Uncorrected Standard Penetration Resistance

[owillis28]

A standard penetration test is conducted 10 ft below the surface of a sand for which the unit weight is 120 lb/ft3. The water table is at a depth of 15 ft. The number of hammer blows required to drive the sample for each of three 6 in increments is 4, 6, and 8, respectively. What is most nearly the uncorrected standard penetration resistance?

10

12

14

18

 

[Hockeyfan960]

14....the first 6 inch blow count is for seating....

 

[Old as Dirt Geo]

When using a 24" sampling spoon the uncorrected SPT N-value is the middle 2 6-inch increments. Also remember that when correcting the SPT N-value, the correction factor normalizes the N-value to 1-tsf of overburden pressure. This means that the correction factor will, in general, increase the N-value at depths less than 15 ft and decrease the N-value at depths greater that 15 ft. This assumes that the unit weight of the soil is approximately 120 to 130 pcf.

OADG