Geological dependence of resistance factors for deep foundation design

This research addresses the issue of geological dependence of deep foundation designs resistance factors for driven pile and drilled shaft designs in different locations. For the proof, two sets of databases were used: one from the NCHRP 507 report and another driven pile and drilled shaft database with static load tests and soil profiles from the different locations in Vietnam were used to evaluate resistance factor design for different axial pile capacity prediction methods. Eight different static analysis methods were used for driven pile capacity evaluation: α-Tomlinson, α-API, λ, β, Nordlund, Thurman, Meyerhof SPT, and the Shmertmann SPT method. For drilled shafts the FHWA and Reese & Wight methods were used. In the analyses the correlations between Nspt and soil parameters were used. First Order Second Moment (FOSM), First Order Reliability Methods (FORM) and Monte Carlo simulations were used to evaluate the based analyses in the determination of the resistance factors. The following notable benefits were attained in this project: 1) Resistance factors are made available for the LRFD designs of driven piles and drilled shafts in Vietnam; 2) The results show that the resistance factors vary with methods, geomaterial types and geological locations; 3) The found resistance factors for Vietnam give substantially greater factored capacities as compared to the 2012 AASHTO-LRFD recommendations.