Geoscience Reference
In-Depth Information
Table 11.4
Strain levels.
Application
Type
Strain level
Typical
Shear strain
Applicable
movement
(%)
testing
(mm)
Pavement
Rigid
Very small
5-10
0.001
Dynamic methods
<
Flexible base
Large
5-30
>
0.1
Dynamic methods/
Sub base
Small/large
5-20
0.01-0.1
local gauges
Subgrade
Small/very small
5-10
0.001-0.01
Haul/access
Very large
50-200
0.5
Conventional soil
>
Unpaved road
Large
25-100
0.1
testing
>
Foundations
Pile shaft
Small
5-20
0.01-0.1
Local gauges
Pile tip
Small/medium
10-40
Shallow
Small/large
10-50
0.05-0.5
Local gauges
Embankments
Large/very large
50
0.1
Conventional soil
testing
>
>
Retention
Retaining wall
Active - Small
10-50
0.01-0.1
Local gauges
systems
Passive - Large
50
0.1
>
>
Tunnel
Large
10-100
>
0.1
Conventional soil
testing
•
Retention Systems and tunnels have both horizontal and vertical movements.
•
Horizontal movement typically 25% to 50% of vertical movement.
•
Different modulus values also apply for plane strain versus axisymetric conditions.
•
The modulus values for fill can be different for in situ materials for the same soil
description.
11.5 Modulus applications
•
There is much uncertainty on the modulus values, and its application.
•
The table provides a likely relative modulus ranking. Rank is 1 for smallest values
and increasing in number to larger modulus. However this can vary between
materials. For example, an initial tangent modulus without micro cracks in clay
sample could have a higher modulus than the secant modulus at failure, which is
different from the rank shown in the table.
•
The relative values depend on material type, state of soil and loading factors.
•
Some applications (eg pavements) may have a high stress level, but a low strain
level.
In such cases a strain criteria applies.
In other applications, such as
foundations, a stress criterion applies in design.
•
In most cases, only 1 modulus is used in design although the structure may
experience several modulus ranges.
•
Modulus values between small strain and large strain applications can vary by a
factor of 5 to 10.
•
The dynamic modulus can be greater than 2, 5 and 10 times that of a static modulus
value for granular, cohesive material and rock, respectively.
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