Effect of spatial correlation of standard penetration test (SPT) data on bearing capacity of driven piles in sand

In this paper, the effect of spatial correlation of standard penetration test (SPT) data on the bearing capacity of driven piles in sand is analyzed. First, the direct approach for using SPT data to determine the bearing capacity of piles in sand is used to derive the expressions for probabilistic prediction of pile bearing capacity by considering the spatial correlation of the SPT data. To analyze the relationship between the probability of failure and the factor of safety, a procedure based on the advanced first-order, second-moment (FOSM) method is used. Then parametric studies are conducted on the spatial correlation between the spatial average of SPT numbers over the pile length, NLV, and the spatial average of SPT numbers over an interval near the pile base, NbV, and its effect on the bearing capacity of piles. The results indicate that it is important to consider the spatial correlation between NLV and NbV in the probabilistic prediction of pile bearing capacity. Ignoring this spatial correlation will underestimate the probability of failure and lead to unsafe design. Finally, three tested piles are analyzed to demonstrate the probabilistic analysis of piles by considering the spatial correlation of SPT data and the procedure for probabilistic analysis of pile bearing capacity is summarized.