Failure analysis of CPT-based direct methods for axial capacity of driven piles in sand

Due to variety of current pile bearing capacity methods based on cone penetration test (CPT) measurements, there is always a need for evaluating performance of existing methods to make proper choices of methods as well as safety factors for optimum design. In this regard, geotechnical databases are known as useful tools which facilitate evaluation of existing methods. This paper deals with axial bearing capacity of driven piles in sand using CPT-based methods. A database of seventy-six records is employed to analyze different criteria of interpreting static pile load test results to select the most consistent approach with the CPT-based methods. Then, performance of nine commonly used direct CPT-based methods was evaluated. Finally, via a failure probability and cost optimisation approach, optimum safety factors are presented and discussed. Analysis of different failure criteria shows that the Hansen 80% criterion leads to more consistent results with the CPT-based methods. In addition, almost all of the investigated methods showed promising performance. The attained safety factors range from 1.6 to 3.1 for all records, 1.4 to 3.1 for piles in compression, and 1.4 to 2.2 for the piles in tension. Then, efficiency of methods was evaluated and the methods with higher efficiency are introduced.