1st International Conference on Microstructure Related Durability of Cementitious Composites
13-15 October 2008, Nanjing, China
STUDY ON THE TUNNEL SECONDARY LINING CONCRETE
CRACKING PERFORMANCE DURING SERVICE PERIOD OF WUGUANG PASSENGER DEDICATED LINE
Yan Liu (1) Xian Liu (2) Lei Huang (3) Guoping Liu (3)
(1) School of Material Science and Engineering, Tongji University, Shanghai 200092, China;
(2) Department of Geotechnical Engineering; Tongji University; Shanghai 200092; China
(3) Shanghai Royang Innovative Material Technologies Co., Ltd, Shanghai 200092; China
ABSTRACT
This paper is based on the research on the cracking control of the tunnel secondary lining
of Wu-Guang passenger dedicated line (Wu-Guang PDL) during service period and provides
a new method for evaluating the concrete cracking performance of the tunnel secondary lining
during service period. Firstly, research and modeling of the load-bearing mechanism of tunnel
secondary lining are made. Then the secondary lining concrete permeability under cyclic
loading is tested and the crack extension of the micro crack in concrete of tunnel secondary
lining is shown by air permeability coefficient. The test shows that cellulose fibers can
improve the anti-cracking performance of tunnel secondary lining concrete during service
period.
PREFACE
The tunnels of Wu-Guang Passenger Dedicated Line use the structure of shotcrete First
Lining + PVC waterproof board + concrete secondary lining. The speed of PDL can reach the
velocity of 350Km/h.Considering the air pressure and track vibration influence on the tunnel
secondary lining during service period and the similar projects in Germany, reinforcement
mat is generally used to control the crack of secondary lining. But that will cause the cost
rising and construction difficulty and reinforcement mat can not solve the problem of concrete
early age plastic cracking. the tunnel secondary lining of Wu-Guang passenger dedicated line
adopt the cellulose fiber concrete plan and use cellulose fibers as the reinforced material.
The anti-cracking performance is characterized by the concrete early age cracking and
shrinkage. There is no standard method to test and characterize the anti-cracking performance
on concrete during service period. This paper is based on the tunnel secondary lining project
of Wu-Guang PDL and research on the concrete cracking performance during service period.
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1st International Conference on Microstructure Related Durability of Cementitious Composites
13-15 October 2008, Nanjing, China
1. MODELING OF WU-GUANG PDL TUNNEL SECONDARY LINING DURING
SERVICE PERIOD
Firstly, this paper analyzes the load-bearing mechanism of Wu-Guang PDL tunnel
secondary lining and certified the influence factors and index of the secondary lining
concrete. Then, modeling and tests are made to characterize the anti-cracking performance of
secondary lining concrete.
1.1 Study on the load-bearing mechanism of Wu-Guang PDL tunnel secondary lining
It is shown that the problems of tunnel lining were usually caused by track vibration,
foundation changes and durability of construction material in some paper [1-3]. As for the
PDL, its features are:
(1) When the train pass the tunnel with high speed (350Km/h), the air flow in the tunnel
will be influenced which will cause the change of air pressure and may damage the tunnel
lining structure;
(2) Track vibration caused by high speed train passing may damage the tunnel lining
structure;
(3) The foundation changes caused by vibration may damage the tunnel lining structure.
1.1.1Analysis of finite element analysis model on the concrete structure of Wu-Guang
PDL tunnel secondary lining
According to the report of geological investigation of Wu-Guang PDL tunnel, the physical
and mechanical parameters of geo-material in the Dynamic Analysis are resulted by weighted
sums of several earth layers. As the Table 1 shows; Table 2 shows the material parameters of
tunnel secondary lining concrete.
Table 1 the Physical and Mechanical Parameters of Geo-material
density
( Kg / m3 )
1810
elastic
modulus
( Pa )
9.05×106
Poisson
ratio
0.45
cohesion
( Pa )
friction angle
(o)
1300
26
expansion
angle
(o)
26
Table 2 Material Parameters of Tunnel Secondary Lining Concrete
depth
(m )
11.5
diameter
(m )
5.5
thickness
(m )
0.35
elastic modulus
( Pa )
3.55×1010
Poisson ratio
0.15
density
Kg / m3
2500
In this paper, the horizontal and vertical calculating area of tunnel is 54 m (10 times the
tunnel radius) and 200 m long along the tunnel. The depth above and under the tunnel are 11.5
m and 45 m (10 times the tunnel radius).
According to the calculating modelling, the tunnel uses four nodes isoparametric element
and concrete lining uses two nodes beam element. Rock mass use elastoplastic DP
constitutive model and lining uses elastic constitutive model. The tunnel calculating
modelling and detail enlarging figure are shown as Fig1.
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1st International Conference on Microstructure Related Durability of Cementitious Composites
13-15 October 2008, Nanjing, China
Figure 1: The tunnel calculate modelling and detail enlarge figure
To reduce vibration reflection, the damping ratio is 0.45 in the calculating area and the
other material parameters keep constant. Outside the high damp material, the horizontal
displacement is restricted by four vertical sides and all degrees of freedom are fixed by
bottom nodes.
Setting the load of the train on the bottom of the tunnel (modelling), we can get the
dynamic response of the tunnel structure by using Newmark step integration method. Fig.2
shows dynamic response figure of tunnel cross section (t=0.35 s, L=0 m). It shows that
displacement of tunnel dynamic response is mainly at tunnel bottom which is 3-6 times the
displacements of side and top. It is because that the load of the train causes the tunnel bottom
vibration firstly, then the other parts. The vibration was reduced with the distance grows.
Fig.3 shows the static load response displacement of tunnel. The displacement caused by
Dynamic load is higher than static load of same load.
Figure 2: Dynamic response figure of
tunnel cross section
Figure 3: The static load response
displacement of tunnel
Fig.4 shows deformation time-history of the top and bottom of the tunnel lining at L=700m
tunnel cross section and it is supposed that the train arrives this cross section at t=3.5s. The
vibration changed from weak to strong and came to the top point when the train reached this
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1st International Conference on Microstructure Related Durability of Cementitious Composites
13-15 October 2008, Nanjing, China
cross section and then the vibration changed from being strong to weak. The vibration shape
of the lining top is mainly the same as the bottom and the amplitude is 1/4-1/2 times the lining
bottom and there is 0.05s time late than the bottom. The acceleration time history shows the
same feature as fig.5. It is shown that the testing curve is more complex than the calculating
figure curve. It is because that the realistic topographies were made by several earth layers
and vibration energy passing the soil interface will generate new wave source because of the
transmission and reflection and it will result in the distortion of the vibration wave and it is
complex to analyze the vibration stacking caused by wheels of the train.
Figure 4: Deformation time-history of the top Figure 5: The acceleration time history
and bottom of the tunnel lining
1.1.2 Conclusion on the analysis of the load-bearing mechanism of tunnel secondary
lining of Wu-Guang PDL
(1) The vibration load influence on the tunnel lining dynamic response is mainly
concentrated at tunnel inverted arch, arch foot and sidewall and has relatively small influence
on the part of arch waist and the arch top.
(2) The dynamic response problem under dynamic load of high speed train is in essence a
concrete tunnel lining fatigue property problem.
(3)the vibration frequency transported to the tunnel lining is comparatively low and mainly
at the scope of 5ᨺ40 Hz.
1.2 The research modeling of tunnel secondary lining during service period
Based on the analysis of the load-bearing mechanism of tunnel secondary lining, it is
concluded that the dynamic response problem under dynamic load of high speed train is in
essence a concrete tunnel lining fatigue property problem. The research takes the lining
concrete under fatigue load as the test modeling and simulates the control concrete and
cellulose fiber concrete structure under cycling load during service period, then further
research concrete anti-cracking performance of the tunnel secondary lining.
2. TESTING STUDY ON SECONDARY LINING CONCRETE PERFORMANCE OF
ANTI-CRACK DURING SERVICE PERIOD
The permeability of concrete mainly depends on existence and extension of tiny cracks
within concrete [4-6]. Thus, anti-permeability of concrete can character existence and
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1st International Conference on Microstructure Related Durability of Cementitious Composites
13-15 October 2008, Nanjing, China
extension when under load of tiny cracks within concrete. In this test, anti-permeability of
concrete after repetitive fatigue load is introduced and used in token of the high PDL tunnel
secondary lining concrete performance of anti-cracking when during service period.
2.1 Testing mixing ratio
Wu-Guang PDL tunnel secondary lining concrete mixing ratio is adopted in test, as shown
in table 3. Ultra Fiber 500 is used in the test, which is Cellulose fiber and produced by
Buckeye Technologies Inc. According to the standard trial method, 28d compressive strength
of concrete is tested by the sample size of 150 mm×150 mm×150 mm, as shown in table 4.
Table 3: mixing ratio(kg/m3)
composition
C
group
Plain
concrete
Cellulose
fiber
concrete
S
5~10mm
G
10~20mm
16~31.5mm
W
F
A
Fiber
272
781
91
466
580
147
105
4.524
0
272
781
91
466
580
147
105
4.524
0.9
Table 4: 28d compressive strength (MPa)
group
Plain concrete
Cellulose fiber
concrete
Sample 1
21.07
Sample 2
25.20
Sample 3
22.84
Average
23.04
24.36
26.49
23.44
24.76
2.2 Wu-Guang PDL Secondary lining concrete loading test
2.2.1 Sample preparation
Fatigue loading is used in this test, and purpose of this method is to bring the samples
recurrent load and give the samples moderate damnification but not destroy. According to test
equipments, the size of loading test samples is determined as 2100mm×400 mm×500 mm, as
shown in fig.6.
Figure 6: loading test size
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1st International Conference on Microstructure Related Durability of Cementitious Composites
13-15 October 2008, Nanjing, China
2.2.2 Testing method
In order to make comparison of different sample damnification due to different group, the
bending fatigue load testing apparatus is designed as fig.7.
Figure 7: testing apparatus sketch
This bending fatigue load test use the method of same extent sine wave load. Parameters
are assumed according to trial standard.
(1) Level of fatigue load
It can be concluded that the utmost tensile strength is about 2 MPa. As a result, the utmost
load M cr is shown as Eq.(1).
1
M cr = σ c h 2 b = 33.3kN ⋅ m
(Eq.1)
6
Where σ c is utmost tensile strength; h is sample height (500mm); b is sample width
(400mm); According to sample size and pensile point, pensile load M is calculated as Eq.(2)
qL L
qL L
M = 1 2 − 1 1 = 0.92kN ⋅ m
(Eq.2)
2 2
2 4
Where q is concrete average weight of per meter (25 kN/m); L1 is sample length (2.1m);L2
is the distance of pensile point (1.4 m).
According to the service condition, we assume that upper limit load M is 15% and 30% of
M cr , and actual load F is calculated as Eq.(3), as shown in table 5.
F L0 qL1 L1 § F qL1 · L0
−
+¨ +
(Eq.3)
¸×
2 6
2 4 ©2
2 ¹ 2
Where F is actual load( kN ); L0 is the distance of underprop point (1.8 m).
M =−
Table 5: testing load
Load plan
M ( kN ⋅ m )
Plan 1
5
10
Plan 2
10
32
F( kN )
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1st International Conference on Microstructure Related Durability of Cementitious Composites
13-15 October 2008, Nanjing, China
(2) Loading frequency
According to the theory analysis and the capacity of testing apparatus, loading frequency is
chose as 5 Hz. Sample is offloaded after 500,000 times’ recurrent fatigue load. Fatigue
loading test is shown as fig.8.
Figure 8: fatigue loading test
2.3 Anti-cracking performance test of Wu-Guang PDL secondary lining concrete
Because permeability of concrete has close relation with the existence and extension of
tiny cracks within concrete, anti-permeability performance of concrete can show existence
and extension of tiny cracks when under load within concrete. Special test method is
introduced into this test, including test sample and test apparatus. Air permeability is used to
be in token of Anti-crack performance.
2.3.1 Sample preparation
After fatigue loading test, cylinder samples are drilled from the bending section of the
beam in the width direction, which have diameter of 150 mm. and the testing samples are
intercepted by the sample’s thickness of 50 mm, as shown in fig.9.
Fig.9 testing samples
2.3.2 Air permeability testing apparatus
According to the testing standard, oxygen is pressed into the bottom of samples with fixed
pressure, and air permeability of concrete is deduced by testing air quantity in the top of the
samples. Testing pressure is 0.7 MPa, and testing apparatus is shown as fig.10.
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1st International Conference on Microstructure Related Durability of Cementitious Composites
13-15 October 2008, Nanjing, China
Fig.10 air permeability testing apparatus
2.4Testing conclusion
2.4.1Calculation of permeability coefficient
Permeability coefficient is calculated by Darcy law after modification when the air
quantity over cross samples maintains stable. Permeability coefficient under all levels of
pressure can be calculated as Eq.(4)
2 Pa Qi Lµ
ki =
(Eq.4)
2
2
A Pi − Pa
(
)
Where Pa is atmospheric pressure; Qi is the quantity of air bubble in unit time under i level
pressure; L is height of samples; A is acreage of samples’ cross section; µ is dynamical
sticky coefficient of air; Pi is the pressure in i level.
2.4.2 Testing result
In order to make comparison of air permeability in different level of recurrent load, Air
permeability coefficient under different levels of pressure is calculated, as shown in table 6.
From table 6, it can be concluded that when load level is 15% of utmost load, anti-air
permeability under different pressure levels of cellulose fiber concrete is improved than plain
concrete, but not obviously. When load level is 30% of utmost load, anti-air permeability
under 0.2MPa and 0.3MPa levels of cellulose fiber concrete is obviously improved than plain
concrete.
Table 6 air permeability coefficient under different load levels and pressure levels
Load level
Pressure level (MPa)
Plain concrete
cellulose fiber
concrete
Improvement (%)
0.15
6.57E-16
5.57E-16
15᧡
0.2
3.04E-16
2.81E-16
0.3
2.23E-16
1.96E-16
15.1
7.7
12.2%
2.4.3 Result analysis
From the test, it is concluded that:
792
0.15
8.17E-16
8.56E-16
30᧡
0.2
5.98E-16
3.80E-16
0.3
3.86E-16
2.30E-16
—
36.4
40.3
1st International Conference on Microstructure Related Durability of Cementitious Composites
13-15 October 2008, Nanjing, China
(1) Air permeability coefficient increases with load level heightens, which means
damnification within concrete is severer.
(2) After experiencing the same recurrent fatigue load, concrete by adding cellulose fibers
has less damnification inside than plain concrete. Because with same load level, air
permeability coefficient under different pressure levels of cellulose fiber concrete is less than
plain concrete.
(3) The improvement effect on anti-permeability is more obvious by adding cellulose fiber
into concrete when the fatigue load on concrete increases.
Adding cellulose fibers (UF500) into concrete can improve the ability of crack control
within concrete, and the improvement effect on anti-permeability is more obvious when the
fatigue load on concrete increases. It is significant to add cellulose fibers into PDL tunnel
secondary lining concrete, which suffered complex stress when in actual environment. It is
also ensured that it’s effective to improve the ability of in service concrete to resist crack by
adding cellulose fibers into PDL tunnel secondary lining concrete.
3. CONCLUSIONS
−
−
−
Based on the research on the cracking control of the tunnel secondary lining of WuGuang PDL during service period, a new method is mentioned in this paper to evaluate
concrete anti-cracking performance; anti-permeability of concrete after recurrent fatigue
load test can character existence and extension when under load of tiny cracks within
concrete.
After experiencing the same recurrent fatigue load, concrete by adding cellulose fiber
(UF500) has less damnification inside than plain concrete, because with same load level,
air permeability coefficient under different pressure levels of cellulose fiber concrete is
less than plain concrete.
The improvement effect on anti-permeability is more obvious by adding cellulose fibers
(UF500) into concrete when the fatigue loading on concrete increases. It is significant to
add cellulose fibers (UF500) into PDL tunnel secondary lining concrete, which suffered
complex stress when in actual environment.
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In: Proceedings of the 3rd International Symposium on Ground Freezing, Hanover, New
Hampshire, June 1982, 89–96.
[4] Banthial, N. and Bhargava, A. “Permeability of Stressed Concrete and Role of Fiber
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Materials and Structures , 2008, (41): 363-372.
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