Post on 30-Mar-2015
Use of resistivity tomography in underground excavation and
tunneling
Hideo KOMINE
Central Research Institute of Electric Power Industry, Japan
Panelist Presentation by Komine,11th Asian Regional Conference on ISSMGE, Seoul in 1999
Chemical grouting
Chemical grouting is widely used as an auxiliary method when underground structures such as shield tunnels are constructed in large cities.
The main purposes are to reinforce the ground and to reduce the ground permeability.
Use of chemical grouting
▽
Shield tunneling machine
Ground reinforcement
Improved region
Pile foundation
for stabilization of cutting face
Weak point
It is difficult to evaluate the improved region. In chemical grouting, a method to evaluate the region improved by the grouting has not yet been established.
This weak point has been a major obstacle to the enhancement of reliability of chemical grouting.
Electrical resistivity
The electrical resistivity of chemical grout is much lower than that of the ground and ground water.
The resistivity tomography can measure the resistivity distributions of ground before and after chemical grouting in the field.
Advantage of resistivity
Resistivity
Grout << Ground, Ground water
(0.6) (50-300) (20-80)
(): Rough value of resistivity, Unit : m
The resistivity of grout material is one tenth and/or one hundredth of ground and ground water.
It is easy to watch the grouted region by electrical eyes
Potential electrodesC1
C2
Ground surface
:Electrical resistivity of ground
electric line of force
P1
P2
Current electrodes
The potential difference betweenP1 and P2 is measured when theprescribed electric current flowsfrom C1 to C2.
Resistivity tomographyApparent resistivities corresponding the electrodes arrangement.
Start
Initialization of each resistivity block
Calculation of apparent resistivity by FEM
Calculation of residual between theoretical values and measured values of apparent resistivity
Does it satisfy the conversion conditions?
Output of final model ground
Finish
Correction of resistivity values for each block by means of non-linear least-squares method
No
Yes
FEM analysis
Resistivity of grouted sand
Piston
Top cap
Drainage canal
Triaxial cell
Pedestal
To pore water pressure gauge
Insu
lato
r
Co
ppe
r e
lect
rod
e
Specimen Diameter : 50mm Height : 100mm
To electric resistancemeasuring apparatus
Electric wire
Specimen is covered with a rubber membrane
Test apparatus with copper electrodes
There is a close connection between Grout/Void ratio and resistivity.Grout/Void ratio is the volume ratio of grout occupying the void space of ground. It is a representative characteristic of the quality of grouted soils.
40
30
20
10
0120100806040200
Ele
ctric
al r
esis
tivity
sg
:
・m
Grout/Void ratio : %
sg = 90 - 100 ・m, when = 0%
○ : Toyoura sand e = 0.65 - 0.76 w = 10.7 - 22.7 ・m
□ : Mikawa silicate sand No. 3 injected by Grout B e = 0.64- 0.70 w = 34.4 - 50.9 ・m
△ : Mikawa silicate sand No. 7 injected by Grout B e = 0.69 - 0.75 w = 10.2 - 22.4 ・m
sg = 40 - 60 ・m,
when = 0
Resistivity model
We proposed the resistivity model of ground before and after chemical grouting on the basis of laboratory test results.
We investigated the validity of the evaluation proposed.
Rw
As Aw
Ls= Lw =Lg
Rg
Ag
Parallel model for ground after grouting
Sand particle
Rs
Pore water
Grout gel
RwRs
I
VRg
Series model for ground after grouting
As Aw
Ls = Lw
Ag
Grout gel RgLg
Sand particle
Rs Rw
Pore water
Parallel model for ground after grouting
Series model for ground after grouting
Combination model
I
V
I
RwRs Rg
V
RwRs
I
VRwRs
As Aw
Ls Lw
Sand particle
Pore water
Parallel model for ground before grouting
In Komine (1992, 1997)
Validity of resistivity modelE
lect
rical
re
sist
ivity
sg
:
・m
Grout/Void ratio : %
Mikawa silicate sand No. 5
40
30
20
10
0120100806040200
: Result evaluated by the proposed method
: Test results
40
30
20
10
0120100806040200
: Result evaluated by the proposed method
: Test results of Grout A : Test results of Grout B : Test results of Grout C
Ele
ctri
cal r
esi
stiv
ity
sg :
・
m
Grout/Void ratio : %
Toyoura sand
The evaluation of Grout/Void ratio, which is the representative characteristics of the quality of grouted ground, by electrical resistivity was proposed on the basis of the electrical resistivity models of ground before and after chemical grouting.
The validity of the evaluation was demonstrated by the comparison of the evaluation results with the laboratory test results.
1.0
0.8
0.6
0.4
0.2
0.0
注入
後の
比抵
抗
sg/
注入
前の
比抵
抗
sw
100806040200
薬液充填率 α (%)
Res
isti
vit
y r
ati
o b
efo
re a
nd
aft
er
gro
uti
ng
Grout/Void ratio (%)
effectiveness of grouting
A
B
C
Grout/Void ratio established by
ground reinforcement and
reduction of ground permeability
Minimum Grout/Void
ratio having the effect
of chemical grouting
ineffectiveness of grouting
Resistivity ratio before and after grouting - Grout/Void ratio curve
In Komine & Nishi (10ARC, 1995)
We proposed the evaluation of chemical grouted region using the resistivity model proposed and resistivity tomography.
Evaluation using resistivity model and resistivity tomography
Apparatus in the laboratory
Planeview
Vertical section
300 470
580
Model ground
Pole with built-in copper electrodes
Model ground
Injection pipe
Injection pipe
270
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
A
B
C
D
To drainage
: Copper electrode
Unit of dimensions : mm
50
Pressure gauge Injecting chemical grout
To electric resistance measu
To drainage
Example 1 of evaluation
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
0.854 0.500 0.429 0.232 0.382 1.288 0.157 0.605
0.026 0.016 0.013 0.016 0.022 0.030 0.016 0.029
0.009 0.008 0.010 0.013 0.011 0.019 0.031 0.010
0.005 0.012 0.011 0.016 0.013 0.016 0.012 0.030
0.014 0.033 0.050 0.046 0.032 0.026 0.022 0.027
0.027 0.052 0.058 0.023 0.028 0.039 0.035 0.120
3.495 0.609 0.084 0.102 0.370 0.258 0.205 0.178
1.935 0.716 0.489 0.526 1.073 1.167 0.736 0.250
Improved regionevaluated by resistivity
Solidified regionconfirmed by eye
Value shown in blocks : Resistivity ratio before and after chemical grouting
1,2,...9 : Copper electrodes
Example 2 of evaluation
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
1.236 1.906 0.905 2.030 2.159 1.424 2.115 0.587
1.380 1.444 1.239 1.529 1.807 1.519 1.691 1.351
0.790 1.055 2.015 2.039 2.433 1.765 1.694 1.648
0.283 0.570 0.775 0.983 1.285 0.877 0.711 0.272
0.471 0.217 0.465 0.976 1.118 0.587 0.234 0.231
0.010 0.012 0.019 0.027 0.026 0.017 0.011 0.006
0.005 0.012 0.018 0.018 0.017 0.012 0.050 0.003
0.015 0.018 0.036 0.038 0.035 0.014 0.011 0.005
Improved regionevaluated by resistivity
Solidified regionconfirmed by eye
Value shown in blocks : Resistivity ratio before and after chemical grouting
1,2,...9 : Copper electrodes
Resistivity contrast of grout and ground water
C
1
2
3
4
5
6
7
8
9
A
1
2
3
4
5
6
7
8
9
2.000 0.998 0.820 1.535 1.604 0.787 2.679 0.753
0.655 1.446 1.812 0.805 0.735 0.893 1.151 1.250
0.945 0.853 0.566 0.554 0.426 0.416 0.746 0.432
0.045 0.027 0.016 0.029 0.028 0.026 0.020 0.050
0.073 0.013 0.028 0.067 0.086 0.035 0.016 0.039
0.040 0.049 0.010 0.016 0.017 0.011 0.021 0.034
0.098 0.141 0.082 0.052 0.064 0.076 0.136 0.122
0.200 0.212 0.121 0.067 0.043 0.060 0.055 0.064
Contrast of resistivity = High Resistivity ratio Grout/Ground water = 0.020
C
1
2
3
4
5
6
7
8
9
A
1
2
3
4
5
6
7
8
9
0.8941.142 1.354 1.918 1.450 0.619 0.428
0.476
1.443 1.208 4.426 4.354 2.101 0.775 0.338 0.521
0.871 2.980 1.728 1.713 1.795 2.604 0.670 0.442
1.463 2.355 4.283 1.293 1.108 0.755 0.628 0.383
1.154 2.101 2.727 1.972 0.687 0.691 1.222 0.216
0.973 1.979 1.741 1.909 1.257 0.974 0.351 0.904
0.497 2.243 3.026 1.563 0.239 0.390 0.694 0.547
0.822 1.441 1.358 0.548 0.219 0.353 0.655 0.825
Contrast of resistivity = Low Resistivity ratio Grout/Ground water = 0.474
Applicability2.0
1.5
1.0
0.5
1.00.80.60.40.2
Reduction of resistivity is remarkable.
Resistivity ratio, Grout/Ground water≦ 1/10. Improved region can be evaluated by resistivity changes.
0.00.0
Resistivity ratio, Grout/Ground water>1/10. It is difficult to evaluate improved region by resistivity changes.
: Test results,R
esis
tivi
ty c
han
ges
of
imp
rove
d r
egio
n
Resistivity ratio, Grout/Pore water
Typical range of contrast between grout and ground water
Contrast of resistivity between grout and ground water
In Komine & Nishi (IS-Tokyo’96, 1996)
Resistivity of commonly used grouts
Grout material Resistivity m
Hydrated sodium-silicate grout witha concentration of 35%
, hardener material : Glyoxal(non-particulate grout)
0.62
LW grout, cement + sodium silicate
(particulate grout)
1.30
Silica Sol grout 0.4
Water Resistivity : m
Ground water 20-80Surface water 100-300
Sea water 0.3
The resistivity ratio between grout and ground water is generally less than 1/10. Therefore, the evaluation method of improved region by resistivity tomography is available in most cases except near the sea.
Verification by field test
1000 literTotal
575 literWater
25 literGlycerin-triacetate
400 literSodium silicate
Field test site.
1.5m1.5m
Injection pipe
Plane view
boring hole
grouted region
Ground surface
G.L.-7.7m
G.L.-9.7m
3.0m
Shaft
G.L.-6.5m
G.L.-8.1m
G.L.-8.7m
G.L.-9.3m
G.L.-10.3m
4.2m
4.6m
1
2
3
4
5
6
Vertical section
: boring hole
grouted region Injection
pipe
: grouted region
Shaft
Ground condition.
20
15
10
5
0
地盤
深度
(m
)
50403020100
N値
G.L.-7.7 m
G.L.-9.7 m
▽G.L.-1.35 m
Groundwater level
grouted region
De
pth
(m)
N-value
Loam
Fine sand
Tuffaceous clay
Silty sand
Silty sand
Silty fine sand
Grain size distributions.
Proportion of grout.
(Gelling time = 30 - 40 minutes)
100
80
60
40
20
0
Pe
rce
nta
ge
pa
ssin
g
0.001 0.01 0.1 1 10
Grain size : mm
: Test site : Toyoura sand : Mikawa silicate
sand No. 3 : Mikawa silicate
sand No. 7
In Komine (11ARC, 1999)
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Res
istiv
ity r
atio
, sg
/sw
100806040200
Grout/Void, (%)
:Void ratio =0.39
:Void ratio =1.04
sand =1000 ・m
water =15.0 ・m
grout =0.4 ・m
(sg/sw)cr = 0.1
Evaluation by resistivity model
In this site, the region of resistivity ratio, which is less than 0.1, can evaluate the improved region.
How to measure in the field
.
▽ ▽
1
Potentialelectrodes
Currentelectrodes
G.L.-6.5m
G.L.-10.5m
G.L.-12.0m
Dipole length : 500mmShift interval : 250mm
Dipole length: 500mm
Shift interval: 250mm
G.L.-0.0m
P1 P2 C1 C2
1
456789
1011121314151617
23
1
456789
1011121314151617
23
8
1 5
Vinyl chloride pipeDiameter, Inner : 65 mm, Outer : 76 mm
G.L.-12.0m
G.L.-11.0m
G.L.-6.0m
G.L.-9.7m
G.L.-7.7m
Region for sampling(Grouted region)
G.L.-6.5m
G.L.-10.5m
Region ofresistivitymeasurement(4.0m)
Filling upby sand
86 mm
76 mm
Ground surface
Borehole.
Pipe was wrappedby filter forpreventing theinflow of sand.
Measurement of resistivity.
Region ofresistivitymeasurement(4.0m)
Apparatus formeasuring resistivity
Connectionbox
3000 holeswere made.
Results
(a) 1 -2 section
1 2
20 19 18 18 18 18 19 20 25 29
16 15
17
15
14
16
13
16
13
17
14
17
14
17
15
19
15
24
16 16
19 17 15 14 13 13 15 18 23 25
17 16 14 12 10 10 11 13 19 25
11 11 10 9 9 9 9 10 13 20
6 5 5 5 6 6 6 6 6 7
2 2 3 3 3 3 3 3 3 3
3 3 3 4 4 3 3 3 3 6
3 3 3 4 4 4 3 4 4 4
4 4 4 3 3 3 4 4 4 4
4 4 4 3 3 3 3 3 4 5
4 4 3 3 3 3 3 3 4 4
7 6 6 6 6 6 7 8 9 13
11 14 15 16 16 16 16 17 18 18
16 19 22 23 24 24 24 24 23 24
G.L.-6.5m
G.L.-7.0m
G.L.-7.5m
G.L.-8.0m
G.L.-8.5m
G.L.-9.0m
G.L.-9.5m
G.L.-10.0m
G.L.-10.5m
1.53m
(c) 4-5 section
29 25 18 16 15 14 17 3321 20
22 20 17 15 12 10 11 1920 19
12 14 12 10 10 10 13 2714 13
3 5 4 3 4 6 15 475 4
3 4 2 1 2 3 10 513 2
3 2 2 2 2 4 8 172 2
1 1 2 2 3 4 6 102 2
2 2 2 3 4 6 8 72 2
2 2 2 2 2 3 5 102 2
2 1 2 3 3 4 5 71 2
1 1 2 2 4 6 7 71 1
3 2 1 1 1 2 5 61 1
8 7 4 3 4 6 10 205 4
19 19 15 11 10 11 14 1817 14
38 34 26 21 18 17 19 2732 29
61 48 31 26 23 22 28 4442 37
4 5
1.21m
(d) 5-6 section
67 53 56 69 68 62 73 103 314 791
22 27 67 85 68 72 86129 150 122
17 20 38 80 67 77 16479 108 98
51 55 62 109 85 69 9691 96 97
175 44 24 115 138 124 6432 49 84
59 84 40 21 12 14 4633 34 31
24 32 9 7 6 9 379 14 13
11 6 10 11 7 13 2825 33 29
3 7 18 16 7 5 5327 38 29
4 5 8 30 13 13 1725 28 32
550 140 55 111 76 26 957 78 104
113
2 15 24 125 58 10 551 63 95
12 1 4 8 6 5 54 6 7
21 18 21 43 5 4 971 36 16
92 237 451 344 150403 49 14 11
400 222 241 33 25 20 2493 47 42
5 6
1.17m
(b) 2-3 section
429 615 778 668
228 350 433 444
420
368
90 108 159 250 333
85 63 86 158 319
78 79 73 90 159
231 157 108 89 100
92 150 133 120 116
90 73 72 76 97
50 54 67 79 96
44 83 142 173 143
52 103 174 190 138
166 175 168 148 110
337 341 269 176 107
435 610 477 261 94
1314 889 555 256 123
452 601 328 189 98
292 164 137 119 122
246 157 109 99 107
326 237 143 91 97
508 557 402 180 64
279 434 444 275 112
132 160 198 204 139
120 129 134 166 209
121 149 168 182 196
112 136 158 172 129
95 70 66 75 134
84 49 37 45 60
75 50 43 48 67
74 59 49 46 31
74 52 40 33 38
66 43 30 22 15
60 40 29 22 22
2 3
1.58m
No improved region evaluated by resistivity
1 2 3
4 65
: Measurement section
Grouted region (G.L.-7.7m - G.L.-9.7m)
: Improved region evaluated by resistivity
: Solidified region confirmed by boring investigation
No solidified region confirmed by boring investigation of No. 3 hole
Another site (Takenaka Corp.)
100
80
60
40
20Per
cent
age
pass
ing
0.01 0.1 1 10 100
Grain size : mm
This site is gravel ground. Average diameter is 40-50mm
Area of chemical grouting
0.5m
5.5m
G.L.-5.0m
G.L.-11.0m
Region of resistivity measurement (6.0m)
G.L.-6.0~8.0m
Electrodes
Gravelly ground
Site condition
Results
2.36 2.79 3.85 4.65 4.85 5.46 7.71 13.14 16.06 11.46 8.02 6.97 7.26 6.97 5.49 4.293.45 3.99 5.24 6.27 6.56 7.12 8.87 11.87 13.06 10.59 8.56 7.94 8.20 7.74 6.17 4.685.99 6.61 8.01 9.29 9.69 9.69 9.71 9.39 8.62 7.67 7.16 7.15 7.36 6.94 5.82 4.439.13 9.75 11.09 12.34 12.39 10.92 8.69 6.38 4.84 3.99 3.76 3.87 4.15 4.23 3.88 3.1211.61 12.01 12.86 13.34 12.57 9.88 6.74 4.13 2.69 1.99 1.78 1.84 2.04 2.23 2.20 1.8811.07 11.20 11.55 11.50 10.50 7.81 4.90 2.65 1.52 1.01 0.85 0.86 0.98 1.11 1.16 1.057.23 7.42 7.81 7.98 7.47 5.70 3.58 1.85 0.99 0.60 0.48 0.47 0.52 0.60 0.66 0.633.68 3.84 4.17 4.51 4.55 3.82 2.62 1.42 0.76 0.44 0.33 0.30 0.33 0.38 0.42 0.421.68 1.81 2.09 2.44 2.69 2.56 1.99 1.22 0.70 0.41 0.29 0.25 0.26 0.29 0.33 0.340.86 0.93 1.09 1.35 1.61 1.72 1.52 1.07 0.67 0.41 0.28 0.23 0.22 0.24 0.27 0.280.51 0.57 0.68 0.88 1.11 1.28 1.22 0.94 0.63 0.40 0.28 0.22 0.20 0.21 0.24 0.250.38 0.41 0.49 0.64 0.83 0.99 0.98 0.79 0.56 0.37 0.26 0.20 0.18 0.19 0.20 0.210.31 0.34 0.41 0.53 0.68 0.80 0.80 0.65 0.47 0.32 0.23 0.18 0.16 0.17 0.18 0.190.28 0.31 0.36 0.46 0.57 0.65 0.64 0.52 0.39 0.27 0.20 0.16 0.15 0.15 0.16 0.160.26 0.28 0.33 0.41 0.49 0.53 0.51 0.42 0.32 0.23 0.18 0.14 0.13 0.13 0.14 0.140.25 0.27 0.31 0.37 0.42 0.44 0.41 0.35 0.27 0.20 0.15 0.13 0.12 0.12 0.12 0.120.26 0.28 0.31 0.34 0.37 0.37 0.35 0.29 0.23 0.18 0.14 0.12 0.11 0.10 0.10 0.090.29 0.30 0.31 0.32 0.32 0.31 0.29 0.25 0.20 0.16 0.13 0.11 0.09 0.08 0.08 0.070.34 0.33 0.32 0.31 0.29 0.27 0.25 0.22 0.18 0.14 0.12 0.09 0.08 0.07 0.07 0.060.38 0.37 0.34 0.30 0.27 0.24 0.21 0.19 0.16 0.13 0.10 0.08 0.07 0.06 0.06 0.050.44 0.41 0.36 0.30 0.25 0.21 0.18 0.16 0.13 0.11 0.09 0.07 0.06 0.06 0.05 0.050.49 0.44 0.36 0.28 0.22 0.18 0.15 0.13 0.11 0.09 0.07 0.06 0.05 0.05 0.05 0.050.50 0.44 0.35 0.26 0.19 0.15 0.12 0.11 0.09 0.07 0.06 0.05 0.05 0.05 0.05 0.050.46 0.39 0.30 0.21 0.16 0.12 0.10 0.08 0.07 0.06 0.05 0.05 0.04 0.04 0.04 0.050.37 0.32 0.24 0.17 0.12 0.09 0.08 0.07 0.06 0.05 0.05 0.04 0.04 0.04 0.04 0.040.29 0.25 0.18 0.12 0.09 0.07 0.06 0.05 0.05 0.04 0.04 0.04 0.04 0.04 0.04 0.040.22 0.19 0.14 0.09 0.07 0.05 0.05 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.040.17 0.15 0.11 0.07 0.05 0.04 0.04 0.03 0.03 0.03 0.03 0.03 0.04 0.04 0.04 0.050.14 0.12 0.09 0.06 0.05 0.04 0.03 0.03 0.03 0.03 0.03 0.03 0.04 0.04 0.05 0.050.12 0.10 0.08 0.05 0.04 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.04 0.05 0.05 0.060.10 0.09 0.07 0.05 0.04 0.03 0.03 0.03 0.03 0.03 0.03 0.04 0.04 0.05 0.06 0.060.09 0.08 0.06 0.05 0.04 0.03 0.03 0.03 0.03 0.03 0.04 0.04 0.05 0.05 0.06 0.060.08 0.07 0.06 0.05 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.05 0.05 0.06 0.06 0.060.07 0.07 0.06 0.05 0.04 0.04 0.04 0.05 0.05 0.05 0.05 0.06 0.06 0.06 0.07 0.070.07 0.07 0.06 0.05 0.05 0.05 0.05 0.05 0.06 0.06 0.07 0.07 0.07 0.08 0.08 0.080.07 0.07 0.06 0.05 0.05 0.05 0.06 0.06 0.07 0.08 0.08 0.09 0.09 0.10 0.10 0.09
0.08 0.07 0.06 0.06 0.06 0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.12 0.12 0.120.07 0.07 0.08 0.08 0.09 0.11 0.12 0.13 0.14 0.15 0.15 0.15
0.10 0.11 0.12 0.13 0.14 0.16 0.17 0.17 0.170.15 0.16 0.17 0.17 0.17 0.17
0.17 0.17 0.17 0.160.15
Distance (m)
Dep
th (
m)
0
-2
-4
-6
-8
-10
0 1.0 2.0 3.0 4.0 5.0
By Uchida et al. (1998, Proceedings of the symposium on underground space Vol.4, JSCE)
Conclusions We proposed the evaluation of chemical grouted region using
the resistivity model proposed by author and the resistivity tomography.
We investigated the validity and the applicability of this method by laboratory tests. From the laboratory test results, improved regions evaluated by the proposed method almost agreed with the solidified regions. If the resistivity ratio between grout and ground water is less than 1/10, we can confirm the improved region by this evaluation.
We verified this evaluation by field test. From the field test results, we confirmed the availability of the evaluation method in practical fields.
References (in English) Komine, H. 1992. Estimation of chemical grout void filling by
electrical resistivity. Grouting, Soil Improvement and Geosynthetics Proceedings, ASCE. New Orleans: 372-383.
Komine, H. and Nishi, K. 1995. Evaluation of grouted region by resistivity changes. Proceedings of the 10th Asian Regional Conference on Soil Mechanics and Foundation Engineering, Vol. 1: 413-416.
Komine, H. and Nishi, K. 1996. Applicability limit of resistivity to evaluate improved region. Proceedings of IS-Tokyo ユ 96 (Grouting and Deep Mixing), Vol. 1: 159-164.
Komine, H. 1997. Evaluation of chemical grouted soil by electrical resistivity. Ground Improvement, Vol. 1: 101-113.