3
since 2018. Most of these holes are aimed for PB1
cave monitoring where very view of them is effec-
tive to monitor potential lateral cave propagation
towards the PB4 footprint.
• Network Smart Marker (NSM): 27 holes drilled
from MLA and DOZ level which are assigned to
monitor PB2 cave and less part of PB4 west.
Ability to monitor all portion of the cave is limited
to the engineering drift availability. Ex -DOZ and MLA
remain the only access for monitoring stations, some of
which are expected to be consumed by the DMLZ cave
growth. In the absence of monitoring stations, seismic
tomography and interpretation of seismic events utilised to
determine the non-elastic boundary.
PB4 Lower Wedge Volume (LWV) Monitoring Plan
The area below the extraction level (2815/L) is continu-
ously being monitored to identify potential extreme vertical
cave propagation. This area is identified as the lower wedge
volume (LWV), which is a 45-degree angle projected from
50 m vertical distance from extraction level to the south of
PB4E extraction level as can be seen in Figure 4a. The lower
wedge volume geometry is determined from numerical
model and approach of 1.5 – 2 times major pillar width (30
m width between panel). Monitoring plan is emphasised to
Figure 3. Cave monitoring instruments showing three different types of monitoring
Figure 4. Lower Wedge volume in PB4 East a) conceptual of lower wedge volume. b) 25 m radius of LWV monitoring
since 2018. Most of these holes are aimed for PB1
cave monitoring where very view of them is effec-
tive to monitor potential lateral cave propagation
towards the PB4 footprint.
• Network Smart Marker (NSM): 27 holes drilled
from MLA and DOZ level which are assigned to
monitor PB2 cave and less part of PB4 west.
Ability to monitor all portion of the cave is limited
to the engineering drift availability. Ex -DOZ and MLA
remain the only access for monitoring stations, some of
which are expected to be consumed by the DMLZ cave
growth. In the absence of monitoring stations, seismic
tomography and interpretation of seismic events utilised to
determine the non-elastic boundary.
PB4 Lower Wedge Volume (LWV) Monitoring Plan
The area below the extraction level (2815/L) is continu-
ously being monitored to identify potential extreme vertical
cave propagation. This area is identified as the lower wedge
volume (LWV), which is a 45-degree angle projected from
50 m vertical distance from extraction level to the south of
PB4E extraction level as can be seen in Figure 4a. The lower
wedge volume geometry is determined from numerical
model and approach of 1.5 – 2 times major pillar width (30
m width between panel). Monitoring plan is emphasised to
Figure 3. Cave monitoring instruments showing three different types of monitoring
Figure 4. Lower Wedge volume in PB4 East a) conceptual of lower wedge volume. b) 25 m radius of LWV monitoring