2024-03-29_REVISION - M1982121 ‎(2)‎

• Permit No: M1982121
• IBM Index Class Name: Revision
• Doc Date: 3/29/2024
• Doc Name: Adequacy Review Response #2
• From: RMR Aggregates, Inc
• To: DRMS
• Type & Sequence: TR6
• Media Type: D
• Archive: No

KIL D UFF4L RMR Aggregates,Inc.
U N U E R 3 R G U N E. Rock Failure Analyses and Stabilization Report
ENGINEER IN G,INC. Mid Continent Limestone Quarry
Table S. Typical Mine Design Criteria for Slopes
Wesseloo &Read, 20099
Consequence of Failure
Slope Scale
Low Medium High
Bench FOS ? 1.1
Inter-Ramp FOS? 1.15-1.2 FOS? 1.2 FOS? 1.2-1.3
Overall FOS? 1.2-1.3 FOS? 1.3 FOS? 1.3-1.5
For the RMR Aggregate site, the failure path of the slope could impact quarry facilities on the bench,
so the consequence of failure from medium to high was evaluated.This Correlates with the ❑RMS
recommendations reproduced in Table 4, corroborating a FOS of 1.5 was considered as the minimum
acceptable FOS.
Based on the slope stability results for the west wall,the massive limestone is stable for a variety of
bench slope geometries.Slope stability static and pseudostatic results for the west face based on the
above conditions are summarized in Table 6.
Table 6. Summary of Factor of safety for varying bench slope geometries
Bench Slope Static Factor Seismic Factor
Geometry Static Factor of Seismic Factor of Safety w/ of Safety w/
(Horizontal: Safety (long- of Safety Reduced Reduced
Vertical)' term) (long-term) Cohesion Cohesion
1:1 2.74 2.38 1.40 1.30
1.41 2.28 1.82 1.54 1.36
1.67:1 3.43 3.03 1.71 1.62
1. Max bench height of 30 feet
The higher than anticipated factor of safety for the 1:1 geometry is largely a result of the model
considering the massive limestone as a monolithic mass.A tension crack was induced as a release
plane because that joint is a persistent joint set across the site likely a result of structural folding of
the limestone. However, no interbed,joint or zone of weakness has been encountered, either in
geologic mapping or mining operations, in the massive limestone providing a release plane.To
evaluate the potential for an unknown zone of weakness within the massive limestone,the long-term
steady state stability analysis of the west face was run again with a reduced cohesion of 1,500 psf
(70%reduction from the empirical value)to mimic a loss of internal granular cohesion or strength.
9 Wesseloo,J.and Read,J.(2009).Chapter 9-Acceptance Criteria.In:Guidelines for open Pit Slope Design,J.Read and P.
Stacey(eds),pp 221-236.CIRSO publishing.496p.
Page 12
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