Geoscience Reference
In-Depth Information
Figure 5
Mechanical damage. (From Allen and Bathurst, 1994.)
The FHWA (1997) uses
T
all
¼
T
ult
=ð
RF
CR
·RF
D
·RF
ID
·FS
Þ
where
T
all
is the long-term tensile strength.
T
ult
is the ultimate (or yield) tensile strength based on minimum average
roll value (MARV).
RF
CR
is the creep reduction factor.
RF
b
is the durability reduction factor (typically 1.1-2.0).
RF
ID
is the installation damage factor (ranging from 1.05-3.00).
FS
is the overall factor of safety to account for uncertainties in the
geometry of the structure, fill properties, reinforcement properties,
and external applied loads.
For permanent mechanically stabilized earth walls (
.
70
8
), FS
min
¼
1
:
5
:
For reinforced soil structures, FS
¼
1
:
0
;
as the required factor of safety is
accounted for in the stability analysis.
Detailed comparison of the creep data for the yarns and for the product
made of these yarns made it possible to combine the data to confine the
extrapolation to one decade of time.
Later testing at 40
C confirmed the normalized stress-rupture
graph by time-temperature superposition.
8
C and 60
8
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