CPTu-based enhanced UniCone method for pile capacity

• A direct piezocone method for axial pile capacity is reviewed.
• From a large data, improved means of evaluating the pile resistance are recommended.
• An alternative CPT-based soil classification system is used.
• New correlations offer higher reliability via continuous functions for estimating the pile side and base capacity components.

The UniCone direct piezocone method by Eslami and Fellenius (1997) for evaluating the axial capacity of pile foundations is reviewed and improved means of evaluating the soil resistance factors are recommended. This method uses all three piezocone penetration test (CPTu) readings in a soil behavioral type (SBT) classification chart and provides estimations of axial pile capacity for a wide variety of pile types installed in different assortments of geomaterials. In this paper, the earlier method is improved using a dataset of 153 pile load tests and CPTu soundings from 52 worldwide sites. An alternative soil classification system using the CPT material index Ic is used to provide improved correlations of higher reliability via continuous functions for estimating the side and base capacity components of driven and jacked piles, and drilled shafts. An analysis is also included to test the performance of the newly proposed design formulations. Finally, a simplified flowchart is presented for convenient application of the enhanced expressions.