2024-06-25_PERMIT FILE - C1980007 ‎(7)‎

• Permit No: C1980007
• IBM Index Class Name: Permit File
• Doc Date: 6/25/2024
• 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: No

April 22, 2024 Page i
Agapito Associates, Inc.

GEOTECHNICAL ASSESSMENT FOR THE PURPOSE OF PARTIAL PILLAR
EXTRACTION BETWEEN 2 AND 29 CROSSCUTS IN SUNSET MAINS

TABLE OF CONTENTS
Page
1 Introduction ...................................................................................................................... 1-1
2 Geotechnical Environment ............................................................................................... 2-1
3 Pillar Extraction Methods ................................................................................................ 3-1
4 Pillar Stability Criteria ..................................................................................................... 4-1
4.1 Design Standards ................................................................................................. 4-1
4.2 Pillar Strength Methodology ................................................................................ 4-1
4.3 Pillar Loading for Development Conditions ........................................................ 4-1
4.4 Pillar Abutment Loading for Retreat Conditions ................................................. 4-2
4.5 Condition of Existing Pillars in Sunset Mains ..................................................... 4-3
5 Proposed Pillar Extraction Plans ...................................................................................... 5-1
6 Numerical Modeling ........................................................................................................ 6-1
6.1 Pillar Stability Analysis ....................................................................................... 6-1
6.2 Surface Subsidence Analysis ............................................................................. 6-10
7 Ground Conditions Anticipated During Pillar Extraction ............................................... 7-1
8 Conclusion ....................................................................................................................... 8-1
9 References ........................................................................................................................ 9-1