Group Approach to Achieving Optimum Blast Performance
18
Surface Mine Design
The Three Keys to Achieving Optimum Explosive Performance
19
Geological Effects on Blast Performance Physical Rock Properties Physical Rock Properties
Surface Mine Design
Compressive Strength Tensile Strength Poisson’s Ratio Young’s Modulus Density Longitudinal Wave Velocity
20
Surface Mine Design
Geological Effects on Blast Performance Typical Rock Properties
21
Surface Mine Design
Geological Effects on Blast Performance Rock Structure
Massive Rock 22
Surface Mine Design
Geological Effects on Blast Performance Rock Structure
Adverse Bedding Planes
23
Surface Mine Design
Geological Effects on Blast Performance Rock Structure
Deck Loading 24
Surface Mine Design
Geological Effects on Blast Performance Rock Structure
“Blocky” Jointed Rock 25
Surface Mine Design
Geological Effects on Blast Performance Rock Structure
Adverse Effects of Bedding and Jointing on Wall Control
26
Surface Mine Design
Geological Effects on Blast Performance Rock Structure
Deck Loading “Floaters” 27
Surface Mine Design
Geological Effects on Blast Performance Rock Structure
Field Evaluation of Rock Hardness 28
Surface Mine Design
Geological Effects on Blast Performance Rock Structure
Cavities 29
Surface Mine Design
Geological Effects on Blast Performance Rock Structure
Cavity Loading Techniques 30
Rock Fragmentation by Blasting
Surface Mine Design
Basic Rock Breakage Theory
31
Rock Fragmentation by Blasting
Surface Mine Design
Breakage Process
1.
Explosive detonates and expands 1000 times its original volume.
2.
High gas pressures crush the rock in compression for 2 to 3 times charge diameters.
3.
Stress within the rock causes tensile failure for 20 to 30 charge diameters.
4.
Gas expands into existing and newly formed cracks.
5.
Cracks are extended.
6.
Rockmass is displaced along the path of least resistance.
7.
Gas pressure vents and the muckpile is formed by gravity. 32
Efficient Blast Design
Surface Mine Design
Blast Parameters 1.
Bench height.
2.
Charge diameter.
3.
Burden.
4.
Burden stiffness ratio.
5.
Spacing.
6.
Pattern layout.
7.
Subdrilling.
8.
Stemming.
9.
Decking. 33
Efficient Blast Design
Surface Mine Design
Blast Parameters
Bench Height vs. Hole Diameter 34
Efficient Blast Design Blast Parameters
Surface Mine Design
Decoupling
35
Efficient Blast Design Blast Parameters
Surface Mine Design
Loading Density
36
Efficient Blast Design Blast Parameters
Surface Mine Design
Burden Orientation
37
Efficient Blast Design Blast Parameters
Surface Mine Design
Stiffness Ratio
38
Efficient Blast Design
Surface Mine Design
Blast Parameters
Relationship Between Stiffness Ratio and Energy Distribution
39
Efficient Blast Design Blast Parameters
Surface Mine Design
Spacing Orientation
40
Efficient Blast Design Blast Parameters
Surface Mine Design
Reduced Spacing for Ore Control
41
Efficient Blast Design Blast Parameters
Surface Mine Design
Pattern Configurations
42
Efficient Blast Design Blast Parameters
Surface Mine Design
Relationship Between Burden and Desired Displacement
43
Efficient Blast Design Blast Parameters
Surface Mine Design
Pattern Layout and Energy Distribution
44
Efficient Blast Design Blast Parameters
Surface Mine Design
Influence of Dipping Structures on Subdrill
45
Efficient Blast Design Blast Parameters
Surface Mine Design
Stemming Confinement Factors for ANFO (Relative Bulk Strength 1.0)
46
Efficient Blast Design Blast Parameters
Surface Mine Design
Stemming Confinement Factors for HANFO (Relative Bulk Strength 1.0)
47
Efficient Blast Design Blast Parameters
Surface Mine Design
Decking
48
Angle Drilling Considerations
Surface Mine Design
1.
2.
Advantages. a)
Better energy distribution
b)
Reduced overbreak
c)
Better floor control
d)
Improved highwall stability
e)
Increased initial trajectory
Disadvantages. a)
Requires attention
b)
Drill orientation to the free face must be at 90°
c)
Shorter bit life
d)
Greater hole deviation
e)
Higher cost
f)
Requires expert drillers and wider benches
49
Angle Drilling Considerations
Surface Mine Design
Drilling 30°-angled Blastholes
50
Angle Drilling Considerations
Surface Mine Design
Face Angles vs. Slope
51
Surface Mine Design
Average Design Parameters
52
Surface Mine Design
Initial Blast Design Guide - Example
53
Surface Mine Design
Initial Blast Design Cost Evaluation
54
Surface Mine Design
Current Blast Design Evaluation
55
Surface Mine Design
Current Blast Design Cost Evaluation
56
Ground Vibration
Surface Mine Design
Crater and Elastic Zones
57
Ground Vibration Elastic Waves
Surface Mine Design
The blast energy beyond the crater zone takes the form of elastic ground vibrations: P wave – Compressional wave – 6000-20000 ft/sec S wave – Shear wave – 3/5 the velocity of the P wave R waves – Surface waves – lowest frequency and greatest displacement. The speed of the vibration waves through the ground is known as the wave propagation velocity. 58
Ground Vibration
Surface Mine Design
Wave Propagation
59
Ground Vibration
Surface Mine Design
Vibration Time History
60
Ground Vibration Components of ground vibration
Surface Mine Design
Amplitude It can represent velocity, acceleration, or displacement. Typically represents velocity. Velocity The speed the particles are moving back and forth. The maximum rate that the particles are moving is known as peak particle velocity (PPV) and it is recorded in in/sec.
61
Ground Vibration
Surface Mine Design
Relationship Between Velocity, Frequency, Acceleration, and Displacement
62
Ground Vibration
Surface Mine Design
Relative Ground Motion
63
Ground Vibration Frequency considerations Resonant or natural frequency
Surface Mine Design
According to its physical characteristics any structure will vibrate at a natural frequency (3-18 Hz). The maximum response of a building to ground vibrations occurs when the frequency of the ground motion matches the natural frequency of the building. Geological modification of vibration frequency Blast induced modification of vibration frequency
64
Ground Vibration
Surface Mine Design
Residential Criteria and Effects (from Oriard)
65
Surface Mine Design
Office of Surface Mining Vibration Regulations for Surface Coal Mining
66
Surface Mine Design
USBM Vibration Regulations
67
Ground Vibration
Surface Mine Design
Scaled Distance Equation
68
Ground Vibration
Surface Mine Design
Maximum Charge Weight
69
Ground Vibration
Surface Mine Design
Maximum Charge Weight Calculation
70
Ground Vibration Limit vibrations using scaled distance
0 – 300 ft away: minimum allowable SD is 50 Surface Mine Design
301 – 5000 ft away: minimum allowable SD is 55 Over 5000 ft away: minimum allowable SD is 65
