NAVFAC DM7 Method (SPT)
Settlement of spread footing usingaccording to NAVFAC DM7 method is based on the formula:
settlement of spread footing
footing width factor
stress in the footing bottom
modulus of subgrade reaction
GWT influence factor
The formula is derived for imperial units [tsf, tcf, ft] - the program calculates automatically in the units used in the program.
Footing width factor C is determined as follows:
b < 20 ft -> C = 4
b > 40 ft -> C = 2
Intermediate values C are interpolated.
GWT influence factor Cw is determined as follows:
GWT is located between the terrain level and depth of 1,5.bef bellow the footing bottom:
GWT is located bellow the depth of 1,5.bef bellow the footing bottom:
depth of ground water table from the terrain
depth of footing bottom
Modulus of subgrade reaction Kv depends on relative density factor ID:
Determination of modulus Kv (Navfac, 1982)
Relative density factor ID is determined as follows:
uncorrected blowcount at a depth of b/2 under the footing bottom
geostatic stress at a depth of b/2 under the footing bottom
The formula is derived for imperial units [ksf] - the program calculates automatically in the units used in the program.