Assessment of the Unified CPT Design Method for Axial Capacity of Driven Piles in Interlayered Deposits

The ongoing and increasing demand for offshore piles has motivated the development of more reliable design methods and led to the recent development of the ‘Unified’ CPT design methods to predict the axial capacity of driven piles installed in sand deposits and in clay deposits. However, many sites encountered in practice contain both sand and clay layers as well as silt layers and it is therefore important to assess the reliability of these new methods at such sites. This paper presents this assessment using a newly compiled database of pile load tests in interlayered deposits. It is shown that satisfactory predictions of capacities are attained using the sand and clay formulations of the ‘Unified’ method with a correction applied to the sand method to enable prediction of shaft friction in silt deposits.