Uncertainty Analysis of Axial Pile Capacity in Layered Soils by the Piezocone Penetration Test

Abstract

This study presented a framework for uncertainty analysis of the ultimate axial bearing capacity of piles evaluated by the UniCone method in layered soils. The UniCone method by Eslami and Fellenius (1997) is a direct piezocone penetration test (CPTU) method for evaluating the ultimate axial capacity of piles in the reliability design. The spatial variability of CPTU data is modeled as a random field for each soil unit in the soil strata. The empirical correlation coefficients of the UniCone method are assumed to follow lognormal distributions. On the basis of uncertainties of CPTU data and empirical correlation coefficients, the first-order reliability method (FORM) is then applied to the reliability analysis of ultimate axial bearing capacity of piles. The effects of spatial variability of CPTU data and variations of empirical correlation coefficients on the ultimate axial bearing capacity of piles are evaluated by an Excel spreadsheet-based framework. Seven case studies show that the proper identification of different soil units from soil profiles is crucial for estimating the failure probability of pile capacity in the reliability analysis. Uncertainties of CPTU data and empirical correlation coefficients would be over-estimated unless different soil units in soil profiles are identified properly from each other. The over-estimated geotechnical parameters contribute to a higher failure probability of pile capacity. The proposed framework can evaluate the uncertainty of the ultimate axial bearing capacity of pile foundations more rationally.

The Practice and Development of T-Bar Penetrometer Tests in Offshore Engineering Investigation: A Comprehensive Review

“…Recently, with the processive development of new directions and demands in geotechnical engineering, especially marine geotechnical engineering, many international research institutions (e.g., University of British Columbia, Georgia Institute of Technology, Delft University, and Southeast University) and professional in situ test instrument development companies (e.g., Hogentogler, Vertek, ConeTec, and Furgo Corporation) have developed new sensors for CPTU. These new CPTU sensors promote the CPTU test method to develop in the direction of multi-functionality [10,[19][20][21][22][23][24], which further broadens the application field of the CPTU. Figure 1 shows a schematic diagram of the internal structure of a common CPTU.…”