improving ground geomechanical characteristic for...
TRANSCRIPT
1. INTRODUCTION The three approaches for limiting the surface settlement
which are too important in conventional soft ground tunneling
techniques are [21];
1) Improving the ground condition ahead of the
advancing tunnel face with ground modification techniques,
2) Reinforcing the tunnel face with soil nails, and
3) Providing a protective vault over the tunnel face.
Permeation grouting consists of injecting a fluid grout
under moderate fluid pressures within the voids of the initial
soil, and the progressive solidification of the grout will confer
improved mechanical or hydraulic characteristics to the treated
medium. Grouting, by altering the pore structure, exerts a
significant influence over the mechanical and hydraulic
properties of the treated medium, in a way similar to
cementation. Indeed, both grouted and cemented soils pertain
to the family of structured soils, which signifies that their
mechanical behavior is governed by the structuring effect
created by the cementation between the grains, and implies
that the observations made on cemented sands can reasonably
be extrapolated to injected soils [14].
In recent years, grouting has been applied successfully in
many major tunneling projects to limit ground settlement [15].
For example, during tunnel construction projects in Lisbon
and for the underground construction of the Jubilee Line
Extension Project in London, extensive compensation
grouting systems were applied to protect the surface structure
around the area influenced by tunneling construction activities
[16, 17].
ATS11-03322
Improving Ground geomechanical characteristic for Ground movement control in
urban zone H.R.Pasand Masoumi
1, H.Salari Rad
2, K.Sarrafi
3
1Ms.c student in Amirkabir University of Tehran; [email protected]
[email protected] University; bof Amirka professorAssistant 2
3Ms.c of Rock mechanics , Amirkabir University of Tehran
ABSTRACT
Tunneling operation Analyses in 3D conditions is a widely used method to calculate tunneling induced
settlement profiles as well as soil structure interactions. The potential of damage, for the surface and/or
underground structures can be estimated using powerful finite difference method (FDM). However, setting up a
realistic model that would be able to achieve this goal is rather difficult. In this paper, a 3D FDM analysis has been
conducted to assess tunneling induced settlement and stress redistribution phenomena along with movements
around shallow soft ground tunnels excavation. Displacements recorded during construction of the Line 1 subway
Tunnel in Tehran formation were compared with the predicted values to validate numerical estimations. Back
analysis carried out on FDM results of soil zone, the data groups that have best accordance with recorded
measurements were selected. The results show that grouting has significant effect on tunnel stability and back
analysis results have accordance with soil geotechnical properties and grouted zone. Soil strength parameters
improved several times and soil permeability decrease significantly. Surveying groutability showed that an
increasing in grouting pressure, makes grouting possible in this zone.
Keywords
grouting, FDM, settlement, back-analysis, grout ability
Grouting can involve two high usage modes in urban
tunneling; (a) compaction grouting and (b) fracture grouting.
Compaction grouting often involves extrusion of a highly
viscous or mortar into voids in a compressible soil mass to
solidify the soil. Fracture grouting often involves injection of
low viscosity grout. However, hydraulic fracture of adjacent
soil can occur even in compaction grouting, resulting in loss of
control of grouting displacement. Hence, the two above
processes can occur at any stage of grouting. The possible
factors that affect the occurrence of different modes of
behaviors are type of grout, soil type, and stress history of the
soil, stress state, boundary conditions and rate of injection [9].
Surface and subsurface transverse settlement measured
during the Resalat Tunnel construction in 1992 have been
compared with the predicted results. The results of in situ tests
to evaluate strength and deformability properties of the soil
material are reported. These results are compared with those
obtained from numerical back analysis. The measured
convergence of the tunnel is used as an input for the back
analysis [1].
Numerical simulation, such as finite element analysis, is
commonly used to predict the ground movement due to
tunneling prior to construction. However, due to the
complexity of construction operation and soil model adopted,
it is often hard to obtain good agreement between the results
of analysis and actual observation. Therefore, it is necessary to
monitor the ground deformation during tunneling not only to
ensure the safety of construction but also to provide important
information for back-analysis. In this paper, the application of
optimization technique on back-analysis of tunneling induced
ground movement is described. The conjugate gradient
method was adopted for the optimization procedure, and the
equivalent ground loss model was used and modified by
introducing: (1) the angle of the influence zone of ground
settlement, and (2) the factor of backfill grouting derived from
gap parameter to account for the effect of construction [12].In
the present study, 3D Finite difference analyses have been
conducted to investigate ground movement profiles.
In previous research in Tehran urban alluvium, effects of
grouting on settlement control has not been studied, but in this
paper soilcrete geotechnical properties determined by
laboratory tests and back-analysis method, are presented.
2. GEOLOGICAL CONDITION OF TEHRAN
METRO
Tehran is located in geographical meridian 51.00- 51.44
and geographical latitude 35.22- 35.48. The case study is Pol-
e-Roomi region in Shariati Avenue that located in
geographical meridian 51.26 and geographical latitude 35.46.
Geotechnical map of environment civil map are shown in (Fig
1).
Fig 1-Tehran geotechnical map and urban situation [10, 11]
The materials encountered at the site are included of silty
and clayey gravel with sand, pebble, and cobble. Metro line 1
tunnel constructed or excavated approximately with 20m
overburden. Tehran alluvium in this region is silty and clayey
gravel with pebble and cobble. The properties of the soil are
given in table 1. The particle size distribution of Tehran
alluvium is illustrated in (Fig 2).
Fig 2- soil gradation curve [10]
Table 1- soil properties [10]
silty and clayey
gravel with sand,
pebble, cobble (GC)
& (GM)
Geotechnical name
7-9.6 % Water content %
0.32 Void ratio
19.7 Dry density
2.67 Specific gravity
162.5 Deformation modulus
55- 75% Degree of saturation
55 N70(SPT)
20 PI
30 PL
0.35 Poisson ratio
40 Friction angle
43 Consolidate friction angle
0.7 Cohesion
1.7 Consolidate cohesion
0.5 K0
3. TUNNEL CONSTRUCTION
Construction of the trial tunnel was started in 2007 with
the crown, bench, and invert face excavation (Fig.3). This
operation was completed by April 2010. Measurement and
monitoring of the construction process was conducted by the
supervisor engineers. In this project all information about
ground movements in the soil due to tunnel construction were
provided.
0
20
40
60
80
100
0.0010.010.1110100
% p
assi
ng p
rese
nt
particle size( mm)
Tunnel construction was carried out at 20 m crown depth
below the surface with having 8.30m height and 9.45 m width,
producing a 100-meter long running tunnel.
The shotcrete has been represented by elastic beam
elements in the analysis. Properties of these structural
elements are given in Table 2.
Table 2- tunnel support characteristic [11]
Support Thickness
(cm)
Elastic
modulus
(Gpa)
Poisson
ratio
Required
material
Shotcrete 30 10.5 0.25 Frame and
concrete
Lining 50 30 0.25 Lining(Frame
and concrete)
Fig 3 - Excavation phase
4. GROUTING AND LABORATORIAL TESTS
Grouting is a ground treatment method used to improve
soil behavior in areas of instability. The Technique requires
knowledge of certain useful soil parameters in order to take
into account, grouted soils as a material for structural designs
[2].
Nowadays, cement grouting is considered as one of the
major techniques used for soils stabilization in civil
engineering. It consists of injecting cement grout mixture
(with additives) into the soil under controlled pressures and
volumes. The main results expected from this process are a
reduction in permeability or/and an improvement in terms of
mechanical properties [3].
The main goals of shearing and unconfined compressive
tests are to gain compressive strength, peak and residual shear
strength. After 40-meter plan of grouting in the region, tunnel
excavation will be started in that pre-supported region.
Samples have been taken from the tunnel roof. Injected
boulders with dimensions 20-30cm were cut and core in rock
mechanic laboratory. Four samples for shearing test and two
samples for axial test were prepared. Shear test samples
should be in cubical or cylindrical form. Samples horizontal
and vertical strength are shown in table3. Shear-axial stress
curve of grouted samples and that test have been shown in
(Fig 4a).
Specimens for strength testing are required to have a
length-to-diameter (l/d) ratio of 2.00, because the variations in
the l/d ratio will affect the specimen strength [18]. In these
tests, samples are used with 66 mm diameter and 130 mm
length.
In Table 3, the unconfined compressive strength test
results of the 5-inch cement grouted soil samples are shown.
The slope of the tangent line on strain- stress curve at 50%
uniaxial strength is deformation modulus (fig 4b) and slope of
horizontal stress- vertical stress gives friction angle and
cohesion. Laboratorial test results on grouted soil are shown in
table 4.
Table3- shear test results and unconfined compressive strength of
grouted soil for 5-Inch long samples
(a)
(b)
Fig 4- (a) shear-axial stress curve and (b) stress-strain
curve of grouted samples
Tables 4- compare soil properties in grouted and before grouting
0
0.5
1
1.5
0 0.2 0.4 0.6 0.8 1
ho
rize
nta
l str
ess(
Mp
a)
vertical stress(Mpa)
0
2
4
6
8
10
12
0 1 2 3 4 5 6 7 8
vert
ical
str
ess
strain * 1000
shear test samples
Vertical stress
(Mpa)
Horizontal stress
(Mpa)
First 0.15 0.3
Second 0.40 0.8
Third 0.47 1.0
Fourth 0.8 1.35
Vertical
force(KN)
Horizontal
displacement(0.1
mm)
Horizontal
displacement
(0.1 mm)
Horizontal
stress
(Mpa) Strain
0.0 0.0 0.0 0.0 0.0
10 42 19 3.422 3.193
20 70 25 6.844 5.323
25 80 30 8.55 6.083
30 90 39 10.266 6.844
Soil
property
Density
(Kg/cm3)
Deformation
modulus(Gpa)
Cohesion
(Kpa)
Friction
angle
Before
grouting
2.00 0.160 17 43
Grouted 2.60 1.4 130 43
5. CALCULATE PERMEASION RADIUS
For grout permeation in fine sand and silt’s porous media,
we need some of the chemical grout with low viscosity.
Primary theory about permeation radius was based on
Newton’s fluid flow and shear strength in deformation
velocity was used to developing the theory [19].
Sodium silicate and AM-9 consider Newton’s behavior
grout whereas cement, lime and bentonite are Bingham’s
fluid. Whereas viscosity is an important nature of grouting,
their viscosity progressively increases. In Figure 5 Raffle and
greenwood’s investigations about permeation radius (r) of
Newton’s grout have shown [19].
This scheme allows to engineer to obtain an initial estimate
about permeation domain as spherical source with radius (r0)
cm.
(1)
bL
bL
br
log0
(2) )( 22 dLb
L: porous length
d: grout manchette diameter
r0: equal spherical source radius
For a cylindrical injection source, (r0) value equals to
radius that calculated following [14]:
Fig 5- calculate equal radius for cylindrical source [19]
Another relation about permeation domain is Maag
formula:
(3)
1
33
0
2
0r
r
n
n
nr
kht
w
g
ng : grout dynamic 15
viscosity (kg/cm.s)
kw: permeability (cm/s)
1.01
h: piezometric height
(cm)
2000
t: grout time(sec) 14000
n: void ratio % 0.24
r: permeation grouting
domain(cm)
1.18
q: grout fluid ratio
(m3/sec)
0.75*10-3
τf: shear resistant
(kg/cm2)
60*10-5
w : Water density
(kg/m3)
1000
Another relation for calculate (r0) is known as Karol’s
equation.
(4) )/(62.0 3 nnqtnr gw
Consider that values obtained for (r), are based on constant
value (ng). Constant value (ng) can be corrected just for resin
grouting and for considering viscosity increment with time,a
mean value should be estimated [4].
To prevent grout escape during injection, grout pressure in
free surface soil, should be less than overburden weight. To
study grout behavior in the area, Newton or Bingham fluid
results were used for calculations that are important for
engineers [4].In table 5 are shown determined permeation
radius with Maag and Karol equations:
Table 5- permeation radius and other constant
116.24 m
B 499.95
r(maag formula) 1.18 m
r(Karol’s formula) 0.88 m
6. GROUTABILITY
The matters of grout ability (N) in granular soils media
have been studied for many years. First solutions were
developed only based on grain-size of soil and cement,
whereas large-scale tests indicated that an accurate solution to
predict the N of granular soils is directly conducted by
different parameters of soil and grout. These parameters are
the grain-size of soil and that of the suspension grout, finer
content (FC) of soil passing through 0.6-mm sieve, grouting
pressure (P), relative density (Dr) of soil, and water: cement
(w:c) ratio (or viscosity) of grout [5]. Burwell (1958) defined
it for the suspension grouts in the following simple equation:
(5)
Where N is the grout ability of soil, D15 is the diameter
through which 15% of the total soil mass passes, d85 is the
diameter through which 85% of the total grout mass passes.
According to this equation, if N is larger than25 (N>25), then
grout can be successfully injected into the soil. Conversely, if
N is smaller than 11 (N<11), then grout cannot be sufficiently
injected into the soil. However, Burwell (1985) explains that if
N>25, the following equation should be used in addition:
(6)
Where D10 is the diameter through which 10% of the total
soil mass passes, d95 is the diameter through which95% of the
total grout mass passes. In this second situation, if N is larger
than 11 (N>11), grouting is possible, but if N is smaller than 5
(N<5), the grouting is not possible. The newly developed
empirical formula based on test results and Esq.7 is presented
as:
1 1 2 2 3N N K N K N
(7)
Where k1and k2are constant and if we write the values of
N1, N2, and N3in the Eq.(7), we obtain the equation for N:
⁄
(8)
where N is soil grout ability, D10 is soil particle-size, d90 is
the diameter through which 90% of total grout mass is
passing, w:c is water: cement ratio of grout, FC is the finer
content of soil passing through a 0.6-mmsieve, P is the
grouting pressure in KPa, and Dr is relative density of soil
samples. (Unit less) and in 1/kPa are the
constants based on experimental observations to normalize the
N values from Eq. (8). In this study, N1, N2, N3 values of grout
ability were obtained. Percent effect of these elements on
grout ability has been presented in tables 6, 7. Following these
parameters N=29.2>28 are obtained for this state.
Table 6- soil and grouting parameter
rD W:c P(kpa) D15(soil)
D85(grout)
cF
0.58 1:1 1300 0.12mm 0.025mm 0.25
Table 7- parameter values and their effects on grout ability
Parameter N1 K1N2 K2N3
Value 4.8 2 22.4
Percent 16% 7% 77%
7. INSTRUMENTATION IN TEHRAN SUBWAY
LINE 1
There are three general methods for predicting the ground
deformation associated with soft ground tunneling: (1)
analytical methods, (2) empirical methods, and (3) numerical
methods such as the finite element or finite difference
techniques [6].Surface measuring equipments consists of
survey camera were used to measure vertical displacement.
To calculate settlement of tunnel drilling, observation
points should be put on the surface (Fig 6). These points have
been monitored in 8 times (in 85 days) by survey camera
(TCR805). Because of grouting, in some of the monitoring
points the ground surface was uplifted. The uplift was reached
9 mm in some points. Point monitoring had been done from
2009/5/15 until 2009/8/7. Results of these points are shown in
table 8.
Fig 6- survey points arrangement and settlement surface
The typical deformation patterns observed in profile had
approximately 17 mm of ground surface settlement over the
centerline of the tunnel. Approximately 23% of the maximum
settlement occurred before tunnel axis.
Table 8- surface settlement monitoring results
Date
2009/5
/15
2009/5
/22
2009/6
/5
2009/6
/19
2009/7
/3
2009/7
/10
2009/7
/17
2009/8
/7
KM
17+
136.7
0
17+
143.4
7
17+
153.7
3
17+
164.3
0
17+
178.3
0
17+
178.3
0
17+
179.7
5
17+
187.2
5
Points
A1,1 1 0 -1 -2 1 2 1 0
A2,1 1 -3 0 -1 -3 1 0 0
A3,1 -3 0 -1 1 -2 0 1 0
A1,2 4 -3 1 -3 -2 2 0 0
A2,2 -9 -3 1 -1 -4 -1 -1 1
A3,2 -7 -1 -1 -1 -2 0 -2 2
A1,3 0 1 0 -2 -1 3 2 2
A2,3 0 -1 3 2 0 1 0 2
A3,3 -5 0 0 1 -1 5 2 1
A1,4 3 2 -1 -3 -1 5 8 9
A2,4 3 1 3 3 2 4 8 4
A3,4 -9 -2 5 1 -4 7 1 4
A1,5 2 0 2 0 1 5 7 11
A2,5 1 1 2 1 3 2 5 8
A3,5 1 0 4 3 1 6 5 5
A1,6 -8 3 5 3 2 6 8 15
A2,6 2 3 -3 -4 5 5 2 8
A3,6 0 2 1 2 5 7 7 8
A1,7 -9 4 4 2 2 7 9 15
A2,7 1 4 0 2 4 7 6 9
A3,7 3 3 4 2 3 7 8 8
A1,8 -9 5 5 2 3 6 9 13
A2,8 2 3 2 4 6 11 8 10
A3,8 7 3 4 3 3 9 10 9
To study the settlement, quantity of instrumentations data
will check with empirical equations, at the end it will compare
with numerical results.
In the following sections, by using relations of Peck and
Saga seta, the quantity of settlement, volume loss and
horizontal movement for the soil of this region are obtained.
The empirical parameters for Gaussian have a good agreement
with the observed settlement summarized in table 9.
Table 9- empirical settlement parameters
Subsidence
parameter
Values
6.52* 10-3 m
Smax 17 mm
Overburden 20 m
I 8 m
8. BACK ANALYSIS
Back-analysis methods can be categorized in two groups;
direct and inverse. In the inverse manner math formulizing is
opposite of direct method absolutely. In these methods, the
number of measured data should be more than quantity of
undefined data to use optimization technique. Infirmity of this
method is obtaining solving path in geotechnical problem that
be numerically stable [7]. Direct- method minimize different
measured and calculated data. This method takes long time
but it is sufficient for unlined and intricate geotechnical
problem [8].
For insurance back-analysis singularity solves and to
increase processing, parameters should choose in basis of
these conditions as the following [20]:
1) Choosing the parameters that have major effect on
underground structure stability.
2) Choosing the parameters which determination of
them will be hard with the other methods.
3) Decrease in number of unknown parameters if it can.
8. 1. Error-function
In this study, minimal error-function method was used. If
it is supposed that ui is monitored displacement with
instrumentation for (n) points and ui’ is calculated
displacement with numerical modeling in like points, then
error- function (f) defines relevant to minimum square method
in Eq.9 [13].
(9) ' 2
1
( )n
i i
i
f u u
8. 2. Model geometry and boundary condition and
material properties
According to symmetry condition, only half of tunnel was
chose to being simulated into the model. A size of 20 meters
was selected for model width due to its radius of 5 meters. Its
length was also decided as 90 meters in order to cover
completely excavated area in addition to the subjective area in
the face. At last, model height was decided to be 40 so as it
would be able to show the burden and the tunnel floor for
eliminating detected or omitting boundary condition effect.
The model grid used in the analysis is shown in figure 7.
The model was restricted by roller boundary in the horizontal
direction at each side, which means that vertical movement
was allowed, and the bottom part of the boundary was pinned,
so neither vertical nor horizontal movements were allowed.
The top surface of the model was free in three directions. The
construction process of the Tehran metro line-1 consists of
heading and bench excavation. These operations was followed
by the excavation of the heading and primary support such as
shotcrete and mesh, bench excavation and finally closing the
ring of support. In order to imitate the same construction
process in FLAC analysis, sequential excavation model
(SEM) was employed.
Material properties (according to table 1), inside stress
condition, and additional force of 0.1 MPa (as pressure of
surface and surrounding structures), all is applied to the
model. Mohr’s model was used as a solution getting its
required modules (e.g. Yang modulus, Poisson, cohesion).
Figure 7 shows model geometry and injected area as well as
remnant stress counters prior to the drilling.
(a)
(b)
Fig 7- (a) model geometry and injected domain, (b) support in
FLAC3D consist of frame, shotcrete, lining
8. 3. Back-analysis and numerical modeling
Figure 8 shows a flowchart of modeling and solution
process for this project in “Flac3D” software.
Fig 8-Flac3D analysis flowchart for this tunnel excavation and
grouting
8. 4. Back-analysis results
In figures 9, 10the quantities of error- function with
parameters E,c, φ have been showed. To compare between
laboratorial tests and back analysis, results were shown in
table 10.
(a) (b) Fig 9- Error function (f) variations to deformation modulus and
friction angle in (a) C= 0.45, (b) C= 0.3(Mpa)
(a) (b)
Fig 10- Error function (f) variations to deformation modulus and
cohesion in (a) φ= 42, (b) φ= 43
Table 10- grouted soil results in laboratorial tests and back analysis
Soilcrete
property
Deformation
modulus(Gpa)
Cohesion
(Mpa)
Friction
angle
Laboratorial 1.4 0.13 43
Back analysis 1.7 0.35 43
9. COMPARISON BETWEEN GROUTED AND
UNGROUTED CONDITION
9. 1. Tunnel excavation without grouting
For justification of the injection, the amount of subsidence
has to be checked through simulation of the excavation on the
model. The properties of soil before injection is shown in
table 1. The subsidence profile obtained from numerical
analysis shows that maximum amount of subsidence would
reach even to 10 cm. The gradient of longitude subsidence in
injected case is fairly more than of un-injected one.
9. 2. Tunnel excavation with grouting
Injection in the upper zone of the tunnel strengthens soil
parameters and increases the period of self-holding of tunnel
roof. The subsidence curve caused by drilling is shown in
figure 11 to be compared with remnant results.
(a)
(b)
Fig 11- (a) displacement counters without grouting (b)
displacement counters around tunnel after excavation
Figure 12 shows subsidence before reaching to drilling
station. Figure 13 shows subsidence profile after drilling
station advances for 45 meters. Figures 14 and 15 show
subsidence profiles in two different distances: 7 meters (street
border) and 11 meters (footpath).
Fig 12- longitudinal settlement profile at the first of
excavation in A-A′ section (date 2009/4/15)
Fig 13- longitudinal settlement profile in A-A′section(2009/8/7)
Fig 14- settlement profile in B-B′ section (date 2009/8/7)
Fig 15- settlement profile in C-C′ section (date 2009/8/7)
In figure16, settlements caused tunnel excavation
compared in grouted and ungrouted condition. It can be seen
that settlement in ungrouted state is largely higher than
grouted state.
FLAC3D 2.10
Itasca Consulting Group, Inc.Minneapolis, MN USA
Step 58099 Model Perspective21:37:06 Sat Jan 23 2010
Center: X: 1.627e+001 Y: 4.386e+001 Z: 2.000e+001
Rotation: X: 0.000 Y: 0.000 Z: 20.000
Dist: 1.556e+002 Mag.: 1Ang.: 22.500
Plane Origin: X: 0.000e+000 Y: 0.000e+000 Z: 0.000e+000
Plane Normal: X: 0.000e+000 Y: 1.000e+000 Z: 0.000e+000
Job Title: "tunnel shariati" " ghabl tazrigh "
View Title:
Surface Magfac = 0.000e+000
Contour of Z-Displacement Plane: on Magfac = 0.000e+000
-5.2900e-001 to -5.2500e-001-5.0000e-001 to -4.7500e-001-4.5000e-001 to -4.2500e-001-4.0000e-001 to -3.7500e-001-3.5000e-001 to -3.2500e-001-3.0000e-001 to -2.7500e-001-2.5000e-001 to -2.2500e-001-2.0000e-001 to -1.7500e-001-1.5000e-001 to -1.2500e-001-1.0000e-001 to -7.5000e-002
FLAC3D 2.10
Itasca Consulting Group, Inc.Minneapolis, MN USA
Step 116036 Model Perspective20:44:03 Fri Jan 08 2010
Center: X: 1.582e+001 Y: 4.288e+001 Z: 2.000e+001
Rotation: X: 0.000 Y: 0.000 Z: 20.000
Dist: 1.556e+002 Mag.: 1Ang.: 22.500
Plane Origin: X: 0.000e+000 Y: 0.000e+000 Z: 0.000e+000
Plane Normal: X: 0.000e+000 Y: 1.000e+000 Z: 0.000e+000
Job Title: "tunnel shariati"
View Title:
Surface Magfac = 0.000e+000
Contour of Z-Displacement Plane: on Magfac = 0.000e+000
-2.0805e-002 to -2.0000e-002-2.0000e-002 to -1.5000e-002-1.5000e-002 to -1.0000e-002-1.0000e-002 to -5.0000e-003-5.0000e-003 to 0.0000e+000 0.0000e+000 to 5.0000e-003 5.0000e-003 to 1.0000e-002 1.0000e-002 to 1.5000e-002 1.5000e-002 to 2.0000e-002 2.0000e-002 to 2.1992e-002
-4
-2
0
2
4
6
8
10
0 12.5 25 37.5 50 62.5 75 87.5
sett
lem
ent
(mm
)
tunnel axis (m)
longitudinal settlement profile
0
2
4
6
8
10
12
14
16
18
0 10 20 30 40 50 60 70 80 90 100
sett
lem
ent
(mm
)
tunnel axis (m)
longitudinal settlement profile
02468
1012141618
0 10 20 30 40 50 60 70 80 90 100
sett
lem
en
t (m
m)
tunnel axis (m)
longitudinal settlement profile numerical result
02468
1012141618
0 10 20 30 40 50 60 70 80 90 100
sett
lem
en
t(m
m)
tunnel axes
Longitudinal settlement profile numerical result
Fig 16- comparison between grouted and ungrouted conditions
Figure 17 shows stress distribution after drilling, displays
stress concentration in tunnel walls.
Fig 17- stress distribution around tunnel after excavation
10. DISCUTION
In the construction of the Tehran metro Line 1, grouting
operations were conducted to prevent groundwater inflow to
tunnel and improve the soil geotechnical properties.
Waterproofing membrane was place between the primary
support and inner lining due to high permeability of
surrounding soil.
In 10 June 2008 during top-face excavation of north tunnel
in west side encountered to massive boulders that
accompanied by intensive seepage, after removing boulders,
and a cavern was created an overbreak occurred suddenly.
Water seepage enlarged the cavern in dimensions 4*10*8m.
To prevent overbreak, pregrouting scheme for the left parts of
tunnel was proposed. In the following, the pregrouting
procedure was explained.
Geological and geotechnical properties have high affects in
tunnel excavation and support system. Tunnels excavated in
this area because of high water-level are unstable; drainage
can be effective in tunnel stability. Major problem in tunnel
excavation is meeting massive boulders in tunnel roof and
walls that removing them made the cavity unstable.
The grout take for contact grouting also examined with
respect to site and excavation parameters such as groundwater
and soil gradation. Laboratory test results show that grouting
will improve soil geotechnical property. Soilcrete deformation
modulus was improved almost eight times higher than soil,
and cohesion was improved twenty times.
Examination of the stress–strain characteristics of grouted
and cemented soil have shown that the stiffness and the
strength of granular media are significantly improved by an
increase of cement content, while the brittle- to-ductile
transition is shifted towards higher pressures when the
cementation degree increases. Grout ability factor is 29.2 that
shown successful grout. Grouting pressure has an important
effect on grout possibility. Calculation permeation radius by
empirical relations can found for initial design for grouting
borehole arrangement.
By shear and uniaxial tests results supply 46 groups’
geomechanical data to solve them with numerical method.
These subsidence results compared with real subsidence and
with back- analysis to determine error-function for every data
groups. To compare error quantities, selecting a group with
lowest error-function for grouted soil is necessary.
REFERENCES
Periodicals and journal papers: [1] Fakhimi,A., Salehi, D., Mojtabai, N. 2004. Numerical back analysis for
estimation of soil parameters in the Resalat Tunnel project.Tunnelling and
Underground Space Technology.vol 19. pp 57–67
[2] Delfosse-Ribay, E., Djeran-Maigre, I.,Cabrillac,R., Gouvenot, D. 2004.
Shear modulus and damping ratio of grouted sand. Soil Dynamics and
Earthquake Engineering 24.Pp. 461–471
[3] Maghous, S., Saada, Z., Dormieux, L., Canou, J., Dupla, J.C. 2007. A
model for in situ grouting with account for particle filtration. Computers and
Geotechnics.vol 34. Pp. 164–174
[4] Karol, R.H.; 1968; Chemical Grouting technology; Journal of the soil
Mechanics and foundations Division, ASCE, vol 94, pp 175- 204
[5] Akbulut, S, Saglamer, A; 2002; Estimating the groutability of granular
soils: a new approach; Tunnelling and Underground Space Technology, vol
17.Pp 371–380
[6] Loganthan, N., Poulos, H.G.1998. Analytical prediction for tunnelling
induced ground movements in clay. Journal of Geotechnical and
Geoenvironmental Engineering 124(9); pp. 846-856.
[7] Feng, X., Zhao, H., Li, Sh. 2004. A new displacement back analysis to
identify mechanical geo-mechanical parameters based on hybrid intelligent
methodology, International journal for numerical and analytical methods in
geomechanics, vol 28
[8] Sakurai, Sh., Akutagawa, Sh., Takeuchi, K., Shinji, M., Shimizu, N.
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Ground Movement Using Equivalent Ground Loss Model, Geotechnical
Engineering Research Center, Sinotech Engineering Consultants, Inc.
[10] Consultants engineer report Pey- Sang, 2005. Tehran subway line 4,
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[11] Consultants engineer report SANO, 2004. Tehran subway line 1, Initial
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Papers Presented at Conferences (Unpublished): [12] Jafari, M. R., Au S. K., Soga K., Bolton M.D., Karim U. F. A.,
Komiya, K. Experimental and numerical investigation of compensation
grouting in clay
[13] Mahdoori, S., Fathi, E. 2007. Determination rock-mass geomechanic
parameters in Esfehan subway to back analysis. Mining engineering magazine
-100
102030405060708090
100110120130140
0 10 20 30 40 50 60 70 80 90 100se
ttle
me
nt
(mm
)
tunnel axis (m)
grouted ungrouted
FLAC3D 2.10
Itasca Consulting Group, Inc.Minneapolis, MN USA
Step 116036 Model Perspective20:45:44 Fri Jan 08 2010
Center: X: 1.582e+001 Y: 4.288e+001 Z: 2.000e+001
Rotation: X: 0.000 Y: 0.000 Z: 20.000
Dist: 1.556e+002 Mag.: 1Ang.: 22.500
Plane Origin: X: 0.000e+000 Y: 0.000e+000 Z: 0.000e+000
Plane Normal: X: 0.000e+000 Y: 1.000e+000 Z: 0.000e+000
Job Title: "tunnel shariati"
View Title:
Surface Magfac = 0.000e+000
Contour of SZZ Plane: on Magfac = 0.000e+000 Gradient Calculation
-1.0906e+000 to -1.0000e+000-1.0000e+000 to -9.0000e-001-9.0000e-001 to -8.0000e-001-8.0000e-001 to -7.0000e-001-7.0000e-001 to -6.0000e-001-6.0000e-001 to -5.0000e-001-5.0000e-001 to -4.0000e-001-4.0000e-001 to -3.0000e-001-3.0000e-001 to -2.0000e-001
Papers from Conference Proceedings (Published): [14] Bouchelaghem, F., Benhamida, A., Dumontet, H. 2007. Mechanical
damage behavior of injected sand by periodic homogenization
method.Computational Materials Science 38. Pp. 473–481
[15] Mair, R. J., Harris, D. I., Love, J. P., Blakey, D. and Kettle, C. (1994).
Compensation grouting to limit settlements during tunnelling at Waterloo
Station. Proceeding Tunnelling 1994, London, Institution of Mining and
Metallurgy, Chapman and Hall, pp. 279 - 300.
[16] Harris, D. I., Menkiti , C. O., Pooley, A. J. and Stephenson, J. A.
(1996). Construction of low-level tunnels below Waterloo Station with
compensation grouting for Jubilee Line ExtensionÓ. Symposium on
Geotechnical Aspects of Underground Construction in Soft Ground, London,
R. J. Mair and R. N. Taylor Eds, pp. 361 - 366.
[17] Schweiger, H. F. and Falk, E. (1998). Reduction of settlement by
compensation grouting Numerical studies and experience from Lisbon
underground. Proceedings of The World Tunnel Congress 1998 on Tunnel
and Metropolises, Sao Paulo, April, A. Negro and A. A. Ferreira Eds., Vol. 2,
pp. 1047 - 1052.
[18] Journal of American Concrete Institute. 1951. (Unconfined
compressive stress) Vol. 47, No. 6,pp. 417-432
[19] Raffle,J.F. Greenwood, D.A; 1961; The relation between the
rheological characteristics of grouts and their capacity to permate soil,
Proceding of the 5th International Conference on soil Mechanic and
Foundation Engineering, paris, vol 2. Pp 789-793
[20] Sakurai, S. 1997. Monitoring and performance in tunnelling.
Proceeding of the fourteen international conference on soil mechanics and
Foundation Engineering, Humburg, Germany.p.2409-2412
Dissertations: [21] Coulter, P., 2004. Influence of tunnel jet-grouting on ground
deformation at the Aeschertunnel, Switzerland. Msc thesis, geotechnical
engineering in Edmonton, Alberta