2024-01-22_PERMIT FILE - C1980007A ‎(6)‎

• Permit No: C1980007A
• IBM Index Class Name: Permit File
• Doc Date: 1/22/2024
• Doc Name: Exhibit 84 Geotechnical Assessment for Pillar Extraction in Sunset South Mains
• Section_Exhibit Name: Exhibit 84 Geotechnical Assessment for Pillar Extraction in Sunset South Mains
• Media Type: D
• Archive: Yes

December 27, 2023 Page 4-8
Agapito Associates, Inc.
Table 4-1. Input Parameters Used for the Existing Pillars in Sunset Mains South
Pillar Roadway
Height (ft)
Roadway
Width (ft)
Depth of
Cover (ft)
Solid Pillar
Length (ft)
Solid Pillar
Width (ft)
Panel Width
(ft)
Zone 1 10 18 350-460 115.6-180 75 450
Zone 2 10 18 450–560 115.6 75 422
Zone 3 10 18 530-630 112-199 75 422
Zone 4 10 18 600-680 137.6-182 75 422
Zone 5 10 18 300-690 122.5-198.8 75 422
Zone 6 10 18 620-640 75-121.8 75 422
Zone 7 10 18 450-610 75-313.2 72-75 422
The results of the assessment for each zone indicate that all existing pillars have a w/h ratio of
7.2 to 7.5 and the SFs range between 2.7 and 5.5. The results are summarized in Table 4-2.
Table 4-2. Summary of the Stability for the Existing Pillars in Sunset Mains South
Pillar w/h Ratio Pillar Strength
(psi)
Tributary Area
Load (psi)
Safety Factor
(SF)
Zone 1 7.5 3,433–3,715 537-742 4.6–6.9
Zone 2 7.5 3,433 725-903 3.8–4.7
Zone 3 7.5 3,407-3,763 955-1,008 3.4-3.9
Zone 4 7.5 3,559-3,720 920-1,069 3.3-4.0
Zone 5 7.5 3,477-3,762 935-1,088 3.2-4.0
Zone 6 7.5 3,006-3,473 993-1,107 2.7-3.5
Zone 7 7.2-7.5 2,955-3,930 738-994 3.3-5.3