A review of different pile design approaches in chalk used in France and the UK: case studies from French sites.

Design of piles in chalk is considered as an important issue for a number of geotechnical applications in Northern Europe. Few methods exist for predicting the ultimate axial pile capacity in chalk, but little guidance can be found regarding the design of driven piles in this complex material as experience is rather limited. This paper aims to study the short and long-term predictive performance of different pile design methods used in France and the UK where chalk is found widespread in the north-west coast and the south-east coast, respectively. Conventional methods used in France and the UK are compared by considering seven full-scale static load tests performed in Paris Basin and extracted from the LCPC pile database. The ratio of the measured vs calculated pile shaft resistance and base resistance value is analysed and the scatter of each method is studied. The comparison shows large differences between results. Extension of the database is of great importance to improve the predictive reliability. The last part discusses the evolution of the long-term capacity of driven piles in chalk due to ageing effects. Results show an increasing trend after driving, following a hyperbolic evolution curve. [ABSTRACT FROM AUTHOR]