Journal of Engineering Science and Technology
Special Issue on 4th International Technical Conference 2014, June (2015) 13 - 23
© School of Engineering, Taylor’s University
MINIMIZING DEFECTS OCCURRENCES ON SFRC
TUNNEL SEGMENT OF KLANG VALLEY MRT PROJECT
MOHAMMED HAKIMI B. ABDUL RAZAK, AMIRUDDIN ISMAIL*
Sustainable Urban Transport Research Centre (SUTRA) / Department of Civil and
Structural Engineering, Universiti Kebangsaan Malaysia, Malaysia
*Corresponding Author: aismail@ukm.edu.my
Abstract
Steel Fibre Reinforced Concrete (SFRC) precast segment has become more
demanded and common for major tunnelling works in the world. In general the
impact of demand along with the fast progress of the tunnelling works will
eventually affected the quality of the SFRC precast segment where past projects
showed the typical defects occur on the tunnel lining were mainly on concrete
spalling, leakages between the segmental lining and cracks on the precast
segment. This study will focus on the factors that encourage the occurrence of
these defects in order to implement a new method and procedure in minimize
the defects on the precast segment. The data collected such as inspection record,
visual inspection, and questionnaire distributed which aim on the method of
construction were analysed and SPSS were used for descriptive of the data. The
obtain results revealed that when the suggested method from the survey was
implemented during the construction of the Section 2: Tunnel from KL Sentral
Station to Pasar Seni Station, the numbers of leakages were dropped at 40.9%
by installing a secondary lining of Ethylene Propylene Diene Monomer
(EPDM) gasket. For spalling, by using lifting cage during handling of the SFRC
segment bring the number of occurrences dropped at 32.4% and using
protective pad for segment storage show the cracks across the segment dropped
at 34%. On top of the quality control procedure and common method of works,
this result revealed that by improving the area that involved workmanship does
give a biggest impact in minimizing the defects on SFRC precast segment.
Keywords: Tunnel, SFRC precast segment, Quality, Defects.
1. Introduction
In general, the use of SFRC Precast segment for tunnelling works has been
widely used as the fibre reinforcement is inessential for integrity, quality,
production and safety [1]. The quality requirement of the SFRC precast segment
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Minimizing Defects Occurrences on SFRC Tunnel Segment of Klang . . . . 14
has increased as part of the design life on the tunnel itself [2]. Every tunnelling
works in the world will try to avoid and minimize the defects on the tunnel
lining but during the construction works, an area which involves quantity,
progress, procedures and human error has eventually lead to defects
occurrences on the SFRC precast segment.
Past research that has done many experiments and testing from the
manufacturing of the segment until the installation stage of the segmental lining.
Research such as tensile and bend test were done to determine the mechanical
properties of the steel fibre [3]. Finite element analysis use to calculate the
segment stress distribution which will lead to cracks [4]. Study on differential
settlement of the tunnel to determine the contribution of leakages [5]. These
researches were mainly focused on the durability of the material which the results
show a positive used of SFRC precast segment for tunnel lining. This paper
however will focused more on the method of construction where workmanship
will be monitored and analyse as workmanship itself has always been an
important key in quality control of the SFRC segment.
The case study of the existing study is the tunnel works for the Malaysian
Klang Valley Mass Rapid Transit (KVMRT) which is currently the longest
underground tunnel in Malaysia that stretch for 9.5 km in the heart of Kuala
Lumpur. This case study however will be divided into two section of the tunnel
where Section 1: Tunnel from Semantan portal to KL Sentral Station (1.2 km) and
Section 2: Tunnel from KL Sentral Station to Pasar Seni Station (1.25 km). This
is a single case study where section 1 tunnel will be the phase of data collection to
determine the type of defects and the factors that lead to the defects occurrence. In
section 2 tunnel, the suggested method from the study will be incorporated during
the tunnelling works from KL Sentral Station to Pasar Seni Station.
The project records for Section 1: Tunnel from Semantan Portal to KL Sentral
Station was obtained and Table 1 shows the type and number of defects occur on
SFRC precast segment during the construction of the tunnel lining. The most
common defects are leakages and were recorded at 2,037 or 86% of the total
occurrences. This is followed by concrete spall or damage of the SFRC precast
segment which is at 340 occurrences or 14% of the total occurrences. The cracks
on the SFRC precast segment has been recorded as the lowest defects
occurrences, which is at 44 or 1.8% of the total occurrences
Table 1. Type and number of defects for section 1 tunnel.
North Bound
South Bound
Total
Leakages
Spalling
Cracks
743
1294
2037
117
223
340
37
7
44
The highest defect recorded which is the leakages was mainly occurring on the
radial or circumferential joint of the SFRC precast segment. Figure 1 shows the
typical joint leakages between the segmental linings. In general one of the main
contributions for the leakages between the segmental linings is the high
groundwater table or differential settlement of the tunnel [5]. In this case, 15
numbers of water standpipes were installed along the north and south bound
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M. H. B. A. Razak and A. Ismail
tunnel. The reading recorded by geotechnical department is from 1.0 m to 1.5 m
below ground level for a period of 9 months. Table 2 revealed that both south and
north bound tunnel having the average of 1.12 m (m.b.g.l).
Table 2. Water table reading for south and north bound tunnel.
Chainage (m)
Indicative
Depth
Type of Soil /
Average
(m.b.g.l)
Rock
Groundwater
From
To
Level (m.b.g.l)
0–8m
Silty SAND /
6447.093
7400
8m
Silty SILT
1.5 m
Bedrock
Limestone
0 - 10 m
Mainly
7400
8600
10 m
SAND
1.0 m
Bedrock
Limestone
0 - 10 m
Mainly
10 m
SAND
1.0 m
8600
9550
Bedrock
Limestone
Mainly
0 - 10 m
SAND
9550
10308.415
1.0 m
Bedrock
Limestone
As for the waterproofing lining, past research on tunnel waterproofing show
that the use of Ethylene Propylene Diene Monomer (EPDM) gaskets as lining
does play a role in minimize the leakage between the segmental linings [6-8].
However, in this project where the precast segment is using the same
waterproofing method, the occurrences of leakages is still highly recorded. From
the surveillance and survey done at the project site, many has agreed that the main
cause is the inclination of the thrust jack that damage the EPDM gasket thus
resulting in leakages between the segmental linings.
Fig. 1. Joint leakages between the tunnel segmental linings.
The second highest defect recorded according to Table 1 is the concrete spall
on the SFRC precast segment. Many researchers have agreed that these defects
were categorized as normal defect to be recorded during the manufacturing and
delivery stages [2]. From this project inspection record has revealed that concrete
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Minimizing Defects Occurrences on SFRC Tunnel Segment of Klang . . . . 16
spall or damage on the precast segment was normally detected during handling
and installation stages. Figure 2 shows the concrete spall at the edge and surface
of the precast segment. Although the installation of the segmental is semiautomated by the TBM erector, there are few stages where lifting is still using the
manual hoist chain which contributed to the spall.
Fig. 2. Concrete spall at the edge and surface of the precast segment.
Cracks on the SFRC precast segment has been recorded as the lowest
defects on the tunnel lining, affected only on 44 segments out of 17,280
segments install for section 1 tunnel. Although it is the lowest numbers of
defect recorded, cracks on the precast segment are considered a major type of
defects and required a high attention the rectification works. Figure 3 shows the
cracks on the SFRC precast segment.
Fig. 3. Cracks on the SFRC precast segment.
Past research showed that there were a few factors that lead to the cracks such as
eccentricity or inclination of the thrust jack, non-smooth ring joints and during casting
phase [9-12]. All the factors were typical to any other tunnel project and same for this
case as where the excavation is operated by Earth Pressure Balance (EPB) type of
Tunnel Boring Machine (TBM). If the proper installation process is done according to
the procedure, the numbers of crack should have been minimized [11].
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M. H. B. A. Razak and A. Ismail
2. Materials and Method
The methodological for this research consists of the project quality record that
will determine the type and numbers of defects recorded for section 1 and section
2 tunnels. A questionnaire is distribute at the project site and the data collected
will be interprets using SPSS and Microsoft Excel.
For the data collection, a survey was done at the project site with the
respondents for these surveys are the engineers, technicians, general labours and
supervisors at the project site that is handling the tunnel activity. The
questionnaire is kept simple, brief, using dichotomous type in order to get the
firm result. They filled in questionnaire forms at the project site office and at
construction site.
There will be three parts of questionnaires where first part (Part A) is on
leakages, the second part (Part B) is on concrete spalling and the third part (Part
C) is on cracks. For example under part A, leakages type of defects, respondent
will be given 3 choice of answer based on the common factor discovered at the
project site. At the end of every section, the respondent will be asked on their
opinion on how to reduce the defects mentioned in the questionnaire.
Table 3 shows the distribution of the questionnaire at the construction site. A
total of 83 questionnaires were collected in three months (from December 2013 to
February 2014). SPSS Statistics version 17.0 package and Microsoft Excel 2010
were used to analyse the data.
Table 3. Distribution of the questionnaire at the construction site.
Number of
Percentage
survey
of survey
respondents respondents
Total Respondents : 83
Survey distributed : 110
Response rate : 75.45%
N.B Tunnel
Job Title
Tunnel Engineer
Tunnel Supervisor
Technician
QA/QC Engineer
Construction Manager
TBM operators
Total North Bound
S.B Tunnel
Job Title
Tunnel Engineer
Tunnel Supervisor
Technician
QA/QC Engineer
Construction Manager
TBM operators
Total South Bound
Total
11
14
10
3
2
3
43
13.3
16.9
12.0
3.6
2.4
3.6
51.8
18
9
3
4
1
5
40
83
21.7
10.8
3.6
4.8
1.2
6.0
48.2
100.0
With this information gathered for the Section 1: Tunnel from Semantan Portal
to KL Sentral Station, the result will be incorporated during the construction of
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Minimizing Defects Occurrences on SFRC Tunnel Segment of Klang . . . . 18
Section 2: Tunnel from KL Sentral Station to Pasar Seni Station in order to evaluate
and minimize the defects on the tunnel lining using this SFRC precast segment.
3. Results and Discussions
3.1. Leakages type of defects
For leakages type of defects under part A questionnaire, based on Fig. 4, shows
77% respondents agreed that leakages occur on the segmental lining due to the
damaged waterproofing lining, Ethylene Propylene Diene Monomer (EPDM)
gasket, 12% agreed that leakages occur because of the ground water table and
11% stated that due to mix error on the backfilling grouting. Each answer selected
will lead to the sub section of questionnaire based on the respondent answer.
This paper shows the demographic result of the highest percentage answered
by the respondents. Figure 4 revealed that 70% respondents agreed that the
damage of waterproofing lining happened during the installation of the segmental
because of the inclination of thrust jack. Figure 5 shows the inclination of the
thrust jack 22% revealed that the EPDM gasket is not properly intact and checked
before installation and 8% agreed that the waterproofing lining is damaged during
unloading and lifting of the precast segment.
The last section of Fig. 4 shows that when respondents were asked their opinion
on how to avoid damage on the waterproofing lining 82% respondent suggesting
installing another strip of the EPDM gasket as a secondary waterproofing lining will
minimize the leakages. Another 9% respondents agreed that to double check the
EPDM gasket is intact before installation and another 9% stated that proper handling
of the segment during installation also play a role in minimize the occurrence of
leakages. Figure 5 shows an example when the thrust jack pressing the EPDM gasket
during excavation resulting damages to the lining and Fig. 6 shows the installation of
secondary strip of gasket lining to avoid the potential damages.
Part A : Leakages
Why do you think the leakages occur on the lining?
A.1 Due to damage of waterproofing lining
A.2 Due to high water table
A.3 Error in mixing for grouting
Total
Frequency
64
10
9
83
Percent
77.1
12.0
10.9
100.0
If your answer is due to damage of the waterproofing
A.1, what do you think that may lead to this damage?
A.4 Inclination of thrust jack
A.5 EPDM gasket not properly intact
A.6 EPDM damage during lifting works
Total
45
14
5
64
70.3
21.9
7.81
100.0
If your answer is due to inclination of thrust jack
A.2, what is your suggestion to avoid this defect?
Install secondary strip of lining
Proper handling of the segment
To check the intact of the gasket
Total
37
4
4
45
82.2
8.9
8.9
100.0
Fig. 4. Questionnaire data for the Leakages type of defects.
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M. H. B. A. Razak and A. Ismail
Fig. 5. Inclination of thrust jack that
damage the EPDM gasket.
Fig. 6. Secondary strip install at the
precast segment.
3.2. Spall and damaged of the precast segment
From the project surveillance record, most of the spall or damaged of the precast
occur during handling of the segments whether during unloading or during
installation of segmental lining. From the questionnaire, based on Fig. 7, revealed
that 55% respondents stated that the segment was damaged due to poor handling
at the project site. This is including the belt use by the crane is placed at the end
of the segment. 32% respondents agreed that when installing the last key segment,
the aggressive movement of the segment erector does make the segment spall and
12% believe that damage may occur at the manufacturer storage yard.
Part B : Spall and damaged on segment
Why do you think spall and damage occur?
B.1 Due to poor handling at project site
B.2 Due to movement of segment erector
B.3 Already damage from manufacturer
Total
If your answer is due to poor handling at the site
B.1, what is your suggestion to avoid this defect?
Improved the inspection during delivery
To use a lifting cage for unloading work
To improved workmanship on erector
Total
Frequency
46
27
10
83
Percent
55.4
32.5
12.0
100.0
21
22
3
45.6
47.8
6.5
100.0
46
Fig. 7. Questionnaire data for spall and damage of segment.
From the survey result, last section on Fig. 7 shows that when respondents were
asked their opinion on how to avoid spall or damaged on the precast segment, 46%
suggested that to improve the inspection during delivery of the precast segment.
48% agreed that to use a lifting cage when unloading instead of using belt. Others
7% stated that the segment erector to be handle properly during installation.
3.3. Cracks on the precast segment.
From the survey, 84% stated that during transportation and during stacking at the
project site, the segments were placed directly to the concrete support without
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having any rubber pad and cause the segments lay on uneven surface. This is
including the uneven timber support that was stacked between the segments
which distributed an uneven load to the segments which may lead to cracks when
shoving. 12% respondents believe that the segments was cracks due to uneven
thrust load during shoving and 4% respondents say that the segment already crack
at the manufacturer after casting phase. Figure 8 shows the factor that may lead to
the occurrence of cracks on the precast segment.
When the questionnaire asked the respondents on how to avoid the cracks
occurrences on the segment, from Fig. 8 revealed that 84% suggest that to apply a
protection between the concrete support and the segment to avoid any movement
or uneven load distribution to the segment during transportation and during
storage. 10% of the respondents stated that to make sure the stacking in on even
load and 6% suggest improving the inspection during delivery of the segments.
Part C : Cracks on the precast segment
Why do you think cracks can occur?
C.1 Segment placed directly on support
C.2 Due to uneven thrust load
C.3 Cracks occur at the manufacturer
Total
If your answer is due to segment stacking
C.1, what is your suggestion to avoid this defect?
To apply protection on concrete support
To make sure stacking is on even load
To improved inspection during unloading
Total
Frequency
70
10
3
83
Percent
84.3
12.0
3.61
100.0
59
7
4
70
84.2
10.0
5.71
100.0
Fig. 8. Questionnaire data for cracks on the precast segment.
Figure 9 shows the precast segment lay on concrete support without protection
and the use of gunny sack as padding between the segment and the concrete
support during the construction of section 2: Tunnel from KL Sentral Station to
Pasar Seni Station.
Fig. 9. Precast segment placed directly to the concrete support
and using gunny sack as protection during Section 2 Tunnel.
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M. H. B. A. Razak and A. Ismail
From the data collected on the survey, the highest percentage from the
opinions on how to minimize the occurrences of these defects were incorporated
during the tunnelling works for Section 2: Tunnel from KL Sentral Station to
Pasar Seni Station. The suggested method as follow;
• For the leakages between the segmental linings, the respondents suggested
that installing a secondary gasket on the segment lining will minimize the
leakages. Figure 6 shows the secondary lining install at the SFRC precast
segment before installation of tunnel lining.
• For the concrete spall or damage on the segment, the respondents suggested
using a lifting cage during unloading of the precast segment.
• For the cracks, the respondents believe that to apply a protection between the
segments during stacking/transportation. Figure 9 shows that gunny sack will
used as protective pad to avoid any uneven load distribution during stacking
Upon completion of Section 2: Tunnel from KL Sentral station to Pasar Seni
station, data collected from the joint inspection revealed that the total number of
leakages between segmental lining recorded is 833 nos. The concrete spall type of
defects recorded is 110 nos. and cracks on the segment are recorded at 15 nos.
Figure 10 shows the comparison numbers of the defects recorded for both Section
1 and Section 2 tunnel.
The opinion from the respondents were incorporated during construction of
section 2 tunnel show an improvement when the suggested method from the
respondents were implement during the tunnelling works. Table 4 shows that
the percentage for Leakages was dropped at 40.9%, the Spall at 32.4% and
Cracks at 34.1%.
2500
2037
2000
1500
1000
833
340
500
110
44
15
0
Leakages
Spall/Damage
Cracks
Section 1: Tunnel Semantan to KL Sentral Station
Section 2: Tunnel KL Sentral station to PasarSeni station
Fig. 10. Comparison of defects occurrences between section 1 and 2 tunnel.
Table 4. Percentage of defects occurrences between section 1 and 2 tunnel.
Section 1 Tunnel Section 2 Tunnel Percentage
2037
833
40.9
Leakages
340
110
32.4
Spall and damage
44
15
34.1
Cracks
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4. Conclusion
Upon completion of Section 1 : Tunnel from KL Sentral Station to Pasar Seni
Station, the main contractor has issue a Non Conformance Report for the defects
recorded. The suggested method from this questionnaire on how to minimize the
leakages, spall and cracks were used in replying the Non Conformance Report as
a preventive action. During the construction of Section 2: Tunnel from KL Sentral
Station to Pasar Seni Station these preventive actions were used until completion
of the tunnel works.
With the decreased percentage on all the defects during the construction of
Section 2 Tunnel, this study indicates that a simple improvement on the method and
workmanship does give a big impact in minimizing the defects. The suggested
method from the project site personnel who is handling the SFRC precast segment
eventually lead to a better quality result of this project. This is proven when the data
revealed using suggestion implemented on the Section 2: Tunnel from KL Sentral
Station to Pasar Seni Station. The highlight finding of this study is:
• The EPDM gasket will always get damaged due to inclination of the thrust
jack. Having to install a secondary lining that act as a primary gasket will
eventually reduce the leakages.
• As convenient and economical using belting type of lifting method, the result
will always lead to spall or damage on the segment. By using lifting cage,
longer time used during lifting but the numbers of spall on segment has been
minimized.
• On top of all experiments and analysis done on cracking of the segments by
past research, a simple improvement on the protection of the segment during
stacking or transporting actually help in reducing the cracks. This cracks
maybe not visible during stacking due to uneven load or no protection on the
support but after a certain load transferred to the segment during shoving, the
cracks will occur.
The finding of this research can be conclude that the standard quality control
implemented at any tunnelling project should have been improved in the area of
workmanship according to the project surrounding and behaviour in order to
minimize the occurrences of the tunnel lining using SFRC precast segment
Acknowledgment
The authors would like to acknowledge the Sustainable Urban Transport Research
Centre (SUTRA) and Department of Civil and Structural Engineering, Faculty of
Engineering and Built Environment, Universiti Kebangsaan Malaysia and MMC
Gamuda KVMRT Semantan North Portal Tunnel Team for their support given to
accomplish this study.
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