In the Netherlands, the design guideline for basal reinforced piled embankments has been revised (CUR226:2015) adopting a new analytical design model (The Concentric Arches (CA) model, Van Eekelen et al., 2013; 2015). The CA model provides geosynthetic reinforcement (GR) strains which were compared with laboratory and in situ measurements (Van Eekelen et al., 2015). The corresponding discrepancies between the measured values and the values calculated with the new model have been assessed statistically in order to obtain model error statistics as suggested in Eurocode: basis of design (NEN, 2011). Monte Carlo (MC) simulations were carried out to obtain model, material and load factors using several reference cases, in order to calibrate the semi-probabilistic design approach for the revised Dutch Design guideline for Piled Embankments (CUR226, 2015). This paper discusses both the assessment of the model error as well as the calibration of the partial factors, including the lessons learnt.