Wis. Admin. Code Department of Safety and Professional Services SPS 362.1810
Note: The Department has approved the following two dynamic driving formulas, when used within the parameters prescribed below.
1. Washington State Department of Transportation formula:
Rn = 6.6Feff WH ln(10N)
Where:
Rn is the ultimate axial compression capacity in kips.
Feff is an efficiency factor based on hammer and pile type.
W is the hammer weight in kips.
H is the drop height of the hammer in feet.
N is the average penetration resistance at the end of driving, in blows per inch.
Acceptable Feff values are:
0.55 for all pile types driven with an air or steam hammer.
0.37 for open-ended diesel hammers for concrete and timber piles.
0.47 for open-ended diesel hammers for steel piles.
0.35 for closed-ended diesel hammers for all pile types.
2. Corrected FHWA-Modified Gates Equation:
Ru = [(1.75)((e Er)0.5) (log(10 Nb))-100] (Fo) (Fs) (Fp) (Fh)
Where:
Ru is the ultimate axial compression capacity in kips.
e is the hammer efficiency.
Er is the hammer energy in foot-pounds.
Nb is the final penetration resistance in blows per inch.
Fo is an overall correction factor.
Fs is a correction factor for soil type.
Fp is a correction factor for pile type.
Fh is a correction factor for hammer type.
Acceptable hammer-efficiency values are:
0.75 for drop hammers.
0.85 for other hammers, or an efficiency recommended by the hammer manufacturer.
Acceptable correction factors are:
Overall Fo: 0.94.
Soil Fs: 1.00 for mixed soil profile.
0.87 for sandy soil profile.
1.20 for clayey soil profile.
Pile Fp: 1.00 for closed-ended pipe.
1.02 for open-ended pipe.
0.80 for H-Section piles.
Hammer Fh: 1.00 for open-ended diesel.
0.84 for closed-ended diesel.
1.16 for air or steam single-acting.
1.01 for air or steam double-acting.
1.00 for hydraulic.
If at least 1 static load test is performed to field-check the penetration resistance criteria calculated by the above dynamic formulas, a minimum safety factor of 2.5 must be applied to the ultimate axial compression capacity calculated by the dynamic formula to determine the allowable pile load. If only dynamic testing (including signal matching) is performed to field-check the penetration resistance criteria determined by the dynamic formula, a minimum safety factor of 2.75 must be applied to the ultimate axial compression capacity calculated by the dynamic formula to determine the allowable pile load. If no field testing is performed to check the penetration resistance criteria calculated by the dynamic formula, a minimum safety factor of 3.0 must be applied to the ultimate axial compression capacity calculated by the dynamic formula to determine the allowable pile load.
The above formulas are predicated on the following three conditions: (1) static load testing and/or dynamic testing being performed on pile(s) driven in uniform site soil conditions, (2) test pile(s) being driven with the same hammer and cushion used for installation of production piles, and (3) test pile(s) being of the same type and section used for production piles. If any of the three conditions is not met, additional field testing is required. With static load testing and/or dynamic testing, penetration resistance criteria calculated by the dynamic formula must be modified as appropriate based on the results of the field testing. A site must be defined as a project site, or a portion of it, where subsurface conditions can be characterized as geologically similar in terms of subsurface stratigraphy, including the sequence, thickness, geologic history, engineering properties and groundwater aspects.
Wis. Admin. Code Department of Safety and Professional Services SPS 362.1810