settlement_of_shallow_foundations_on_granular_soils (Lutenegger ang DeGroot)

[5.123]
where:
Pn = settlement of a foundation of width B
P 1 =settlement of plate of width B 1
(N,.)B = Nm for the foundation
Note that any size plate may be used in this technique.
The value ofNm is obtained as:
[5.124]
where:
N 1 = N from the base of the foundation to a depth of2/3 B
N 2 = N from 2/3B to 4/3B
N 3 = N from 4/3B to 2B
Where N shows a consistent trend over the depth 2B below the foundation, Nm may be taken as the
N value at a depth of 3/4B below the foundation.
5.6.5 Ghionna et al. (1991)
A technique which uses the results of plate load tests in conjunction with conventional linear
elastic theory and accounting for the dependence of soil stiffness on stress and strain was presented
by Ghionna et al. (1991). The application of elastic theory to plate tests allows for the evaluation
of Young's modulus according to the expression suggested by Oweiss (1979) as:
E = 0.7lq(s/B)
[5.125]
where:
q = average applied stress
s = settlement
B = footing width
The results of plate tests show that resulting values of Young's modulus, evaluated using Equation
5.125, are nonlinear and decrease with increasing values of q. Soil deformation parameters are
obtained by assuming a hyperbolic stress-strain model for soils and assuming that settlements or soil
strains occur over a zone below the foundation related to foundation geometry; i.e., 2B for square
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