1564
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
Figure 1. Distribution of walls classified as damage rank
Ⅱ
or greater
Ⅰ ：91.65%
Ⅴ ：0.35%
Ⅵ：0.28%
Ⅳ：0.70% Ⅲ：0.35%
Ⅱ ：6.67%
Damage rankⅥ：4 walls
Damage rankⅤ ：5 walls
Damage rankⅣ：10 walls
Damage rankⅢ：5 walls
Damage rankⅡ ：95 walls
Damage rankⅠ ：1300 walls
Figure 2. Percentages of each Damage Rank
ランクⅡ ランクⅢ ランクⅣ ランクⅤ
ランクⅥ
震度5強
震度6弱
震度6強
震度7
0
10
20
30
40
50
60
震度5強
震度6弱
震度6強
震度7
Figure 3. Rates between Damage Rank and JMA seismic intensity
ランクⅡ ランクⅢ ランクⅣ ランクⅤ ランクⅥ
H<5m
5m≦ H<10m
10m≦ H<1
15m≦ H 5m
0
10
20
30
40
50
60
70
H<5m
5m≦ H<10m
10m≦ H<15m
15m≦ H
Figure 4. Relationship between Damage Rank and Wall height
Rank VI, meaning damage was so severe that they were no
longer functional; including one wall in a construction site
where measures to counter frost heave were being implemented
before putting the wall into service.
As shown in Figures 3 and 4, the Damage Rank VI walls were
at sites that were hit by upper intensity 5 to lower intensity 6
tremors, and in terms of their damage occurrence rates by wall
height (5 m
H < 10 m, 10 m
H < 15 m). They represent the
same 0.4% rate in each seismic intensity and wall height.
Therefore, the high degree of damage was not necessarily as a
result of the strongest tremors or tallest wall heights.
As for the resulting tsunami waves, which characterize the
collateral effects caused by the earthquake, damage from
overland flows were observed on walls at 14 sites. For two sites
where an exposed sloped earth fill surface was unaccompanied
by any protective cover such as concrete, the earth wall was
severely damaged when the earth fill was washed away. At
other sites, however, walls were classified as Damage Rank I or
II, which means light damage.
For the Tohoku Earthquake, there was no instance where
compromised stability of a Reinforced Earth wall led to the loss
of functional integrity in a supported superstructure such as a
road, thus high earthquake resistance performance was
confirmed.
Photo 1. Wall in the area of
seismic intensity upper 7
(Rank
Ⅱ
)
■
Seismic intensity 7
■
Seismic intensity 6+
■
Seismic intensity 6-
■
Seismic intensity 5+
Rank
Ⅱ
Rank
Ⅲ
Rank
Ⅳ
Rank
Ⅴ
Photo 2. Wall in the area of
seismic intensity 7(Rank
Ⅰ
)
Rank
Ⅵ
2 DISASTER CONDITIONS OF DAMAGED
STRUCTURES
Disaster conditions are described by their causes for structures
in areas subjected to high-intensity seismic tremors and those
whose rating was at Damage Rank VI.
2.1
Minimally damaged structures at a site hit by strong
tremors (intensity upper 6 to 7)
Surveyed walls at sites hit by strong tremors (intensity upper 6
to 7) were all classified as Damage Rank I or II.
2.1.1
<Case 1.1 wall H
max
= 15.7 m , bank h = 0.0 m, Total
length L = 46 m, Area of wall A =285 m
2
>
Rank
Ⅱ
Rank
Ⅲ
Damage to a pair of wing walls constructed adjacent to an
abutment in an area hit by intensity 7 tremors (shown in Photo
1) was evaluated as Damage Rank II, and the only defects that
Rank
Ⅳ
Rank
Ⅴ
Rank
Ⅵ
