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Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
5 MONITORING RESULTS
To validate and modify lining analyses and design, a series
of instruments was installed at the ductile segments. Figure 11
shows one selected section for instrumentation. In total, there
are nearly 380 m of the up-track line tunnel employed with
ductile segments where there are 8 cross-sections selected for
monitoring. The instrument layout for the cross-section at
chainage 0+690 m, the location where the closed clearance
(about 1.5m) is encountered, is shown on the figure as a
representative. An automatic monitoring system was built to
take hourly response from strain gauges and daily response
from earth pressure cells and pressure transducers. Figure 12
presents representative monitoring results at chainage 0+690 m.
Figure 11. Layout of instrumentaion
As illustrated by the figure, the passage of succeeding tunnel
stirred up a remarkable reaction in the readings. The readings
first remained at the relative high level when the segments of
preceding tunnel were erected and compensation grouting was
implemented. They then declined gradually to a level that is
equivalent to the in-situ stress and strain condition until a
sudden rebound at the tunnel passage.
For the earth pressure, a significant increase of about 50~70
kPa was observed at the locations that are closed to the
succeeding tunnel (i.e. EP6041 and EP6045). The increased
level remained after the tunnel passed by. For the hydraulic
pressure, the sudden increase of pore pressure (about 60 kPa)
was only obtained at the closest point to the succeeding tunnel
(i.e. EPE6041). After the tunnel passed by, the pressure dropped
to a level that is about 20 kPa higher than the previous in-situ
condition. As for the strain gauges, all the readings displayed
revealed significant increase at the tunnel passage and the
increased level remained afterwards. It is of special noted that
the lining could subject to tension (e.g. with strains on the order
of 10
-4
at CS6188) as a result of proximity effect.
6 CONCLUDING REMARKS
The ductile segments have been an alternative approach applied
to resist additional surcharge and deformation arisen from
proximity effect. While 2-D or even more sophisticated
numerical schemes can be exploited to investigate the
interaction between soils and tunnels or the proximity effect,
measurements from a thorough monitoring system would
provide invaluable retrofits to analysis and design. Engineering
judgment, however, should always be emphasized.
7 ACKNOWLEDGEMENTS
Permission for publishing this paper from Moh and
Associates, Inc. and Department of Taipei Rapid Transit
Systems of Taipei City Government is gratefully appreciated.
Special thanks to Dr. R.N. Hwang who helped prepare the
manuscript.
Figure 12. Monitoring results
8 REFERENCES
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Chin, C.T., Chen, J.R., Hu, I.C., Yao, D.T.C. and Chao, H.C. 2006.
Engineering characteristics of Taipei Clay.
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Properties of Natural Soils
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CSI. 2008.
SAP 2000 integrated software for structural analysis &
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Version 12, Computer & Structures, Inc.
ITASCA. 2000.
FLAC user
’
s guide
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JRCEA. 1977.
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Japanese Railway Civil Engineering Association. (in Japanese)
Kang, S.M., Guo, J.H., Chua, H.Y., Whang, Y.H. and Kao, C.C. 2007.
Design of the bored tunnel lining segments with close proximity
effects for Songshan Line of Taipei MRT System.
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International Structural Engineering & Construction Conference
(ISEC-4)
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Sstrait Seminar on Ground Engineering
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Kao, C.C., Kang, S.M., Lin, C.T., Su, T.C. and Whang, Y.H. 2007.
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Taipei Rapid Transit Company Web Site
,
.
-500
-400
-300
-200
-100
0
100
200
2010/7/21
2010/9/9
2010/10/29
2010/12/18
2011/2/6
2011/3/28
2011/5/17
Date
Strain
,εx10-6
CS6185
CS6186
CS6187
CS6188
CS6189
CS6190
CS6191
CS6192
8/12
8/27
compensation grouting
preceding tunnel (up-
track line)erected
succeeding tunnel(down-
track line)passingby
3/10
CS6188
CS6191
CS6189
CS6186
CS6190
CS6187
CS6185
CS6192
0
50
100
150
200
250
2010/11/18
2010/12/8
2010/12/28
2011/1/17
2011/2/6
2011/2/26
2011/3/18
2011/4/7
Date
WaterPressure, kPa
EPE6041
EPE6042
EPE6043
EPE6044
EPE6045
succeeding tunnel(down-
track line)passingby
3/10
EPE6043
EPE6044
EPE6045
EPE6041
EPE6042
0
100
200
300
400
500
600
2010/7/21
2010/9/9
2010/10/29
2010/12/18
2011/2/6
2011/3/28
2011/5/17
Date
Earth Pressure
,kPa
EP6041 EP6042 EP6043 EP6044 EP6045
8/12
8/27
compensation grouting
preceding tunnel (up-track
line) erected
succeeding tunnel(down-
track line)passingby
3/10
EP6041
EP6045
EP6042
EP6043
EP6044
(a) Earth pressure
(b) Hydraulic pressure
(c) Strain on lining
(a) Plan view
(b) Cross-section at
chainage 0+690 m
3.39
3.04
BelowNanjingW.Rd
BelowTaipeiCircle
BelowTianshuiRd
0+746
0+690
(the closest)
0+632
1.53
Ductile Segments for
Chainage 0+630~0+750 m
UT:up-track line
DT:down-track line
UT
DT
UT
DT
UT
DT
EP: earthpressure cell
EPE:pressure transducer
CS: straingauge
EPE6041
EPE6042
EPE6043
EPE6044
EPE6045
10
°
40
°
20
°
40
°
10
°
20
°
40
°
