of single homogeneous material. For pile groups and pile system, correlation characteristics between soil properties and layer thicknesses, at various pile locations are considered in determining the degree of correlation between capacities of piles in a group and between groups in a pile system. Possibility of block failure mode in a pile group is also considered. Model error analysis of group capacities is evaluated based on full-size group tests.; The levels of risk implied by the current methods for predicting axial capacity of a friction pile are evaluated for both onshore and offshore sites. Procedures for determining appropriate probability - based factors for pile design are demonstrated, reflecting the level of the uncertainties involved and the desired level of design safety. The procedure is also extended to the case of pile group/system by taking into account group effect, correlation between individual pile capacities, and also the reserve strengths offered by inner piles in a typical pile system.; Methods are developed to update the systematic pile capacity model error for a specific site based on results of in situ pile tests and/or pile driving information. In the case of multiple pile test at a given site, correlation between individual pile test results is included in the formulation. Error arising from load measurement is also considered. (Abstract shortened with permission of author.)... |
