Model factor for the bearing capacity of piles from pressuremeter test results - Eurocode 7 approach

This paper focuses on the establishment of a model factor for the calculation of the ultimate limit state (ULS) bearing capacity of piles in compression from Menard pressuremeter tests results. First, the requirements of Eurocode 7 are presented: calculation methods used for pile foundations must be validated against the results of static load tests and a model factor can be introduced to reach a target safety. This model factor is meant to take into account the scatter of the calculation model, whereas the spatial variability of the ground properties is dealt with by means of statistical methods. Then an analysis of a database of 174 full-scale static pile load tests carried out by the Laboratoire Central des Ponts et Chausees (LCPC, now called IFSTTAR), over the last 40 years, mainly in France, is performed and a new calculation model is established based on pressuremeter test results. Finally, the calibration procedure for deriving the model factor used in the recent French standard for pile design following Eurocode 7 is explained using two approaches: one compares the dispersions of the former and new calculation models and the other performs statistical analysis combining the scatter of the calculation model and the spatial variability of ground properties. This model factor is introduced into the recent French standard for pile design following Eurocode 7.