This study investigates effects of variation in soil on bearing capacity of piles. Resistance factors of shaft friction and tip resistance are estimated with using N-value measured at several points in a site. The resistance factors decrease with increasing variation of N-value. This trend is more remarkable in tip resistance than in shaft friction. This is because, in tip resistance, the variation of designed values is small and the variation of soil has an impact on resistance factors. In the case, in which soil profile is not uniform, it is important to consider the spatial distribution of soil.
