Geoscience Reference
In-Depth Information
The purpose of this paper is to use MSEW software to identify issues and
nonissues related to block wall design. The presentation shows that while an issue
might be important in metal strip wall design, it is actually not important in
geosynthetic block wall, and vice versa. Finally, a practical remedy in design and
construction is suggested for the identified issue.
2 NONISSUE (FOR POLYMER REINFORCEMENT)
Consider an example problem taken from the Demo 82 manual (pp. 143-149).
That is, wall design height of 7.8m, traffic surcharge of 9.4 kPa, reinforced soil
having C
u
.
18.8 kN/m
3
, f
7, g
¼
¼
34
8
and c
¼
0 retained soil having
18.8 kN/m
3
and f
g
¼
¼
30
8
F*
¼
2.0, Fs(direct sliding)
¼
1.5, eccentricity
,
L/6, and Fs(pullout)
1.5. For a wall reinforced with metal strips (with panels of
1.5 by 1.5m) the layout of the reinforcement and data related to resistive pullout
length are summarized in Table 1 (see Demo 82 for further details). Large
horizontal pressures at the upper portion of the wall combined with
low overburden pressure and small interface area of each (ribbed) strip
require significant pullout length when compared with the overall strip length
(see
Fig. 1a
and b). In fact, pullout controls the dimensions of the wall structure.
Clearly, pullout resistive length is a major design issue in walls reinforced by
metal strips.
Consider now the situation for geosynthetic walls where continuous
reinforcement is used. To address this issue objectively, a comparison is
conducted specifying the same wall geometry, including geosynthetic layers at
¼
Table 1
Example Problem: Layout of Metal Strips (Problem Details Given in Demo 82;
Calculations by MSEW Software)
Elevation (m)
S
h
(m)
L (m)
K/Ka
F*
a
T
max
(kN/m)
Pullout: Fs
0.375
0.75
5.50
1.200
0.67
1.00
37.9
1.75
1.125
0.75
5.50
1.200
0.67
1.00
34.3
1.59
1.875
0.75
5.50
1.206
0.69
1.00
31.3
1.79
2.625
0.75
5.50
1.269
0.85
1.00
28.9
1.51
3.375
0.75
5.50
1.331
1.02
1.00
26.1
1.51
4.125
0.60
5.50
1.394
1.19
1.00
23.0
1.50
4.875
0.75
5.50
1.456
1.35
1.00
19.8
1.58
5.625
0.75
5.50
1.519
1.52
1.00
16.2
1.61
6.375
0.75
5.50
1.581
1.68
1.00
12.1
1.57
7.125
0.50
5.50
1.644
1.85
1.00
9.3
1.60
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