Research Journal of Applied Sciences, Engineering and Technology 4(22): 4840-4844, 2012
ISSN: 2040-7467
© Maxwell Scientific Organization, 2012
Submitted: May 08, 2012
Accepted: June 08, 2012
Published: November 15, 2012
Experimental Research on Ground Deformation of Double Close-spaced
Tunnel Construction
Zhongchang Wang and Huijun Wu
School of Civil and Safety Engineering, Dalian Jiaotong University, Dalian 116028, China
Abstract: In this study, we obtain the optimal ratio of similar materials of soil layers by similarity principle
and uni-axial compression tests. The two-dimensional similar material model is established for Dalian
double-tube parallel tunnels line No.1. The laws of ground deformation for successively construction are
obtained by measuring the internal displacement of model. It is shown that the subsidence rate of early
period of construction is larger than that of lately period of construction. The vertical settlement rate of
shallow stratum is greater than that of deep stratum. The surface subsidence of two tunnels is
superimposed. The settlement is larger in the side of early excavating tunnel. The characteristic of non
symmetrical two peak of the vertical deformation of stratum is obvious. The horizontal displacement of
axis of two tunnels approximately decreases linearly with the increase of the depth. The horizontal
displacement in the location of center line and axis of two tunnels is not 0. The obvious shear layer appears
in the inner of the soil layers. The pile and shear wall within this range is easy to appear the crack owing to
tunneling.
Keywords: Double-tube parallel tunnels, ground settlement, model experiment, shear layer, the optimal
ratio
INTRODUCTION
The condition of the rock layers in Dalian area is
complex and changeful. The mining method becomes
the preferred construction method in interval and
subway station construction. The deformation and
disturbance of soil is complex owing to excavation of
two close-spaced tunnels. The studies of the double line
tunnel construction such as Gauss curve based on the
superposition theory (Suwansawat, 2007), normal curve
of double-round tunnel settlement (Addenbrooke and
Potts, 2001), settlement calculation formula caused by
soil loss (Wei et al., 2011), equivalent circle model
(Qinghuo, 2006), revised Peck method (Liu et al.,
2006), the random prediction method (Liu et al., 2008),
similar material model test of multi-arch tunnel of
highway (Li, 2008, Liu et al., 2010), centrifugal model
test of close spaced tunnel (Qinghuo, 2006) and
numerical analysis of double-line tunnel (Li et al.,
2010; Lin et al., 2009; Song et al., 2008) focused
mainly on settlement analysis of ground surface and
much research focused on shield tunnel. There are few
researches on deformation mechanism of different rock
layers by mining method. The similar material model
test which is used to study soil movement of tunnel
excavation is intuitive and effective method that can
avoid the mathematics and mechanics modeling
difficulties. Taking interval of double-line tunnel with
mining construction between Dalian xueyuan square
and maritime university as a model, the optimal ratio of
similar materials of soil layers is obtained by similarity
principle and uni-axial compression tests. The twodimensional similar material model of double tunnel is
established. The laws of deformation and disturbance
caused by construction are obtained by monitoring
internal displacement of the model. The scientific
reference is provided for tunnel construction (Ling
et al., 2010).
In this study, the optimal ratio of similar materials
of soil layers is obtained by similarity principle and uniaxial compression tests. The two-dimensional similar
material model is established for Dalian double-tube
parallel tunnels line no. 1. The measurement of inner
displacement of tunnel is conducted. The main results
are that the change of vertical displacement of different
strata with time can be seen as negative exponential
function of time; moreover, the settlement of double
tunnels is similar to superposition of single tunnel and
the horizontal displacement between two tunnels is very
small.
THE DESIGN OF SIMILAR MATERIAL
MODEL TEST
The range of interval of Dalian Metro Line no.1
project is located at AK18+406.03-AK19+621.10. The
Corresponding Author: Zhongchang Wang, School of Civil and Safety Engineering, Dalian Jiaotong University, Dalian
116028, China
4840
Res. J. Appl. Sci. Eng. Technol., 4(22): 4840-4844, 2012
3m
3m
4m
4m
axis of tunnel
10m
Fig. 1: Structural section of twin tunnel
Table 1: Mechanical parameters for soils of metro tunnel
Types of soil
Plain fill
Clay
Pebble
Strong weathering slate
Medium weathering slate
Thicknenss /m
4.1
2.2
1.7
3.5
30.5
Density
/kN/m3
16.2
17.9
19.3
24.6
25.1
Elastic
modulus
/MPa
19.5
22.4
24.8
29.7
43.8
Possion’s
ratio
0.37
0.33
0.32
0.27
0.24
Cohension
/kPa
10.7
21.2
4.2
35.4
55.3
Table 2: Similar materials test table of Sand, lime, gypsum, mica and water
Soil
Ratio of material
Plain fill
8.0: 0.7: 0.2:0.1: 1.0
Clay
8.0: 0.5: 0.2: 0.1: 1.0
Pebble
8.0: 0.5: 0.3: 0.2: 1.0
Strong weathering slate
8.0: 0.4: 0.4: 0.2: 1.0
Medium weathering slate
8.0: 0.4: 0.6: 0.1: 1.0
Equivalent reinforcing layer
6.0: 1.5: 0.3: 0.0: 1.0
Uniaxial
compressive
strength/MPa
10
8.4
14.5
10.9
21.7
Frictional
angle/°
13.2
24.1
25.4
33.8
38.2
Compressive strength /kPa
125
105
181
136
270
375
0.40
Stress (Mpa)
Ratio of pebble
Ratio of equivalent reinforcing layer
Ratio of weathered slate
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.8
4
0.6
3
0.4
6
0.3
0
0.1
7
0.1
2
0.0
9
0.0
6
0.0
5
0
0.0
0
Fig. 2: Compression test of different mixture ratio of sample
Strain (10×-2)
length is 1215.07 m. The bottom elevation of structure
is -14.3-3.20 m. The mining construction and composite
Fig. 3: Different compression test of different mixture ratio of
lining is used. The thickness of C25 concrete of initial
sample
support is 300 mm. The diameter of mortar anchor at
side wall is 22 mm. the length is 3.5 m. The space of
sand. The retarder is borax. To obtain similar physical
mortar anchor is 800×1200 mm. The diameter of the
and mechanical properties of materials, the
advanced small pipe is 42 mm which is set within the
compression test is conducted by 162 samples with
15° of arch. The space of steel mesh is 150×150 mm.
different ratio. The dimension of samples is 8×4×4 cm.
The space of steel grid frame is 800 mm. The
the number of samples with each ratio is 3. The days of
waterproof reinforced concrete of C35 and P8 is used in
natural conservation are 7 days. The test machine of
the two lining. The thickness is 400 mm. the space of
WE-2 is used to load. The loading rate is 2 mm/s. The
two tunnels is 10 m. The mean buried depth is 15 m.
uni-axial compressive strength of sample is determined.
The section diagram of tunnel is shown in Fig. 1. The
The compression test of samples with different material
mechanical parameters are shown in Table 1.
proportioning is shown in Fig. 2. The complete stressThe stratified medium is moca. The cementing
strain
material is gypsum and lime. The aggregate is fine
4841 Res. J. Appl. Sci. Eng. Technol., 4(22): 4840-4844, 2012
Table 3: Similarity ratio of material parameter
Name of similar
ratio
Value
Name
Length
50
Frictional angle
Density
1.6
Displacement
Stress
80
Possion’s ratio
Elastic modulus
80
Strength
Cohension
80
Time
Stress
1
External load
F
G
H
I
780mm
115mm
E
Value
1
50
1
80
7.07
2×105
R6
0
R6
0
A
B
C
D
1
2
3
4
5
6
7 pressure sensor
800mm
The pre-buried micro pressure sensors are used to
obtain internal stress of soil. The type of sensor is
BW11-2. The sensitivity is 0.01 kPa. The sensors are
connected with YE2539 high speed static data
acquisition system. The arrangement of sensors is nonequal interval. The arrangement of sensors is dense
when it is close to the tunnel. The surface displacement
of model is measured by the drawing grid lines. DJ6 the
odolite is used to measure the angle change of
intersection of grid lines on the fixed position. It is
shown in Fig. 4. The continuous monitoring of the soil
stress is conducted by stress sensor after the model is
completed. The displacement monitoring is conducted
when the stress field is stable after a day. Then the
tunnel is excavated. The successively tunneling is used.
The interval is 24 h. It is equivalent to the actual 7 days.
The supporting ring is installed when the tunnel is
excavated through. The continuous measurement is
conducted after excavation and support is completed.
The interval of displacement measurement is 4 h. The
interval of stress measurement is 30 min. The
arrangement of measuring points of stress and
displacement is shown in Fig. 4 and 5.
800mm
Fig. 4: Plane model and sensor placement
THE ANALYSIS OF EXPERIMENTAL
RESULTS
-3.5
C2
D2
E2
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
Time/h
Fig. 6: Time-settlement curve of 2# stratum
4842 192
96
112
12
8
14
4
16
0
17
6
80
48
64
32
0
0
curve of samples with different ratio is shown in Fig. 3.
The reasonable ratio and mechanical parameters are
shown in Table. 2. The first Digital of ratio number
indicates ratio of sand binder, the second, third or
fourth digital in one cement indicates the ratio of lime,
gypsum, mica powder. The ratio of 3:40: 40:20 denotes
3:1 of the sand binder ratio. In one cement, the ratio of
lime, plaster, mica is 0.4, 0.4, 0.2. The ratio of water is
1/9 of the mixture. The specimen is dried to 8% of
moisture content.
The physical and mechanical parameters, initial
conditions and boundary conditions should be all
similar on the basis of similarity ratio of bulk density
and geometric in elastic range. The geometric similarity
ratio is which is determined according to practical
tunnel buried depth and size of two tunnels and the size
of test table. The length×high×width of similarity
model is equal to 2.80×0.78×0.30 m. The radius of
tunnel model is 0.12 m. It is equivalent to 6 m. The
space of tunnel is 0.20 m. It is equivalent to10 m. The
similarity relations of model test are shown in Table 3.
16
Fig. 5: Displacement measurement
(mm)
A large number of test data are received after the
excavation of tunnel and 200 h of continuous
monitoring. The measuring points C2, D2, E2 and C5,
D5, E5 is selected to analyze vertical settlement rules of
stratum with time.
The vertical deformation curves of 2 and 5# ground
with time after tunnel excavation are given in Fig. 6 and
7. It can be seen that the settlement rate is larger within
the interval of 0-40 h. The settlement rate decreases to
be slow within the interval of 40-60 h. The settlement
rate increases after 60 h and be stable until about 100 h.
The maximum value of vertical displacement is located
nearby the axis of the tunnel, rather than the center of
two tunnel connection. The soil between two tunnels
has a pillar effect. The space of two d tunnels can
Res. J. Appl. Sci. Eng. Technol., 4(22): 4840-4844, 2012
-6.0
-4.5
C5
D5
E5
-5.0
-4.0
-3.5
-3.0
(mm)
-4.0
(mm)
2#line
4#line
5#line
-3.0
-2.0
-2.5
-2.0
-1.5
-1.0
-1.0
-0.5
0
-80 -60 -40 -20 -10
6
19
2
17
14 4
16
0
112
12
8
80
96
64
48
32
0
16
0
Fig. 7: Time-settlement curve of 5# stratum
-3.5
First day
Second day
Third day
Fifth day
Eighth day
(mm)
(mm)
-2.5
-2.0
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-0.2 -80
-0.4
-0.6
-0.8
-1.5
-1.0
-0.5
0
10
(Cm)
20
10
20
40
60
80
Fig. 10: Settlement trough of different strata at the third day
-3.0
0
-80 -60 -40 -20 -10
0
Time/h
Time/h
40
60
80
2#line
4#line
5#line
-55
-31
-7
12
36
61
(Cm)
Fig. 11: Horizontal curves of strata at the third day
The laws of settlement of 5 and 2# lines have similar
features. The proportion of settlement of 5# horizontal
line is bigger than that of 2# horizontal line with 5 days.
Fifth day
First day
The subsidence trough curve of different stratum is
Eighth day
Second day
shown in Fig. 10 at the third day.
-6.0
Third day
The value of settlement increases with the increase
-5.0
of depth. The width of settlement trough decreases with
the increase of depth. The width of settlement trough is
-4.0
about 30 cm. The settlement of double tunnels is similar
to superposition of single tunnel. The curve of
-3.0
settlement trough of first tunnel is shaped of typical
-2.0
normal distribution. The depth and width of settlement
trough is smaller. The settlement trough of double
-1.0
tunnels is obvious asymmetry. The settlement is larger
0
in the side of early excavating tunnel.
-80 -60 -40 -20 -10
0
10 20 40 60 80
The curve of lateral displacement of different
(Cm)
stratum at the third days is given in Fig. 11.
The lateral displacement of soil after tunnel
Fig. 9: Settlement trough of 5# horizontal line
excavation completed has closer trend to the center.
The variation range of lateral displacement is about effectively reduce the mutual disturbance. The vertical
0.6-1.0 mm. The extreme point of horizontal
displacement of upper stratum is slightly lower than
displacement of 2 and 4# stratum is located in about 20
that of lower stratum.
cm position of the distance of center line of double
The vertical settlement of 2 and 5# stratum is
tunnels. The trend is symmetrical. And the lateral
shown Fig. 8 and 9.
displacement is larger in the side of early excavating
The characteristic of non symmetrical two peak of
tunnel.
vertical deformation of stratum is obvious with the
The horizontal displacement of 5# stratum is
increase of depth. The settlement of upper stratum is
different
from that of 2 and 4# stratum. The point of the
larger than that of lower stratum. The ground
maximum horizontal displacement is located in 15 cm
subsidence of 2# stratum is bigger within the first three
of left side of center line of double tunnels. The point of
days. The value is about 70-80% of total settlement.
4843 (mm)
Fig. 8: Settlement trough of 2# horizontal line
Res. J. Appl. Sci. Eng. Technol., 4(22): 4840-4844, 2012
the maximum horizontal displacement of right tunnel is
same with that of 2 and 4# stratum. The horizontal
displacement of axis of two tunnels approximately
decreases linearly with the increase of the depth. The
horizontal displacement in the location of center line
and axis of two tunnels is not 0.
The lateral displacement of 5# stratum change
complex. The variation of lateral displacement of soil
between double tunnels does not have a consistent. The
variation of lateral displacement of measuring point on
both sides of tunnel is severe. The orientation of the
lateral displacement of 2 and 5# stratum is reversed at
the location X = ±5 and X = ±30 cm, as is shown in
Fig. 9. The soil layer with shearing motion is called
shear layer caused by tunnel excavation.
CONCLUSION
The optimal ratio of similar materials of soil layers
is obtained by similarity principle and uni-axial
compression tests. The two-dimensional similar
material model is established for Dalian double-tube
parallel tunnels line no. 1. The measurement of inner
displacement of tunnel is conducted. The main
conclusions are as follows:
•
•
•
The change of vertical displacement of different
strata with time can be seen as negative
exponential function of time. The settlement rate of
vertical displacements is different in different
monitoring time for the different measuring points
of same stratum. The initial settlement rate is larger
than later settlement rate. The settlement rate of
vertical displacements is different in measuring
points of different stratum for different monitoring
time. The settlement rate of shallow stratum is
larger than that of deep stratum.
The settlement of double tunnels is similar to
superposition of single tunnel. The curve of
settlement trough of first tunnel is shaped of typical
normal distribution. The depth and width of
settlement trough is smaller. The settlement trough
of double tunnels is obvious asymmetry. The
settlement is larger in the side of early excavating
tunnel.
The horizontal displacement between two tunnels
is very small. The horizontal displacement of axis
of two tunnels approximately decreases linearly
with the increase of the depth. The horizontal
displacement in the location of center line and axis
of two tunnels is not 0. The obvious shear layer
appears in the inner of the soil layers. The pile and
shear wall within this range is easy to appear the
crack owing to tunneling.
ACKNOWLEDGMENT
The author would like to thank the financial
support by the National Natural Science Foundation of
China (Grant No. 51009015) and Education
Foundation of Liaoning (No. L2010038).
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