Virtual reality geological modelling for the Horonobe Underground Research Project
Takayuki MOTOSHIMA, Civil Engineering Dept., Nuclear Facilities Division, TAISEI Corporation
Makito NAGO, Advanced Technology Development Dept., Taisei Technology Center, TAISEI Corporation
Yuji IJIRI, Civil Engineering Dept., Nuclear Facilities Division, TAISEI Corporation
1-25-1 Nishi Shinjuku, Shinjuku-ku, Tokyo
Keywords; Virtual Reality, Horonobe URL, geological information

Abstract
As high-level waste disposal programs are projects with great public interest, the site selection process should be
conducted via open discussion with all necessary information being shared. Providing only information requiringexpert knowledge for interpretation, such as conventional two-dimensional drawings (e.g. geological maps) and
one-dimensional data (e.g. boring logs), may be insufficient to develop public understanding at discussion
forums.
Virtual reality (VR) and construction information management technologies are effective for the collection,
examination and visualisation of underground geological information, which cannot be easily visually confirmed.
In this study, a VR model was created by integrating geological data, photographs and a three-dimensional
profile of a tunnel face acquired during the construction of the Horonobe Underground Research Laboratory,
which is owned and operated by the Japan Atomic Energy Agency. The unique and important element of the VRmodel is this use of field data.
In this VR model, various details can be viewed at any point and compared. The use of the VR model allows forthe project staff to have simultaneous visual access to the geological information and to achieve smoothcommunication. In addition, the model provides visually clear discussion materials, such as allowing access togeological data obscured by concrete after construction. The model can also be used to plan subsequent
construction work and research studies. The use of the VR model will not only provide information for the
discussion forum during the investigation stage but also contribute to enhancing the safety and theinterpretability of the disposal project by incorporating and updating the geological information acquired during
the construction and operation of the repository.

1. Introduction
1.1 Background
High-level radioactive waste (HLW) generated by
nuclear power plants has a very high level ofradiationandcontains
various
long-lived
radionuclides. Therefore, it needs to be kept awayfrom human living environments for many years. To
isolate HLW from the biosphere, geological disposal,
i.e. placing radioactive waste in bedrock at a great
depth, is being studied internationally as a final
disposal method. In some countries such as Finland,
the construction and operation of geological disposal
facilities are in progress. Japan has also selected
geological disposal as a final disposal method for
HLW, and this project will proceed from theselection of the repository site to its operation.
In the construction and operation of HLW disposal,
collecting, analysing and visualising data concerning
the disposal facility and its surrounding geologicalcharacteristics at each step of the project, e.g. site
selection and facility construction, is important forthe development of the project. Specifically, suchinformationisusefulfortheplanning,
implementation and safe management of theconstruction work. Furthermore, the visualisation ofsuch information using virtual reality (VR) andconstruction information modelling, an approachinitiated by the Ministry of Land, Transport andTourism Infrastructure of Japan, as well as
conventional one- and two-dimensional depictions ofdata helps in building consensus with local
communities and governments as well as with theentire nation.
Recently, in the construction industry, thevisualisation of information related to construction
projects
usinginformation
communication
technologies such as VR and building information
modelling is being encouraged (Yabuki, 2016, Sato etal., 2009). The visualisation of such information is aparticularly effective technique for undergroundregions that cannot be easily visually confirmed.
Using VR technology, this study was conducted tofacilitate information sharing between project
members by visualising geological data in the VR

6th East Asia Forum on Radwaste Management Conference
November 27-29, 2017, Osaka, Japanspace and to increase understanding of geologicalinformation by modelling and reviewing various
details together. In this study, geological informationsuch as geological observation data, photographs andthree-dimensional (3D) scanning data of the
excavated rock surface acquired at the time of
construction of the Horonobe Underground ResearchLaboratory (URL) was simulated in the VR space. In
the VR space, various details can be viewed at any
point and compared.
1.2 Site Geology
The Horonobe URL project is being conducted by
JAEA in Horonobe, Hokkaido, Japan. This project
includes fundamental research and development
activities to verify the technical reliability of thegeological disposal of HLW and to develop safetyassessment methods. The planned elements of the
Horonobe URL include (a) a ventilation shaft(diameter: 4.5 m) and east and west access shafts(diameter: 6.5 m) with depths up to 500 m and (b)experimental galleries/niches at depths of 140, 250,
350 and 500 m. The construction of the URL beganin November 2005 (see Figure 1). As of June-end
2015, the ventilation and east-access shafts reacheddepths of 380 m, the west-access shaft reached adepth of 365 m and the experimental galleries at
depths of 140, 250 and 350 m were completed.
Currently, in situ experiments are being conductedusing the 350-m-level galleries.
The host rock of the Horonobe URL site is
predominantly composed of diatomaceous mudstone
up to a depth of 250 m and siliceous mudstone below
250 m and is subjected to an anisotropic in situ stressfield (Morioka et al., 2008).
The Horonobe URL site is located in Neogene
sedimentary rock. The diatomaceous mudstone of the
Koetoi Formation is distributed up to a depth of 250
m, overlaying the siliceous mudstone of the
Wakkanai Formation. Even though there is noaccepted theory regarding the boundary between
these formations, the boundary is marked here by thepresence of opal CT in the Wakkanai Formation, i.e.
it is defined by an opal-A/opal-CT transformation
boundary. The Koetoi and Wakkanai formations haverelatively large porosities, small unit weight and low
strengths (Morioka et al., 2008) (see Table 1). Bothformations are classified as soft rock according totheir uniaxial compressive strengths of approximately
5 MPa for the Koetoi Formation and a maximum of
25 MPa for the Wakkanai Formation. The
deformation coefficients of the Koetoi and Wakkanai
formations are approximately 200–640 MPa and
900–1200 MPa, respectively (Morioka et al., 2008).
Several types of measurements were conductedduring construction to monitor the rock mass
behaviour and to confirm the support robustness.

Table 2 lists the measurement items, which aregrouped into A and B depending on their objectives(Inagaki et al., 2014; Aoyagi and Kawate, 2015).
Ventilation Shaft

West Shaft

East Shaft

GL.-140m

GL.-250m

GL.-350m

GL.-500m

Figure 1. Layout of the Horonobe URL.
Table 1. Physical properties of the rock masses(Morioka et al., 2008).
KoetoiWakkanai
Property
Form.
Form.
Unit Weight [kN/m3]
14–16
16–18
Porosity [%]
60–65
40–50
Uniaxial strength [MPa]5
5–25
Hydraulic conductivity
10−11–10−6
10−9–10−8[m/s]
Table 2. Measurement items during the excavation of
the gallery at −350 m (Inagaki et al., 2014;
Aoyagi and Kawate, 2015).
Measurement
Measurement item
group
convergenceAcrown settlement
fracture mappingrock mass displacement
stress of support elements
borehole load test
amount of groundwater inflow
Brock core observations
fracture mapping of the tunnel
floor
cross-section profiling

6th East Asia Forum on Radwaste Management Conference
November 27-29, 2017, Osaka, Japan2. Virtual reality modelling approach
2.1 Overview
The VR model was created to allow users to walkthrough the shafts and the galleries and to interact
with point cloud data, photographs and geologicalobservation data of the excavated rock surface
acquired during construction as well as 3D models of
underground structures such as the galleries andshafts using computer-aided design (CAD) software.
By translating the point cloud data and CAD
models into VR, the system provides users with aunique experience walking through the structure froma depth of 250 to 350 m in the east shaft and then to
the ventilation shaft through the loop gallery locatedat a depth of 350 m.
In VR, users can observe the condition of the rockat the time of excavation of the shafts and thegalleries. The photographs and images of theobservational data of the excavated rock surface canbe reviewed and compared at each observation point.
2.2 Geological information collected in the
Horonobe URL
During the construction of the Horonobe URL,
laser scan point cloud data, photographs andgeological observational sketches of the excavatedrock surface were acquired at every excavation step.
(a) Point cloud data
When constructing the Horonobe URL, point clouddata of the excavated rock surface were acquired
using a 3D laser scanner (See Figure 2). The scanninginterval was approximately 2 cm, and geometrical
data such as the roughness of the rock excavation
surface and the RGB colour information wererecorded (See Figure 3 and Table 3).
The point cloud data were saved as text data andwere then grouped and converted into VR. The
coordinate accuracy was maintained by adjusting thereference coordinates.
(b) Photographs
Photographs of the excavated rock surface were
captured using Nikon D70 cameras. These
photographs were saved as digital data after
correcting for lens aberration and curvature. The
photographs were exported together with the point
cloud of the excavated wall surface of the ventilationand east shafts in OBJ format and then incorporated
into VR as a texture model.
(c) Geological sketches
When constructing the URL, observations of the
excavated rock surface were made by geologists.
Geological sketches were made onsite describing therock types and bedrock condition and then were
saved as CAD data. Image data of the sketches andthe CAD model of each of shaft and gallery were
exported in OBJ format and then translated into VR
as a texture model.

(d) Underground structures
Three-dimensional polygon models replicating theshafts and galleries of the URL were created andincorporated into the VR model.

3D Laser scanner

Bottom of excavation

Figure 2. Collection of point cloud data in the shaft
using a 3D laser scanner

Figure 3. Shape of wall rock surface of the ventilation
shaft obtained by 3D laser scanning (from a depth ofdepth 251 m to 281 m) ( Tsusaka et al., 2012)
Table 3 Specifications of 3D Laser Scanner whenused in shafts in the Horonobe URL
Horizontal scan line
distance
Field of view
Scan angle
Scanning interval
Number of scan points
Vertical scan line
distance
Field of view
Scan angle
Scanning interval
Number of scan points
Total
Scan points
Scan speed
Measurement time

16,650 mm
360Max. 0.22
10 mm
1,665
3,000 mm
35Max. 0.22
10 mm
318 points
Approx. 570,000
1,000 points/sec
600 sec

6th East Asia Forum on Radwaste Management Conference
November 27-29, 2017, Osaka, Japan

2.3 VR system configuration
VR content compatible with this system was createdusing Hybridvision, a VR system owned by Taisei
Corporation.
Hybridvision is a rear projection system comprised oftwo stereoscopic projectors and a large screen with aheight of 2.4 m and a width of 4.2 m (see Figure 4).
The projected image can be controlled using a 3D
mouse and a joypad. Stereoscopic viewing is possible
when wearing a pair of liquid crystal shutter glasses.
Several of its functions and their definitions are
summarised below.
(a) Large screen
The use of large screens is effective when project
members and stakeholders meet together and helps
develop discussions while watching reproduced
images.
The use of large screens facilitates the extraction ofproblems and makes it easier to form a consensus forsolving them, thereby reducing the discussion time.
Further, the use of a large screen where the entire
field of view fits on the screen provides a sense of
immersion.
(b) Stereoscopic vision
It is difficult to provide a sense of space, 3D
effects and the scale of a structure when only usingdrawings, models and movies. Stereoscopic vision iseffective when a greater degree of realism is requiredor when the 3D behaviour of various physicalphenomena needs to be confirmed.
(c) PC-compatible content
Two-dimensional content that runs on Windows®
PC was prepared along with content compatible with
Hybridvision even though it cannot be used to
produce 3D stereoscopic images.

Figure 6 shows the control panel of the model.
Figures 7 and 8 show the 3D laser scanning data of
the shaft and gallery walls, and Figure 9 (b) shows
photographs of the shaft wall.
The information incorporated into the model
extends from the surface to a depth of 380 m in the
URL, where construction and data acquisition has
been completed. As for the photographs, only a partof the photos of the ventilation and east shafts were
imported into the model due to time constraints on
the conversion of the data and the creation of themodels.
In the VR model, it is possible to move theviewpoint to an arbitrary location using a 3D mouseor controller. The models can be viewed from boththe inside and outside of the galleries.
The user can move to an arbitrary location andbrowse the 3D laser scanner data, the photographs ofthe excavated rock surface and the wall observation
data at an arbitrary point by switching the displayed
objects. For example, it is possible to compare thegeological maps with the photographs and then use
them to identify the occurrence of a fault (see Figure9). Figure10 shows that it is also possible to compare
two screens side by side.
However, the identification of the geometry anddirection of the fractures and the fault structure was
unsuccessful owing to the poor resolution of theoriginal data even though it was initially assumed to
be possible.

Twoprojectorunits

3D mouse
Five PC units
dedicated to
VR projection

JoypadServer for large-scale datavisualization and analysis

Liquid crystal
shutter glasses

Figure 4. System configuration of Hybridvision.
(Sato et al., 2009)
3. Virtual reality model
The VR model of the Horonobe URL was createdby converting each type of geological data into aformat compatible with the VR system and byincorporating it into the VR space. Figure 5 shows an
overall image of the created VR model is shown, andFigure 5. Geological map and underground structureof the Horonobe URL.

6th East Asia Forum on Radwaste Management Conference
November 27-29, 2017, Osaka, Japan

Figure 6. User interface.
(a) Point cloud(b) Photographs of the excavated rock surface
Figure 7. Point cloud in VR.

(c) Geologic maps drawn using CAD
Figure 9. Comparison of different datasets at thesame section and from the same viewpoint.
(a) Shaft(b) Loop gallery

Figure 10. Comparison of point cloud and geologicalmap side by side.

Figure 8. Visualisation of the roughness of the
excavated rock surface using 3D laser scanning data.

6th East Asia Forum on Radwaste Management Conference
November 27-29, 2017, Osaka, Japan4. Discussion and Conclusions
In this study, a VR model was developed as a newcommunication tool using data collected during theHoronobe URL project. The application of the VRmodel allows for the project members to share thecollected geological information and to achieve
seamless communication by providing visually clear
discussion materials, such as access to the rocksurface even after the installation of concrete.
The VR model can also be used to plan subsequent
construction work and research studies. For example,
in construction projects that are implemented 24/7
such as the Horonobe URL, for all the construction
members to meet and observe the condition of the
excavated rock surface on site is difficult. Therefore,
information sharing between the project members is achallenge and may cause delays in decision-making
with respect to construction and safety. By improving
the immediacy of our VR modelling, the model cancontribute to prompt decision-making. The VR modelis also expected to be useful for investigations at
high-risk sites such as slopes and high places. As thecurrent VR system requires a large screen, a systemusing a portable projector is being developed so that
VR can be more accessible anywhere. (see Figure
11).
Using the 3D laser scanning data shown in Figure
6, the roughness and geometry of the excavatedsurface are effectively visualised. Understanding
discontinuous structures such as faults and fractures
is important to ensure the structural stability ofsubsurface structures. From the viewpoint ofradioactive waste disposal, the safety assessment of
the disposal facility is also important because highly
permeable zones are potential flow paths forgroundwater. Our future study will include
improvements in the density of the point cloud data
and the rendering speed, which will decrease as theamount of data increases, by locally changing thedensity of the data.
In this study, a model focusing on geologicalinformation was created as the first step towards
building a VR model for the Horonobe URL project.
However, in this project, not only geological data but
also mechanical data—such as the stress anddisplacement of the rock masses and support
elements—andgroundwater
data—suchasgroundwater pressure and water quality—are being
acquired. Such data are also important for the safety
and performance of underground structures. In
radioactive waste disposal facilities particularly, thisinformation is key for evaluating the capability of theenvironmental barriers with respect to nuclide
confinement. Therefore, a future task is toincorporate these measurement data into the VRmodel to ensure safety during the construction andmanagement of the project and to facilitate better
communication.

Figure 11. Development of VR system using portableprojector.
We are grateful to Mr. Hayano and researchers of
Horonobe Underground Research Unit in JAPANATMIC ENERGY EGENCY for helpful discussions
about geological interpretation and VR modelling.
References
Aoyagi, K.; Kawate, S. (2015): Collection of
Measurement Data in 2013 Fiscal Year at the
Horonobe
Research
Laboratory
Project,
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Aoyagi, K. and Nago, M. (2017): Development of theobservational construction technology in the
Horonobe Underground Research Laboratory,
Geotechnical engineering magazine, 65(8),12-15.
Inagaki, D. (2014): Collection of URL measurement
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Underground Research Laboratory Project, Japan
Atomic Energy Agency, JAEA-Data/Code2013-022, 116 pgs., 2014.
Morioka, H. Yamazaki, M.; Matsui, H.; Orukawa, G.;
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6th East Asia Forum on Radwaste Management Conference
November 27-29, 2017, Osaka, Japan