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Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
by the piles to the effective load and that to the total load in the
tributary area versus time. The ratio of the load carried by the
piles to the effective load was estimated to be 0.70 just before
the end of construction and increased only slightly to 0.71 in
November, 2012. Meanwhile, the ratio of the effective load
carried by the deep mixing walls to the effective load was 0.14
and the ratio of that carried by the intact soil to the effective
load was 0.15 in November, 2012.
0
10
20
30
40
50
0
5
10
15
20
Dept h (m)
Axi al l oad (MN)
Mar. 29, 2010
Mar. 1, 2011
Mar. 16, 2011
Nov. 15, 2011
Nov. 3, 2012
5.4
Effects of earthquake on settlement and load sharing
On March 11, 2011, nine months before the end of construction,
the 2011 off the Pacific coast of Tohoku Earthquake struck the
site of the building. At the site of the twelve-story residential
building, the peak horizontal ground acceleration of 1.75 m/s
2
was observed (Yamashita et al. 2012). Although the contact
pressures between the raft and the deep mixing walls were
increased markedly as shown in Fig. 9(a), no significant
changes in the foundation settlement or the load sharing
between the raft and the piles were observed after the
earthquake, as shown in Figs. 5 and 11.
6 CONCLUSIONS
Field measurements were carried out on the foundation
settlement and the load sharing between the raft and the piles
for the large-scale piled raft with the grid-form deep cement
mixing walls on soft ground in Tokyo. The foundation
settlement reached 21 mm and the ratio of the load carried by
the piles to the effective load in the tributary area was estimated
to be 0.71 11 months after the end of construction. During the
construction period, the 2011 off the Pacific coast of Tohoku
Earthquake struck the site of the building. Based on the
measurement results, no significant changes in the foundation
settlement or the load sharing were observed after the
earthquake. Consequently, it is confirmed that a large-scale
piled raft, combined with grid-form deep mixing walls, works
effectively in grounds consisting of liquefiable sand and soft
cohesive soil.
7 ACKNOWLEDGEMENTS
The authors are grateful to Messrs. H. Matsuzaki, H. Nagaoka
of Takenaka Corporation and Mr. N. Nakayama (formerly of
Takenaka Corporation) for their contribution to the foundation
design.
8 REFERENCES
Katzenbach, R., Arslan, U. and Moormann, C. 2000. Piled raft
foundation projects in Germany, Design applications of raft
foundations, Hemsley J.A. Editor, Thomas Telford, 323-392.
Poulos, H.G. 2001. Piled raft foundations: design and applications,
Geotechnique 51, No.2, 95-113.
Tokimatsu, K., Mizuno, H. and Kakurai, M. 1996. Building damage
associated with geotechnical problems, Special Issue of Soils &
Foundations, 219-234.
Yamashita, K., Yamada, T. and Hamada, J. 2011a. Investigation of
settlement and load sharing on piled rafts by monitoring full-scale
structures”, Soils & Foundations, Vol.51, No.3, 513-532.
Yamashita, K., Hamada, J. and Yamada, T. 2011b. Field measurements
on piled rafts with grid-form deep mixing walls on soft ground,
Geotechnical Engineering Journal of the SEAGS & AGSSEA,
Vol.42, No.2, 1-10.
Yamashita, K., Hamada, J., Onimaru, S. and Higashino, M. 2012.
Seismic behavior of piled raft with ground improvement supporting
a base-isolated building on soft ground in Tokyo, Soils &
Foundations, Vol.52, No.5.
Just after
casting slab
Figure 8. Axial load distribution on pile P1
0
10
40
50
0
0
10 20 30 40 5
SPT N-Value
20
30
Depth（m）
-50
0
50
100
150
0
200
400
600
800
1000
Pressure (kPa)
Ti me (days)
200
E1
E2
E3
-50
0
50
100
150
200
0
200
400
600
800
1000
Pressur e (kPa)
Ti me (days)
D1
D2
D3
(b) Contact pressures between raft and soil
(a) Contact pressures between raft and deep mixing walls
Mar.11,2011
▽
End of construction
▽
Figure 9. Measured contact pressures and pore-water pressure beneath raft
Foundation slab
Nov.3,2012
▽
▽
Pore-water pressure
Pore-water pressure
Mar.11,2011
End of construction
Foundation slab
Nov.3,2012
▽
▽
▽
▽
Nov.3,2012
▽
0. 0
0. 2
0. 4
0. 6
0. 8
1. 0
0
200
400
600
800
1000
Rat i o of l oad carri ed by pi l es
Ti me (days)
Mar.11,2011
▽
End of construction
▽
Figure 11. Ratios of pile load to effective load and total load in tributary area
Total load
Effective load
Nov.3,2012
▽
0
10
20
30
40
50
60
70
80
0
200
400
600
800
1000
Load ( MN)
Foundation slab
▽
Piles
Soil
Buoyancy
Mar.11,2011
▽
End of construction
▽
Deep mixing walls
Design load 64.0 MN
Ti me ( days)
Figure 10. Time-dependent load sharing between raft and piles in tributary area
Foundation slab
▽
