1565
Technical Committee 203 /
Comité technique 203
could be observed were displacement in the foundation of a
protective fence and broken corners of a single wall panel.
2.1.2
< Case 1.2 wall H
max
= 6.0 m, bank h = 0.0 m, L =
20 m, A = 60 m
2
>
All of the 10 walls in the surveyed area that were subjected to
high-intensity tremors (upper 6 to 7) resulted in classifications
of only Damage Rank I or II. In the wing wall shown in Photo
2 that was constructed adjacent to an abutment in an area hit by
intensity 7 tremors, no distress could be observed at all, hence
its classification as Damage Rank I.
2.2
Examples of structures damaged by the earthquake
2.2.1
< Case2.1 wall H
max
= 9.0 m, bank h = 4.0 m, L = 76
m, A = 453 m
2
>
Shown in Photo 3 is a wall whose panels displaced, not because
of earthquake tremors, but rather from increased earth and water
pressures coupled with decreased pullout resistance by steel
Photo 3. Collapse of embankment and the deformation of wall’s surface
reinforcing strip members. Damage was brought about by
incursion of rain water into the wall due to inadequate drainage
and earth turning into mud, because of slaking earth fill,
normally unsuitable for the use in reinforced fill structures.
Since the wall facing panels displaced, earth fill flowed out of
the wall, and the surface pavement of a road over the earth fill
subsided approximately 700 mm. The structure was determined
to be at Damage Rank VI.
2.2.2
< Case 2.2 wall H
max
= 9.0 m, bank h = 5.0 m, L = 200
m, A = 1,500 m
2
>
Along the boundary of a manufacturing site located in an area
hit by lower intensity 6 tremors, a wall slipped forward by up to
7.0 m, accompanied by the uplift of the ground in front (by 3.0
m) and the subsidence of the embankment at its back (Photo 4 ).
The structural integrity of the wall itself was confirmed through
a strength test on the steel reinforcements and panels, an in-situ
pull-out test on the reinforcing strips and laboratory tests on the
embankment fill. The presence of very soft foundation ground
was confirmed as a result of the in-situ boring and SPT tests
carried out after the earthquake (Figure 5); the entirety of the
reinforced earth fill seems to have slipped forward due to
general movement at depth with soil characteristics lower than
assumed during the design stage. This mechanism of general
sliding was confirmed by an analysis of safety rating carried out
considering soil characteristics assumed to have been present at
the time of the earthquake.
2.3
Example of damage caused by tsunami waves
2.3.1
< Case 3.2 wall H
max
= 6.0 m, bank h = 0.0 m, L = 60
m, A = 332 m
2
>
A levee for land reclamation which was retained with a
Reinforced Earth wall was washed away by the tsunami (Photo
5). Scouring of the foundation soil, loss of fill
,
and road
subsidence on top of the structure were observed near the
intersection point between the levee and the wall (Photo 6). The
height of the tsunami that went upstream exceeded the height of
the wall. The Reinforced Earth wall was divided into two walls
on each side of the levee, a seaside wall and a land-side wall.
Photo 4 . TA wall damaged by slipping forward
Figure 5. Result of boring survey
Since the earth levee was washed away, the bottoms of the walls
along the levee were exposed and subjected to severe erosion. It
can be presumed that this strong scouring caused the Reinforced
Earth fill to wash away and panels to fall down. Also, at some
locations, there were lower panels that may have been removed
because the foundation structure near the intersection with the
earth levee was exposed by the tsunami that washed away earth
fill from this point, which certainly further increased the local
water flow rate.
The noted phenomenon of erosion seems to have occurred due to
the shallow depth of wall embedment at 0.5 m, which was similar
to the standard depth provision for support of local road sections.
Another wall situated at a different point on the same peninsula,
with a 1.5m depth embedment, was subjected to the same
magnitude of tsunami waves and only rated Damage Rank I.
Photo 5. Upper view around wall and direction of the tsunami
Photo 6 . Damages of facing panels caused by the tsunami