The method for evaluating the difference of SPT N-values is investigated based on the nine SPT at the same site, and the trial design on bearing capacity of the pile considering the SPT N-values variations is conducted. It is shown that (1) The coefficient variation of the average N-values of the layers is comparatively small, though the coefficient variation that uses all N-values is very large; (2) The bearing capacity of the pile obtained from the limit state design is larger than the allowable stress design, if the difference of the ground constants is appropriately evaluated.
