settlement_of_shallow_foundations_on_granular_soils (Lutenegger ang DeGroot)

OCR= [K(OC)/(1-sin ~ )](1 10·' sinll
8. Calculate the initial vertical effective stress at the center of the layer.
9. Determine the preconsolidation pressure at the test elevation as:
10. Determine the stress increment at the center of the layer due to the applied load
(assume 2: 1)
II.
Determine the final stress at the center of the layer as:
cr'
f
= cr' vo + L1cr'
12. Determine that portion of the load increment that will be in the OC range R,(OC) and
in the NC range R,(NC) as:
R,(OC) = (P',- cr'v,)/(cr'r- cr'vo)
R,(NC) = (cr'r- P',)/(cr'r- cr'vo)
13. Determine the average E 0 value for the layer.
14. Determine the strain influence factor, Iz, for the layer from Schmertmann's B(2:2B
approximation).
15. Calculate the settlement for the layer from:
[5.114]
5.6 Plate Load Test
The use of the plate load test has in the past been an attractive approach to predicting the
settlement of shallow footings on granular soils, largely because the plate acts as a prototype
foundation and load is applied in the same direction as anticipated by the foundation. In order for
the results of a plate load test to be useful in predicting settlements the test must be performed on
soil which is representative of that to be stressed by the foundation, which means that the surface
where the plate test is to be performed must be undisturbed and that the soil throughout the zone of
influence of the plate and the foundation is the same. However, since the stiffuess of granular soils
is related to the stress level in the ground (i.e. modulus is stress dependent) errors maybe associated
with evaluating stiffness from small plate tests (typically 0.3m) and then extrapolating the results
to larger footings.
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