6
However, scan data from a previous project had been col-
lected in June 2019.
Therefore, July 2022 scans could be compared to June
2019 scans in entry N3N2. Changes were detected in the
roof of N3N2 at an angle perpendicular to the principal
horizontal stress direction as shown in Figure 12.
GROUND FAILURE MAPPING
In order to map areas of current and potential ground fail-
ure across the Subtropolis Mine, researchers utilized geo-
logic mapping conducted by the operator and analyzed the
data using ArcGIS. Researchers found that certain char-
acteristics or indicators were deemed the most important
when trying to predict areas of instability at the Subtropolis
Mine. Table 1 lists the indicators used in this study and the
ratings used to map these hazardous areas. The first indi-
cator is the orientation of the headings at the Subtropolis
Mine. Two major orientations were used, the North–South
Baseline 3D LiDAR scanning of the collapse area was
conducted in July of 2022. Scans were captured using the
Maptek I-Site 8200 stationary scanner, and 360-degree
scans were collected at each entry and crosscut along the
collapse area approximately 50 ft apart. Each scan was then
registered to each other using Maptek’s PointStudio pro-
gram and georeferenced to the Subtropolis Mine map. This
allowed researchers to visualize the collapse area (Figure 9).
Figure 10 shows two images of the baseline pointclouds at
a mine level view. Under a previous research project, the
southern portion of the collapse area had been scanned
prior to the majority of the failure. This acts as a very early
baseline scan for that particular part of the collapse
area. These baseline scans have been compared to other
scans collected at later dates to look for the amount of
change over time. Over the course of this study, changes
have been seen in two portions of the collapse area. One
area is the southern portion of entry N3N2, and the other
is the northernmost portion of entry N3N7.
The northernmost portion of entry N3N7 as shown
in Figure 11 saw changes to the rib and to the roof from
July 2022 to October 2022. A separation of the lower layer
of limestone in the roof occurred around a concrete crib.
A large fracture opened up around the concrete crib and
perpendicular to the entry. The southern portion of entry
N3N2 saw significant changes to the west in the N3N1
entry, which was inaccessible to scanning in July 2022.
Figure 9. 3D Lidar pointcloud ariel image of
massive roof collapse
Figure 10. 3D LiDAR pointcloud images of the massive roof
collapse at mine level
However, scan data from a previous project had been col-
lected in June 2019.
Therefore, July 2022 scans could be compared to June
2019 scans in entry N3N2. Changes were detected in the
roof of N3N2 at an angle perpendicular to the principal
horizontal stress direction as shown in Figure 12.
GROUND FAILURE MAPPING
In order to map areas of current and potential ground fail-
ure across the Subtropolis Mine, researchers utilized geo-
logic mapping conducted by the operator and analyzed the
data using ArcGIS. Researchers found that certain char-
acteristics or indicators were deemed the most important
when trying to predict areas of instability at the Subtropolis
Mine. Table 1 lists the indicators used in this study and the
ratings used to map these hazardous areas. The first indi-
cator is the orientation of the headings at the Subtropolis
Mine. Two major orientations were used, the North–South
Baseline 3D LiDAR scanning of the collapse area was
conducted in July of 2022. Scans were captured using the
Maptek I-Site 8200 stationary scanner, and 360-degree
scans were collected at each entry and crosscut along the
collapse area approximately 50 ft apart. Each scan was then
registered to each other using Maptek’s PointStudio pro-
gram and georeferenced to the Subtropolis Mine map. This
allowed researchers to visualize the collapse area (Figure 9).
Figure 10 shows two images of the baseline pointclouds at
a mine level view. Under a previous research project, the
southern portion of the collapse area had been scanned
prior to the majority of the failure. This acts as a very early
baseline scan for that particular part of the collapse
area. These baseline scans have been compared to other
scans collected at later dates to look for the amount of
change over time. Over the course of this study, changes
have been seen in two portions of the collapse area. One
area is the southern portion of entry N3N2, and the other
is the northernmost portion of entry N3N7.
The northernmost portion of entry N3N7 as shown
in Figure 11 saw changes to the rib and to the roof from
July 2022 to October 2022. A separation of the lower layer
of limestone in the roof occurred around a concrete crib.
A large fracture opened up around the concrete crib and
perpendicular to the entry. The southern portion of entry
N3N2 saw significant changes to the west in the N3N1
entry, which was inaccessible to scanning in July 2022.
Figure 9. 3D Lidar pointcloud ariel image of
massive roof collapse
Figure 10. 3D LiDAR pointcloud images of the massive roof
collapse at mine level