3
been widely used in other underground structures, e.g.,
[9], [6], [10]. Figure 1 depicts an exemplary configuration
for the installation of DFOS in tunnel tubes. It provides
distance ranges (length of the sensing fiber) of more than
50 km, and a spatial resolution (defined as the smallest dis-
crete event that can be resolved with a specified accuracy) of
50 cm and smaller [11].
This Brillouin frequency shift depends on the local
density of the medium (silica of the optical sensing fiber),
linking it linearly to strain and temperature. Since the
density is an inherent material characteristic, Brillouin dis-
tributed temperature and strain sensing measurements are
extremely long-term stable. However, the longevity of fiber-
optic sensing cables depends on mechanical properties and
external factors and must be considered individually for the
desired environment. [8]
In the MOVIE project, it was decided to apply the
fiber-optic sensing cables onto the rock surface along the
full length of the underground laboratory for a full longitu-
dinal strain measurement. Figure 2 illustrates a preliminary
examination of the fiber-optic sensing cables to ascertain the
optimal adhesive bonding method. This process employs
gluing compound that adheres under the present ambient
temperatures, surface roughness, dust and humidity. As the
measurements are contingent upon the physical attach-
ment between the optical sensing fiber (inside the sensing
cable) and the rock or grout structure comprehensive pre-
installation assessments were conducted under this chal-
lenging underground environment. It is only at the rock
bolt test rig that fiber-optic sensing cables will be integrated
into the rock orthogonally to the surface, i.e., parallel to
the rock bolts.
MODELS AND THEIR COUPLING
The overarching objective of the MOVIE project is the
coupling of the geometrical, geological, geomechanical and
ventilation models. These four individual models and the
fully coupled model (computing time optimization of the
hybrid model) will be interactively visualized in a virtual
reality (VR) environment.
The Geometrical Model
The shape of the underground structure, i.e., geometri-
cal data, was acquired using the Zoller+Fröhlich (Z+F)
FlexScan 22 mobile mapping SLAM platform. The Z+F
FlexScan 22 solution uses a Z+F IMAGER 5016 laser scan-
ner, which is mounted on a backpack solution and therefore
combines the high spatial resolution of the previously static
laser scanner and the flexibility of a moving platform. The
technology makes use of the simultaneous localization and
mapping (SLAM) approach to create a map of the environ-
ment while acquiring the data, which is typically used in
robotics [12 and references therein]. The Z+F FlexScan 22
data for the drift length of about 60 m were captured during
two field campaigns with an approximate acquisition time of
20 minutes each. The high spatial resolution of the resulting
point cloud in the order of millimeters ensures precise cap-
turing of the complex geometry of the drift. Figure 3 depicts
the point cloud of the entire underground laboratory along
with a detailed illustration of the conical Chamber 1.
Data preprocessing steps include loop closure, intensity
based filtering and manual cleaning of noisy data points
using the software Z+F LaserControl 10.0.7.1.
On the one hand, the point cloud is used to plan the
installation of the fiber-optic sensing cables by estimating
the required lengths of cables directly in the point cloud.
The acquisition of another point cloud after installation of
the fiber-optic sensing cables to support strain and tem-
perature measurement localization is planned for a later
stage of the project. On the other hand, the point cloud
will undergo a process of meshing and will subsequently be
utilized as an input for the other models.
Figure 2. Impressions from the preliminary examination of
the fiber-optic cables (here colored in blue) to ascertain the
optimal bonding method [TUBAF]
Figure 1. DFOS cable network installed in tunnel tubes [6]
been widely used in other underground structures, e.g.,
[9], [6], [10]. Figure 1 depicts an exemplary configuration
for the installation of DFOS in tunnel tubes. It provides
distance ranges (length of the sensing fiber) of more than
50 km, and a spatial resolution (defined as the smallest dis-
crete event that can be resolved with a specified accuracy) of
50 cm and smaller [11].
This Brillouin frequency shift depends on the local
density of the medium (silica of the optical sensing fiber),
linking it linearly to strain and temperature. Since the
density is an inherent material characteristic, Brillouin dis-
tributed temperature and strain sensing measurements are
extremely long-term stable. However, the longevity of fiber-
optic sensing cables depends on mechanical properties and
external factors and must be considered individually for the
desired environment. [8]
In the MOVIE project, it was decided to apply the
fiber-optic sensing cables onto the rock surface along the
full length of the underground laboratory for a full longitu-
dinal strain measurement. Figure 2 illustrates a preliminary
examination of the fiber-optic sensing cables to ascertain the
optimal adhesive bonding method. This process employs
gluing compound that adheres under the present ambient
temperatures, surface roughness, dust and humidity. As the
measurements are contingent upon the physical attach-
ment between the optical sensing fiber (inside the sensing
cable) and the rock or grout structure comprehensive pre-
installation assessments were conducted under this chal-
lenging underground environment. It is only at the rock
bolt test rig that fiber-optic sensing cables will be integrated
into the rock orthogonally to the surface, i.e., parallel to
the rock bolts.
MODELS AND THEIR COUPLING
The overarching objective of the MOVIE project is the
coupling of the geometrical, geological, geomechanical and
ventilation models. These four individual models and the
fully coupled model (computing time optimization of the
hybrid model) will be interactively visualized in a virtual
reality (VR) environment.
The Geometrical Model
The shape of the underground structure, i.e., geometri-
cal data, was acquired using the Zoller+Fröhlich (Z+F)
FlexScan 22 mobile mapping SLAM platform. The Z+F
FlexScan 22 solution uses a Z+F IMAGER 5016 laser scan-
ner, which is mounted on a backpack solution and therefore
combines the high spatial resolution of the previously static
laser scanner and the flexibility of a moving platform. The
technology makes use of the simultaneous localization and
mapping (SLAM) approach to create a map of the environ-
ment while acquiring the data, which is typically used in
robotics [12 and references therein]. The Z+F FlexScan 22
data for the drift length of about 60 m were captured during
two field campaigns with an approximate acquisition time of
20 minutes each. The high spatial resolution of the resulting
point cloud in the order of millimeters ensures precise cap-
turing of the complex geometry of the drift. Figure 3 depicts
the point cloud of the entire underground laboratory along
with a detailed illustration of the conical Chamber 1.
Data preprocessing steps include loop closure, intensity
based filtering and manual cleaning of noisy data points
using the software Z+F LaserControl 10.0.7.1.
On the one hand, the point cloud is used to plan the
installation of the fiber-optic sensing cables by estimating
the required lengths of cables directly in the point cloud.
The acquisition of another point cloud after installation of
the fiber-optic sensing cables to support strain and tem-
perature measurement localization is planned for a later
stage of the project. On the other hand, the point cloud
will undergo a process of meshing and will subsequently be
utilized as an input for the other models.
Figure 2. Impressions from the preliminary examination of
the fiber-optic cables (here colored in blue) to ascertain the
optimal bonding method [TUBAF]
Figure 1. DFOS cable network installed in tunnel tubes [6]