REALISTIC SYNTHETIC KEY BLOCK ANALYSIS TO

COMPARE DIFFERENT SUPPORT SCENARIOS

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METHODOLOGY

Methodology

Geotechnical data

• Data gathering.

• Stereographic projections and discontinuity analysis.

• Statistical analysis, processing and quality control.

Key block analysis input

parameters

• Key block creation

• Define a support scenario

• Hazard Analysis

• Correlation between FOG database and synthetic database

Comparative key block analysis

• Compare different support scenarios

GEOTECHNICAL DATA Geotechnical

data

• Data gathering.

• Stereographic projections and discontinuity analysis.

• Statistical analysis, processing and quality control.

Geotechnical Data

• Data gathering.

Mining Direction

Dip

Strike Scan Line

Dip

Sca

n L

ine

Geotechnical Data

• Data gathering.

• Stereographic projections and discontinuity analysis.

Friction Angle

• Point Estimate Method applied to the Barton and Bandis equation.

• JCS derived from Schmidt hammer rebound number.

• σn estimation can be derived from Examine 2D.

• JRC is derived from field observations.

Geotechnical Data

• Data gathering

• Stereographic projections and Discontinuity analysis

• Statistical analysis, processing and quality control.

Joint Data 1

Joint Data 2

KEY BLOCK ANALYSIS INPUT PARAMETERS Key block

analysis input parameters

• Key block creation

o Key block creation limits

o Generate 100 000 key blocks

• Define a support scenario

o Represent support used inside the time period of FOG database

• Run Hazard Analysis

o Block filtering: tall thin block clamping

• Correlation between FOG database and synthetic database

o Fallout distribution of volume

Project flow of JBlock

• Now we have a geo-domain

• Build excavation

• Generate key-blocks o Creation limits

• Define support scenario o In-use at time of FOG DB

o External loading

Stress in skin of excavation

• Run hazard analysis

o Block filtering

Key block creation limits

• Block creation

o Max aspect ratio considered

0.00%

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100.00%

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0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5

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Aspect Ratio: Longest Edge

Series1

Series2

Aspect ratio = longest edge/volume1/3 Max =5.4

FOG database

Project flow of JBlock

• Now we have a geo-domain

• Build an excavation

• Generate key-blocks o Creation limits

• Define support scenario o In-use at time of FOG DB

o External loading

Stress in skin of excavation

• Run hazard analysis o Block filtering

Analyse a support scenario

Filter blocks for clamping or extreme size…

Batch run several scenarios

Filter block sizes/clamping to use in analysis

Block filtering input parameters

• Block filtering

o Tall thin block clamping

Mid height

Height to face area ratio

Block filtering: Mid height

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Histogram: Thickness

Series1

Series2

Mid height = Max thickness / 2 Max = 3.5

Mid height = 1.75

Block filtering: Height to face area ratio

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0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2

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Height to face area ratio

Series1

Series2

Height to face area ratio = thickness/face area1/2 Max =1.1

Is the synthetic database realistic? • Block creation

oMax aspect ratio considered

• Block filtering o Mid height

o Height to face area ratio

• Correlation: FOG database vs synthetic database o Compare different clamping stresses

Correlation Coefficient

Kolmogorov-Smirnov: Two Sample Test

Clamping Correlation

0%

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.82

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Fallout: Volume

Clamping Correlation: Volume

2kPa

4kPa

6kPa

8kPa

10kPa

Actual: FOG DB

40% 80%

Clamping Correlation

Clamping Stress [kPa]

Correlation coefficient [%]

Max Error [%]

Avg Error [%]

2 92% 38% 15% 4 92% 38% 17% 6 94% 32% 16% 8 96% 27% 9%

10 94% 30% 15%

Kolmogorov-Smirnov: Two Sample Test

Correlation coefficient

Clamping Correlation

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Clamping Stress [kPa]

Correlation: Clamping Stress

Correlation

MaxD

COMPARATIVE KEY BLOCK ANALYSIS

Comparative key block analysis

• Compare different support scenarios

• Compare support strategies

• Different tendon lengths.

• Optimize support spacing

When analyzing a support scenario

• Evaluate blocks that can fail

• This implies that we want to evaluate: – Stable by support – Failed support – Failed by rotation – Failed between support

• We don’t want to take into account: – Stable over solid – Stable by friction – Stable no sliding – Tall clamped blocks

Support Comparison

RESULTS EXPRESSED AS FALLS PER 10 000m2

What is driving the Mode of Failure?

What is driving the Support Failure?

Size distributions of failed key blocks?

Different tendon lengths?