Soil borings are drilled to investigate subsurface conditions at a planned construction site. Soil samples are obtained using the standard penetration test procedure. The drilling equipment utilizes...

Soil borings are drilled to investigate subsurface conditions at a planned construction site. Soil samples are obtained using the standard penetration test procedure. The drilling equipment utilizes an automatic hammer for driving the soil sampler. Resistance blow-counts are N = 18, N = 22, N = 23, and N= 19 for samples obtained from the topmost soil stratum. Assume that the blow-count data will be applied to preliminary foundation design using foundation bearing capacity information based on a sample drive hammer efficiency of 60 percent. Modify the blow-count values obtained with the automatic hammer to relate to the N₆₀
data.