settlement_of_shallow_foundations_on_granular_soils (Lutenegger ang DeGroot)

N =field measured blowcount
p' =effective overburden stress at the location of the blowcount (in ksf)
The mean effective stress, cr'm"' at the midpoint of each layer is calculated according to:
cr'mo = [(1 +2Ko)P']/3 [4.15]
where:
Ko = at rest coefficient of earth pressure
p' = effective overburden stress at the layer midpoint
Obviously, this calculation requires an estimate of both the unit weight of the soil and Ka,
which may either be made based on other soil characteristics or may be estimated by other means.
The change in mean effective stress, ~cr'nu
footing stress, q, is given from:
at the midpoint of each layer, resulting from the applied
~cr'm = uq [4.16]
where:
a. = an influence factor dependent on the depth and location of desired settlement estimate (i.e.,
edge or center for flexible footings). The value of a. is obtained from Figure 4.15, after
Oweiss (1979). For a rigid footing, the value of a. may be estimated by interpolating
midway between the edge and center curves shown in Figure 4.15.
The settlement factor, 'Vv for each layer is calculated from:
where:
[ 4.17]
F 1 =factor at the bottom of each soil layer
F 1 . 1 =factor at the top of each soil layer
The factors F; and F;. 1 are obtained from Figure 4.16. The depth to the bottom of each layer, Z 1 and
the top of each layer, Z;.J> are used to evaluate values ofF.
A strain parameter, A," is calculated for each layer as:
[ 4.18]
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