2024-02-02_REVISION - M1982121 ‎(6)‎

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

KILDUFF RMR Aggregates, Inc.
U N D E R G R a U N D Rock Failure Analyses and Stabilization Report
E N G I N E E R I N G.I N C Mid Continent Limestone Quarry
Long Term Inspection Program
An effective proactive approach to slope stabilization will require a consistent, long-term program of
inspections and periodic maintenance of the berm and catchment area. Rockfall blocks should not be
permitted to accumulate. Damaged portions of the berm should be repaired immediately. Periodic
inspections of the slope and outcrops by an engineering geologist or geotechnical engineer will be
required over time to investigate natural deterioration of the stability conditions due to 1)
weathering/erosion of the surface rock, 2) increases in fracture aperture by water causing loosening
of surficial blocks, 3) loss of block interlock or support following minor block failure, and 4) growth of
vegetation roots. Inspections after seasons of significant precipitation should be a high priority,
particularly with freeze-thaw potential.
6. LONG-TERM STABILIZATION AND CONFIGURATION
Long-term steady state stability analysis of the west face highwall within the massive limestone was
performed to evaluate the potential bedrock failures along simulated discontinuities in the rock mass.
No weak interbeds or adverse bedding planes daylight in the massive limestone in the active quarry
wall. The January 2023 ground event failed along the lower weak bed above the massive limestone.
The massive limestone was modeled at various slopes angles to determine the stability of the lower
limestone layer.The slope geometry was analyzed using limit equilibrium method slope stability
analyses using the software program Slope/W from Geostudio. Geologic input parameters defined
above were used for stability modeling.
Using this methodology, the factor of safety for a given geometry is determined by calculating the
ratio of resisting forces to driving forces on trial failure surfaces. Slip surface scenarios analyzed for
this report were block specified. The slip surface with the lowest factor of safety against sliding is
described as the minimum factor of safety for the defined conditions.The Long-term steady state was
analyzed to consider the extended term stability of the highwall, and the rock strength is
characterized by effective stress parameters. A factor of safety is calculated by modeling the effects
of joint shear strength, friction angle, and water pressure within tension cracks.
Based on information provided by RMRA mining staff and KUE site reconnaissance, no known tension
cracks or discontinuities are visible or known to exist within the massive limestone layer. For the
analysis, tension cracks were placed within the upper slope of the highwall to simulate long-term
weathering and the release plane comparable to the ground event of the west slope. The tension
cracks were modeled as 50%water-filled plane. Strength properties of the massive limestone utilized
empirical values similar to those used within the west slope back analysis to provide a conservative
factor of safety due to no site-specific strength testing having been completed.
The Colorado Department of Reclamation Mining and Safety (DRMS) recognizes that a suitable
minimum factor of safety is dependent on the engineering analyses performed, accuracy of model
input parameters and level of impact to life and facility safety. The FOS values recommended by the
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