Shaft capacity of non-displacement piles in silts and clays

This paper presents a new database of static load tests comprising 38 instrumented bored and continuous flight augered piles in sedimentary and residual silts and clays from 20 sites worldwide. The unit shaft friction of the database piles calculated using the total stress method and recent CPT-based methods are compared with the measured frictions. These comparisons highlight the level of uncertainty associated with various methods. It is seen that recently developed CPT-based approaches using the soil behaviour type index (Jc) give better predictions than other existing methods. It is also shown that there is a considerably higher level of uncertainty associated with the estimation of shaft friction for piles in residual soils compared with allu­vial/sedimentary deposits.