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May 8th, 2017 Aristotle University of Thessaloniki - Research Dissemination Centre
Engineering Geology and Innovation: Research –Infrastructure - Sustainable Development
(I.A.E.G)
Application of Core Logging Data to
generate a 3D Geotechnical Block Model
Eleftheria Vagkli, M.Sc.| Senior Geologist,
Skouries Geological-Geotechnical Dpt.
Hellas Gold SA |Eldorado Gold Corp.
1
May 8th, 2017
INDEX
Scope, Data collection, Data analysis for the Generation of 3D GeotechnicalBlock model
Skouries Geological and Mining Context (Underground)
Rock Mass Properties - Data Collection
2013-2014 Geotechnical Drilling Program
Detailed Geotechnical logging parameters (Laubscher’s RMR90 components)
RQD - Methodology, Data analysis and Results
Laboratory Results – UCS statistical analysis
Structural Data and Model
Spatial variability assessment of rock mass characterization
GEOTECHNICAL BLOCK MODEL
− Generation and Methodology
− Comparison of high and low confidence Data
− Spatial continuity assessment
RMR Block Model Criteria
ResultsAristotle University of Thessaloniki -
Research Dissemination Centre2
May 8th, 2017
Rock Mass Properties - Data Collection.
• Diamond Core Drilling
• Information from Underground Mapping − GSI – Geological Strength Index –Marinos and Hoek, 2000− Q – Rock Tunnel Quality Index – Barton, 1974− RMR – Rock Mass Rating – Bieniawski, 1989 and Laubscher, 1990
• Laboratory Testing – In-situ Strength− UCS, Young’s Modulus, Poisson’s ratio− Shear Strength− Tri-axial Strength− Point Load (field testing)
Geotechnical Data Analysis
• Software− Dips (local)− Leapfrog (local and external)− Slide and Phase2 (external)− Proprietary external software for spatial continuity assessment
• Consultants− SRK – Vancouver – for underground geotechnical block model− David Rhyss – Structural Geologist− SRK - Cardiff – for open pit design recommendations− Golder Associates – UK & Enveco for hydrogeology
The scope of the Underground block model was to generate a tool to spatially assist with excavationdesign of Skouries Underground Mine.
Generation of 3D Geotechnical Block model
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May 8th, 2017
Skouries Geological Context (Underground)
The Skouries Au-Cu porphyry system occurs within poly-deformed amphibolite grade schist and gneiss of the Vertiskos Assemblage where it is intruded by a pipe-like composite intrusive body of early Miocene age.
• Two prominent lithologies− Porphyry (intrusive)− Schist (biotitic and amphibolitic)
Minor Gneiss
• Three alteration styles− Potassic (shell shape around porphyry)− Propylitic /chloritic (schist mainly)− Argillic (local, structural associated)
• Major structures− Damage zone isolated; lack obvious continuity− Historically recorded as more prominent in schist
• Hydrothermal veining and microdefects prevalent− Impact rock strength ( porphyry and schist)− Heavy veining associated with high grade ore− Zoning not explicitly defined
• Clay degradation− Strength reduction upon exposure− Important geotechnical aspect− Zoning unclear 4
May 8th, 2017
Skouries Mining Context (Underground)
• Sub-level Open Stopping (SLOS) mine beneath planned Open pit
• Underground mine vertical extents from 390mRL to -100mRL
• Crown pillar
Lower
Stopes
Aristotle University of Thessaloniki -Research Dissemination Centre
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May 8th, 2017
Available geotechnical data
per drilling campaign
Database compilation
(Final Database)
Rock Mass Properties - Data Collection
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May 8th, 2017
• Ten (10) Open Pit Geotechnical drill holes
• Ten (10) SLOS drill holes
• Six (6) infrastructure holes
• All bore holes oriented with triple tube (HQ3)
• In total almost 12,400 m were drilled
2013-2014 Geotechnical Drilling Program N
Aristotle University of Thessaloniki -Research Dissemination Centre
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May 8th, 2017
Detailed Geotechnical logging _ Recorded parameters
• Total Core Recovery (TCR)
• Rock Quality Designation (RQD)
• Intact Rock Strength (IRS)
• Fracture counts (joints, cemented joints, foliation and mechanical breaks)
• Assessment of joint conditions (roughness, alteration of wall rock, fill type)
• Number of joint sets
• Assessment of micro defects
• Strength of fill in closed features
• Joint Orientation (alpha and beta angle)
LAUBSCHER’ S RMR90 COMPONENTS
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May 8th, 2017
SLOS4_RQD
•Total length of core pieces that are longer than 10cm.
•Consider mechanical and man handling breaks as solid core.
•Consider joints along the core axis as solid core.
ROCK QUALITY DESIGNATION (RQD) - METHODOLOGY
SLOS2_ High RQD:100%
SLOS6_ Low RQD: 20 - 25 % 9
May 8th, 2017
RQD –All Data analysis – Porphyry vs Schist
• UCS data reviewed below +420RL
• All schist grouped together based preliminary analysis (k-altered schist included)
• Review of SLOS-series, UCS data suggests that porphyry has higher strength than schist
• Porphyry UCS mean: 110MPa (StDev=29)
• Schist UCS mean: 90MPa (StDev=29)
Laboratory Results – UCS analysis
• All Data (below +420RL ) suggest that porphyry is more massive than schist
• Potassic altered schist not segregated
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May 8th, 2017
STRUCTURAL DATA
Oriented core data set was considered as highestconfidence data
Lower hemisphere Stereonet of the oriented faults measured inthe drill holes, decline and face mapping.(A) Faults in the porphyry. (B) Faults in the Schist
Joint analysis –Selected Joint Sets in Porphyry and Schist (Underground)
FAULTS
JOINT SETS FOLIATIONDominant fabric (foliation) at NE dip direction (for S1) and SE (for S2)
N
PORPHYRY JOINT SETSSCHIST JOINT SETS
11
Porphyry and Schist has different fault trends:
• Porphyry: N-S
• Schist: NW-SE (S1)
May 8th, 2017
Looking West
Plan View
N
FINDINGS
• A total of 39 faults have been modelled.
• The 3D analysis of the structural data indicated limited faults continuity
• No indications of regional intense major fault zones, rather discrete gouge filled structures.
Data Sources:
• Oriented core data (fault andfoliation)
• Drillhole RQD, FF and structuralinterval logging
• In-pit structural mapping (Rhys,others)
• Surface mapping data
• DXFs, scanned sections and plans(fault and foliation)
STRUCTURAL MODEL
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May 8th, 2017
• No significant variance in RQD and PointLoad Test (PLT) data among the upper,middle and lower stopes
• UCS and higher confidence RMR data notnumerous enough to do more advancedper stope assessment
• Variance exists between schist andporphyry for RQD and UCS
• Despite some variance, k-altered schistand schist don’t require segregation forstope and development design purposes
• Recommended to group all stopes(upper, middle and lower), focus onlithology review and isolation of weakerzones
Middle Stopes
Upper Stopes
Lower Stopes
Rock mass characterization - Variability assessment for upper, middle and lower stopes
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May 8th, 2017
GEOTECHNICAL BLOCK MODEL
The scope of the Underground block model was to generate a tool to spatially assist with excavation
design.
The following workflow has been applied for the generation of the geotechnical block model:
• RQD data was utilized from historical and new (2012 to 2014) drilling data sets
• RQD block model interpolated based on statistically supported criteria.
• RMR90 calculated for a large number of drill holes according to:
RQD data converted to Fracture Frequency rating (0-40 range) using established empirical formulamodified (Priest & Hudson, 1981)
Intact rock strength (IRS) from laboratory testing
Joint condition values determined from new drilling data and SRK’s site logging
All blocks from RMR model populated using FF+IRS+JC= RMR90
For the Final RQD Block Model interpolation thefollowing methodology was used:
• RQD data was adjusted using completed regressionanalysis
• All RQD data was split into 5m intervals
• A two pass ID2 interpolation was completed:
− Small 30x20x10mH porphyry search ellipsoid,30x10x20mH schist search ellipsoid, using only highconfidence data.
− Large 60x40x20mH porphyry search ellipsoid,60x20x40mH schist search ellipsoid, using high andlow confidence data.
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May 8th, 2017
GEOTECHNICAL BLOCK MODEL
Comparison of high and low confidence RQD DataMethod 1• Nearest Neighbor-blocks estimated from one compositeMethod 2• RQD estimated by Inverse Distance (ID2) from different data types within 20m sphere• Estimated blocks averaged within large 40x40x40 m panels
Spatial continuity assessment for search ellipsoid - Porphyry
Spatial continuity assessment (Average distance between drill holes: 20-50m)
The following search ellipsoids have been applied in order to avoid over-smoothing of the estimated RQD values:
Spatial continuity assessment for search ellipsoid –Schist
Looking North-East Looking North- West
Best spatial continuity dip/dip direction: 60/260
Best spatial continuity dip/dip direction: 65/335
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May 8th, 2017
GEOTECHNICAL BLOCK MODEL- RMR Block Model Criteria
The following approach was used in the RMR90 generation process
• Intact Rock Strength (IRS) recommendations:
− Used representative IRS values for Schist, Potassic Schist and Porphyry
− Applied 25% reduction in IRS rating where RQD<50%
• Fracture Frequency (FF) recommendations:
− Converted RQD to FF based on the empirical relationship derived by Priest and Hudson
− Converted to FF rating presented in Laubscher’s RMR90criteria, assuming three point sets.
• Joint Conditions (Jc):
− Used deterministic values for Jr and Ja for Schist, Potassic Schist and Porphyry lithotypes
− Assumed dry conditions
− Converted Jr and Ja values to corresponding joint roughness, joint alteration and joint infill values using Laubscher’s RMR90 criteria
− Used 25% reduction in fill quality where RQD<50%
− Assumed moderate conditions for large scale joint roughness. Assume curved large scale joint expression with a value of 0.85
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May 8th, 2017
RMR90Model–DrillHoleComparison:4480N
RQDRMR90
High confidence drill hole SLOS 4
RMR90 block data correlates
reasonably well with new high
confidence (SLOS) drill hole logging 17
May 8th, 2017 Aristotle University of Thessaloniki - Research Dissemination Centre
Thank you
Application of Core Logging Data to
generate a 3D Geotechnical Block Model
Eleftheria Vagkli, M.Sc.| Senior Geologist,
Skouries Geological-Geotechnical Dpt.
Hellas Gold SA |Eldorado Gold Corp. 18
May 8th, 2017 Aristotle University of Thessaloniki - Research Dissemination Centre19
May 8th, 2017 Aristotle University of Thessaloniki - Research Dissemination Centre20
May 8th, 2017 Aristotle University of Thessaloniki - Research Dissemination Centre21
May 8th, 2017 Aristotle University of Thessaloniki - Research Dissemination Centre22