settlement_of_shallow_foundations_on_granular_soils (Lutenegger ang DeGroot)

5.5 Dilatometer Test
Marchetti (1980) suggested that the Dilatometer Modulus, En, could be used to estimate the
one-dimensional constrained modulus, M 2 and provided an empirical approach to estimating
settlement. This was also shown by Schmertmann (1981) to be a reasonable approach as evaluating
soil stiffness.
The DMT has proven especially useful for rapid and economical preliminary estimates of
settlements of shallow foundations and has been used in a number of different soils as summarized
in Table 5.8. Each DMT produces a predicted modulus value at a particular point in the foundation
soil, and at the particular effective stress condition existing at that point at that tirue. The engineer
can calculate this condition by computing total vertical overburden pressure and the equilibrium
water pressure at each point. All soil modulus values are effective stress dependent to varying
degrees on vertical and horiwntal pre-stress magnitudes, cementation, etc. In some problems it may
be advisable to adjust the DMT -determined modulus values to better match the vertical stress
changes imposed by the structure involved during its construction and service life as outlined by
Schmertmann (1986).
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Table 5.8 Reported Use of Dilatometer For Settlement
Predictions of Shallow Foundations
Foundation
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Soil Type
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Reference
misc. miSC. Hayes (1986)
miSC. miSC. Schmertmann (1986)
misc. miSC. Saye & Lutenegger (1988)
misc. residual Mayne & Frost (1991)
0.9mx 0.9m Sand Skiles & Townsend (1994)
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5.5.1 Schmertmann (1986)
Schmertmann (1986) recommended a procedure to estimate footing settlements based on the
work by Janbu (1963, 1985) in which it was pointed out that among other things, using a siruple
modulus concept could significantly simplify the understanding and calculation of consolidation
settlements. Janbu suggested using the following equation of calculate consolidation settlement:
where:
[5.112]
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