Geoscience Reference
In-Depth Information
Table 11.5
Modulus applications.
Rank
Modulus type
Application
Comments
1
Initial tangent
Fissured clays.
Following initial loading and closing
•
(Low)
modulus
•
At low stress levels. Some
of micro-cracks, modulus value
distance away from loading
then increases significantly. For an
source, eg at 10% q
applied
intact clay, this modulus can be
•
Low height of fill
higher than the secant modulus.
2
Constrained
Wide loading applications
Used where the soil can also
•
modulus
such as large fills
fail, ie exceed peak strength.
Wide embankments
•
3
Deformation
Spread footing
Most used “average'' condition,
•
(secant)
Pile tip
with secant value at ½ peal load
•
modulus
(ie working load).
4
Elastic tangent
Movement in incremental
The secant modulus can be
•
modulus
loading of a multi-storey
20% the initial elastic tangent
building
modulus for an intact clay.
•
Pile shaft
5
Reload
Construction following
Difficult to measure
•
(resilient)
excavation
differences between Reload/Unload
modulus
Subsequent loading from
or cyclic. Resilient modulus term
•
truck/train
interchangeably used for all of them.
Also called dynamic modulus
of elasticity.
6
Cyclic modulus
Machine foundations
•
Offshore structures/
waveloading
•
Earthquake/blast loading
•
7
Recovery
Heave at the bottom of an
•
(unload)
excavation
modulus
•
After loading from truck/train
Excavation in front of wall
and slope
•
Varies
Equivalent
Simplifying overall profile,
Uncertainty on thickness of
•
modulus
where some software can
bottom layer (infinite layer
have only 1 input modulus
often assumed). Relevant layers
depend on stress influence.
11.6 Typical values for elastic parameters
•
The strength of metals is significantly higher than the ground strength. There-
fore movements from the ground tend to govern the performance of the
structure.
- Modulus values of 30,000MPa for industrial concrete floors would apply.
11.7 Elastic parameters of various soils
•
Secant modulus values are used for foundations. This can be higher or lower
depending on strain levels.
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