For drilled piers or piles placed in predrilled holes, the value of Nq can be obtained from Figs. 6.5 and 6.6 based on the friction angle f of the cohesionless soil located at the pile tip. However, for driven piles, the Nq values from Figs. 6.5 and 6.6 are generally too conservative. Figure 6.12 presents a chart prepared by Vesic (1967) that provides the bearing capacity factor Nq from several different sources. As shown in Fig. 6.12, for f = 30°, Nq varies from about 30 to 150, while for f = 40°, Nq varies from about 100 to 1000. This is a tremendous variation in Nq values and is related to the different approaches used by the various researchers, where in some cases the basis of the relationship shown in Fig. 6.12 is theoretical, while in other cases the relationship is based on analysis of field data such as pile load tests.