Appendix A (G-A) Pit Stability and Modeling

Select Phase Geotechnical Report —
Pit Stability and Modeling
Kings Mountain Mining Project
North Carolina, USA
Rev03
ABRIDGED REPORT (NO APPENDICES)
The deleted portions of this report may be provided upon request.
Report Prepared for
Albemarle Corporation
A\ ALBEMARLE(D
Report Prepared by
. consulting
SRK Consulting (U.S.), Inc.
SRK Project Number USPR000576
Albemarle Document Number: KM60-EN-RP-9057
April 9, 2024

SRK Consulting(U.S.), Inc.
Select Phase Geotechnical Report—Pit Stability and Modeling—Kings Mountain Page i
Select Phase Geotechnical Report -
Pit Stability and Modeling
Kings Mountain Mining Project
North Carolina, USA
Rev03
Albemarle Corporation
4250 Congress Street
Charlotte, North Carolina 28209
U.S.A.
SRK Consulting (U.S.), Inc.
999 17th Street, Suite 400
Denver, CO 80202
United States
e-mail: [e-mail]
website: www.srk.com
Tel: [phone]
Fax: [phone]
SRK Project Number USPR000576
Albemarle Document Number: KM60-EN-RP-9057
April 9, 2024
Authors:
Michael Bierwagen, BSc, Consultant (Rock Mechanics)
Fei Wang, PhD, Senior Consultant (Rock Mechanics)
Reviewed by:
Ed Saunders, P.Eng, Principal Consultant (Rock Mechanics)
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Table of Contents
1 Introduction.................................................................................................................. 1
1.1 Property Location................................................................................................................................1
1.2 Property History ..................................................................................................................................2
1.3 Project Overview.................................................................................................................................3
1.4 Project Layout.....................................................................................................................................3
1.5 Purpose and Scope of Report.............................................................................................................6
1.6 Reliance on Other Experts..................................................................................................................7
1.7 Descriptive Terms and Standards.......................................................................................................7
2 Proposed Pit Development ......................................................................................... 9
3 Historic Open Pit Status............................................................................................ 12
3.1 Pit Status and Geometries................................................................................................................12
3.2 Observations from Site Visit..............................................................................................................13
4 Geotechnical Field Program ..................................................................................... 16
5 Geology....................................................................................................................... 18
5.1 Deposit Geology................................................................................................................................18
5.2 Pit-Scale Geological Units ................................................................................................................18
5.3 Structural Geology ............................................................................................................................22
6 Rock Mass Conditions............................................................................................... 28
6.1 Weathering........................................................................................................................................28
6.2 Rock Mass Rating.............................................................................................................................28
6.3 Intact Strength...................................................................................................................................29
6.4 Rock Mass Strengths........................................................................................................................31
6.5 Minor(Discontinuities) Structures.....................................................................................................31
6.6 Discontinuity Shear Strength ............................................................................................................35
7 Geotechnical Domaining........................................................................................... 38
7.1 Approach...........................................................................................................................................38
7.2 Domain Summary .............................................................................................................................38
7.3 Domain Rock Mass Strength Parameters.........................................................................................41
7.4 Domain Discontinuity Sets................................................................................................................41
7.5 Shear Strength..................................................................................................................................42
8 Hydrogeology............................................................................................................. 45
8.1 Conceptual Hydrogeological Model..................................................................................................45
8.2 Groundwater Contours......................................................................................................................46
8.3 Pore Pressure Modeling Approach and Limitations..........................................................................47
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9 Slope Stability and Design Approach ...................................................................... 51
9.1 Slope Design Definitions...................................................................................................................51
9.2 Rock Slope Failure Mechanisms ......................................................................................................51
9.3 Slope Design Approach ....................................................................................................................52
9.4 Bench Configuration..........................................................................................................................52
9.5 Design Acceptance Criteria ..............................................................................................................53
9.5.1 Discussion and Data Confidence..........................................................................................53
10 Bench-Inter-Ramp Kinematic Stability Assessment............................................... 55
10.1 Kinematic Stability Review................................................................................................................55
10.2 Probabilistic Bench Stability Analyses..............................................................................................61
10.2.1 Planar Sliding Undercutting...................................................................................................61
10.2.2 Bench-Berm Scale SBlock Analyses ....................................................................................62
10.3 Major Structure Review.....................................................................................................................65
10.4 Bench Design....................................................................................................................................67
11 Inter-Ramp and Overall Stability Analyses.............................................................. 70
11.1 Stability Sections...............................................................................................................................70
11.2 Rock Mass Strength Parameters......................................................................................................71
11.2.1 Rock Mass Anisotropy (Rock Bridging).................................................................................71
11.2.2 Disturbance Factor (D)Zones...............................................................................................71
11.3 Seismic Coefficients..........................................................................................................................71
11.4 LE Stability Analyses Results ...........................................................................................................72
11.4.1 Overall Static Analysis...........................................................................................................72
11.4.2 Overall Slope Pseudo-Static Analysis...................................................................................74
11.4.3 Rapid Drawdown Sensitivity Analysis...................................................................................75
11.5 Limitations and Assumptions ............................................................................................................78
12 Pit Slope Design......................................................................................................... 79
13 Design Implementation Strategy .............................................................................. 83
13.1 Blasting .............................................................................................................................................83
13.1.1 Shallow Footwalls..................................................................................................................84
13.1.2 Trialing or Refining The Blast Design....................................................................................85
13.2 Scaling and Clean-up........................................................................................................................86
13.3 Geotechnical Pit Mapping.................................................................................................................86
13.4 Structural Geology ............................................................................................................................87
13.5 Pit Slope and Groundwater Monitoring.............................................................................................87
13.6 Updated Stability and Pore Pressure Analyses................................................................................88
14 Conclusions ............................................................................................................... 90
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14.1 Summary...........................................................................................................................................90
14.2 Impacts..............................................................................................................................................90
14.3 Opportunities.....................................................................................................................................91
15 References.................................................................................................................. 92
Disclaimer........................................................................................................................ 93
Copyright ......................................................................................................................... 93
List of Tables
Table 4-1: Geotechnical Drillholes....................................................................................................................16
Table 5-1: Geological Model Units ...................................................................................................................18
Table 6-1: Summary of Rock Mass Properties by Rock Type..........................................................................30
Table 6-2: Rock Mass Strength Parameters ....................................................................................................31
Table 6-3: Discontinuity Sets by Lithology........................................................................................................34
Table 6-4: Summary of Shear Strength By Rock Type ....................................................................................36
Table 7-1: Domain Discontinuity Shear Strengths ...........................................................................................43
Table 7-2: Geotechnical Domain Discontinuity Sets ........................................................................................44
Table 9-1: Overview of Stability Assessment Approach and Software............................................................52
Table 9-2: Kings Mountain Pit Slope Design Acceptability Criteria..................................................................53
Table 10-1: Kinematic Risk Summary Prior to Slope Design Mitigation ..........................................................56
Table 10-2: SBlock Simulations for the North Wall ..........................................................................................64
Table 10-3: SBlock Simulations for the West Wall...........................................................................................64
Table 10-4: SBlock Simulations for the South Wall..........................................................................................65
Table 10-5: Recommended Bench Slope Design Configurations....................................................................67
Table 11-1: Kings Mountain Seismic Coefficients............................................................................................72
Table 11-2: Summary of 2D LE Stability Analyses Results for Proposed Final Pit..........................................72
Table 12-1: Minimum Setback Distance from Pit Crest....................................................................................81
Table 13-1: Preliminary Prism and Radar Monitoring Details ..........................................................................88
List of Figures
Figure1-1: Location Map....................................................................................................................................2
Figure 1-2: Preliminary Kings Mountain Mining Project Site Map......................................................................5
Figure 1-3: Historic Exposed Pit Slopes Looking at the East Highwall ..............................................................6
Figure 2-1: Proposed Kings Mountain Pit Phases (colored by pit phase)........................................................10
Figure 2-2: Proposed Final Pit (Phase 4 at end of Year 8.5) ...........................................................................11
Figure 3-1: Aerial View of Historical Open Pit Footprint...................................................................................12
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Figure 3-2: Historic Slope Geometries for West and East Walls......................................................................13
Figure 3-3: Historic Exposed Pit West Highwall — Looking North ....................................................................13
Figure 3-4: Dominant Joint Set Daylighting into Historic Southeast Highwall — Looking Northeast.................14
Figure 4-1: Location of Geotechnical Drillholes and Drillholes with ATV/OTV Surveys...................................17
Figure 5-1: Stratigraphic Column and Local Geology Cross-Section...............................................................19
Figure 5-2: Kings Mountain Geology Map........................................................................................................20
Figure 5-3: Overview of Major Deposit Rock Types Showing: A) Amphibole Gneiss-Schist, B) Marble Schist,
andC) Spodumene Pegmatite ............................................................................................................21
Figure 6-1: RMRay Median, Lower, and Upper Quartiles by Unit.....................................................................28
Figure 6-2: Percent RQD Values from Kings Mountain Geotechnical Logging................................................29
Figure 6-3: Structural Orientations from Kings Mountain ATV/OTV Logging...................................................31
Figure 6-4: Foliation Structures Forming the Bench Faces Along the East Highwall ......................................32
Figure 6-5: Overall Pit Scale 3D Foliation Trend Model...................................................................................33
Figure 6-6: Contact Gouge Direct Shear Sample DS276-117.5......................................................................35
Figure 6-7: Available Direct Shear Testing Data Overlain on PH04 Pit...........................................................36
Figure 6-8: Summary of Direct Shear Results by Rock Type...........................................................................37
Figure 7-1: Kings Mountain Geotechnical Domains.........................................................................................39
Figure 7-2: Overview of Pegmatite Domain Boundary.....................................................................................40
Figure 7-3: Plan Showing the Distribution of the Overburden Unit ..................................................................41
Figure 7-4: Summary Stereonet by Geotechnical Domain...............................................................................42
Figure 8-1: Groundwater Contours and Flow Direction for the Current Condition Around Kings Mountain Pit46
Figure 8-2: Example of Water Table Input from Regional Groundwater Model, for Cross Sections 1 and 3,
UltimatePit Shell .................................................................................................................................48
Figure 8-3: Seepage Faces Predicted by Regional Groundwater Model at End of Phase 4 Mining ...............49
Figure 9-1: Schematic Representation Pit Slope Design Terminology ............................................................51
Figure 10-1: Foliation structures forming the exposed benches along the Historic Pit East Highwall .............59
Figure 10-2: Steep Benches along Historic Pit North Wall...............................................................................60
Figure 10-3: Exposed Benches Along Historic Pit West Wall ..........................................................................61
Figure 10-4: Summary of East Wall Bench Undercutting from Foliation..........................................................62
Figure 10-5: Example of Screening Level SBlock Simulation for Schist Domain Unit.....................................63
Figure 10-6: 3D Fault Interpretation and Intercepts Through Diamond Drilling ...............................................66
Figure 10-7: Logged Fault Intercepts in Drillholes and Pit Mapping ................................................................67
Figure 10-8: Domains Utilized for Bench Design .............................................................................................68
Figure 11-1: Stability Section Location Plan.....................................................................................................70
Figure 11-2: LE Static Stability Analyses Result for Section 1, East Wall........................................................73
Figure 11-3: FIE Static Stability Analyses Result for Section 1, East Wall .......................................................74
Figure 11-4: Pseudo-Static Stability Analysis Result for Section 4, West Wall................................................75
Figure 11-5: Rapid Drawdown Analysis Cross Section Location .....................................................................76
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Figure 11-6: Rapid Drawdown Analysis Cross Sections— East Wall...............................................................77
Figure12-1: Design Sectors.............................................................................................................................80
Figure 13-1: Evidence of Half-Barrels Along the Historic Pit North Wall..........................................................84
Figure 13-2: Conceptual Stab-Hole Blasting Design for the Shallow Footwall Slopes ....................................85
Figure 13-3: Blast Review and Trial Workflow..................................................................................................86
Figure 13-4: Example Hydrograph Showing VWP Water Level Responses to Rainfall and Excavation.........88
Figure 13-5: Summary of Total Station Monitoring Locations and Visible Pit Aspects for Each Mining Phase89
Appendices
Appendix A: Site Visit Photographs
Appendix B: Factual Field Data Report
Appendix C: Discontinuity Analysis
Appendix D: Kinematic Stability Analysis
Appendix E: Overall Stability Analyses
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List of Abbreviations
The US System for weights & units has been used throughout report for site specific data (unless
otherwise stated). Rock mass classification schemes and geotechnical analysis figures may be
referenced in their original metric units. All currency is in U.S. Dollars (US$) unless otherwise stated.
Abbreviation Unit or Term
Albemarle Albemarle Corporation
ASL above sea level
ATV acoustic televiewer
BFA batter face angle/bench face angle
CLE Contin enc Level Earthquake
cm centimeter
cm2 square centimeter
cm3 cubic centimeter
CSIR Council for Scientific and Industrial Research
CV coefficient of variation
D disturbance factor
° degree(degrees)
DD dip direction
DE Design Earthquake
dia. diameter
DST Direct Shear Testing
FES Field Estimated Strength
FF Fracture Frequency
FoS Factor of Safety
ft foot feet
ft2 s uare foot feet
ft3 cubic foot feet
acceleration due to gravity
GPa gigapascaI
GSI Geological Stren th Index
IRA inter-ramp angle
ISRM International Society for Rock Mechanics
Ja joint alteration number
Jc jointing condition
Jn joint set number
kg kilograms
KH horizontal seismic coefficient
KM Kings Mountain Project
km kilometer
km2 s uare kilometer
kN kilonewton
lb pound
LoM Life-of-Mine
m meter
m2 square meter
m3 cubic meter
Max. maximum
mi mile
Min. minimum
mm millimeter
mm2 square millimeter
mm3 cubic millimeter
MPa megapascal
MRE mineral resource estimate
MUS$ million U.S.dollars
NI 43-101 Canadian National Instrument 43-101
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Abbreviation Unit or Term
OLE Operational Level Earthquake
OS overall slope
OTV optical televiewer
Pa pascal
percent
PGA peak horizontal ground acceleration
PLT point load testing
PoF Probability of Failure
psi pounds per square inch
QA/QC Quality Assurance/Quality Control
RI Reliability Index
RMR Rock Mass Rating
RMR69 Bieniawski's 1989 rock mass rating system
RQD Rock Quality Designation
sec second
SF Safety Factor
SRK SRK Consulting (U.S.), Inc.
Std. Dev. standard deviation
TCR total core recovery
TCS triaxial compression strength
the Project Kings Mountain
TS tensile strength
TSF tailings storage facility
UCS uniaxial compressive strength
VWP vibrating wire piezometer
RSF Rock Storage Facility
year
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1 Introduction
Kings Mountain Mining Project (the Project) is an historical open pit lithium mining operation located
in the city of Kings Mountain, North Carolina, in the southeastern United States. The Project is a
lithium pegmatite deposit that is currently being investigated for redevelopment by Albemarle
Corporation (Albemarle) as part of a prefeasibility-level analysis. Albemarle commissioned SRK
Consulting (U.S.), Inc. (SRK) to develop prefeasibility-level (Evaluate and Select phases, per
Albemarle's internal conventions) designs for an expansion of the existing pit, rock storage facility
management, water management, and ancillary infrastructure to aid Albemarle in making informed
decisions concerning advancement of the Project.
1.1 Property Location
Situated in Cleveland County, the mine is approximately 35 miles west of Charlotte, North Carolina.
Located amidst rolling hills of the Piedmont Plateau, the Project is in a predominantly rural setting
within the city of Kings Mountain. The mine site covers a significant land area, which includes both
the proposed extraction areas and associated processing infrastructure. Figure 1-1 shows the
location and extent of the mine.
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Figure 1-1: Location Map
1.2 Property History
The following summary highlights the history of the site, compiled from records available to SRK:
• Mining started in 1883 with the discovery of cassiterite, a tin-bearing mineral, within the
outcropping pegmatites.
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• Subsequently, open pit mining for tin occurred sporadically between 1903 and 1937 (Horton
and Butler, 1988).
• Between 1943 and 1945, under the sponsorship of the U.S. government, Solvay established
a processing plant and mined for spodumene from the outcropping pegmatites (Garrett,
2004).
• In the early 1950s, Foote, a subsidiary of Newmont Mining Corporation, purchased the
property and began open pit mining (assumed at the beginning of 1955) and extracting
lithium from the spodumene.
• In 1993, exploration and mining operations ceased when the open pit bottom reached
approximately 660 feet(ft) above mean sea level (amsl).
• In early 1994, an open pit lake started to form due to rebounding groundwater, and the pit
lake reached an elevation of 817 ft amsl (as of January 2023).
• During the groundwater recovery period (1994 to present), water was sporadically pumped
from Kings Mountain pit lake to a nearby quarry (Martin Marietta) to support quarry
operation.
• Albemarle acquired the site in 2015, resuming exploration and mine development activities.
1.3 Project Overview
The Project ore deposit is a Lithium-bearing rare-metal pegmatite intrusion that has penetrated along
the Kings Mountain shear zone, a regional structural feature known to host multiple lithium bearing
pegmatites along its trend. The pegmatite field at Kings Mountain is approximately 1,500 ft wide at its
widest point in the historic pit area and narrows to approximately 400 to 500 ft in width at its
narrowest point south of the historic pit. The field has a lithium mineralization strike length of
approximately 7,500 ft and is predominantly contained in the mineral spodumene. The spodumene
pegmatite bodies exhibit a texture-based variation in lithium grade, spodumene grain size, mineral
alteration, and rock hardness.
After dewatering the historic pit, the lithium deposit is to be mined using conventional open pit mining
techniques. Blasting will fragment the ore and waste where it will be loaded and hauled to either the
processing facilities (ore) or the waste storage facilities (overburden). The current plan includes
mining in the existing pit and expanding the pit to the southwest. Ore would be drilled, blasted,
loaded, and transported by haul truck to a new processing plant at a rate of —2.98 million tons per
annum of ore (-8,150 tons per day) and processed to produce 385 to 440 thousand tons per annum
of spodumene concentrate. The concentrate will be filtered to approximately 11% moisture by weight
and transported off site for further refinement into lithium hydroxide monohydrate at a separate
facility.
Tailings from the spodumene concentrate process will be filtered to approximately 10 to 15%
moisture content by weight and transported off-site to a nearby facility for disposal. A portion of the
waste with economic value as aggregate will also be transported off-site for sale.
1.4 Project Layout
The Project layout is presented in Figure 1-2 showing the relative locations of the major components
of the Project. The project is bisected northeast to southwest by Interstate 85. The headwaters of
Kings Creek are located immediately northeast of the site and the creek leaves the Project area at
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the southern side of the Project area. The Phase 1 Open Pit outline is shown in the northeast area of
the Project, along with the ultimate (Phase 4) pit extents. Haul roads are shown connecting the Pit to
the rock storage facilities; RSF-X located south centrally for Potentially Acid Generating (PAG)waste
and RSF-A located in the southwest for non-PAG (non-PAG)waste. The haul roads will also connect
to the Non-Processing Infrastructure (NPI) located in the northwest portion of the site and the ore
sorting area and the ore stockpiles, located on the east side of the project, just north of Interstate 85.
A bridge over Interstate 85 will connect the ore stockpile area to the processing area, located
immediately south of Interstate 85. South of the Processing Area, the Water Storage Basin 1 (WSB-
1) will collect all contact water produced within the Project area before being discharged from the
site.
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IV
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,+silk consulting _•. _ ""I
AALHEMARLE ' FIGURE 01
Figure 1-2: Preliminary Kings Mountain Mining Project Site Map
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1.5 Purpose and Scope of Report
Albemarle Corporation (Albemarle)commissioned SRK Consulting (U.S.), Inc. (SRK)to complete the
pit slope stability and design work in support of a Select Phase Study for the project. This report
presents a summary of the open pit slope stability and design study completed for the Kings
Mountain Project(historic Kings Mountain open pit shown on Figure 1-3).
Source:SRK,2022
Figure 1-3: Historic Exposed Pit Slopes Looking at the East Highwall
A diamond drilling program was conducted during 2018 for resource, hydrogeological and
geotechnical purposes. The geotechnical program along with hydrogeological investigations were
advanced during 2022. The programs were designed to collect data needed to characterize the
deposit for Select Phase pit slope design purposes. The results of the field geotechnical investigation
have been documented in a separate report (SRK, 2023). The results of this investigation are
relevant to geotechnical conditions applicable to pit design are summarized in this report.
The purpose and scope of this report includes:
• Perform slope stability analyses and kinematic assessments for the design pit slopes,
including Factor of Safety results for the analyzed sections based on groundwater drawdown
estimates and the completed geotechnical and hydrogeological investigation programs.
• Provide open pit slope design bench face angles, bench widths, inter-ramp angles and
overall slope).
• Identification of areas requiring further design development /opportunities and future work to
advance the pit slope design study to Define Phase level.
The stability and design work summarized in the report is supported with following appendices:
• Appendix A: Site Visit Photographs
• Appendix B: Factual Field Data Report
• Appendix C: Discontinuity Analyses
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• Appendix D: Kinematic Stability Analyses
• Appendix E: Overall Stability Analyses
The quality of information, conclusions, and estimates contained herein is consistent with the level of
effort involved in SRK's services, based on:
• Information available at the time of preparation.
• Data supplied by outside sources.
• The assumptions, conditions, and qualifications set forth in this report.
This report is intended for use by Albemarle subject to the terms and conditions of its contract with
SRK and relevant securities legislation.
1.6 Reliance on Other Experts
SRK's opinion contained herein is based on information and data provided to SRK by Albemarle,
throughout the course of the investigations. SRK has relied upon the work of other consultants in the
project areas in support of this geotechnical report including the following:
• Logan Drilling conducted the core drilling for the 2018 Select Phase geotechnical drillholes.
• Dahrouge Geological Consulting conducted the geotechnical logging of the holes. SRK
provided QA/QC for the 2018 Geotechnical Program. SRK has reviewed the data (refer to
the 2023 SRK Factual Report) and has relied on the collected data for this report.
• DGI Geoscience conducted the Optical and Acoustic Televiewer logging of the 2018
geotechnical holes.
• Survey of the holes was completed by Logan Drilling (collected using a Reflex EZ-SHOT).
• Agapito Associates conducted all the strength laboratory testing and Advanced Terra
Testing conducted all the discontinuity direct shear laboratory testing. SRK has relied on
laboratory test results for strength and deformation properties of the various rock types.
• GeoVision Geophysical Services conducted seismic survey lines for surface P-wave and S-
wave velocities.
• Lettis Consultants International computed peak horizontal ground accelerations (PGA's) for
the project site based upon three design earthquakes.
• Albemarle provided the preliminary, interim, and final Select Phase Level pit design shells.
1.7 Descriptive Terms and Standards
The geotechnical data utilized by SRK for the Select Phase geotechnical investigation was collected
using standards that are broadly consistent with the following rock mass characterization systems:
• Council for Scientific and Industrial Research (CSIR) Rock Mass Rating (Bieniawski, 1976).
• Engineering Rock Mass Classifications 1989 Rock Mass Rating (Bieniawski, 1989).
• Guidelines for Open Pit Slope Design (LOP) (Read, & Stacey, 2009).
• Guidelines for Open Pit Slope Stability in Weak Rock masses (Martin & Read, 2017).
SRK used terms and standards to describe the geotechnical character of a rock mass that are
broadly consistent with terminology recommended by the International Society of Rock Mechanics
(ISRM). Key ISRM standards for the description of rock mass and discontinuities include the
following:
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• Suggested Methods for the Quantitative Description of Discontinuities in Rock Masses
(1978).
• Basic Geotechnical Description of Rock Masses (1989).
• Rock Characterization Testing and Monitoring: ISRM Suggested Methods (1981).
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2 Proposed Pit Development
The proposed pit is to be developed in five phases, termed PHO to PH4 Pits (Figure 2-1). The early
pit phases advance the depth of the historic open pit to about 450ft (PHO-PH3), and pushback the
East Wall toward its final position. The final PH4 pit phase comprises a push-back to form the West
Wall crest and advances the pit floor to an elevation of 285 ft (Figure 2-1 and Figure 2-2). The overall
slope heights range from 650 ft (East Wall) to 705 ft (West Wall). The proposed pit is to be
excavated across an 8.5-year period.
SRK understands that an updated pit design was undertaken in March 2023, and that a revised pit
design was undertaken in late August 2023. These have been considered in the overall slope
modelling. Remaining geotechnical study aspects are undertaken with respect to the PHO to PH4
design pit shells.
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PHI
PH4 Qy
.q
+545000 N
PH2 1
+S 4000 N
f ,
PH4
+543000 N
PH3
+542000 IN
0 250 500 7501000
1295000 E +1296000 E +1297000 E +1298000 E
A .'A'
B g°
o 125 - 5500,1
Source:SRK,2022,LeapFrog Model
Figure 2-1: Proposed Kings Mountain Pit Phases (colored by pit phase)
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f
Plunge
Azimuth 000
Looking North
0 250 500 750
Source:SRK 2023, modified from Albemarle 2023 Pit Shells
Figure 2-2: Proposed Final Pit (Phase 4 at end of Year 8.5)
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3 Historic Open Pit Status
3.1 Pit Status and Geometries
A pit lake has formed within the historic open pit (Figure 3-1). The pit lake has formed to the 785 ft
elevation with two to three benches exposed above water level (Figure 3-2 and Figure 3-3).
Figure 3-2 shows the historic as-built pit slopes on the west and east walls. The West Wall has an
overall slope angle (OSA) of about 50 degrees and East Wall about 40 degrees (Figure 3-3). The
exposed benches are vegetated and shows a higher degree of fracturing than the underlying fresh
rock recovered during the drilling programs.
The current ground elevation is approximately 975 ft and 850 ft on the west and east sides of the
historic pit, respectively. The historic pit depth is 660 ft.
216
a
I
t
S t;
I
p
+929 +l 0 E
Source:Google Earth,2022
Figure 3-1: Aerial View of Historical Open Pit Footprint
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W West OS = 50' E W East OS = 40' E
Jr
West Wall East Wall
l
Source:SRK,2023
Figure 3-2: Historic Slope Geometries for West and East Walls
0 1070E (T) OO 35.225707, -81 .355301 ±42ft A 822ft
-
�
h,
Source:SRK,2022
Figure 3-3: Historic Exposed Pit West Highwall —Looking North
3.2 Observations from Site Visit
SRK conducted a site visit in January 2022 to inspect the exposed bench slopes. Photographs from
the visit are presented in Appendix A. The following observations were made:
• The first bench historic pit was in soil/weathered rock all the way around the pit. The existing
vegetation is likely helping to stabilize these slope materials.
• The upper rock benches were highly fractured and weathered. Block volumes and shapes
were observed to be variable, ranging from 8x18x20 to 20x2Ox2O inch in dimension. In the
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lower portions of the exposed benches, the rock was becoming more massive with a
decrease in open fractures.
• A dominant joint set representing foliation is exposed in the eastern and western benches.
The foliation ranged from about 60 to 75 degrees, with some variability observed across
bench strike. The structures can be slickensided and are continuous at bench heights
observed. On the Southeast Wall, benches had broken back to foliation with some planar
failures (Figure 3-4). On Northwest Wall, the dominant set was noted to have toppling failure
potential.
• There was no significant evidence that wall control blasting was utilized in the exposed
slopes above the lake level.
• Seepage was observed on the Northwest Wall, near the movie theater screen where running
water was observed exiting halfway down the first bench, at the bottom of the soil layer.
• Northwest and North Wall benches are observed to be near vertical with narrow berms.
There are half-barrels observed in the exposed benches that is evidence of pre-split wall
control drilling.
• Seepage was observed in two locations on the South and Southeast Walls. The seepage
areas correlated with zones of higher fracture frequency and had altered/stained the
surrounding rock.
• Typical rock strength was estimated to be R4 (50 to 100 MPa) range.
These observations have supported the characterization, bench-kinematic stability assessment and
design (i.e., steep bench faces formed in the north and west).
36"NE (T) * 35.222087, -81 .35191 ±18ft 1 734ft
: ' �.:�• f
ar r x5 �Sl? x
Source:SRK, 1/2022
Note:Joint set observed in mica shist. Looking NE.
Figure 3-4: Dominant Joint Set Daylighting into Historic Southeast Highwall — Looking
Northeast
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AA
.F_. `d
Source:SRK,2022
Figure 3-5: Steep Bench Faces Formed in the West Wall showing Pre-Split Half-Barrels
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4 Geotechnical Field Program
SRK completed a geotechnical investigation program that included eight oriented drillholes between
2018 and 2022, as shown in Figure 4-1. The drillholes were inclined around the historic open pit.
Core recovered from these drillholes was logged by Dahrouge Geological Consulting (Dahrouge),
which included the collection of specific parameters to estimate Rock Mass Rating (RMR) values as
defined by Bieniawski (1989). Core samples were also collected from these holes for laboratory
strength testing (SRK, 2023). Table 4-1 and Figure 4-1 (shown in yellow) display the coordinates and
orientation of the drillholes.
Table 4-1: Geotechnical Drillholes
Hole ID Northing ft Eastin ft Elevation ft Azimuth Dip Length ft Target ft
DDKM18-276 544,004.8 1,297,518.1 801 103 -80 452.8 455
DDKM18-281 543,597.9 1,297,205.8 820 103 -80 298.6 300
DDKM18-282 545,383.7 1,296,652.9 901 200 -70 1,236.9 1250
DDKM18-291 545,288.4 1,297,924.0 883 225 -70 1,207.4 1200
DDKM18-298 544,926.6 1,296,525.9 937 20 -70 1,080.1 1050
DDKM18-312 543,381.9 1,295,947.5 883 310 -70 1,295.9 1300
DDKM18-327 543,532.5 1,296,938.0 818 180 -65 1,404.2 1400
DDKM18-340 541,460.2 1,295,037.5 915 180 -70 1,197.5 1200
Source:SRK,2022
In addition to the data obtained from the eight dedicated geotechnical holes, the following other
relevant data was collected:
• Basic geotechnical parameters were collected from exploration holes by Dahrouge. The
parameters included rock quality designation (RQD), recovery, and fracture spacing —
63 drillholes to 59,470 ft.
• Optical televiewer (OTV) and acoustic televiewer (ATV) scans including processing of
discontinuity orientation data - 119 drillholes to 101,548 ft.
The OTV/ATV scans were performed in approximately 33 percent (%) of the total drilled length of
310,028 ft. The televiewer scans and processing were carried out by DGI Geoscience. Figure 4-1
shows the locations of drillholes where OTV/ATV scans were performed (shown in white). Further
description from the field program is included in Appendix B — Field Factual Report.
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..
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Select Phase Geotechnical Report—Pit Stability and Modeling—Kings Mountain Page 18
5 Geology
5.1 Deposit Geology
The Kings Mountain deposit lies within North Carolina's tin-spodumene belt and is located within a
larger-scale shear zone (the Kings Mountain Shear Zone - KMSZ). The shear zone is a northeast-
striking, steeply to moderately dipping zone of ductile and semi-brittle deformation. The zone is at
least 37 miles (mi) long and is no more than a few hundred feet (ft) wide. The shear zone is a
boundary between two terrains within the Piedmont Plateau, including the Kings Mountain and Inner
Piedmont Belts. The belts are described as:
Kings Mountain Belt: Located east of the KMSZ and composed primarily of meta-sedimentary
rocks (quartzite, conglomerate, marble) associated with mica schists (meta-sedimentary and meta-
volcanic in origin), as well as the High Shoals Granite.
Inner Piedmont Belt: Located west of the KMSZ and composed of primarily of mica gneiss and
mica schist (commonly with low undulatory dips). At a local scale, this includes the Cat Square
terrane, which is represented by muscovite schist and amphibolite, which have been intruded by the
(weakly-foliated) Cherryville Granite (and its associated pegmatite stocks, including spodumene
pegmatites).
5.2 Pit-Scale Geological Units
Surface exposures on the KM property are limited to areas of historical open pit. The remainder of
the property is either blanketed under a deeply weathered profile, rarely preserving any remnants of
the protolith, or overlain by historical spoils or stockpiles.
Units of the Cat Square terrane (Inner Piedmont) dominate the property and host the spodumene
pegmatite deposits through the center and western limits. The eastern limit of the former open pit
mine on the KM property coincides with the KMSZ (mica gneiss, mica schist and marble)
The represented lithologies at deposit/property scale (geological model units as classified by
Dahrouge, 2020) are listed in Table 5-1. Figure 5-2 shows a geologic map of the KM property and
Figure 5-1 shows a stratigraphic column of the local geology.
The three major deposit-forming rock types include Amphibole Gneiss-Schist, Marble/ Marble Schist
and the ore-bearing Spodumene Pegmatite. A representative set of core photos for each major unit
is shown in Figure 5-3.
Table 5-1: Geological Model Units
Lithology Model Unit Grouped Rock Units
Pegmatite (peg) Pegmatite (peg)
Intrusives: Muscovite pegmatite (msc peg) Muscovite pegmatite (msc peg)
Spodumene pegmatite(spd peg) Spodumene pegmatite s d e
Spodumene-muscovite pegmatite s d-msc e
Upper mica sch (upper mica sch) Upper mica sch (upper mica sch)
Shear schist 1 (shear sch1)
Inner Piedmont Shear schist(shear sch) Shear schist 2(shear sch2)
Terrane Holmquistite schist(him sch)
Amphibole gneiss-schist(amp gn-sch) Hornblende(+/-biotite)gneiss(hbl gn)
Horn blend e-epidote gneiss(hbl-ep gn)
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Lithology Model Unit Grouped Rock Units
Hornblende(+/-biotite)schist(hbl sch)
Hornblende gneiss-schist breccia(hbl gn-sch
brc
Biotite gneiss(bt gn)
Mica schist(mica sch)
Garnet-mica schist(grt-mica sch)
Mica schist(mica sch) Pyrrhotite-mica schist(po-mica sch)
Quartzolite(qtzle)bands
Tourmalinite(turt)bands
Chlorite schist(chi sch) Chlorite schist(chi sch)
Silica mica schist(silica mica sch) Silica mica schist(silica mica sch)
Kings Mountain Silica mica schist-marble transition Silica mica schist-marble transition zone(sch-
Belt(Blacksburg zone sch-mbl mbl
Formation) Marble(marble) Marble(mbl)
Phyllite (phyllite) Phyllite(phyllite)
Source:Dahrouge,2020
480
.--ti �I� . r•�1 f�� i 1 �. d7
500lie
•i L (_)
4a G upper mica schist w
(� (upper mica sch)
Es 520 0 0}
L 1— CL? a- -0
sda 0 G A- V a)
W w
amphibole C
S60 gneiss-schist(amp 27
gn-sch);shear schist d E
6. (shear schist)
E CL
X� � LO
SBO L CL
r+3 E r
�a0 c c
CL CD
U 0 Mz
++ E mica schist mica seh) �y
620 U 0) LO
m
v 03 C
6+40 CL a+ silica mica schist(silica a)
'' LO
�y
0 G r. mica sch);silica mica _ ,j
CD m schist-marble
transition zone
ti60 Z E = ` (sch-mbl) >
LL
L
6B0 marble(mbl) m
O a c
7 2CL
V) 6.D CL
700 _ phpilite(phyllite)
720 x kvx�
Source: Dahrouge,2020 Horton,2008
Figure 5-1: Stratigraphic Column and Local Geology Cross-Section
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1294500 1295000 1295500 1296000 1296500 1297000 1297500 1298000 1298500
1 I 1 1
Mcp
4a
ware
W E v
yy
o
-
-
- r
91
$ A
t
6,
a,• k
pro, d n
_ ✓, as V _
f
.1-1119
B >01
/ r� oid w�rymtP .4-aq� p�
P
n � Mc
t ,a
r
r
� 1 „fy' �zblm Legentl d
iv
g a� -� s - F ry 9 Iscs�rs rrn:�dm�neredst ° a
-� � y Y ��,Ks93M„sramsn,arms,
f �'k Melor Fain.rceow�d
t
r � f--�a Insse m� t• uneaoar,
T
e ko
�O� wr.°PPera�P 9�-sen.amP aq-�ea,near ern nmt �5
-
S ,eras l�m. n n ss ce9
WPa1 e _ +I
Zbl- rol
PnYe
0 250 500 1,060 1,500
A 8895a Pia ornG a_FPS3200Feet FwI= bq, meam —q te
IOK '226, -ty:E SG
1 1
1294500 1295000 1295500 1296000 1296500 129T000 1297500 1298000 1298500
Source: Dahrouge,2018
Note:Bedrock geology shown with overburden removed.
Figure 5-2: Kings Mountain Geology Map
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I
B
� 1
Source:SRK,2023
Figure 5-3: Overview of Major Deposit Rock Types Showing: A) Amphibole Gneiss-Schist, B)
Marble Schist, and C) Spodumene Pegmatite
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5.3 Structural Geology
The rocks of the district have been extremely folded, metamorphosed, and faulted. The structural
features resulting from extreme compression generally run northeast, as is usual in the
Appalachian Mountains and Piedmont Plateau. Deformation on the KM property mirrors the regional
events; however, evidence of all six events was not observed on the property. Two major ductile
events and a later stage brittle/brittle-ductile event were recognized (Stryhas, 2017; Uken, 2018):
• D1 (Pre-pegmatite deformation):
o Pervasive bedding parallel, L-S type foliation, Li-Si (mineral lineation in the plane of a
foliation), fabric preserved within the amphibole units.
o F, isoclinal transposed and rootless folds, interfolial to lithologic bedding and S,
pervasive foliation; fold axes are sub-parallel to parallel to the L, mineral lineation and
plunge moderately NNW.
o L, plunges moderately to steeply to the NW.
o S1 pervasive foliation dips moderately to steeply to the NW.
• D2 (Syn-to post pegmatite deformation):
o Heterogenous.
o Ductile shear zones preserved as contact strain along pegmatite contacts and within
micaceous country rocks.
o Deformation of pegmatites in shear zones.
o Development of gneissic to mylontic S2, shear zone foliation, where shear zones cut
pegmatites.
o S2 is sub-parallel to St with the development of shear bands and an S-C fabric.
o F2 open crenulation folds; fold axes trend NE or SW with shallow to moderate plunges.
• D3 (Late brittle faulting):
o Post pegmatite emplacement EW striking brittle faults.
o Brittle reactivation along pegmatite contacts.
o Brecciation and hydrothermal alteration of pegmatite, amphibolite and amphibole gneiss-
schist.
Ductile deformation is the dominant structural regime observed on the KM property; ductile shearing
is evident in both surface exposures and recovered drill core. Geometries for the units on either side
of the KMSZ have been most strongly influenced by the ductile deformation events and generally
conform to the regional strain, striking NE-SW, for this area.
A series of E-W trending, moderately to steeply dipping, late brittle faults were observed in outcrop
and in recovered drill core. Commonly these brittle faults have a normal sense of movement and
negligible apparent displacements. Only one brittle fault, EW-01, was interpreted to have a
significant displacement on the property. EW-01 is a major normal fault occurring at the northern end
of the current pit; it has an east-west trend and a sub-vertical dip. This fault truncates the extension
of spodumene-bearing pegmatites in the north wall and has caused extensive damage and alteration
in the surrounding rock.
Interpretation of the primary and secondary fault structures is required to advance the design
study to a Define Phase level. This aspect is current a gap in the study that needs to be
addressed to confirm the stability assessment and design included in this report.
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Major fault locations relative to the topography and 8.5 year pit from the current fault interpretation
are shown in Figure 5-4. Core photo examples of each fault major fault shown in Figure 5-4
(`Unnamed' Fault, Kings Mountain Shear Zone, Fault S_Flex, and Fault EW-01) are shown in
Figures 5-5 through 5-8.
Fault-EW-01
I
Unnamed Fault
j
I f�
lex
oF
J 9'
Kings Mountain
Shear Zone
l
�\ 4 I►/�IIA
Year 8.5—
Ultimate Pit'
Current �� Plunge '-go
r
Azimuth 000 )
Topography Looking down
- 0 §O.Q 7501000
Source:Leapfrog model modified by SRK 2023
Note:Modelled faults shown relative to plan view of topography with 8.5 year Ultimate Pit overlay.
Figure 5-4: Modelled Major Faults
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To: 9-5�, . N
YCM
r
c
5 _
J - .
�y 9
• R
fl r MM.
' M-I
�1.
115111111
1.
■
} a.
_ -
E ,
Source:SRK,2023
Note:Logged fault in DDKM18-327 at 253.88-255.00ft
Figure 5-5: Example of`Unnamed' Fault
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39 B
i 90 ,0q7 7s*�'�,
-
11� ;
jr
"v:
t
1.
1
k
I '
I - �
1 -
t
f k f(
I
Source:SRK,2023
Note:Logged fault in DDKM18-348 at 208.73-310.14ft
Figure 5-6: Example of Kings Mountain Shear Zone
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DDKM17-031
FROM : 112.88FT
TO: 131.23FT
BOAC: 13-14
0.10.2 0.3 0.40.5 D.60.70.8
f
x .
I
w4tj
+�+ k
flu,
•
N
x
� 4
w�
Source:SRK,2023
Note:Logged fault in DDKM17-031 at 121.20-122.08ft.
Figure 5-7: Example of Fault S_Flex
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Select Phase Geotechnical Report—Pit Stability and Modeling—Kings Mountain Page 27
KM 17 017
4 FROM: 454.32FT
TO: 480.44 FT
BOAC: 46-48
. . . . FT
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
it • .
r
x -
- - - -_ •.es. "'(;".�`�..')� �"1•• Thy
W
4�
Q'
l5
T I
■ r
ir
Ilk
e
a •
mow"
Source:SRK,2023
Note:Logged fault in DDKM17-017 at 459.00-473.00ft.
Figure 5-8: Example of Fault EW-01
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6 Rock Mass Conditions
The field and laboratory data has been previously summarized in SRK's factual report (SRK, 2023),
included in Appendix B. The data has been used to evaluate the rock mass conditions for
geotechnical domaining purposes.
6.1 Weathering
The initial bench exposed represents soil and weathered rock materials. The slope design are based
on a weathered unit that comprises the initial single benches around the proposed open pit.
6.2 Rock Mass Rating
Rock mass ratings (RMR89) for the primary lithologies are summarized in Figure 6-1. The ratings
indicate most rocks to have an RMR89 value greater than 65 which can be described as good rock
using Bieniawski's 1989 RMR system. The values correspond to rock masses that are typically
blocky and strong. Review of the Rock Quality Designation (RQD) data collected from resource
definition drilling indicates the rock mass to be similar good quality near the center of the proposed
final pit (Figure 6-2). Lower RQD values so align with weathered rock materials located in the upper
bench elevations. A summary of the rock mass rating values is provided in Table 6-1.
Rack Mass Rating (1989)
100
80
0) 60 71 1 70 65 72 i 70 67 76 72 74
I
�
40
20
0 Amphibole Chlarite Mica Schist- Shear Silica Mica
Gneiss- Schist Marble Schist Phyllite Marble Schist Schist Spod Peg
Schist
—Lower quartile 65 62 58 67 68 62 73 67 69
—Upper quartile 77 74 70 77 75 72 81 76 78
■Median 71 70 65 72 70 67 76 72 74
Source:SRK,2023
Figure 6-1: RMR89 Median, Lower, and Upper Quartiles by Unit
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% RQD
100
80
-Now 60
t 40
20
so
Plunge+45 0
Looking North
0 250 500 7501000
Source:SRK 2023, modified from Albemarle 2023 Leapfrog Geo Geologic Model
Figure 6-2: Percent RQD Values from Kings Mountain Geotechnical Logging
6.3 Intact Strength
A summary of the intact strengths for each primary lithologies are summarized in Table 6-1. The
intact strengths are based on Unconfined Compressive Strength (UCS), tensile strength, Young's
Modulus and Poisson's Ratio.
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Table 6-1: Summary of Rock Mass Properties by Rock Type
Rock Type
Avg. UCS Std. Avg. Poisson Density RMR 89 Tensile Tensile Young's RMRsy Logged
(kg/m
UCS Dev. Strength Std. Dev. Modulus 3) ts�i m; Mean Standard Length
(GM) (MPa) (MPa) (MPa) (MPa) (Gpa) Ratio Deviation (m)
Amphibole 111 51.3 11.1 0.4 58.65 0.17 3,01 105.7 9.1 71 10.1 2010
Gneiss-Schist
Marble 57.7 28.2 - 25.9 0.19 2,742 64.810.71 6 7.9 984
Mica Schist 45.5 23.8 14.4 49.26 0.21 2,864 43.6 9.7 72 7.2 1237
Silica Mica 77.4 43.3 19.2 4.2 48.9 0.21 2,82 66.411.6 72 5.5 1101
Schist
Pegmatite 140 63.7 11.3 3.9 61.21 0.21 2,691142.610.5 74 8.4 1783
Schist-marble 48.6 23.4 - - - - 2,78 48.6 - 67 8.3 676
Shear schist 78.5 34.8 - - - - 2,968 78.5 - 76 8.1 86
Phyllite 50 3.6 - - - 2,828 50.0 - 70 4.1 60
Chlorite _ _ _ _ _ - _ 70 8.5 124
Schist
Source:SRK,2023
Rock Mass Rating (1989)
100
s0
0 71 70 65 72 i 70 67 i 76 72 74
oa 60
o�
40
20
0 Amphibole
Chlorite Mica Schist- Shear Silica Mica
Gneiss- Schist Mare Schist Phyllite Marble Schist Schist Spod Peg
Schist
-Lower quartile 65 62 58 67 68 62 73 67 69
-Upper quartile 77 74 70 77 75 72 81 76 78
■Median 71 70 65 72 70 67 i 76 72 74
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6.4 Rock Mass Strengths
The Hoek-Brown GSI approach was used to estimate rock mass strengths. A summary of the
parameters are shown in Figure 6-3. The Geological Strength Index (GSI) was calculated from the
RMRas values summarized in Section 6.2. Rock mass strengths were not calculated for the schist-
marble, shear schist, phyllite and chlorite schist as these did not comprise significant length of the
rock drilled and will ultimately be combined with the other lithologies (during the geotechnical
domaining work, Section 7).
Table 6-2: Rock Mass Strength Parameters
Unit Uniaxial Geological Lower
Rock Type Weight Compressive Strength Index Quartile mi mb s a
(kN/m3) Strength (UCS) (GSI) GSI
MPa
Amphibole 29.4 111 66 60 9.1 3.162 0.0373 0.5013
Gneiss-Schist
Marble 26.9 57.7 60 53 10.7 2.99 0.0189 0.5021
Mica Schist 28.1 45.5 67 62 9.7 2.569 0.016 0.5023
Silica Mica 27.7 77.4 67 62 11.6 4.118 0.0399 0.5013
Schist
Pegmatite 26.4 139 69 65 10.5 2.574 0.0147 0.5025
Source:SRK,2023
6.5 Minor (Discontinuities) Structures
Structural orientation data collected from the OTV/ATV surveys has been used to evaluate the minor
discontinuity patterns. Most of the data has been collected from drillholes near the center of the pit,
however, is considered representative of the discontinuity patterns near the proposed pit walls
(Figure 6-3).
40
1 kin
Laakin.Ng North
o zso soa Aso
Source:SRK 2023, modified from Albemarle 2023 Leapfrog Geo Geologic Model
Note: Major Open Joints/Fractures shown in red and Bedding/Banding/Foliation shown in green. Other structures not shown
for clarity.
Figure 6-3: Structural Orientations from Kings Mountain ATV/OTV Logging
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A summary of the foliation and joint set patterns for each of the primary lithologies is summarized in
Table 6-3. A pervasive foliation exists within each lithology and typically two to three joint sets.
The majority of picked featured from the ATV/OTV surveys represent foliation features (Figure 6-3).
This is similar to the dominant foliation sets observed in the historic pit bench slopes (Figure 6-4).
The wider range of foliation orientation measures may also represent formation of the rock fabric
through several deformation events.
A 3D form interpolant representing foliation orientation at the inter-ramp scale was developed using
Leapfrog modelling software (Figure 6-5). The model provided a tool to visually assess kinematic
risks and guiding the bench design. The model should be advanced to refine the Define Phase level
bench design, including potential changes influences on the Bench Face Angle (BFA) at each bench
elevation. Foliation dip angles can vary by 5 to 10 degrees between bench elevation, and the design
risks/opportunities associated with this variability near the interim and final pit slopes requires further
understanding.
® 20-N (T) OO 35.222266, -81.351778 ±20ft A 786ft
r
�-1`— -
r
Source:SRK,2022
Note; Foliation dipping into the pit(white arrows)
Figure 6-4: Foliation Structures Forming the Bench Faces Along the East Highwall
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r
'AMR
�F
�y
Plunge+50
Looking North
0 250 500 750 1000
Source:SRK 2023, modified from Albemarle 2023 Leapfrog Geo Geologic Model
Note: Structural interpolants shown (blue) overlain on Ultimate Phase 4 pit (gray), representing general pit-scale foliation
trends
Figure 6-5: Overall Pit Scale 3D Foliation Trend Model
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Table 6-3: Discontinuity Sets by Lithology
Foliation A Foliation B Joint Set JS 1 JS2 JS3 JS4
Unit Measurements Dip DirectionDIP Range Dip Direction Range Dip Direc Diin Range Dip Direction Range Dip Direction Range Dip Direction Range
(°) ° (°) (°) (°) (°) (1 (°) (°) (°) (°) (°) (°)
Amphibole Gneiss-Schist 19,265 55 302 ±30 - - 9 122 ±20 73 4 ±15 49 174 ± 10 -
Chlorite Schist 216 54 297 ±20 - - 30 136 ±10 - - - - - - - -
Marble 1,233 50 302 ±20 82 301 ±15 15 113 ±20 - - - - - - - -
Mica Schist 3,625 60 295 ±30 62 328 ±15 19 115 ±30 75 348 ±10 52 167 ±15 - -
Musc Peg 259 51 300 ±20 - - - 8 210 ±20 - - - - - - - -
Peg 292 56 297 ±15 - 7 182 ±10 77 348 ±20 - - - - -
Ph llite 71 49 300 ±15 - - - - - - - -
Schist-Marble 732 53 302 ±25 - 22 102 ±15 - - - - - -
Shear Schist 2,542 60 302 ±30 49 336 ±15 7 136 ±30 - - - - -
Silica Mica Schist 998 58 300 ±30 - - - 25 115 ±20 - - - 70 177 ±5
S od Peg 10,701 63 295 ±60 - - - 7 127 ±40 76 358 ±15 65 22 ±15
Upper Mica Schist 552 59 314 ±30 83 289 ±20 11 151 ±30 - - - - - - - - -
PO Mica Schist 2,146 1 62 298 ±35 - 16 116 ±20 - 54 171 ±10 -
Note:Range is±3 standard deviations from mean.
Source:SRK,2023
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6.6 Discontinuity Shear Strength
Direct shear testing was undertaken on a representative number of samples across major deposit
rock types. A total of 22 single stage tests were undertaken, where a peak and residual strength was
assessed at a single confinement level.
Three samples were collected of gouge material at the contact between the Marble and Schist units
in the footwall of the deposit. An example test surface from the gouge-filled feature is shown in
Figure 6-6. These tests have been individually assessed from to help inform fault gouge strength.
The location of available test results is shown in Figure 6-7 with test quantities and results
summarized in Table 6-4 and Figure 6-8. Direct shear testing results were further evaluated as part
of the geotechnical domaining process (Section 7). The direct shear test results by lithology are
presented in Figure 6-8. The peak strengths from direct shear testing were too high for design, and
therefore the residual strengths selected to represent the discontinuity features. Direct shear values
were recognized as being suspiciously high. Further testing should be carried out at the Define
Phase level to categorize strengths further on a joint and foliation basis.
J2 : Z : 2: 2:
CLIENT SRK Consulting BORING NO. 216
JOB NO 2030-163 DEPTH t 17.5
PROJECT SAMPLE NO. ID5276-117.5
PROJECT NO. TEST Direct Shear
LOCATION ROCK Marble Contact Gouge
`AT7
Figure 6-6: Contact Gouge Direct Shear Sample DS276-117.5
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Amphibole Gneiss Schist
Marble
jw Marble Contact Gouge
Mica Schist
Silica Mica Schist
N
0 250 500 7501000
Source:SRK 2023, modified from Albemarle 2023 Leapfrog Geo Geologic Model
Figure 6-7: Available Direct Shear Testing Data Overlain on PH04 Pit
Table 6-4: Summary of Shear Strength By Rock Type
#of Peak Strength Residual Strength
Rock Type Samples Cohesion
Tested Friction Angle(°) Friction Angle(°) Cohesion (kPa) (psi)
Amphibole Gneiss 4 55 36 182 26
Schist
Marble 3 50 31 106 16
Mica Schist 5 42 35 132 19
Silica Mica Schist 7 51 32 163 24
Contact Gouge 3 46 27 176 26
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Direct Shear-Amphibole Gneiss Schist Direct Shear-Marble Direct Shear-Contact Gouge
3000 1400 2500
2500 ■Peak Strength Phi-55' 1200 Peak Strength Phi-50" ■ *Residual Strength Phi-46'
*Residual Strength 2000 \
a •Residual Strength \ a 1000 1tl
6 2000 -x.. y •Peak Strength
N _• N 800 m 1500 •
2 1500C 400
, ' ___• m
600
000
1000
w _ _ Phi-36° m - Phi-31"\ y 500
500 — _ - Cohesion-182kPa(26 psi) 200 Cohesion-106kPa(16 psi) •••• Phi-27"\
I/ 0 .. Cohesion-176 kPa(26 psi)
0 0
0 500 1Coo 1500 2000 2500 0 200 400 600 800 1000 1200 0 500 1000 1500 2000 2500
Normal Stress[kPa] Normal Stress[kPa] Normal Stress[kPa]
Direct Shear-Mica Schist DirectShear-Silica Mica Schist
2000 3000
I 1800 ■peak Strength Phi-42` 2500 Peak Strength Phi-51°
1600 Residual Strength
a 1400 *Residual Strength • m
■ ,/�1 2000
N 1200 • ,,,�' 1 u�i
v 1000 - Phi-35° P 1500 ■
w 800 Cohesion-132 kPa(19 psi) N --"_•
= 600 t 1000 •
m 400 ■ N
Phi-32"\
200 500 ■ Cohesion-163 kP
0 —
0 500 1000 1500 2000 2500 0
Normal Stress kPa] 0 500 1000 1500 2000 2500
Normal Stress[kPa]
Figure 6-8: Summary of Direct Shear Results by Rock Type
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7 Geotechnical Domaining
7.1 Approach
The objective of a geotechnical domain model is to spatially identify zones representing similar
geotechnical and/or stability characteristics. For Kings Mountain the domaining approach was based
on the following approach:
1. Lithology: Using the lithology model as the primary input to the domain model.
2. Bounding Major Structures: Identification of the continuous fault structures that mark
apparent changes in the observed rock mass conditions.
3. Rock Mass Conditions: Characterizing the rock mass within each domain using the field
and laboratory data. The rock mass conditions were firstly evaluated on a primary lithology
basis, and then combined into a respective geotechnical domain unit based on similar
strength and quality characteristics (and geological formation history).
7.2 Domain Summary
The Kings Mountain geotechnical domaining is largely based on an overburden unit and combining
the primary lithologies into a Pegmatite, Schist and Marble unit (Figure 7-1). The domain units
incorporate the following lithologies:
• Schist: Schistose rock types found on the footwall of the main pegmatite intrusion zone.
• Amphibole: Schistose rock found on the hangingwall of the main pegmatite intrusion zone.
The domain appears to be more massive in current pit exposure with higher UCS test
strength than remaining Schist domain.
• Pegmatite: All pegmatite units, with some lenses of Amphibole domain found between
lenses of pegmatite intrusions (Figure 7-2).
• Marble: Both the marble and marble schist rock types found on Eastern extent of the
deposit.
The determination of the three units considered the following rock mass conditions:
1. Higher intact strengths and RMR for Marble, Amphibolite and Pegmatite compared with the
surrounding schist.
2. Bench-scale performance in historic pit from Schist units.
3. Lower intensity and frequency of foliation in the pegmatite compared to the schist, as observed
in televiewer data and bench exposure.
The geotechnical domain model includes an overburden unit, which is generally comprised of silty-
sand material, weathered bedrock (saprolite), and any historic spoils or stockpiles. Figure 7-3 shows
the relative location of historic surface deposits and the relative thickness of the overburden unit.
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Overburden
Pegmatite
Schist
Amphibole
Marble
0 ro F
talk

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t900
Pegmatite
Intrusions
Pegmatite domain
Boundary
Figure 7-2: Overview of Pegmatite Domain Boundary
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Historic Waste Rock Dumps
MOverburden Soils
+5 550G N
Bedrock
+5 5500 N
s�
�1
f
+5d 40130 N
V
r5 3500 N
x� Y
+= 3D00 N
1
+5 2503 N
0 125 250 3 5500
•1295506 E +I 96000 E. +1296500 E 11297000 E [.1297500 E �+1 240000 E 11-298SI
Figure 7-3: Plan Showing the Distribution of the Overburden Unit
7.3 Domain Rock Mass Strength Parameters
Although the geotechnical domains were defined, the rock mass strength parameters for each
primary lithology was utilized for the overall stability analyses. The rock mass strength parameters
are summarized in Table 6-2.
7.4 Domain Discontinuity Sets
Representative discontinuity sets were assigned to each domain units based on patterns observed.
The sets are shown in Figure 7-4, Table 7-2 and Appendix C. Each domain has a characteristic
west-dipping foliation and shallow dipping joint set. The discontinuity patterns are described below:
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• Pegmatite: Moderate dipping foliation and two joint sets representing cross-joint patterns.
• Schist/Amphibole: Moderate dipping foliation and three joint sets representing cross-joint
patterns not observed in other domains.
• Marble: Moderate dipping foliation and a shallow dipping joint set.
A range of dip/dip directions have been included in Table 7-2 to demonstrate variability within each
unit. These ranges are considered in the bench-scale kinematic stability work.
Marble Pegmatite Amphibole/Schist
o., 01 o°
3301 30, 330, 30, 330° 30°
S .
300, 60° 300` 60° 300° '"s - 60°
270° 90° 270°'. /t i i') *.' 90° 270 .r W .. 90'
240° - / ( -�--.�r Z 120' 240° 'A1; x 120' 240` ,m'[. .'- i20°
1
210° 150° 210° �L 150° 2l0" .❑ ° 150°
180° 180° 180°
ry N ry
I`
W E V! - 1 E W lmt E
gym: im.
s s s
Figure 7-4: Summary Stereonet by Geotechnical Domain
7.5 Shear Strength
The direct shear tests were evaluated on an individual lithology and then geotechnical domain basis.
As there are statistically fewer direct shear tests, it was decided that the tests would be combined
into the geotechnical domains, with the composite strength applied into the primary lithology units
modelling in the overall analyses. The peak strengths from direct shear testing were too high for
design, and therefore the residual strengths selected to represent the discontinuity features. Direct
shear values were recognized as being suspiciously high. Further testing should be carried out at the
Define Phase level to categorize strengths further on a joint and foliation basis.
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Table 7-1: Domain Discontinuity Shear Strengths
Design Residual Shear Strength
GT Domain #of Samples Tested Friction Angle Cohesion (kPa) Cohesion (psi)
Schist/Amphibole 11 35 155 23
Marble 3 31 106 16
Pegmatite 5 34 190 28
Sheared Contact 3 27 176 26
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Table 7-2: Geotechnical Domain Discontinuity Sets
FOILJS1 JS2 JS3 JS4
Measurements
GT Domain # is Dip Dip Range Dip Dip Range Dip Dip Range Dip Dip Direction Range Dip Dip Range Direction Direction o Direction o oDirection
Marble 1,965 54 302 ±35 19 109 ±20
Schist/Amphibole 29,442 56 301 ±40 11 123 ±40 80 356 ±20 51 173 ±25 68 17 ±20
Pegmatite 11,252 64 294 ±40 5 136 ±30 75 357 ±20
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8 Hydrogeology
The section represents a summary description of the hydrogeological conditions, completed
modeling, and findings for the mine site. For further details and references, please refer to
appropriate factual, field and modeling reports.
8.1 Conceptual Hydrogeological Model
The conceptual hydrogeological model subdivides the groundwater system around the pit into two
main components, namely, surficial deposits, and bedrock system.
Surficial deposits are made up of a mix of overburden rock, saprolite, and weathered bedrock. These
units have relatively higher hydraulic conductivities than the deeper bedrock. Groundwater inflow to
the pit through the surficial deposits is believed to be substantial in the current condition and
expected to be a major contributor during the initial stages of mining. However, their relative
contribution to pit inflow and pore pressure is expected to decrease rapidly in time, as the surficial
units become dewatered through pit excavation and in-pit sump dewatering.
In contrast, the underlying bedrock groundwater system is expected to be the most important
component in terms of pit inflow and pore pressure distribution during mining. This system is
understood as bedrock units with low hydraulic conductivity and storage parameters decreasing with
depth. The main flow pathways in this system occur through fracturing and weathering of the
bedrock, which is more pronounced in the upper parts of the system, just underneath the surficial
deposits. Saturated fracture networks and faults in the bedrock will be the main source of pit inflow
and could control pore pressures through compartmentalization of different blocks, as discontinuities
could act as either flow conduits or barriers at the local scale.
Additional to these components, hydraulic testing in the area indicates that there are two major
water-bearing corridors in the bedrock, at geological contacts east and west of the Kings Mountain
pit. The contact between Amphibole Gneiss-Schist and Upper Mica Schist on the western side, as
well as the contact between Silica Mica Schist and Schist-Marble on the eastern side have been
identified as major water-bearing features when intercepted by drillholes. Packer testing along these
contacts also indicates higher hydraulic conductivities, even at depths approximately between 200
and 600 ft below ground surface. These corridors have been labeled as "Shear Contacts" in
corresponding hydrogeological reports. Even though they are expected to affect the regional
groundwater system, the current pit shells do not intercept these contacts at depth, and thus they are
not anticipated to be a direct contributor to inflow or pore pressures distribution at the pit slopes.
This, however, might change if pit shells are re-designed in the future.
Groundwater inflow to the system occurs mainly through recharge from precipitation. As it reaches
the surface, a fraction of the precipitation infiltrates the surficial deposits, and percolates through the
different units until it recharges the groundwater system. In the bedrock system, this occurs mainly
through fractures and the weathered areas among the intact rock. By regional and local estimates,
the amount of groundwater recharge around the Kings Mountain pit area is expected to be between
10% and 20% of Mean Annual Precipitation, depending on the local soil conditions and level of
urbanization.
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The main groundwater outflow from the system occurs through regional flow and as discharge to the
creeks and streams. In the area of pit lake, groundwater generally flows from the northwest to the
southeast. Around the Kings Mountain and Martin Marietta pits, groundwater contours have been
affected by legacy mining, forming a concentric flow towards the excavations. In terms of the Kings
Mountain pit, it currently holds a pit lake that has been increasing in level through the past decade
(recorded), pointing to it gaining flow from the surrounding groundwater. The following sections
describes current water levels and the flow regime around this pit in more detail.
8.2 Groundwater Contours
The current groundwater contours around the Kings Mountain pit and direction of the flow are shown
in Figure 8-1. The figure also shows water level measurements for different wells, from July 2022
onwards. At each observation point, the latest water measurement is shown.
129450
o _ _
Legend Q
/ Water Level Measurements ej0 e
(ft amsl)
0
_ Groundwater Contours
January 2023(ft amsl) 926 '.'
939 ggg 8.15 8228iq az0 =
Flow Direction 811 &47 848g
885
gTi A'O 867
i
seo
91 c
_ 908
Ica
ry0
Y .. 818
889 Sao
030 909 905 ePo 861 gp0 a
o � o
N 918 877
�0 910
877
912 922 910 902 g
911 g10 8fi1
919 90fi � �
s,a 907 .�
909
900 904 � �
897 879
1294500 1296000 1297500 1299000
Source:SRK,2023
Figure 8-1: Groundwater Contours and Flow Direction for the Current Condition Around
Kings Mountain Pit
At the local scale, groundwater contours follow the hilly topography around the pit area, while the
Kings Mountain and Martin Marietta pits have formed cones of depression, directing groundwater
flow towards them.
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Water table gradients around the Kings Mountain pit are not homogenous, as shown by the density
distribution of contour lines. The western and southern pit walls show the steepest gradients,
meaning that water levels are higher along these pit walls. In contrast, the northern and eastern walls
of the pit appear to be more drained, meaning a flatter water table around these areas. This is
probably due to the dewatering related to the Martin Marietta pit. Overall, however, the Kings
Mountain pit appears to be a gaining hydrogeological system, meaning that the pit lake is still filling
up from the groundwater flow towards it.
Following the expected hydrogeological behavior for open pits, groundwater flow in proximity to the
pit slopes is expected to have a vertical component. Downward vertical gradients are expected near
the topmost saturated part of the slope, forcing flow towards the toe of the pit slope. Flow directions
gradually change approaching the pit bottom, where upwards flow gradients are expected. This
behavior is currently observed for the pit and is expected to be more pronounced once the pit-lake is
fully dewatered and further excavation takes place.
8.3 Pore Pressure Modeling Approach and Limitations
For the current iteration of pore pressure modelling, water table predictions from the regional scale
groundwater model were used as input to geotechnical analyses.
The MODFLOW-USG numerical regional groundwater flow model used to predict pit inflows and
environmental impacts to ground and surface water was also used to extract pore pressure inputs for
pit-slope stability analyses, in the form of predictive yearly water tables for each analyzed cross
section.
An example of the water tables provided as input for pit-slope stability analyses is shown in
Figure 8-2. As is shown, the regional groundwater model predicts that at the end of mining the
eastern wall will have slightly elevated pore pressures as compared to the western wall. This is
mostly because the model, using an equivalent porous media approach, simulates the units east of
the pit with lower hydraulic conductivities than those found west of the pit. Another simplification
made by the model is the simulation of the pegmatite areas with an equivalent porous zone. In this
regard, local heterogeneities are not considered explicitly in the model, leading to possible
uncertainty in results. This is denoted in Figure 8-2 by the question mark ("?'), as the given water
table is a plausible prediction, but local features could cause slightly different saturation along the pit
wall.
Figure 8-3 shows the seepages faces predicted by the model at the end of mining. As shown in the
image, the regional groundwater flow model estimates that most of the lower benches will be
completely saturated at the end of mining. The area near the northeast corner of the pit near the
critical cross section (cross section 1 - Figure 11-1) is expected to be saturated in its majority at the
end of mining. Additionally, the southern corner of the pit is expected to be highly saturated.
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Cross Section 3 Cross Section 1
I
Z
- - - - - - - - - - - - - -
January 2023 Conceptual Water Table current Topography
(derived from field measurements)
eaa.
FF
IF
Projected ultimate pit shell
:07
Source:SRK,2023
Figure 8-2: Example of Water Table Input from Regional Groundwater Model, for Cross
Sections 1 and 3, Ultimate Pit Shell
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8
IPA
Ultimate pit shell
—Cross Sections for Analyses
Seepage faces at end of mining
Groundwater contours at end of mining(R amsp
Flow Direction
Source:SRK,2023
Figure 8-3: Seepage Faces Predicted by Regional Groundwater Model at End of Phase 4
Mining
The MODFLOW-USG hydrogeological model has been extensively calibrated using historical water
level measurements, river baseflows, and hydraulic parameters obtained in the field by a variety of
hydraulic tests. In this regard, the numerical model has a solid foundation for predictive simulations,
with a satisfactory degree of reliability.
The main limitation of using this model's outputs is that pore pressure distribution was not its primary
objective. Being a model focused on inflow and hydrogeological impacts, the model is built at a
regional scale, making it lose the detail and refinement in the pit area achieved with a pit-slope
specific approach. Additionally, conservative assumptions in terms of inflows might not translate to
conservativeness in terms of pore pressures. For example, certain hydrogeological units might have
been modeled with a slightly higher hydraulic conductivity values (for conservative evaluation of pit
inflows and drawdown propagations) than what would have been used for pore-pressure predictions
with a pit slope stability focus.
Even with this being the case, it is considered that the yearly water table outputs used from the
MODFLOW-USG regional hydrogeological model are satisfactory for the current stage of the pit-
slope stability analyses. With the current state of hydrogeological information, it is likely that a 2D
slope-scale model would have yielded a similar water table and pore pressure distribution. Although
the hydrogeological understanding at the regional scale is relatively advanced, local features and
flow behaviors are still uncertain. Further hydraulic testing will help establish these local conditions,
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but it is likely that the data prompting the need for a detailed 2D pit-scale pore pressure model will
only be fully available once the excavation process is taking place.
It is recommended that predictive water table and pore pressure distributions are revised after each
new field or data collection campaign, as well as if mine designs are updated. One factor that could
cause a major shift in groundwater predictions is the interception of pit-shells with the high
conductivity corridors described in section 8.1. This is not currently the case under current
excavation plans, but these might change in the future.
Additionally, it is recommended that once excavation begins, 2D detailed pore pressure models are
generated for each cross section being analyzed, and progressively updated with new critical
information. Mapping of structures at the local level, as well as observations made during excavation
might change previous assumptions, and require a reconceptualization of flow in the pit walls.
No depressurization of the pit slopes is currently recommended, as the slope design was not shown
to be sensitive to the expected pore pressure conditions and ultimately was governed by the
achievable bench scale stability conditions. However, depressurization through horizontal or vertical
wells could be considered if the slope performance is worse than expected, as identified through
inspection and monitoring strategies.
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9 Slope Stability and Design Approach
9.1 Slope Design Definitions
A pit slope has three major components: bench configuration, inter-ramp slope, and overall slope, as
shown in Figure 9-1. The bench configuration is defined by the vertical bench separation (bench
height), catch bench width and bench face angle (BFA). The inter-ramp slope is formed by a series
of uninterrupted benches or stack. Final overall slope angles are formed by a series of inter-ramp
slopes separated by haul roads or wide geotechnical berms.
The inter-ramp angle (IRA) corresponds to the angle subtended by a line joining the toes of the
benches on the wall and the horizontal. The overall slope angle (OSA) corresponds to the angle
formed by the line joining the toe of the lowest bench with the pit crest and the horizontal. The
incorporation of ramps onto a wall will result in a slope that has a shallower overall slope angle than
the inter-ramp angle.
Geotechnical
Berm
Berm Bench Stack Height
Width
Bench Face Angle(BFA)
Inter-Ramp Angle(IRA) Ramp
Bench toe-to-toe
Bench Stack Height
Bench Face Angle
(BFA)
T Bench
Height
Bench Stack Angle(BSA)
Note:"Maximum bench stack height"is the height before bench toe to ramp crest
which a step-in(ramp or geotechnical bench)is required
to de-couple the slopes.
Source:SRK
Figure 9-1: Schematic Representation Pit Slope Design Terminology
9.2 Rock Slope Failure Mechanisms
Potential rock slope failure mechanisms that can influence the stability of the pit slopes need to be
understood to develop safe and practical design. Rock slopes can generally be classified according
to two principal failure mechanisms:
• Kinematically Controlled Failure Mechanisms: Structurally controlled failure in rock
occurs as the result of sliding along pre-existing structures or discontinuities.
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• Rock Mass Strength Failure: Slopes excavated in weak or heavily fractured rock masses,
or very high slopes, can be susceptible to overall rock mass failure, which involves the
development of step-path or pseudo-circular type failure zones through intact rock and along
discontinuities.
For Kings Mountain, the pit slope is expected to be structurally controlled with the design primary
governed by the bench to inter-ramp kinematic stability conditions. The magnitude and frequency of
structurally controlled failures are directly related to the continuity of the structures along which
sliding can occur. Structures that exhibit limited continuity, such as the high-frequency intersecting
joints may result in small bench-scale failures that are rarely of consequence to overall slope stability
but may affect access ramps or fixed equipment adversely. Conversely, larger scale failures can
occur along continuous, through-going structures.
9.3 Slope Design Approach
For this current study, the expected bench, inter-ramp, and overall stability conditions were assessed
with multiple approaches using a combination of software packages, as summarized in Table 9-1.
Table 9-1: Overview of Stability Assessment Approach and Software
Pit Slope Scale Analysis Approach Software Utilized
• Empirical slope performance • DIPSTM
Bench 0 Kinematic stability analyses(deterministic and 0 Leapfrog TM
probabilistic) 0 SBIockTM
• Empirical slope performance • DIPSTM
Inter-ramp to 0 Kinematic stability analyses • Leapfrog TM
overall 0 2D LE stability analyses 0 Slide2TM
• 2D FE stability analyses 0 RS2TM
Source:SRK,2023
9.4 Bench Configuration
The stability approaches detailed in the report consider the requirement to design 30 ft high single
benches and 60 ft high double benches. Other recognized industry guidance has been utilized,
including the Modified Richie Criteria for rock fall containment on bench widths (Ryan and Pryor,
2000). The Modified Richie Criteria is based on the following:
Minimum Catch-Bench Width = 14.8 ft+ (0.2*Bench Height)
The modified Ritchie criteria was reviewed and compared vs. rockfall analysis on open pit
geometries by Storey, 2010. In general, the Modified Ritchie methodology results in rockfall impacts
being retained greater than 90% of the time while retaining 80% of rockfalls on the bench.
For the 30 ft design bench heights, a resulting Modified Richie minimum berm width of 20 ft is
calculated, and for the 60 ft design bench heights, a resulting minimum berm width of 26 ft is
calculated. As discussed, the Modified Richie Criteria was adopted a basis for back-break to design
catch-bench configurations analyzed with SBIockTM (Section 10.2.2).
Alternate catch bench designs may be based on a spill width volume. The premise of this approach
is that back-break and failures from the bench crest do not occur while excavating the bench and
take place over a longer time period. The volume of wedge and plane shear failures is estimated
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from either back-break or a removable key block approach and the bench is designed to contain the
material at an angle of repose.
9.5 Design Acceptance Criteria
Design Acceptance Criteria (DAC) are based on the data reliability, consequence of failure and the
design level of the project. The DAC accounts for safety, social, economic, and industry best
practices. The provided acceptance criteria for Factors of Safety (FoS) and probabilities of failure
(PoF) are based on SRK's experience in accordance with the consequences of potential ground
failures. These criteria may change as the project design advances due to additional data being
collected and the impact of consequences are assessed using proper risk assessment
methodologies.
SRK utilized acceptance criteria based upon internationally accepted practice provided in Read &
Stacey 2009. These criteria are summarized in Table 9-2. An DAC of >1.3 FoS was applied to
overall slopes (interim and final walls) under static loading conditions and >1.05 FoS was applied to
overall slopes (interim and final walls) under the analyzed pseudo-static (dynamic) conditions. At
inter-ramp scale, the DAC of>1.2 FoS was applied, however a minimum of 1.5 FoS was applied at
inter-ramp scale where ramps are located above or below due to the potential high consequences of
failure (due to production designed to come out of a single ramp). This set of values will be used to
assess the stability of the pit slopes for the project. The acceptance criteria list is only a guideline
and must be considered in terms of the specific economical and safety risk profiles.
Kinematic analysis is used for optimization of bench face angles. To control potential bench scale
instability, a PoF of <20% is recommended for bench face angle design. The quantity of potential
spillage is calculated in each case to ensure that berm capacity is sufficient to contain any spillage
material during the process of using the PoF.
Table 9-2: Kings Mountain Pit Slope Design Acceptability Criteria
Acceptance Criteria
Slope Scale FoS(min) FoS(min)(pseudo- PoF(max)P[FoS<_
static static 1
Benches >1.1 NA <25%
Inter-ramp >1.2 >1.0 <10%
Inter-ramp (above and below >1.5 >1.05 <5%
ramps
Overall Slope (interim and final >1.3 >1.05 <5%
walls
Source:SRK 2023, modified after Read and Stacey,2009
9.5.1 Discussion and Data Confidence
Slope failures in open pit mines rarely develop instantaneously; rather they tend to develop gradually
over time and can be assessed in the interim using monitoring. Therefore, determination of a
sufficient margin of safety may not be as simple as selecting an appropriate value for FoS or PoF.
There needs to be some level of geotechnical knowledge in identifying potential failure modes and
confidence in the selected input data used for analysis, as well as an understanding of the way
specific failures progress over time.
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Frequently FoS computed from stability analyses are defined using design input strength values. In
some cases lower-bound input values are selected to compensate for low confidence in certain input
parameters. The PoF must also be considered in terms of data reliability, quality, quantity, and
variety. In cases where the data is poor or limited, the PoF should not be used for design purposes.
In those situations, a sensitivity analysis should be carried out instead to determine design
acceptability.
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10 Bench-Inter-Ramp Kinematic Stability Assessment
As discussed, the Kings Mountain pit slope stability is expected to be structurally controlled.
Kinematic bench to inter-ramp stability were evaluated using the software programs SBlockTM
SWedgeTM, Dips TM, and Leapfrog TM. The kinematic analyses detailed in the following subsections
were based on available orientation data with consideration to the observed historic pit slope
performance. The results of the bench to inter-ramp kinematic stability assessment are summarized
in the following subsections and in Appendix C.
10.1 Kinematic Stability Review
Kinematic analyses were carried out using Dips TM for each domain and all applicable slope face
directions (Appendix D). The analyses were carried out to identify the potential kinematic
failure modes that could limit the design. A risk-based matrix was developed for each domain
based on the potential kinematic failure mode for a given pit wall direction prior to design mitigation.
The risks are based on the following semi-qualitative criteria:
• Low: The frequency and orientation of the analyzed discontinuity sets indicate that a
kinematic failure is not probable for a given bench/inter-ramp angle, and slope face direction.
• The frequency and orientation of the analyzed discontinuity sets indicates there
is a potential kinematic failure for a given bench/inter-ramp angle, and slope face direction.
However, the frequency or persistence of the discontinuity may be low or is oriented
obliquely to the analyzed slope face.
• The frequency and orientation of the analyzed discontinuity sets
indicates there is a potential kinematic failure for a given bench/inter-ramp angle, and slope
face direction. The potential kinematic failure could limit the design and will require
operational management strategies.
• High: The frequency and orientation of the analyzed discontinuity sets indicates there is a
potential kinematic failure for a given bench/inter-ramp angle, and slope face direction.
There is clear evidence in the historical slope performance to support the requirement to
mitigate the design based on this identified kinematic failure mechanism.
The results are summarized in Table 10-1. The potential kinematic failure mechanisms considered a
high risk were further evaluated and considered in the design. These are discussed in the following
subsections.
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Table 10-1: Kinematic Risk Summary Prior to Slope Design Mitigation
Mode of Instability with Likelihood of Occurrence
Geotechnical Domain Applicable Slope Dip Direction (°) Pit Wall (Rigid-Block Kinematic Analyses) Comments
Planar Wedge Toppling
Bench Inter Ramp Bench Bench
000-060 S/W/N Low Low Low Low Dip directions not applicable to domain
240-270 E Moderat Low Low Low
FOL
Marble 270-300 E High Moderate Low Low
FOL FOL
300-330 E/S High Moderate Moderate Low
FOL FOL FOL, JS1
330-000 E/S Mode...... Low Low Low
FOL
000-030 S Moderate Low High Low
JS2 FOL, JS1,JS2
030-060 S/W Moderate Low Low Low
JS2
060-090 W Low Low Low Moderate to High
FOL
090- 120 W Low Low Moderate derate to High
JS1, FOL FOL
120- 150 W Low Low Moderate to High
FOL
150- 180 W/N Low Low Moderate to High
Pegmatite JS1, JS2 FOL, JS2
180-210 N/E Low Low Moderate to High
JS2
210-240 E Low Low High ate
FOL, JS2 JS2
240-270 E Moderate Low Low Low
FOL
270-300 E High :rate Low
FOL, JS2 FOL JS1, FOL
300-330 E/S High moderate Low Low
FOL FOL
330-000 E/S Moderate Low Low Low
FOL
Schist/Amphibole 000-030 S High Moderate High Moderate to High
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Mode of Instability with Likelihood of Occurrence
Geotechnical Domain Applicable Slope Dip Direction (°) Pit Wall (Rigid-Block Kinematic Analyses) Comments
Planar Wedge Toppling
Bench Inter Ramp Bench Bench
Schist/Amphibole JS2,JS4 JS2,JS4 FOL, JS1,JS2, JS3,JS4 JS3
030-060 S/W High Moderate High Low
JS4 JS4 JS1,JS2,JS3,JS4 JS3
060-090 W Low Low High Moderate
JS1 JS2,JS4 FOL
090- 120 W Moderate Low Low Moderate to High
JS1 FOL
120- 150 W High Moderate Moderate to High
JS1, JS3 JS1,JS3 JS1,JS2 FOL, JS2
150- 180 W/N High Moderate High Moderate to High
JS1,JS3 JS1,JS3 FOL, JS1,JS2,JS3,JS4 FOL, JS2,JS4
180-210 N/E High Moderate High Moderate to High
JS3 JS3 FOL, JS1,JS3,JS4 JS2,JS4
210-240 E Low Low High Moderate
JS3 FOL, JS2,JS3 JS4
240-270 E Moderat Low High Low
FOL FOL, JS2,JS3
270-300 E High Berate Moderate Low
FOL FOL FOL, JS2,JS3, JS4
High 'loderate Low
300-330 E/S FOL FOL FOL, JS2, JS4 JS3
330-000 E/S Moderate Low High -
FOL,JS4 FOL, JS2, JS3, JS4 JS3
Source:SRK,2023
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Planar Sliding Failure Mechanisms
Potential planar sliding failure modes have been identified at the bench and inter-ramp scale along
the East Wall. The planar sliding risks are associated with foliation that is also been observed in
exposed benches (Figure 10-1). Although identified as high-risk, planar sliding failures are mitigated
by the recommended design to excavate BFAs parallel or shallower than foliation dip (60-degree
BFA, East Wall Design Sector 1). It should be noted that planar sliding risks at the bench scale will
still occur as the foliation data indicates that features can be shallower than 60-degrees.
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• ! 120 150
: 1
0-146a E (T) 35.219937.0 -81 .355069 ±28ft ■ 762ft
xv.
{
IL
Wr
Ilk
Pr
r.
{
'fir - '-2f! i�fe iJ'► 14 :a�
} 1 4 r
f•I'41i •�'
i ,
ive
I
� sl
Source:SRK, 1/2022
Figure 10-1: Foliation structures forming the exposed benches along the Historic Pit East
Highwall
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Review of the historic West, North and South Wall benches shows that planar features have
contributed to back-break, however, on a limited basis. An example of this is shown on Figure 3-6
along the South Wall. This South Wall observation does support the findings of the kinematic risk
review included in Table 10-1.
Wedge Failure Mechanisms
Potential higher risk wedge failure modes have been identified at the bench scale for most pit wall
aspects. The following comments are related to potential wedge failure mechanisms.
• The orientation data identified intersections leading to bench-scale wedge failure modes.
Unstable wedges can detach from the bench faces during the blasting cycle.
• The historical bench performance shows limited influence from wedges at the crests.
• Although considered moderate risk on the inter-ramp scale, high foliation frequency, more
massive rock fabric, and lower persistence of joint sets will generally restrict wedges to the
bench or multi-bench scale.
VA
WIT
w e �w®R � x
Source:SRK, 1/2022
Figure 10-2: Steep Benches along Historic Pit North Wall
Toppling Failure Mechanisms
The orientation data indicates that toppling failure modes are possible along the West Wall due to
the west-dipping foliation sets and a shallow east-dipping basal joint. However, the fracturing of the
rock units is expected to widen at depth reducing the potential for long, slender blocks to form and
topple. Inspection of the historical West Wall shows that benches were excavated steep without
obvious toppling failure mechanisms occurring (Figure 10-3). For these reasons, the kinematic risk to
bench scale design is considered moderate to high.
As the current geotechnical dataset indicates that open foliation is generally wider spaced, and the
rock mass strengths are high, steep bench faces have been recommended along the West Wall.
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Should the incipient foliation features develop and open under poor wall control blasting, then there
may be a need to relax the BFA to limit toppling potential at the bench-scale.
Major structure at
low-angle to pit wall
Major structure
6-
wrc s V
NAT.
23 ll
7
Source:SRK,2022
Figure 10-3: Exposed Benches Along Historic Pit West Wall
10.2 Probabilistic Bench Stability Analyses
10.2.1 Planar Sliding Undercutting
Planar sliding mechanisms along the proposed East Wall were further evaluated using cumulative
frequency approaches. Foliation orientation data applicable to the East Wall was selected for
analyses with a friction angle ranging from 30 to 45 degrees evaluated. The results are shown in
Figure 10-4. The results indicate that a recommended 60-degree BFA design has a Probability of
Failure (POF) between 25% and 36% based on the applied friction angle. According to Read &
Stacey (2009), a maximum DAC between 25% and 50% is considered acceptable for high and low
consequence of failure, respectively. Given the variability in the foliation measures along strike and
depth at the deposit scale, it was decided that all bench scale failure mechanisms cannot be fully
eliminated for a realistic operational design with a strategic wall control blasting required to safely
strip along foliation. In some cases, foliation will be steeper than the design BFA (60-degrees) and
these opportunities need to be evaluated on a bench-by-bench basis at the Define Phase level. Wall
control blasting comments are provided in Section 13.1.
At the inter-ramp scale, the planar sliding risks from foliation should have a sufficient low probability
due to the recommended design IRA shallower than most of the orientation data and the larger scale
waviness contributing to shear resistance.
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Combined Footwal Foliation Orientation
25% 100%
LO
LI
I II 90%
200/0 I �I 80%
CDI I of
�I
al I ❑I u
LLCD
I =
c �
a 15% Q I Q NI fiG% c
c C C
= F_ O
U I [�.7 I 50% 7
li LL I �_
LL 101/. I I 40%
s=
73 7 I 6
mI m � u
3096
CL
5% 0 I CL I 200/.
I i ' 10%
0% I 0%
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90
Foliation Dip
%Bench Undercutting
BFA Phi=30' Phi=35' Phi=40' Phi=45'
55 24% 21% 17% 13%
60 36% 33% 29% 25%
65 52% 49Yo 45% 41%
70 74% 71% 67% 63%
75 85% 82% 78% 74%
801 92% 89% 86% 82%
Note:All foliation measurements from televiewer holes along east wall considered for assessment.
Figure 10-4: Summary of East Wall Bench Undercutting from Foliation
10.2.2 Bench-Berm Scale SBlock Analyses
Bench scale probabilistic stability analyses were carried out using the software program SBIockTM
(Esterhuizen, 2004). The software analyses key-block formation of the discontinuity sets
probabilistically using Monte-Carlo simulation. For each combination of slope orientation,
discontinuity spacing, and length are both assumed to follow negative exponential distributions.
SBIockTM analyzes the expected bench break-back from planar and wedge sliding failure
mechanisms only. The results of the bench-berm stability analyses are presented in Appendix E.
The analyses evaluated wedge and planar sliding mechanisms along the proposed pit slopes. An
initial screening level simulation was carried out to understand possible back-break for a range of
simulated BFA's, and then secondary simulations for the selected design BFA.
An example of the screening level simulations for the Schist Domain Unit shown in Figure 10-5. The
screening level simulation shows that the back-break for the slope aspects between 60 and 85
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degrees. Figure 10-5. Also shows the significant impact from a conceptual steep bench along the
East Wall where foliation would undercut (as discussed in Section 10.2.1. The simulations also show
limited back-break in the other pit walls.
Average Bench Width Remaininr,after rdiluren, (Sk-nist)
'4
28
26
24
$ Z2
• ��
Z4
L
C
a
16
14
12
14
2oqS � 7, 44 A � i CD CD CD CD CD CD
4_1 MRC-4
A HFQR � � �i � �
Dip Direction(')
■BFA 65 ■BFA 74 ■BFA 75 ■BFA 80 ■BFA 85
Figure 10-5: Example of Screening Level SBlock Simulation for Schist Domain Unit
The design analyses are summarized in Table 10-2 to Table 10-4. The analyses were carried out at
a BFA design of 78-degrees with a planned catch-bench width equal to Modified Richie (27 ft from a
60 ft bench height). The results indicate the following:
• North Wall (Domain 2):
o Pegmatite: Expected back-break of about 2 ft and an effective BFA of 76 degrees.
The back-break results in an effective catch-bench width of 24 ft.
o Schist: Expected back-break of about 3 ft and an effective BFA of 76 degrees. The
back-break results in an effective catch-bench width of 23 ft. Back-break does
increase in the northeast corner where the design does already transition into the
shallower Domain 1 configuration.
• West Wall (Domain 3):
o Pegmatite and Schist: Expected back-break of about 2 ft and an effective BFA of 76
degrees. The back-break results in an effective catch-bench width of 24 ft.
• South Wall (Domain 4):
o Pegmatite and Schist: Expected back-break of about 2 ft and an effective BFA of 76
degrees. The back-break results in an effective catch-bench width of 24 ft.
The results indicate that there will be some back-break and reduction in the effective BFA beyond
the planned design configurations (included in Section 10.4). Therefore, best practice wall control
blasting, scaling and clean-up is required to reduce the rock fall hazards.
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Table 10-2: SBlock Simulations for the North Wall
Pit Dip BFA Bench Modified Modified Resulting
Wall Domain Direction (°) Height Ritchie Bench Ritchie Bench Average
° ft Width ft Width ft Backbreak ft
150 78 60 27 2.0 76
160 78 60 27 2.0 76
170 78 60 27 2.0 76
180 78 60 27 2.0 76
Pegmatite 190 78 60 27 2.0 76
200 78 60 27 2.0 76
210 78 60 27 2.0 76
220 78 60 27 2.0 76
230 78 60 27 2.0 76
North 240 78 60 27 2.0 76
Wall 150 78 60 27 2.3 76
160 78 60 27 2.0 76
170 78 60 27 2.0 76
180 78 60 27 2.6 76
Schist 190 78 60 27 2.6 76
200 78 60 27 2.6 76
210 78 60 27 2.6 76
220 78 60 27 5.9 73
230 78 60 27 2.6 76
240 78 60 27 5.2 73
Table 10-3: SBlock Simulations for the West Wall
Pit Dip Bench Modified Modified Resulting
Wall Domain Direction BFA Height Ritchie Bench Ritchie Bench Average
(°) ( ) (ft) Width ft Width ft Backbreak(ft)
70 78 0 27 0.0 76
80 78 60 27 0.0 76
90 78 60 27 2.0 76
100 78 60 27 2.0 76
Pegmatite 110 78 60 27 2.0 76
120 78 60 27 2.0 76
130 78 60 27 2.0 76
140 78 60 27 2.0 76
West 150 78 60 27 2.0 76
Wall 70 78 60 27 2.0 76
80 78 60 27 2.0 76
90 78 60 27 2.0 76
100 78 60 27 2.3 76
Amphibole 110 78 60 27 2.3 76
120 78 60 27 2.0 76
130 78 60 27 2.0 76
140 78 60 27 2.3 76
150 78 60 27 2.0 76
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Table 10-4: SBlock Simulations for the South Wall
Modified Resulting
Applicable Bench Resulting
Pit BFA Ritchie Average
Wall Domain Dip Direction (°) Height Bench Width Average Effective BFA
(°) (ft) ft Backbreak(ft)
0 78 0.0 27 0.0 76
10 78 60.0 27 0.0 76
20 78 60.0 27 2.0 76
Pegmatite 30 78 60.0 27 2.0 76
40 78 60.0 27 2.0 76
50 78 60.0 27 2.0 76
60 78 60.0 27 2.0 76
South 70 78 60.0 27 2.0 76
Wall 0 78 60.0 27 8.1 71
10 78 60.0 27 2.3 76
20 78 60.0 27 2.0 76
Schist 30 78 60.0 27 2.0 76
40 78 60.0 27 2.0 76
50 78 60.0 27 2.0 76
60 78 60.0 27 2.0 76
70 78 60.0 27 2.0 76
10.3 Major Structure Review
Interpretation of three primary fault structures were provided to SRK, including Fault EW01, Fault S-
Flex and Un-Named Fault (Figure 10-6). The faults represent vertical features that are constrained
by the drillholes completed to date. These three faults have been included in the overall stability
analyses with the mechanisms considered as tension crack release (Fault EW01, North Wall) or
planar sliding structures (Fault S-Flex, East Wall). Where the faults were orientated obliquely to the
design section, the faults were not included in analyses.
Review of other fault intercepts from drilling and pit mapping data indicates that other primary and
secondary (non pit scale continuous) faults exist (Figure 10-7). The interpretation of other primary
and secondary fault structures is required to advance the design study to a Define Phase level. This
aspect is current a gap in the study that needs to be addressed to confirm the stability assessment
and design included in this report.
In most cases, the logged faults represent foliation-parallel shear structures (Figure 10-7). Therefore,
the higher risks would be related to planar sliding along foliation parallel slopes. The bench design is
based on limited planar sliding from foliation, and this accordingly reduces the probability that a
similarly orientated fault can negatively impact the bench and multi-bench performance. At the inter-
ramp scale, almost all the faults dip steeper than the East Wall design IRA which will limit the
potential for a higher consequence event that could impact stacks and ramps.
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w
...� ! FaWt Pit
A � -
A•
l.o eG F"Interce s
a �o
i - 9000tl
.. B
� 6 •35 7rV 3 e em
+1295maE I9750 [ .sjq[pW •12%S70[ •1247W0[ • 47 S]OE •Ir9.L0.f •1 SG
A Historic Pit
J
Urina Fault
FFAI
�x
y PHN Pit
i
�s
a
0 7{q pup 300
V
FiR
s I
Foult•S Flex �� FFaa
,s — Unna edIt
Fautt•EW61
Source: Leapfrog model modified by SRK 2023
Figure 10-6: 3D Fault Interpretation and Intercepts Through Diamond Drilling
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Legentl
All Mine Mapping - Structures Dyke
0, Fault
Foliation
3300 300 joint
i Shear
300, 60°
270' 90'
r•
240. 120°
210' 150°
180,
250 50 i NO i Soo 25 0
Fee
Source:SRK,2023
Figure 10-7: Logged Fault Intercepts in Drillholes and Pit Mapping
10.4 Bench Design
Bench design is based on the geotechnical characterization, domaining and kinematic stability
findings are presented in Table 10-5. These are based on the pit wall aspects and geotechnical
domains presented in Figure 10-8. Single and double benching are provided for Design Sectors 1, 2
and 3. Single benching approach is recommended for Design Sector 1 to account for potential higher
risks of planar sliding. Note that the full bench to overall slope design is provided in Section 12 along
with implementation guidelines (Section 13).
Table 10-5: Recommended Bench Slope Design Configurations
Geotechnical Pegmatite, Schist, Pegmatite, Pegmatite, Pegmatite,
Domain Marble Schist, Schist, Schist,
Design Sector 1 2 3 4
Pit Wall East North East South
Bench Configuration Single Single Double Single Double Single Double
Bench face angle 60° 78° 78° 78° 78° 78° 78°
Bench width 20 ft 20 ft 26 ft 20 ft 26 ft 20 ft 26 ft
Bench height 30 ft 30 ft 60 ft 30 ft 60 ft 30 ft 60 ft
Inter-ramp angle 1 38.80 1 48.7° 57.1° 1 48.7° 57.1° 1 48.7° 57.1°
Source:SRK,2023
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- Overburden
. Pegmatite Sector 2
Eii Schist D D = 195'
a Amphibole
Marble
Design Transition
Design Transition
Sector 3
DD — 1200 '450]N
' +544000 rt
Sector 1
Design Transition D D = 300' g
4^
.saasoo k
ilk
Sector 4 aN
D D = 035'
Design Transition +542500N
0 125 25 375 500
♦1297500 E -7 1 AL 29B090F
Source:SRK,2023
Note: Four domains are shown relative to the Select Phase Ultimate Pit(Albemarle 2023).
Figure 10-8: Domains Utilized for Bench Design
The following other comments are provided:
• Bench widths were determined using an empirical criterion. Catch benches serve two
primary functions. The first is to arrest rockfalls and raveling from reaching the working level.
A second function is to retain any rock material from wedge or plane shear failure that fall
after the bench has been excavated. The bench width is designed on the rockfall catchment
criteria, as the spillage volume design would result in an overly conservative design. A catch
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bench or rock trap above the working level of an open pit is generally recommended to
protect personnel and equipment from rockfall from the above benches.
• The 60' bench face angle utilized for the East Wall (Design Sector 1) is consistent with the
existing faces in the historic pit East Wall. Mapping along the exposed East Wall bench
indicates that both the dip and dip direction of foliation joints are variable as well as the
continuity of the fractures. These 2 factors give confidence that the 60' bench face for
Domain 1 is feasible. Bench widths have been designed to a width such that should there be
bench scale failures, 75% of the time the failures will be caught entirely on that bench. The
benches are designed wide enough that, if necessary, the maintenance program can clean
the benches.
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11 Inter-Ramp and Overall Stability Analyses
The inter-ramp to overall stability was evaluated using 2D Limit Equilibrium (LE) and Finite Element
(FE) stability analyses. The LE analyses were carried out using Rocscience Slide2 and the FE
analyses using Rocscience RS2. The analyses were performed to confirm the design that are
primarily governed by the kinematic stability conditions (Section 10). In addition, analyses were
carried out to evaluate stability under pseudo-static conditions and during rapid drawdown as the pit
lake is pumped. The following sections describe the main findings from the overall stability analyses
work. The results are summarized in Appendix E.
The stability analyses considered the potential for overall non-circular failures through anisotropic
rock masses (i.e., step-path failure mechanism), which combines influence of adverse structural
orientations and potential for shearing through intact rock. The groundwater pore pressure inputs are
discussed in Section 8.3.
Preliminary analyses were initially carried out using a simplistic groundwater case that represented
limited to no drawdown with excavation. Thereafter, the pore pressure predictions from the numerical
hydrogeological models were utilized for the design stability analyses summarized in this report.
11.1 Stability Sections
Design stability analyses were carried out for seven cross sections through the proposed final pit
(Figure 11-1). The design sections were selected to include the expected geotechnical domain
conditions and representative pit wall aspects.
I
Source:SRK,2023
Note:Stability analysis cross sections are shown relative to the Select Phase Final Pit(Albemarle 2023).
Figure 11-1: Stability Section Location Plan
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11.2 Rock Mass Strength Parameters
Design rock mass strength parameters were selected to represent the geotechnical domains are
included in Table 6-2. The design values were based on the work completed in Sections 0 and 7.
The Domain units were modeled using Hoek-Brown parameters, excluding any overburden material.
11.2.1 Rock Mass Anisotropy (Rock Bridging)
Rock mass anisotropy has been incorporated into the stability modeling using the orientation of the
most adverse discontinuity set(s) with respect to the pit wall. Strength properties for the anisotropy
was determined from the results of the geotechnical logging and laboratory testing. Anisotropy was
added to the modeled to replicate a plausible step-path failure mechanism. With the case of the
weaker units, any pervasive banding joint was included as this likely will contribute to the basal
sliding at the base of a failure. The antistrophic inputs are shown in Appendix E.
The most adverse discontinuity sets were determined from the results of the kinematic analyses. The
persistence and spacing parameters related to the discontinuity were evaluated for each set. The
persistence of discontinuities used in the anisotropy ranged from 80% to 90% (or 10% to 20 % intact
rock bridging along a modeled ubiquitous discontinuity surface).
Equivalent friction and cohesion values for the most adverse discontinuity sets were determined
using equations as presented in Read and Stacey(2009):
ceq = (1 — k)c + kc
tan(O,q) _ (1 — k)tan(0) + k tan(oj)
Where k= coefficient of continuity along the rupture plane, c = cohesion and =friction angle of rock
bridge, c =joint cohesion and �1 =joint friction angle.
11.2.2 Disturbance Factor (D) Zones
The Hoek-Brown Disturbance (D)zonation has been used in the 2D limit equilibrium analysis and 2D
numerical models to simulate rock mass damage induced by blasting and/or by stress relaxation as
the pit slope becomes unconfined with mining. The following damage zone inputs were used in
modeling:
• Blast Damage Zone — Depth of zone modeled at 1.5 times the bench height (10 m). A
constant D-value of 0.85 was applied throughout. This is representative of good wall-control
blasting techniques (Hoek, 2012), as is currently being implemented on site.
• Stress Damage Zone — Depth of zone equal to 30% of the total slope height being
modeled. Damage gradationally decreases from the blast damage zone laterally towards the
stress damage limit. This is support by guidance from Stillwell and Shand (2015), Guzman
and Perez (2015), and Rose et al. (2018).
11.3 Seismic Coefficients
A site-specific seismic hazard study has been conducted as part of the Select Phase work for the
project (Lettis, 2023 and GEOVision, 2023). The seismic coefficients used in the pseudo-static
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stability analysis are based on predicted peak ground accelerations (PGA). Table 11-1 summarizes
the (hard rock and ground surface) PGA's and the horizontal seismic coefficients for:
• Operational Level Earthquake (OLE) - 2% probability of exceedance in 80 years; 3,960-y
return period.
• Design Earthquake (DE)- 2/3 of the 2,475-year return period ground motions.
• Contingency Level Earthquake (CL) -475-y return period.
Following international practices, pseudo-static inputs for the stability analyses was based on a PGA
that equals 1/2 of the DE (0.0815 g).
Table 11-1: Kings Mountain Seismic Coefficients
Return Period (Tr Design Hard Rock PGA(m/s2) Ground Surface PGA(m/s2) KH
Earthquake Tr Tr X
475 CLE 0.033 0.096 0.048
2475 - 0.092 0.245 -
- DE 0.061 0.163 0.0815
3,960 OLE 0.119 0.299 0.1495
Source: Lettis,2023
11.4 LE Stability Analyses Results
The results of the LE stability analyses are summarized in Table 11-2 and presented in Appendix E.
The results were compared against a minimum DAC of a FOS equal to or greater than 1.3 that
represents an inter-ramp or overall slope with a medium to high consequence of failure (Table 9-2).
The analyses were completed for the final pit configuration and selected interim pit phases.
In general, the following overall stability mechanisms were modelled:
• Planar sliding along foliation and rupture through the rock mass at the base of pit slope. This
was analyzed for the East Wall sections which included foliation anisotropy parallel to the
2D slope model section.
• Non-circular failure mechanism that includes the influence rock mass anisotropy. This is
considered a pseudo step-path failure mechanism with sliding generally along single or
multiple joint or foliation sets and failure through the rock mass.
Table 11-2: Summary of 2D LE Stability Analyses Results for Proposed Final Pit
Pit Wall Stability Section Static FOS Pseudo-Static FOS
East 1 2.2 2.0
North 2 3.2 2.8
West 3 1.5 1.2
West 4 1.6 1.4
South 5 3.7 3.6
East 6 2.6 2.3
Source:SRK,2023
11.4.1 Overall Static Analysis
The LE static results indicated that minimum DAC is achieved for all six sections through the final pit
walls (Table 11-2). The analyzed pit walls represent the final pit that was provided by Albemarle.
Although the results are greater than FOS of 1.5, the governing design is based on the bench scale
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stability which is designed to mitigate against kinematic failures and provide rock fall containment.
Should there be better kinematic stability than expected during operations, the presented results for
the overall stability analyses would support optimization opportunities. The results also indicate a
lower sensitivity to pore pressures at the overall scale. An example showing the Section 1 stability
analyses result is shown in Figure 11-2.
FOS:2.2
/ FOS Model Result
LEGEND:
_Amphibole Gneiss-Schist Schist Marble
Spodumene Pegmatite Marble
_Chlorite Schist ' Phyllite
Mica Schist Overburden
Po Mica Schist Fault
Shear Schist
-Silica Mica Schist
Figure 11-2: LE Static Stability Analyses Result for Section 1, East Wall
A FE analyses was carried out for Section1 through the East Wall to confirm the result of the LE
analyses. The results indicate that a Strength Reduction Factor (SRF) greater than 2 is expected.
The SRF is similar to the results of the LE and provides confidence in the design stability analyses
summarized in Table 11-2. The FE result for Section 1 is shown in Figure 11-3.
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SRF > 2.0 {{
Total f {
Displacement
ry
00 {
I
{
10.00 , {
I � {
5.04 / {
20.00 I {
{
25.00 f {
{
30.00 {
{
35,00 {
40.00 / {
Figure 11-3: FE Static Stability Analyses Result for Section 1, East Wall
As discussed, LE stability analyses were completed for selected interim pit phases. The results of
the interim pit analyses achieved the minimum DAC. The results were typically above FOS of 2
which is expected for the strong rock masses and the corresponding interim pit heights which are not
significantly high.
11.4.2 Overall Slope Pseudo-Static Analysis
The pseudo-static results indicated that minimum DAC is achieved for all six sections through the
critical pit walls (Table 9-2). In general, the pseudo-static results represented a 10% to 15%
reduction in the resulting FOS when compared to the static results. The results also indicated a lower
sensitivity to pore pressures during an event. An example showing the Section 4 stability analyses
result is shown in Figure 11-4.
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lava
Ultimate Pi
_ LEGEND:
Amphibole Gneiss-Schist Shear Schist
_Spodumene Pegmatite Silica Mica Schist
-Chlorite Schist Upper Mica Schist
Mica Schist Overburden
Po Mica Schist
Source:SRK,2023
Pseudo-Static loading result for 9-year pit under drained condition.
KH=0.0595
Looking North.
Figure 11-4: Pseudo-Static Stability Analysis Result for Section 4, West Wall
11.4.3 Rapid Drawdown Sensitivity Analysis
To evaluate slope performance of existing pit walls under pit lake pumping, a rapid drawdown
analysis (static loading)was conducted for the East Wall (critical wall). The analyzed case included a
water level reduction from +820 ft ASL to +690 ft ASL. Figure 11-5 shows the NW-SE section
location relative to the existing topography. Figure 11-6 illustrates a graphical representation of the
rapid drawdown results with water level lowering. The critical failure surface is through the Mica
Schist. The FoS reduces from 1.9 to 1.6. This result achieves the minimum DAC under static loading
conditions.
Based on this result, pumping of the pit lake is not expected cause major instabilities at the overall
scale along the East Wall. The stability of the other pit walls during the pumping is expected to
exhibit a FOS greater than the analyzed case.
The bench slope performance below the pit lake is relatively unknown, and it is likely that minor
bench scale instability will still occur as the water level is reduced. A geotechnical inspection
program should be established to identify any new hazards introduced as the lake is drained.
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urrent
! • i
Plunge•9D
Azimuth DDD
Looking down
P n-
0 125 2eD 375 3DD
v�
Source:SRK,2023
Plan view of existing pit topography.
Figure 11-5: Rapid Drawdown Analysis Cross Section Location
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FOS = 1.881
Z = 820 feet
(a)
1.
FOS = 1.553
Rapid drawdown (130 ft.)
Z = 690 feet
(b)
l•
FOS = 1.952
Drained condition
(c)
Source:SRK,2023
Static loading results for existing pit looking North(refer to Figure 5-15 for cross section location).
(a) Pit lake+820 ft ASL water level.
(b) 130 ft rapid drawdown of water level to+690 ft ASL.
(c) Drained pit lake condition.
Figure 11-6: Rapid Drawdown Analysis Cross Sections—East Wall
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11.5 Limitations and Assumptions
Stability Model Limitations
The LE method for analyzing pit wall stability performance remains a useful tool despite inherent
limitations in the methodology. The limit equilibrium method of slices is based purely on the principle
of statistics; that is, the summation of moments, vertical forces and horizontal forces. The method
says nothing about strains and displacements, and as a result, does not satisfy displacement
compatibility. It is this key piece of missing physics that creates many of the difficulties with the limit
equilibrium method. As with any limit equilibrium models, the potential slide is considered a rigid
block not accepting deformation, this consideration is reflected in a conservative approach. The
model is purely elastic, and no residual rock mass strength is considered as part of the FoS
calculation.
Stability Model Assumptions and Input Parameters
A summary of the assumptions and input parameters for the analyses are listed below:
• SRK accepts the Kings Mountain Select Phase Level pit design as valid.
• SRK accepts the Kings Mountain geological model as valid.
• SRK validated and accepts the Kings Mountain Select Phase Level geotechnical data (refer
to 2023 SRK Factual Report for statistical analysis of data and rock mass parameter values
used for stability analysis).
• Limit equilibrium modeling was used for determining the Factor of Safety and Probability of
Failure. General limit equilibrium methods were accepted as good estimators of the FoS and
PoF. 2-D limit equilibrium assessment was selected due to the pit shape.
• Isotropic functions (Hoek-Brown) were used for representing the rock mass parameters of
each wall direction.
• Modified Hoek-Brown strength parameters were calculated using:
o RocData software (Rocscience, 2020) to compute Mi and 6ci parameters estimated from
analysis of rock strength laboratory testing data from the Select Phase rock strength
testing program (refer to 2023 SRK Factual report).
o Estimated lower quartile GSI values as presented in Table 6-2.
o A groundwater surface was estimated near the pit slope surface on each section
analyzed with wet conditions, based on hydrogeologic modeling results.
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12 Pit Slope Design
The Kings Mountain slope stability and resulting design is defined by:
• The orientation of the regional moderate west-dipping foliation structures (East Wall); and
• Kinematic stability related to the major joint sets (all pit walls).
Therefore, the design is predominantly driven by the bench kinematic stability assessment with
BFA's adopted to reduce the undercutting potential from high-angle planar sliding and wedge
intersections.
Pit slope design is presented for single (30 ft) and double (60 ft) bench height strategies, expect for
Design Sector 1 for the East Wall. A single bench strategy is recommended for Design Sector 1 due
to the variability of foliation across the proposed pit wall. A single bench height reduces the potential
back-break distance where a localized but continuous foliation structure undercuts the design slope
face. Additionally, the foliation moderate dip can result in challenging blasting and excavation
conditions to successfully strip at the double bench height without exposing drillers and operators to
high rock fall hazards, especially during the early years of operations where the rock mass behaviour
isn't well understood.
The slope designs are presented in Table 10-5. These are based on the pit slope aspects and
geotechnical domains shown in Figure 12-1. Where transitioning between design sectors, the lower
of the recommended design should be adopted.
Review of the 2023 final pit design shows that the rock slope design criteria has been implemented
through the uppermost overburden unit. Future pit designs would need to implement the overburden
criteria included in Table 10-5.
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- Overburden 29
. Pegmatite Sector 2
0 Schist _ DD = 1950
Amphibole
aMarble
Design Transition
1
Design Transition
Sector 3
DD = 120° '4500N
- +544p00 N
Sector 1
Design Transition DD = 350°
,( ,s43soa n
+543000 N
Sector 4
DD = 035° j
Design Transition +542500N
7 a 0 125 251 375 500
'286000 +1297=01)E I.129B00
Source:SRK,2023
Note: Four domains are shown relative to the Select Phase Ultimate Pit(Albemarle 2023).
Figure 12-1: Design Sectors
In addition, the following design guidelines are provided:
• Re-profile overburden slope materials to a configuration that would reduce the potential for
slumping into benches and ramps.
• With pit wall heights of 490 feet and greater, there is a need for geotechnical catch bench in
the to prevent multi-bench rockfalls from going down to the working area of the pit. It is
recommended that the pit design has a geotechnical catch bench (or ramp) no more than
492 ft apart vertically (479 ft is an inter-ramp stack of 16 single benches) and the bench
width no less than 40 ft.
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• Incorporate a set-back bench at the overburden-rock contact with surface water interception
ditches to capture and divert water flow from the pit crest.
• Any irregular bedrock-overburden profile will need to be considered in the pit design work.
• The foliation parallel BFA's are based on achievable blasting approaches that will need to be
trialed
• Bullnoses (convex slopes) of one or more stack heights should be stepped-out and assigned
a lower IRA, depending on their size, location, and radius of curvature.
• Implementation of a two-ramp approach through the pit phases to reduce consequences of
an instability location above or below critical access.
Table 12-1 provide recommended setback distances from the pit crest.
Table 12-1: Minimum Setback Distance from Pit Crest
Infrastructure Pit Depth
Shallow<150 ft Deep> 150 ft
Property limit 100 ft 150 ft
Waste dump 50 ft 100 ft
Rail 90 ft 150 ft
Buildings 90 ft 150 ft
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Table 12 1: Recommended Bench and Inter-ramp Design Criteria
Design Sector Design Recommendation Design Stability Limitations and Comments
Design Slope Dip Bench Bench OVB
Geotechnical BFA Bench Design Maximum Stack Geotechnical Berm
Domain(s)Sector Location Direction (°) Height Width Step-out
Name From To (°) Configuration (ft) (ft) IRA(°) (ft) Height(ft) Width (ft)
Overburden All Pit - - 65 Single 15 10 41 20 - - Step-out required at overburden and bedrock contact.
Sector 1 Pegmatite, Schist, Marble East Wall 250 300 60 Single 30 20 39 Design constrained at the bench-scale by planar sliding
risk along foliation
Sector 2 Pegmatite, Schist North Wall 150 210 78 Single 30 20 49 Design constrained at the bench-scale by wedge failure
Double 60 26 57 Design constrained at the bench-scale by wedge failure
Single 30 20 49 - 490 40 Design constrained at the bench-scale by wedge failure
Sector 3 Pegmatite, Schist, West Wall 080 140 78 and possible toppling along foliation
Amphibole Double 60 26 57 Design constrained at the bench-scale by wedge failure
and possible toppling along foliation
Sector 4 Pegmatite, Schist South wall 300 080 78 Single 30 20 49 Design constrained at the bench-scale by wedge failure
Double 60 26 57 Design constrained at the bench-scale by wedge failure
Source:SRK,2023
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13 Design Implementation Strategy
13.1 Blasting
Albemarle should plan to implement a full-height pre-split and flitch-height trim design approach.
There is evidence of half-barrels in the historical bench slopes are enabled the steeper BFA's to be
formed (Figure 13-1).
The pre-split should be fired first preferably followed by the rear production blast. The trim blast
should be fired last after the pre-split and production blast. This trim blast should be no more than
three to four rows wide and designed with to at least one free face parallel to the rows. Double
stitching on the pre-split back row is recommended to prevent toe flare (hard toes).
There should be no sub-drill on the final row of the trim blast and possibly not in other holes in the
proximity of the underlying bench crest. Burden should be adjusted relative to underlying crest
position to prevent damaging the underlying crest. For the Trim blast, designs should be simple and
avoid "V" shapes. Trapezium and parallelogram sequences are optimal to prevent ending up with
closed corners where excessive energy can damage the face. Care should be taken not to damage
the trim zone with the rear production blast. Consider using a reduced charge final row of the
production blast.
The following comments are made for blast implementation and QA/QC:
• Electric detonation will provide improved control.
• The depth control, including QA/QC, is significantly important to successful excavation.
Consideration to a contract driller may be given.
• Thorough QA/QC of the hole depth, pattern, deviation, and charges is needed for each
pattern continuously during the trials.
• If blast holes are wet, do not use cuttings in place of granular stemming. Do not top-load the
blast holes.
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r ;
bfV
.'F �, s�✓ �?� �`it�lo I �A ��� lE 4- t '��( :,�!� r�l�. -tip �:i
t - � �fit} � 1E�` r r`�•
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Figure 13-1: Evidence of Half-Barrels Along the Historic Pit North Wall
13.1.1 Shallow Footwalls
Shallow footwalls though the East Wall may require a stab-hole blasting approach that include a
three to four trim blast (Figure 13-2). This may be required where there are difficulties in achieving
pre-split BFA's at or below 60-degrees. The following conceptual stab-hole blast are provided for the
footwalls that are formed along shallower foliation:
• Design to incorporate two stab-holes along the design BFA surface plus a three or four row
trim. A stab-hole stand-off of 1 m from the design BFA surface should be included.
• Stab-hole diameter should be less than 8". The trim holes can include a larger diameter.
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• Initially, the stab-holes should be loaded half-height and/or the stab-holes may be decked to
increase fragmentation higher in the hole. The trim rows loaded with reduced charge height
(with no stemming)to allow breakage and help prevent block heave.
• Incorporate a tighter spacing during the initial trials, starting at 3 m.
• Do not include stemming in the first stab-hole. The second stab-hole will require limited
stemming to reduce the energy charge. Possible to use decking in the second stab-hole.
• The second stab-hole may need less control (for collar) damage but important to ensure that
drillhole does not undercut the design BFA.
• The blast design will require two free faces to reduce energy confinement.
Berm viidth Stab-holes Trim Block
First 15 m
Flitch
50` Design BFA
Second 15 m
Flitch
50' Dipping Foliation
Structures
Source:SRK,2023
Figure 13-2: Conceptual Stab-Hole Blasting Design for the Shallow Footwall Slopes
13.1.2 Trialing or Refining The Blast Design
The blast design will need continued adjustments and trialed before an optimum design is being
implemented. Albemarle should continually update the current Blast Master Plan incorporating input
from geology, geotechnical and operations. This plan should document, review and re-assess all
blasts to continually improve performance.
A general workflow for blast review and/or trailing is presented in Figure 13-3.
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aBlast Design
7
rr- Design BenchRefinement -r.
BlastingBlast Review
Meeting Q Q
ExcavationPost Pre-Blast
Assessment
Excavation Post Blast
Control - -
Figure 13-3: Blast Review and Trial Workflow
13.2 Scaling and Clean-up
Good scaling and bench clean-up are essential to reduce the rock fall hazard and maximize bench
performance. Given the narrow pit limits, scaling using a long-reach excavator will be needed, and
this is considered appropriate for the jointed and foliated rock mass at Kings Mountain. The
operators should be trained by the geotechnical team to understand the objectives of the work, and
bench slope hazards either existing following the blast or newly created due to over-excavated
bench faces.
13.3 Geotechnical Pit Mapping
The slope design should be verified with regular pit wall mapping as the new benches are exposed.
Structural and rock mass condition data should be routinely collected and evaluated by the
geotechnical team. It is important that structural mapping is analyzed on an ongoing basis to review
potential wedge and planar sliding mechanisms. The geotechnical mapping is critical to evaluating
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the dip and dip direction of the foliation structures as they are exposed. Techniques such as laser
scanning should be used to collect data safely and rapidly between production blasts as the walls
are pushed back.
13.4 Structural Geology
Interpretation of the primary and secondary fault structures is required to advance the design study
to a Define Phase level. This aspect is current a gap in the study that needs to be addressed to
confirm the stability assessment and design included in this report.
The structural model also assists with the ground control management. Verifying and updating the
model with new data collected from exposed bench slopes is a critical responsibility of the
geotechnical and geological teams. An up-to-date model enables the prediction of slope risks and
allow establishment of strategic monitoring and design mitigation activities.
13.5 Pit Slope and Groundwater Monitoring
A robust slope monitoring system must be implemented for the pit, with particular emphasis on high-
risk areas and the expected mode of failure. Trigger levels/thresholds should be defined by
Albemarle and modified as required. Slope monitoring procedures should include:
• Daily inspections: these inspections should be completed along all currently active mining
areas by a member of the geotechnical staff. Inspections should include checks for sliding
potential, especially on West Walls, checks on tension cracking, dilation, scaling and clean-
up requirements, surface water conditions etc. Inspections should be well documented and
discussed at daily meetings with geotechnical and operation superintendent as required.
Inspections should be carried out with the operators from time to time. Hazards and failures
should be logged in a database which will be useful for stability review and any future
empirical design work.
• Tension Crack inspections: these are often the first indications of slope instability.
Inspections should be done daily and after periods of heavy rainfall, and more frequently
depending on rate of opening. Weekly inspections should be carried out on the pit crests and
wider benches. Crack widths should be measured and plotted up to investigate acceleration.
• Prism Monitoring: placement of prisms in suitable areas around the pit must be completed.
Prisms should be surveyed from a base station set-up by an experienced survey engineer.
The base stations need to be on stable ground and should be made of concrete. The base
stations need to be located so that they are largely looking perpendicularly at the higher risk
slope areas to reduce.
• Tactical Radar Unit: A single radar unit should be available to monitor slope aspects not
visible from prism monitoring, or to be used in the case where slope deformation is observed
and requires greater resolution than prism monitoring or other methods may provide.
• Vibrating Wire Piezometers (VWP): VWPs should be installed sub-parallel to interim and
final pit wall slopes. Installation should occur prior to mining to observe steady state
groundwater elevations and the response to progressive mining activity and precipitation. An
example VWP plot from an operating mine is included in Figure 13-4.
It is recommended that a baseline monitoring strategy using theodolite robotic total stations and a
tactical radar unit be considered throughout the mine life. Table 13-1 outlines the sequencing and
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priority of monitoring types and locations relative to pit stage. Figure 13-5 outlines the location of total
station and the pit aspects which can be monitored through the life of mine. A tactical radar unit
should be deployed to monitor any occluded areas from prism monitoring, or for greater resolution in
the event that pit slope deformation is observed.
zoo
so0
41111
1so
�t
460
E �
E �
100 =
440 Lake Elevation(mamd)
■ Rainfall
w Pit Tae Elevation(mamd)
5ensar
—MHO-GT-16A 6
420
--sensor
50 MHO-GT-16A_5
5ensar
/ —MHO-GT-16A_4
400 r/
—sensor
—MHO-GT-16A_I
5ensar
MHO-GT-16A_2
0
2015 2016 2017 201 a' 2019 2020 2021 2022 2023
Figure 13-4: Example Hydrograph Showing VWP Water Level Responses to Rainfall and
Excavation
Table 13-1: Preliminary Prism and Radar Monitoring Details
Monitoring Max Range Monitoring Target Pit Pit Phase
Approach (ft) Location Wall Phase Phase Phase Phase Phase
0 1 2 3 4
Total 4921-9842 Crest-West Wall East Wall X X X X X
Station- ft Crest-East Wall West Wall X X X
Prism
Radar 16,404 ft Tactical Unit X X X
13.6 Updated Stability and Pore Pressure Analyses
New stability analyses should be carried out to verify any new medium and long-term pit designs.
Data collected from the exposed bench faces and monitoring instruments should be used to update
the design inputs and evaluate expected stability, including any deviation from the Select Phase level
design analyses.
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`Pit Stage - PHg Pit Stage — PH Pit Stage — PH2 Pit Stage — PH3 Pit Stage — PH4
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1 � :w., r•.�xi--. �rx�� � LB ri+RSE I WKY TCIi45TAT1ON � +9 vn�vexrnrsu TaTA�srwncw - . . � - 5
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'.FCC .i 1�� ��'156iE � 1�. r�'1•S�&E � -•i � fc'CLE v ..-�. �uP'�C[
�iFF �nypff
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-'l•: r IHl.`.Ji5 - _ $.r. I�:-J '::L _ S:.V: �i.i IS '.'25 1.•AG j .� i4- I[ n-. S I
Fee[ Fee[ Fr,�l � Fggt ! �ir��' cFCCI IJ
Source:SRK,2023
Figure 13-5: Summary of Total Station Monitoring Locations and Visible Pit Aspects for Each Mining Phase
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14 Conclusions
14.1 Summary
Based on the findings from the Kings Mountain slope design study, the following concluding
comments are provided:
• The quantity, quality and coverage of the data is appropriate for the Select Phase level pit
slope design study. There remain geotechnical drilling gaps in specific final pit areas,
including reduction of current drillhole orientation biases near the proposed final pit walls.
• The stability is expected to be structurally controlled with the slope design governed by the
achievable bench configurations, including rock fall mitigation:
o East Walls governed by planar sliding impacts along continuous foliation. The
shallower design configurations are intended to reduce bench-scale instabilities and
eliminate inter-ramp scale planar sliding impacts.
o The North and South Walls are governed wedge intersections; however, foliation
structures are orientated perpendicular to the slopes and are expected to reduce the
persistence of the wedge-forming joint sets. Steep bench profiles are observed in
the legacy open pit.
o The West Wall is expected to be governed by wedges and planar sliding features
impacting crests. Toppling cannot be fully eliminated with foliation dipping
moderately into the slope, however, is not considered to be constraining the stability
of the design bench slopes. Toppling impacts do need ongoing evaluation through
future studies.
• Overall stability analyses indicate that minimum DAC is achieved for the recommended
slope design, including under pseudo-static and rapid drawdown conditions.
• The West, North and South slope design configurations are considered steep and will rely on
best practice implementation (i.e., wall control blasting, clean-up) and strict ground control
management (i., e, inspections, slope/groundwater monitoring) to safely excavate. There
may be challenges to consistency excavate the East Wall along the moderate dipping
foliation and several blasting options will be required based on structural conditions.
14.2 Impacts
Based on the findings of this study, the following risks should be considered:
• Interpretation of the primary and secondary fault structures is required to advance the design
study to a Define Phase level. This aspect is a current gap in the Select Phase study that
needs to be addressed through additional data collection and updated structural modeling to
confirm the stability assessment and designs included in this report.
• The design bench configuration is reliant on best practice blasting to successfully implement
the slopes which are considered steep in the North, West and South Walls. The kinematic
stability work indicates the bench slopes are susceptible to planar sliding along foliation
(East Wall) and wedge intersections (all walls). These mechanisms can contribute to back-
break and rock fall issues with improper implementation and there is a risk that design
adjustments will be required to reduce risks during operations.
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• With respect to the East Wall, the design BFA's of 60-degrees may still need be shallower to
manage planar sliding risks at the bench scale. This is a potential that a refined foliation
interpretation will identify zones where the BFA's will need to be reduced to mitigate against
multi-bench instabilities.
• With respect to the East Wall, there is currently a gap in the current drill spacing along the
East Wall that is necessary to fully characterize the Kings Mountain Shear Zone, the S-Flex
& Un-Named Faults, any previously unrecognized faulting or deep-seated structures,
foliation, and jointing in the East Wall. This current gap in the Select Phase study needs to
be addressed to confirm the stability assessment and designs included in this report.
• With respect to the West Wall, the design BFA's of 78-degrees may need to be reduced
where a toppling risk does exist. There may be a greater toppling risk that currently expected
where foliation is more closely spaced and rock quality is poorer than the current
geotechnical logging indicates. In addition, closer spacing due to incipient features opening
during the blast cycles.
• There may be cases where foliation has limited influence on the bench faces in the massive
rocks and hang-ups occur (i.e., gneissic rocks, marble). This may result in rock fall risks and
challenges to implement the shallower East Wall designs.
• Alteration influence on the rock masses is not well understood. There could be weaker
materials at depth not captured in the diamond drilling.
• Albemarle are planning to adopt a single-lane ramp strategy with multiple access routes
across the open pit. The single-lane strategy can represent a high geotechnical risk profile
as there is little contingency for a larger back-break event.
• The bench slope performance below the pit lake is relatively unknown, and it is likely that
minor bench scale instability will occur as the water is pumped.
• With respect to direct shear testing results, peak values were recognized as being
suspiciously high. Additional direct shear testing should be conducted at the Define Phase.
• With respect to geotechnical core logging, RQD data is considered high and may be
indicative of unlogged natural fractures leading to an overestimated GSI.
14.3 Opportunities
The following opportunities are considered:
• Should the kinematic controls be less influential on stability there may be opportunities to
increase the design BFA, and resulting IRA, in some sectors. There will require successful
wall control blasting techniques.
• Should the rock mass conditions within Pegmatites have less influence from continuous
foliation structures, there may be opportunities to form steeper design BFA's along the East
Wall (where the rock is too massive to be impacted by undercut foliation).
• With respect to the East Wall, the design BFA's of 60-degrees may be significantly shallower
than the orientation of foliation in specific areas of the pit. This is a potential that a refined
foliation interpretation will identify zones where the BFA's can be increased.
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15 References
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Disclaimer
SRK Consulting (U.S.), Inc. (SRK) has prepared this document for Albemarle Corporation
(Albemarle), our client. Any use or decisions by which a third party makes of this document are the
responsibility of such third parties. In no circumstance does SRK accept any consequential liability
arising from commercial decisions or actions resulting from the use of this report by a third party.
The opinions expressed in this document have been based on the information available to SRK at
the time of preparation. SRK has exercised all due care in reviewing information supplied by others
for use on this project. While SRK has compared key supplied data with expected values, the
accuracy of the results and conclusions from the review are entirely reliant on the accuracy and
completeness of the supplied data. SRK does not accept responsibility for any errors or omissions in
the supplied information, except to the extent that SRK was hired to verify the data.
Copyright
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