10th Asian Regional Conference of IAEG (2015)

Verification of seismic survey results ahead of a tunnel face using
drilling vibration data of ultra-long controlled boring
Masahito YAMAGAMI(1) ,Tomoyuki AOKI(1),Yoshiaki YAMANAKA(2),Toru TAKAHASHI (3) and Kenichiro NANBA(4)(1) TAISEI Corporation Technology Center, Yokohama, Japan
E-mail:ymgmsh01@pub.taisei.co.jp(2) SUNCOH Consultants Corporation, Japan, (3) Fukada Geological Institute, Japan,(4) West Nippon Expressway Company Limited, Japan
Abstract
In the preliminary investigations of mountain tunneling, a seismic refraction survey
from the ground surface is conventionally conducted, and a tunnel support pattern isdesigned based on the seismic wave velocity of the ground, as evaluated by the survey. The
resolution of the velocity profile by this technique, however, is poor as the tunnel
overburden becomes large. In response to this problem, the authors developed a new survey
method in which drilling vibration data were used, called tunnel seismic probe drilling(T-SPD), to estimate the seismic wave velocity distribution ahead of the tunnel face so thatit could be used in the design of tunnel support patterns. We conducted field demonstration
tests of the T-SPD at three tunneling projects (Yamagami et al., 2012a; 2012b; 2012c;
2014a; 2014b). In this study, we report the results from the project using a drill rig with adrilling capacity of 1,000m (ultra-long controlled boring). The P-wave velocity distribution
estimated by the T-SPD was found to agree with those estimated by the seismic refraction
surveys from the ground surface and from the tunnel floor. The T-SPD can be thus analternate exploration method for seismic refraction in cases where seismic refraction fromthe ground surface is difficult due to large tunnel overburden. According to a comparison
between the P-wave velocity distribution and drilling specific energy data, which indicatesthe energy required for drilling per unit volume of rock, it is evident that the T-SPD iscapable of properly evaluating ground conditions even where borehole logging may resultin misleading information in areas with cuttings in a drilled hole. We suggest that thedetection accuracy of poor ground conditions such as fracture zones can be improved bysimultaneously conducting the T-SPD and the borehole logging.
Keywords: Mountain tunnel, Survey ahead of a tunnel face, SWD, T-SPD
1. Introduction

information on the position and direction of the
discontinuous surface using TSP or HSP. However, it
is not possible to obtain property information such as
the width of the fracture zone, which is important for
designing tunnel support patterns. The drill machinedata based method provides the specific energy
distribution (MJ/m3), which is related to the strengthof the rocks, and is defined as the energy consumed todrill the rock per unit volume. Although boreholelogging method provides data and drainage forgroundwater at the same time, its disadvantages arethat the drilling cross-sectional area is small relative
to that of the tunnel face, and that it is difficult tocorrelate the drilling specific energy with the rockclassification.
Therefore, we developed the tunnel seismic probe
drilling (T-SPD) as a new exploration method thatcan evaluate the seismic wave velocity distribution

In conventional planning of mountain tunnels,
seismic refraction surveys from the ground surface
are performed as preliminary surveys. Tunnel support
patterns are then designed based on the seismic wave
velocity of the ground, as obtained by the seismic
refraction survey. The resolution of the velocity
profile estimated by this technique, however, is poor
as the tunnel overburden becomes large. In suchconditions, a survey ahead of the face during tunnel
construction is considered to be more effective than
the seismic survey from the ground surface. Two
methods are generally used in the surveys ahead of
the tunnel face: seismic reflection method known astunnel seismic prediction (TSP) or horizontal seismic
profiling (HSP), and borehole logging known as
drilling survey system (DRISS). We can obtain1

10th Asian Regional Conference of IAEG (2015)

ahead of the tunnel face in order to assist properly
designing tunnel support patterns. Using a drill rig
with a drilling capacity of 100m, we conducted fielddemonstration tests at two tunneling projects toconfirm the effectiveness of the T-SPD (Yamagami etal., 2012a; 2012b; 2012c). At another tunnelingproject, we previously presented the results of two
field demonstration tests using ultra-long controlledboring with a drilling capacity of 1,000m, and haveconfirmed effectiveness to a total drilled length of
250m (Yamagami et al., 2014a; 2014b). In this study,
we report and verify the results for the remaining
section of the previously reported project andadditional field demonstration tests for a total drilledlength of 710m where the tunnel excavation has been
completed. We also add drilling specific energy datafrom borehole logging to the verification data.
2.

the swivel of the drill rig (pilot sensor) and thoseplaced on the ground surface at some distance awayfrom the drill rig (receiver sensors).
In Fig. 1, Tp is the travel time of wave from thedrill bit to the receiver sensor on the ground surface,
while Tc is the travel time of the cross-correlated
waveform, and Td is the travel time calculated fromthe auto-correlated waveform at the pilot sensor. A
velocity profile of the seismic waves can be createdfrom the arrival times obtained from these procedures.
The T-SPD is a seismic method for estimating theseismic wave velocity profile ahead of a tunnel face
and is based on the same principle as the SWD (Fig.
2).
3.

Field Test

3.1 Site overview
The field test was performed in a road tunnel
with a width of about 11m (Fig. 3). The maximum
overburden was 150m. The geological features
include mixed rock (shale, sandstone, and chert) in
the Mesozoic age. Shale is mainly distributed overthe survey area. Refraction survey results from theground surface, conducted during a preliminary
investigation phase, showed the presence of four low
velocity zones ranging from 3.0 to 3.2km/s and those
ranging from 4.4 to 4.6km/s along the tunnelalignment. In the section where the tunnel passed
under rivers with a small overburden, a watertightPrinciple of T-SPD

In the exploration of petroleum resources, theseismic while drilling (SWD) using the vibrations
generated by the drill bit is used to investigate the
distribution of seismic wave velocity of the drilledsection on the basis of the direct wave and to generate
subsurface images by the reflected waves (Ashida,1997). The SWD principle with the use of direct
waves is shown in Fig. 1. The vibration generated by
the drill bit is measured by the sensor attached toFig. 2 Method for determining travel time in
T-SPD by using SWD principle（Plan view）

Fig. 1 Schematic chart of T-SPD（Sectional view）

Fig. 3 Field test site and refraction survey results from the ground surface(longitudinal section）

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10th Asian Regional Conference of IAEG (2015)

structure is to be adopted to conserve the surrounding
aquatic
environment.
To
understandthehydrogeological structure of the sections, we
conducted probe drilling twice （ for total drill
lengths of 676m for the first and 718m for the second,with an overlapping length of 217m ） using anultr a-long controlled boring. In accordance with thesp ecification requirements, the data to be acquired forthe evaluation of ground conditions included thevolume of groundwater inflow to the tunnel in agiven section, the rock type determined using cuttings,
andthe drilling specific energy distribution. We alsoacquired P-wave velocity by applying the T-SPD tothe ultra-long controlled boring.

drill bit (inset) are shown in Photo 1. To advance theexploration borehole, we deployed an ultra-longcontrolled boring. The drilling dir ection is controlled
by managing the rotation of the string of the drill
pipes. When drilling straight ahe ad, both the downhole motor and string are rotated (Fig. 6 left). When
drilling in a curved trajectory, the down hole motor isactivated without rotating the st ring, to direct thedrilling in the direction of the bent sub equippedbehind the drill bit (Fig. 6 right). All vibration data
are continuously recorded whether drilling a straightor a curved borehole.
In the first test, we placed thereceivers in a 21 mlong borehole drilled from the right side of the tunnel
wall looking toward the tun nel face. Seven
3-component geophones were placed at 3.0 m
intervals in the borehole. Fig. 4 shows the layout of
the receivers in this test. The length of forward
drilling (=exploratory length) was 676 m.
In the second test, a 12 m long borehole was laidout 10m from the drill rig toward the tunnel face inorder to reduce the machine noise. Two 3-component
geophones were placed at 3.0 m intervals from thebottom of the borehole. Fig.5 shows the layout of thereceivers in this test. The length of exploration
borehole advanced was 718m. Seismic dataprocessing was performed advancing the borehole 5m
at a time to improve the S/N ratio. Regardless of thetunnel excavation work, measurements wereconducted continuously during drilling. To verify theeffectiveness of the T-SPD for a total drilling lengthof about 710m, we compared the P-wave velocity

3.2 Data acquisition
A T-SPD was conducted in the enlarged part of atunnel. Schematic diagrams of the T-SPD are shownin Figs. 4 and 5. The experimental condition and a

Fig. 4 First test layout of T-SPD

Photo. 1 Experimental condition anda drill bit (inset)

Fig. 5 Second test layout of T-SPD

Fig. 6 Ultra-long controlled boring method (left: straight drilling, right: control drilling)3

10th Asian Regional Conference of IAEG (2015)

distribution predicted by the T-SPD with the resultsof the seismic refraction surveys from the groundsurface and on the tunnel floor, the results of tunnel
face observations, and the drilling specific energy
distribution.

observed at 20 and 80Hz. After removing the noise atthese frequencies with a band-pass filter, we
identified a peak at around 100Hz propagating
through the string of the drill pipes, as shown in Fig.
8. We clearly observed this wave as it propagatedalong the string to a length of about 500m, and it
appeared to have reciprocated three times between
the swivel and the drill bit tip repeatedly. This
multiple reflection indicates that string of the drill
pipe propagating wave velocity was 4.8km/s.

3.3 Field test results
Fig. 7 shows the spectrum of the pilot sensor, while
Fig. 8 shows the auto correlation trace of the pilot
sensor for the first test. In Fig. 7, two peaks may be
Length (m)Length (m)Time (ms)Time (ms)

500

310

White dash line is a multiple reflection traveled
3 times between the tip and pilot sensor

Fig. 7 Auto correlation traces and spectrum ofpilot sensor (before applying band-pass filter)

Fig. 8 Auto correlation traces and spectrum of pilot
sensor (after applying band-pass filter 100-200Hz)

Time (ms)Length (m)Fig. 9Travel-time curve (first test）

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10th Asian Regional Conference of IAEG (2015)

Fig. 9 shows the clearest cross-correlated trace ofthe seven receivers at 21m in length along theborehole. To obtain the velocity profile shown in
Fig.9, we corrected the travel times calculated by thevelocity of the waves from their first breaks as they
propagated to the string of the drill pipe. The firstarrivals at the 0 -30 m and 180-200 m intervals were
excluded in the determination of the velocity because
they were either affected by the receiver offset(0-30m) or were unclear (180-200m).

Fig. 10 shows the spectrum of the pilot sensor,
while Fig. 11 shows the auto correlation trace of thepilot sensor for the second test. In Fig. 10, a peak
emerged at 20Hz. Using a band pass filter, weremoved the noises, to reveal a spectral peak ataround 100Hz that had propagated through the string,as shown in Fig.11. We clearly observed this wave
propagating along the string to about 500m, and it
also appeared to have reciprocated between theswivel and the drill bit tip, as in the first test. This

Length (m)Length (m)Time (ms)Time (ms)

500

310

White dash line is a multiple reflection traveled
3 times between the tip and pilot sensor

Fig. 11 Auto correlation traces and spectrumof pilot sensor (after applying band-pass filter
100-200Hz)

Fig. 10 Auto correlation traces and spectrum ofpilot sensor (before applying band-pass filter)

Time (ms)Length (m)Fig.12 Travel time curve (second test）

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10th Asian Regional Conference of IAEG (2015)

multiple reflection indicates that the velocity of the
wave propagating along the string of the drill pipe
was 4.8km/s. It also suggests that direct waves fromthe drill bit reached a length of about 500m at thestudied site. Therefore, the effective length was foundto be 500m for the analysis of wave propagations.
Fig. 12 shows the cross correlated traces of thereceiver installed at a length of 9 m in the borehole,which were clearer than those of the receiver installedat the borehole. Travel times calculated from theirfirst breaks were corrected by the string propagating
wave velocity to obtain the velocity profile shown in
Fig. 12. The first arrival of waves at the interval of
0-20 m interval was not used for determining thevelocity as they were considered affected by thereceiver offset.
As to the reason the effective survey length was
limited to about 500 m, we presumed that the S/Nratio became small when the length was longer than
500 m due to the use of smaller drill bits and theattenuation of the vibration of the drill bit.
4.

on the tunnel floor. Correlations of the T-SPD results
are also compared with the tunnel face observationand drilling energy observation.
It may be seen that P-wave velocity by the
T-SPD varies from 2.3 to 4.9 km/s. We found three
low velocity zones at total lengths of 30-125 m,
500-614 m, and 744-789 m.
P-wave velocity distribution by the seismic
refraction survey from the tunnel floor varies from
3.7 to 5.2 km/s. We found the low velocity zones at
total lengths of 50-120 m and 590-620 m. A low
velocity zone at total lengths of 50-120 m agreed withthat at total lengths of 30-125m by the T-SPD. While
the other low velocity zone at total lengths of
590-620 m agreed with that of 500-614m by the
T-SPD. It is clear that the T-SPD results are generally
consistent with the results of the seismic refraction
from the tunnel floor.
The seismic refraction survey from the groundsurface gave three low velocity zones as shown in
Fig.13. The low velocity zone 1 is consistent with the
low velocity zone at total lengths of 30-125 m by the
T-SPD. The low velocity zone 2 is consistent with the
low velocity zone at total lengths of 500-614 m by the
T-SPD. The low velocity zone 3 is consistent with the
low velocity zone at total lengths of 744-789 m by the
T-SPD. It is evident that the T-SPD results are
generally consistent with the results of the seismic

Discussion

Fig. 13 compares the P-wave velocity
determined from the T-SPD along the length of the
exploration borehole with those from the seismic
refraction investigations from the ground surface andPoor ground
Poor ground

Good groundFig. 13 Field tests results

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MJ/m3

10th Asian Regional Conference of IAEG (2015)

refraction from the ground surface. T-SPD cantherefore be utilized as an alternate seismic refraction
method in cases where the use of seismic refraction
from the ground surface is difficult due to a large
overburden.
The face evaluation score by the tunnel faceobservation varies from 20 to 50. The low velocity
zone at total lengths of 30-125 m by the T-SPD
agreed with the section of face evaluation score
around 20. The low velocity zone at total lengths of
500-614 m by the T-SPD agreed with the section of
the face evaluation score 25-35. The low velocity
zone at total lengths of 744-789m by the T-SPD
agreed with the section of the face evaluation score30-40. We found that the T-SPD results are generally
consistent with the face evaluation score, and that the
T-SPD could evaluate poor ground conditions as
relatively low velocity zones (pink rectangles in
Fig.13).
On the other hand, the relatively high P-wave
velocity zone at the total lengths of 200-510 m by the
T-SPD is generally consistent with the section of theface evaluation score around 40. We found that the
T-SPD could evaluate the good ground condition as
the relatively high velocity zone (blue rectangles in
Fig.13).
In addition, we compared these results with thedrilling specific energy distribution. On the basis ofdrilling specific energy, we identified a poor groundsection at total lengths around 600m. However, we
did not observe the poor ground section at total
lengths around 100m. Since frequent jamming
occurred around 100 m length, the drilling specificenergy distribution might have presumably become
high owing to the presence of cutting slime in theborehole, thus yielding a misleading result that the
ground condition was good. We suggest that thedetection accuracy of poor ground conditions such as
fracture zones can be improved by simultaneously
conducting T-SPD and borehole logging.
All in all, it is clear that the T-SPD method canbe a very effective means of predicting andevaluating the ground geology and geotechnicalproperty of the ground ahead of the tunnel face.
5.

influence of using smaller drill bits and theattenuation of the vibration from these drill bits at
lengths greater than 500 m.
・Where verification has been completed, the T-SPD
results using a drill rig with a drilling capacity of
1,000m, showed relatively good agreement with theface observations and P-wave velocity distributions
estimated from seismic refraction surveys performed
from the ground surface and from the tunnel floor fora total lengths of 710m. The T-SPD can be utilized as
an alternate seismic refraction method in cases where
the use of seismic refraction from the ground surface
is difficult due to a large overburden.
・ In addition the T-SPD results are generally inaccordance with the drilling energy evaluation,
except that at a depth about 100m, the drilling energy
is evaluated rather high. Reviewing the drilling record,
there were considerable jamming at that depth, andhence the drilling energy might have been
overestimated.
・All in all, it is clear that the T-SPD method can be avery effective means of predicting and evaluating the
ground geology and geotechnical property of theground ahead of the tunnel face. We suggest that thedetection accuracy of poor ground conditions such as
fracture zones can be improved by simultaneously
conducting T-SPD and borehole logging.
As a future study, we plan to validate theeffectiveness of using T-SPD at total drilling lengthsof 710 m and beyond, where low velocity zones havebeen observed. We also plan to adopt the use of
T-SPD at other mountain tunnels using controlledboring.
References
Asida,Y. (1997):
SWD(Glossary),Butsuri-Tansa,50,vol3,252-259 in
Japanese.
Yamagami, M., Imai, H., Aoki, T. ,Tomono, Y. andMitani,K. (2012a): Survey ahead of the tunnel by
the use of SWD (Seismic While Drilling),
Proceedings of the 67th JSCE Conference, Japan
Society of Civil Engineers in Japanese.

Conclusions

To evaluate a new seismic method, T-SPD, weperformed field demonstration tests using the drill rig
with a drilling capacity of 1,000m. We can draw thefollowing conclusions from these two tests.

Yamagami, M., Imai, H., Aoki, T. ,Yamanaka, Y. andTakahashi, T. (2012b): Case study on fracture zone
evaluation by tunnel face survey with the use ofdrilling vibration data, JSEG, 2012 Meeting, 2012
in Japanese.

・We clearly observed a wave propagating along thestring of the drill pipe to a length of about 500 m,
which appeared to reciprocate between the swivel anddrill bit tip. We therefore limited the effective
exploration to length of about 500 m, on theassumption that the S/N ratio became small due to the

Yamagami, M.,Imai, H.,Aoki, T. ,Nakahara, F.
(2012c): Development of survey Ahead of the7

10th Asian Regional Conference of IAEG (2015)

Tunnel by the use of Drilling Vibration DATA,
Proceedings of tunnel engineering, JSCE, vol.22,
157-161 in Japanese.
Yamagami, M.,Imai, H.,Kato, H. ,Misumi,
H.,Yamashita, M. (2014a): Development of survey
ahead of the tunnel by the use of drilling vibration
data with the ultra- long advanced boring,
Proceedings of the 69th JSCE Conference, Japan
Society of Civil Engineers in Japanese.
Yamagami, M.,Imai, H.,Aoki,T. ,Takahashi,T.,Yamanaka, Y.,Aizawa, T. (2014b): Seismic
Survey Ahead of the Tunnel Face by the Use ofDrilling Vibration Data, 8th Asian Rock Mechanics
Symposium, 2014.

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