10th Asian Regional Conference of IAEG (2015)

Case study of the reconsidering of the measurement data and geological survey results ofthe tunnel with time-dependent behaviour
Kenji OKAZAKI(1), Hiroumi NIWA(2), Hideyuki MURAYAMA(2), Yoshihiko ITO(1),Terukatsu SASAYA(2) and Toshiyuki KURAHASHI(1)(1) Public Works Research Institute, Civil Engineering Research Institute for Cold Region, Japan
E-mail:90185@ceri.go.jp(2) Fujita Corporation, Japan
Abstract
In order to characterize the geological situation leading to the tunnel deformation
with time-dependent behavior and in order to build a new evaluation method, we carried out
long-term observations, swelling tests and X-ray diffraction tests using core samples
obtained from deformed zones in two tunnels. These two tunnels are a new national roadtunnel by NATM was opened in 2014, which provides an alternative route to a pre-existingtunnel that was constructed by conventional methods and opened in 1976. The geology ofboth tunnels is hydrothermally altered pyroclastic rock. Heaving occurred in two sections
replaced by timbering in a hydrothermally altered andesite zone in the new tunnel after
completion. In the old tunnel, countermeasures against deformation were carried out on
three occasions. In this survey, we focus on the minerals involved in the degradation of therocks for time-dependent behavior. The results of survey showed that the core samples
degraded in 18 months after drilling. Most of this degradation occurred within one week ofdrilling. Therefore, it is useful to observe core samples in a one week just after drilling.
Comparing results obtained by X-ray diffraction tests just after drilling with ones at a later
period, we found differences in combination of mineral content.
Keywords: time-dependent behavior, tunnel, countermeasure, design, construction
1.

Introduction

data on the amount of convergence (Matsunaga et al.,2009). However, few studies have addressed the basic
geological factors and causes of time-dependent
behavior.
In the past, the authors collected data on cases ofdeformation in tunnels and clarified the geologicalconditions. It was found that many of the tunnels with
time-dependent behavior are in volcanic rock areas(Okazaki and Ito 2011, 2013). One of the causes oftime-dependent behavior is the gradual release ofstress in fresh bedrock and the swelling of the plastic
zone due to tunnel excavation. In addition, this freshrock is in contact with the air and ground waterleading to changes in saturation and oxidation. In
addition, the strength of rock decreased due toactualized cracks, grain refining and pulverizing. In
addition, depending on the combination of minerals
in rock, iron hydroxide and gypsum were producedby chemical changes, which these sometimes also
promote the degradation or swelling of the rock
(Tanaka et al., 1985, Oyama et al., 1998, Shikazono
et al., 2002).

There have been many reported cases in which
deformation, such as tunnel ground heaving andsqueezing of sidewalls, occurred in a tunnel days,
months or even decades after construction (JSCE
2003, 2013, Nakata and Ito 2000., Watanabe et al.,2007., Nihei et al., 2010). Even those tunnels thatshowed no evidence of problems with regard to theresults of a conventional evaluation for the possibilityof swelling (JSCE 2006), nor any increase indisplacement resulting from excavation when they
were constructed, still have the potential to undergo
time-dependent behavior. Therefore, there is anurgent need to establish a method for evaluating andpredicting such deformation during tunnel
construction or in the early stages of maintenance.
In order to determine the effectiveness ofcountermeasures against deformation and the likely
progress of such deformation, a ground degradation
model has been formulated and numerical analysis
has been conducted based on long-term measurement1

10th Asian Regional Conference of IAEG (2015)

In this study, we compiled measurement datafrom tunnel construction through hydrothermallyaltered andesite in Hokkaido, Japan and examined theresults of advanced drilling data (HRDB 2014) incases where heaving occurred as the time dependence
behavior after the tunnel completion. In addition, themineralogical analysis, changes in the number ofcracks and number of days up to the maximum
swelling stress were examined using the drilling cores
after the passage of a certain period from excavation
to understand the relationship between timedependent behaviors.
In the present paper, survey results obtained
during construction were compared with thoseobtained later, with the aim of clarifying the causes oftime-dependent behavior. In addition, this paper
discusses the results of a study that was conducted toclarify how to predict time-dependent behavior
during construction.
2.

sections where deformation occurred had undergonehydrothermal alteration, and smectite was found inlarge amounts in those sections. According to thereport of tunnel constructor (Sasaki et al., 2013), thedeformation was caused by the combined action of
the loosening of surroundings due to excavation andthe swelling pressure of clay minerals. These
deformations could not be predicted by theconventional rock estimation method. Therefore,
more rational and economical method for both rockestimation and maintenance systems are required tomitigate such issues.
At the old tunnel, deformation occurred in fivesections (those parts in Fig.1 (b)), andcountermeasures against deformation were carriedout three times. The ground at those sections where
deformation occurred had undergone hydrothermal
alteration, and smectite was found in large amounts in.
According to the report of tunnel constructor (HRDB
1993), the deformation was caused by combined
action of the loosening of surroundings due to
excavation and the swelling pressure of clay minerals.

Outline of study

2.1 Tunnel geology and deformation(1) Tunnel geology
The present research was conducted on a newnational road tunnel (about 3,000m in length) thatwas opened in 2014 as alternative to an older tunnel(about 1,900m in length) which was constructed byconventional methods and opened in 1976. The
geology of both tunnels consists mainly of andesitic
lava, dacite that includes auto-brecciated lava andpyroclastic rock (Fig.1).

2.2 Test for mineralogical properties of rock(1) Observation of long-term change in the cores
After deformation, the drilling cores excavatedfrom the deformed sections in a new tunnel wereobserved in order to find out how those drilling cores
would change in state over time, and in order toanalyze the change in degradation state and the extent
of degradation of rock. In addition, drilling cores also
were also excavated from the deformed section in theold tunnel, in order to confirm the geology andunderstanding of aging degradation. The drilled cores
were observed by mainly focusing on the number ofcracks generated in succession until 17 to 23 days
from the after digging. The number of cracks that
occurred in drilling cores was compared with the(2) Deformation in the tunnel
The heaving occurred in the tunnel at two sections
with maximum overburden near the tunnel piercing
point (those parts in Fig.1 (a)), soon after the tunnel
cleared; requiring re-excavation. The ground at both

(a)

(b)

Fig. 1 Surveyed tunnels

2

10th Asian Regional Conference of IAEG (2015)

difference of geology, the rock classification and
RQD (10). The rock classification was divided into
four grades as the CH, CM, CL and D based on thestate of cracks, the core hardness and shape (Table.1).
Cores of each tunnel had been stored in a tunnel until
approximately one month from their excavation.
After that, cores of new tunnel were stored at theoutdoor site of the tunnel operator by covering withvinyl sheet

Table .1 rock classification method
RockClassification
CH

Hardness

Shape

B

II
I
I-II
I-II
II
II
II-III
III
III

B-C

B-C

(2) Swelling test of rockA swelling test (JGS2121 1998) was conducted
on cores excavated in the drilling survey conducted in
the deformed sections of the new tunnel. In addition
to the swelling rate being measured, the smectite,
content was determined by X-ray diffraction test. The
relation between the maximum swelling stress andthe number of days that it took for the swelling stress
to reach the maximum was examined.

CM

C

II

State of
Cracks
b
c
b
c
b
c
b
c

B-C

III-IV
II-III
III
C
III-IVIVII
II-III
III
C-D
c
CL
III-IV
IV
IV-V
II
II-III
D
III
IV
IV-V
II
II-III
D-E
c
III
III-IV
IV-V
D
IV
c
V
Photo. 1 Long termchange VI
in the drilling core.
E
d
VII
VIII

(3) X-ray diffraction test
With regard to advanced drilling cores excavatedincluding sections where deformation occurred,
samples were collected from two types of sections: a
section where swelling occurred, and a section where
swelling did not occur in the new tunnel. Moreover,samples were collected from the drilling cores of theold tunnel. Then, an X-ray diffraction test was
conducted on those samples. The smectite content
was determined by X-ray diffraction using theinternal standard method. After the minerals
contained in the samples were identified, the strength
ratio was determined based on the diffraction peaksof quartz and smectite. Then, the strength ratio,quartz intensity for smectite (hereafter, QISm) andthe identified minerals were analyzed in combination.
Quartz is found in many rocks. Thus, QISm is a value
to indicate quantitatively the content of smectite
relative to the content of the quartz. QISm shows thevalue of the smectite when the peak intensity of thequartz is 100. Among the identified minerals, Pyrite,
Carbonate and Gypsum, were addressed in previous
studies (Tanaka et al., 1985, Oyama et al., 1998,
Shikazono et al., 2002) were carefully investigated;
the relation between the combination of thoseminerals, the presence or absence of swelling of cores
and QISm were compared.

Item
Hardness(Hammer blow sound)

Shape

State of Cracks

3

Rank
B
C
D
E
I
II
III
IV
V
VI
VII
VIII
a
b
c
d

Condition
Piercingly
Dingdong
Subdued soundSilence
Over 50 cm
15-50 cm
5-15 cm
5cm or less
Form of grabel
Form of sandForm of clay
Slime
Not degradation
Slightly degradation
Degradation extends inside
Not recognizable as a crack

10th Asian Regional Conference of IAEG (2015)

3.

Results and discussion

3.1 Observation of long-term change in the cores(1) Degradation state and extent of the rock
Photo-1 shows the state of the drilling core
immediately after excavation following deformationand the change in the state of the core after thepassage of the time. Observation of the core
immediately after excavation showed that, in places,
some degradation had already occurred. When thecore was re-observed 1week after excavation, it was
found that the extent of degradation had increased.
586 days after that, it was found that the extent ofdegradation had increased along the cracks and had
expanded from the location where degradation was
found a one week after excavation. However, theextent of degradation found 586 days after excavation
was roughly the same as that found at a one week
after excavation. Thus it was shown that, in somecases, re-examining cores shortly after excavation
may be a reasonable indicator of how further
degradation will expand in the medium and longterm.
(2) Number of generations of cracks
Table 2 shows the results of core observation for
the number of generations of cracks. Drilling survey
results showed the core is the andesite and tuff
breccia, RQD is more than 80% in the CH - CM class,tending to 70% or less in the CL - D class. On theother hand, the number of initial cracks number is not
significantly different (between 4 and 8 per 1m)
except for CL class andesite. The ratio of the initial
crack number to final crack number, is less than 2.0
in CH - CM grade, but increases to 2.0 or more in CL D class.
Figure 2 shows the time variation of the crack
number for each rock classification. A tendency todecrease in order of CH, CM, CL, and D are seen in thenumber of cracks. When the much number of initial
cracks exists, many cracks occur afterwards. The
number of the cracks almost converges in five days
after drilling. Re-observation of the core is possible to

Photo. 1 Long term change in the drilling core.

become one of the methods for predicting thedegradation of rock due to the occurrence of
cracking.
3.2 Swelling and smectite content of rock
Table 3 shows the results of a swelling test ofrocks, the smectite content and swelling ratio of rock

Table. 2 The results of core observation for the number of generations of cracks.
Geology
Andesite

Tuff-breccia

RockClassification

Observation
length (m)Observation
days of cores(days)

RQD(10)(%)

Initial cracks(numbers)

Final cracks(numbers)

Final/Initialratio of craks

CH
CM
CL
D
CM
CL
D

10
7
11
11
6
16
6

22
17
23
17
18
18
20

98
89
54
39
81
68
16

4
6
15
8
8
8
4

7
11
37
18
15
20
15

1.8
1.8
2.5
2.3
1.9
2.5
3.8

4

10th Asian Regional Conference of IAEG (2015)

Number of cracks (CH) (counts/m)

30
CH H31
CH H34
CH H37
CH H40

CH H32
CH H35
CH H38CH Ave.

Table. 3 The results of a swelling test of rocks, thesmectite content and swelling ratio of rock type.

CH H33
CH H36
CH H3920

Rock type10

pyroclastic
rock

0
0

5

10

15

20

Lapsed days (days)

25

Number of cracks (CM) (counts/m)

30
CM V18
CM V30
CM H18

CM V22
CM H13
CM H27

CM V23
CM H14
CM Ave.

CM V24
CM H15

CM V25
CM H1620

Dacite1000Number of cracks (CL) (counts/m)

80

5

CL V3
CL V8
CL V17
CL H4
CL H20
CL H26

60

10

15

20

Lapsed days (days)
CL V4
CL V9
CL V19CL H6
CL H21
CL H28

CL V5
CL V11
CL V21
CL H10
CL H22
CL Ave.

CL V6
CL V12
CL H2
CL H11
CL H2325

CL V7
CL V13CL H3
CL H19CL H2540

Andesite
Lava

20

0
0

5

10

15

20

T.D.
(m)

ND: Non-deformedD:deformed

Smectite
content(wt%)

Swelling
ratio (%)
NT:
Not tested

603
614
1,100
900
950
1,000
1,050
1,150
1,200
1,250
1606-11606-21606-31606-41711-1
1711-2
1711-3
1,300
1,350
2,190
2,230
2,280
2,330
2,400

ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
D
D
D
D
D
D
D
ND
ND
ND
ND
ND
ND
ND

20
21
15
13
12
11
10
12
22
8
31
23
37
31
32
16
13
4
4
4
13
8
5
4

－
－
－
－
－
－
－
－
－
－
10.4
6.4
－
18.3
10.6
3.6
0.6
－
－
－
－
－
－
－

25

Lapsed days (days)
Number of cracks (D) (counts/m)

80

60

D V10
D V20
D V29
D H9
D H29

D V14
D V26
D H5
D H12
D H30

D V15
D V27
D H7
D H17
D Ave.

10

15

20

D V16
D V28
D H8
D H24

the deformed sections was 26-wt%. Additionally,
when smectite exceeds 30-wt%, the swelling rate
exceeds 10%. However, some rock samples from thenon-deformed sections did not experience
deformation, despite showing high smectite of morethan 20-wt%, which indicates the possibility of somefactors other than smectite content contributing to
deformation.
Figure 3 shows the relationship between thenumbers of days until converge of swelling stress andmaximum swelling stress by the swelling test of
dacite cores out of the deformed sections. There are
two cases relationship between the numbers of days
until convergence of swelling stress and maximum
swelling stress. One of the cases is fewer days andsmaller maximum swelling stress, and another case is
many days and larger maximum swelling stress. In
the case of fewer days up to the maximum swelling
stress can be evaluated by the existing test method.
However, where swelling stress continues to increase
for a long period, it is not possible to evaluate thetime dependent behavior of rock degradation using
the short-term existing methods. Therefore, it isnecessary to develop longer-term indicators and test
methods.

40

20

0
0

5

Lapsed days (days)

25

Fig. 2 The time variation of the crack number of eachrock classification. (V: vertical borehole, H:
horizontal borehole, figures shows drilled depth)

type. The smectite was examined for each type ofrock in tunnel. At the same time, the test results forthe non-deformed section and the deformed sections
were compared, and the swelling ratio of rock in the
deformed sections was examined. The smectite washighest in dacite, followed by pyroclastic rock andthen andesitic lava. The smectite content of all therock was under 37-wt%, though, 20-wt% is used as
an index for evaluating the swelling of rock. In
contrast, the average value for smectite of dacite in5

Maximum swelling stress (KN/㎡)

10th Asian Regional Conference of IAEG (2015)

deteriorated core samples and 35 cores were found to
be non-deteriorated core samples. QISm of thedeteriorated core indicates the 4 samples of the 9
samples have a value of 1.0 or more. On the other
hand, QISm of the non-deteriorated core indicates the
6 samples of the 35 samples have a value of 1.0 or
more, and the ratio that QISm becomes more than 1.0
is smaller than deteriorated core. The investigation
found that with regard to the deteriorated cores, when
the Py+Gy was detected, QISm was 1.0 or less. With
regard to the non-deteriorated cores, however, Py+Gy
was not found in the samples in which Cb+Py was
detected even when QISm was 1.0 or more. From this,
it is presumed that when rock contains Cb and Py, therock experiences the leaching of elements and thesecondary formulation of Gy due to environmental
changes resulting from excavation, which leads tochanges in the density of the rock, promotes its
degradation and lowers the physical strength of therock. On the other hand, Py is detected in several
non-degraded cores. However, chemical change from
Py to Gy hardly proceeds to include the alkaline Cb at
the same time, as a result the volume change might
have been suppressed. Thus, even when the Sm is
low, QISm is 1.0 or less; it seems to lead to thedegradation of the rock.
Thus, the results of X-ray diffraction method andcore observation, coupled with the reference value ofthe Sm content and focusing on the combination of
Py, Cb and Gy is effective as an index to estimate thetime dependent behavior of rock degradation.

600
500
400
300
200
100
0
0

50

100

150

Numbers of days until converge of swelling stress (days)

Figure 3 The relationship between the numbers ofdays until converge of swelling stress and maximum
swelling stress.

Frequency

Deteriorated cores
3
2
1
0
0.5

1.0

1.5

Quartz index for smectite (QISm)：Pyrite + Gypsum：Carbonate + Pyrite：Carbonate

4.

：Carbonate, Pyrite, Gypsum (Non-detected)

Frequency

Non-deteriorated cores
6：Data of new tunnel

5：Data of old tunnel

The present research can be summarized asfollows.
1) The results of the observation of long termchanges in cores indicated that, in some cases,
re-observation of cores at an early stage ofdegradation makes it possible to identify how
degradation will develop over the medium and longterm.
2) The results of the long-term observation ofchanges in the number of generations of cracks,
many cracks occur at a relatively early stage, then,the occurrence of the crack decreases and changes toconverge. The increase in the number of cracks
increases after drilling tends to converge at about 5
days. Thus, re-observation of the core is a potential
method for predicting the degradation of rock due tothe occurrence of cracking.
3) The results of the test for mineralogicalproperties of rock indicated that, in some cases, theprediction of degradation and swelling can be mademore effectively by considering the combination ofminerals contained in rock, in addition to employing
the traditional method of evaluating the swelling of
the rock.

4
3
2
1
0
0.5

1.0

Conclusions

1.5

Quartz index for smectite (QISm)

Figure 4 The results of an X-ray diffraction test.

3.3 X-ray diffraction test
Figure 4 shows the results of an X-ray diffraction
test conducted on rock collected from the deformed
section. The following minerals were identified in the
X-ray diffraction test: Cb: carbonate minerals (Cal:calcite, Dol: dolomite and Sid: siderite), Si: silicate
minerals (Q: quartz, Tri: tridymite, Cri: cristobalite),
Sf: sulfide mineral (Py: pyrite), Su: sulfate minerals(Gy: gypsum, Roz: rozenite) and smectite.
QISm ranges between 0.1 and 1.6. Fromadvanced drilling cores, 9 cores were found to be6

10th Asian Regional Conference of IAEG (2015)

In the present research, the geological conditions
and mineralogical properties associated with theoccurrence of deformation were analyzed based on
the results of geological surveys conducted in thetunnels where such deformation occurred. The
ground heaving occurred due to the compound actionof loosening of the tunnel ground and swelling ofclay minerals; therefore, it is necessary to establish
new methods for evaluating and predicting
deformation during construction. To prevent
deformation such as that which occurred in this case,the authors are determined to continue to conduct
tests and analyses in order to develop methods forpredicting the state of degradation on short-term andlong-term bases.

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Road Tunnel (National Highway No.46), JSCE, Vol.
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Tunnel in Service, 23rd Proceedings of Tunnel
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Tunnel After Its Services Commencement,
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Shikazono, N., Kimura, S. and Iwai, S. (2002):
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Acknowledgements
We would like to express our appreciation to the
Study Committee on Measurement Technology for
Tunnel Deformation Surveys for helping us with thecompilation of the research results by providing
valuable
opinions.
In
addition,
regardinginvestigation, we received a great deal of cooperationfrom those at the Hokkaido Regional Development
Bureau of the Ministry of Land, Infrastructure,
Transport and Tourism. This research was
implemented with support from the “Construction
Technology Research and Development Subsidy
Program” of the Ministry of Land, Infrastructure,
Transport and Tourism for the “Development of
Geological Evaluation and Diagnostic Techniques for
Deteriorating Tunnels with Deformation”.
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