4
continuously identify the latest pillar condition. Potential
ledges from PB1E cave back inside LWV was identified as
additional risk, therefore, additional monitoring drilling to
cover LWV has been completed in May 2022, as described
in Figure 9b. These holes are positioned in front of the drift
edges monitor the fractured/yielded propagation.
Estimation the propagation rates as the function of
drawing rates is important to identify its impact to the
LWV and ultimately the infrastructures. Indication of a
continuous failure/ subsidence in the LWV pillar can pro-
vide early indication of an increasing risk to personnel
working above it.
ESTIMATING THE IMPACT OF
SUBSIDENCE TO PB4 FOOTPRINT
Actual Production Rate
The actual material pulling at the Production Block#2
(PB2) draw points at the 2590/L creates a void triggering
the cave to grow over time. There are several extraction
panels that sit underneath the PB4 footprint ranging from
P08-P28 mainly at the southern perimeter of PB2. High
rate pulling (200 tpd) is shown at P15 to P24, and P27
(Table 1).
Vertical and Horizontal Cave Propagation
Quarterly cave shape reports since 2021 up to 2023 allow
the reconstruction of vertical and horizontal propagation
of the cave (Figure 5). A statistical approach is made to the
data relative to each PB4 Panel drift from P53-P72 to find
correlation of lateral cave progression to the actual drawing.
Table 1. Average Production Rate (tons per day) at PB2
PB2
PAnel
ID
Affected
Panel
in PB4
Average Production Rate (tpd)
QI-
2021
Q2-
2021
Q3-
2021
Q4-
2021
QI-
2022
Q2-
2022
Q3-
2022
Q4-
2022
QI-
2023
Q2-
2023
Q3-
2023
Q4-
2023
P08 P53, P54 — — — — — — 16 34 11 15 72 89
P09 P54, P55 — — — — 1 25 55 76 58 78 70 109
P10 P55, P56 2 11 16 21 34 55 62 22 61 61 67 79
P11 P56, P57 15 17 8 49 62 70 97 86 51 74 111 76
P12 P57, P58 27 36 44 53 80 93 135 104 72 104 131 125
P13 P58, P59 21 22 49 29 62 100 113 96 123 130 83 164
P14 P60 11 10 27 33 59 47 78 68 72 102 105 121
P15 P61 39 46 62 52 121 144 190 170 193 198 216 278
P16 P62 45 72 97 65 193 289 369 293 355 442 394 581
P17 P63 36 81 65 78 201 166 182 290 358 402 408 591
P18 P63, P65 86 62 79 121 242 253 138 371 380 394 379 535
P19 P66 40 99 110 87 242 207 280 334 324 328 336 414
P20 P67 84 110 102 91 172 119 306 357 370 333 308 377
P21 P68 87 92 144 79 73 231 312 358 366 182 283 261
P22 P69 72 117 220 154 181 223 332 391 351 284 324 250
P23 P70 12 37 93 102 144 181 313 305 324 347 257 220
P24 P71 7 42 45 134 239 210 250 296 280 245
P25 P72 — — — 85 50 179 236 231 208 177
P26 P73 — — — — 0 18 76 150 202 178
P27 P74 — — — — — 0 15 1 23 209
P28 P75 — — — — — — — — 0 90
Figure 5. Section View of Cave Growth Q1/21-Q4/23
Relative to PB4 Footprint
continuously identify the latest pillar condition. Potential
ledges from PB1E cave back inside LWV was identified as
additional risk, therefore, additional monitoring drilling to
cover LWV has been completed in May 2022, as described
in Figure 9b. These holes are positioned in front of the drift
edges monitor the fractured/yielded propagation.
Estimation the propagation rates as the function of
drawing rates is important to identify its impact to the
LWV and ultimately the infrastructures. Indication of a
continuous failure/ subsidence in the LWV pillar can pro-
vide early indication of an increasing risk to personnel
working above it.
ESTIMATING THE IMPACT OF
SUBSIDENCE TO PB4 FOOTPRINT
Actual Production Rate
The actual material pulling at the Production Block#2
(PB2) draw points at the 2590/L creates a void triggering
the cave to grow over time. There are several extraction
panels that sit underneath the PB4 footprint ranging from
P08-P28 mainly at the southern perimeter of PB2. High
rate pulling (200 tpd) is shown at P15 to P24, and P27
(Table 1).
Vertical and Horizontal Cave Propagation
Quarterly cave shape reports since 2021 up to 2023 allow
the reconstruction of vertical and horizontal propagation
of the cave (Figure 5). A statistical approach is made to the
data relative to each PB4 Panel drift from P53-P72 to find
correlation of lateral cave progression to the actual drawing.
Table 1. Average Production Rate (tons per day) at PB2
PB2
PAnel
ID
Affected
Panel
in PB4
Average Production Rate (tpd)
QI-
2021
Q2-
2021
Q3-
2021
Q4-
2021
QI-
2022
Q2-
2022
Q3-
2022
Q4-
2022
QI-
2023
Q2-
2023
Q3-
2023
Q4-
2023
P08 P53, P54 — — — — — — 16 34 11 15 72 89
P09 P54, P55 — — — — 1 25 55 76 58 78 70 109
P10 P55, P56 2 11 16 21 34 55 62 22 61 61 67 79
P11 P56, P57 15 17 8 49 62 70 97 86 51 74 111 76
P12 P57, P58 27 36 44 53 80 93 135 104 72 104 131 125
P13 P58, P59 21 22 49 29 62 100 113 96 123 130 83 164
P14 P60 11 10 27 33 59 47 78 68 72 102 105 121
P15 P61 39 46 62 52 121 144 190 170 193 198 216 278
P16 P62 45 72 97 65 193 289 369 293 355 442 394 581
P17 P63 36 81 65 78 201 166 182 290 358 402 408 591
P18 P63, P65 86 62 79 121 242 253 138 371 380 394 379 535
P19 P66 40 99 110 87 242 207 280 334 324 328 336 414
P20 P67 84 110 102 91 172 119 306 357 370 333 308 377
P21 P68 87 92 144 79 73 231 312 358 366 182 283 261
P22 P69 72 117 220 154 181 223 332 391 351 284 324 250
P23 P70 12 37 93 102 144 181 313 305 324 347 257 220
P24 P71 7 42 45 134 239 210 250 296 280 245
P25 P72 — — — 85 50 179 236 231 208 177
P26 P73 — — — — 0 18 76 150 202 178
P27 P74 — — — — — 0 15 1 23 209
P28 P75 — — — — — — — — 0 90
Figure 5. Section View of Cave Growth Q1/21-Q4/23
Relative to PB4 Footprint