Comparing in-situ cone resistance and pile jacking force

Pile jacking is a relatively recent piling technique, characterized by low vibrations during execution, small size installation equipment and good axial bearing capacity performance. These features make it a viable alternative to traditional dynamic pile driving, particularly for historical buildings and urban sites. The prediction of the short-term resistance encountered during installation, generally different from the medium-term bearing capacity, is important in any application of the technique. For this purpose, a correlation between the short-term jacked pile installation force and the CPT tip resistance will improve the prediction reliability. Data from a well documented field study in Italy are reported, in which a number of jacked piles were installed and their short-term base resistance recorded. The subsoil is composed of a predominantly clayey and silty fraction with local sandy layers. Data analysis is provided and comparison with previous studies and CPT-based design methods discussed.