11/16/2013 1 TAC –Rock Tunnelling Workshop Vancouver, BC November 16, 2013 By: Gordon Revey OVERVIEW OF TUNNEL AND SHAFT BLASTING TECHNOLOGY SCOPE • Blasting versus Mechanical Methods • Managing Risk • Identifying and Controlling Blast Effects • Case Histories Demonstrating Controlled Blasting Techniques Drill - Blast Drill - Blast Mechanical Mechanical EXCAVATION METHODS TO BLAST OR NOT TO BLAST? Use of mechanical or blasting methods depends on: • Volume of material • Hardness and structure • Schedule • Cost ? GFR
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11/16/2013
1
TAC –Rock Tunnelling Workshop
Vancouver, BC
November 16, 2013
By: Gordon Revey
OVERVIEW OF TUNNEL AND SHAFT BLASTING TECHNOLOGY
SCOPE• Blasting versus Mechanical Methods
• Managing Risk
• Identifying and Controlling Blast Effects
• Case Histories Demonstrating Controlled Blasting Techniques
Drill - BlastDrill - Blast
MechanicalMechanical
EXCAVATION METHODS TO BLAST OR NOT TO BLAST?
Use of mechanical or blasting methods depends on:• Volume of material• Hardness and structure• Schedule• Cost
?
GFR
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2
RISKS OF “NO BLASTING”
114 Mpa (16,500 psi)
RQD =96
RISK MANAGEMENT
SAFE & EFFICIENT
BLASTING
Ov
ers
igh
t1
RISK INCREASES WHEN ANY OF THESE SUPPORTING MEASURES AND CONTINUITY
OF PURPOSE ARE WEAK
3
4
2P
requ
alification
De
sig
n
Sp
ec
ifica
tion
s
BLASTING PROCESS
The Blasting Process
Rock Characteristics
INFLUENCINGFACTORS
Explosive Properties
Design Variables
Fragmentation
RESULTS
Broken Rock Profile
Damage
COMPLEXBLAST
PHYSICS
PHYSICAL PROPERTIES
Stress = F/A (MPa or psi)
D
Force (F) F
A
No Load
After LoadArea (A)
1/2 w
d
Direct Strain = d/D Tangential Strain = w/W Poisson's ratio = w/d
W
Young's Modulus = F/{d/D} (GPa or psi)
1/2 w
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3
ROCK PROPERTIES
Static Static Rock Density Young's Compressive Tensile Type (g/cm3) Modulus Strength
Modern explosives are much safer than the old "Dynamite and fuses" seen in Hollywood Movies
The effects of controlled construction blasts look nothing like the gasoline explosions used to create spectacular movie scenes
Commercial blasts are very controlled and carefully regulated
EXPLOSIVES
Molecular and Composites
EMULSIONS
Oxidizer Salts in Aqueous Phase,Oxidizer Salts in Aqueous Phase,Surrounded by Oil-Phase MatrixSurrounded by Oil-Phase Matrix
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SENSITIVITY
0
300
600
900
1200
1500
1800
2100
2400
2700
Bu
llet V
eloc
ity N
eede
d To
Initi
ate
(ft/s
ec)
PROJECTILE IMPACT TEST
DYNAMITE
H.E. Emulsion
ANFO
H.E.Watergel DYNAMITE VERSUS EMULSION EXPLOSIVE GAP SENSITIVITY
Dynamite Propagation Gap =18 to 24 inches
2 to 3 in.Open Gap
Detonator
RECEPTOR
DYNAMITE
EMULSION
DONOR
Emulsion Fails to detonate throughcardboard separation
Zero Gapwith Cardboard
DONOR
DONOR
RECEPTOR
RECEPTOR
EMULSION
EXPLOSIVES HANDLING AND SECURITYThe Canada Explosives Act (R.S.C., 1985, c. E-17)Canada Department of Natural Resources
Blasting Explosives and Initiation Systems -Storage, Possession, Transportation, Destruction and Sale Rules, March 2008Guidelines for Bulk Explosive Facilities –Minimum Requirements, July 2010
Transport Canada Transportation of Dangerous Goods Regulations and Transportation of Dangerous Goods Act.
BLAST EFFECTS
Shock Front
ReactionZone
UnreactedExplosive
Tensile StressCracks
Gas ExpansionHeaving &Displacement
Shock & Heave EnergyCracking and RuptureVibration and Overpressure
RADIAL CRACKING
RadialCompressive Stress
Limited Blasthole Crushing--in hard rock
TangentialTensile Stress
Stress/StrainWave Front
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ROCK STRUCTUREBedding PlanesPartings & JointsCaves and Mud SeamsFaults
JOINT EFFECTS
JOINTING EFFECTS ON CRACK PROPOGATION
Minor Joints or fissures
Open Joint
Radial CracksPass Through
Cemented Joints
Cemented Joint
CrackFronts areStopped byOpen Joints
ENERGY LOSS
Gas Venting Though Open Joints
B locky F ragm entationand poor breakage
Blast gases venting through open joints (Lost heave energy)
PLASTIC DEFORMATION
Deformation in Soft / Porous Material
Explosive energy is Lostto the Rock's Internal friction
LimitedRadialCracks
Hole Expands (Plastic Deformation)
-Argillite-Wollastonite-Marble-Conglomerate
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TUNNEL BLASTING
Drill Jumbo
LaserBeam
RockBolts
Face
DRILLING
Tunnel FaceInvert
Crown
LaserBeam
Shotcrete
RockBolts
LOADING2
1
Tunnel Face
BLAST AND VENTILATE
Tunnel Face
Tunnel Face
SUPPORTING TUNNEL
Load Haul DumpUnit
SCALE & MUCK
Tunnel Face
TEMPORARY GROUNDSUPPORT
5
Tunnel Face
6
Muck
Shotcrete
Air & Water
Material Hopper
Scaling
Shotcrete
Muck
Scaling
GROUND SUPPORT
FINAL SUPPORT7
8
Bolter
Tunnel Face
Shotcrete
Concrete Pump Surveyor
Tunnel Face
LaserSpot
Alignment Laser
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TUNNEL ROUND ELEMENTS
Spacing
Lifters
Buffer Holes
RibHoles
Burden
Smoothwall orBack Holes
Knee Holes
Cut
DRILLING GEOMETRY
CutHoles
Lifters
Buffer Holes
RibHoles
Smoothwall Arch Holes
KneeHoles
Perimeter HoleSpacing (S)
Burden (B)
SpringLine
GradeLine Loaded
Cut Holes
Burn Cut Detail
Void(unloaded)Cut Holes
TUNNEL BLASTING
Perimeter Hole Look-out Angle(Just enough for drill room)
Over drillthe burncut
ExpectedBreak
Round Advance
Cut holes
B u ffe r H o le
P e rim e te r (b ac k ) H o le
K ne e H o le
Lifter H ole
Designed overexcavation tocreate room for Drilling
MinimumTunnelDimensions
CUT METHODS
Fan Cut Round
1 2 3 4 5
1 2 3 4 5
6
6
7
7
11 11 1212
8 7 7 8
109910
Timing Sequence
Z1
2
3
4
5
56
6
3 " Reamed Hole
12"
14"
16"
18"
SHIELDED BLASTHOLE BURN CUTFOR 1 3/4 to 2 inch JUMBO ROUNDS
3'
6"
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EXAMPLE TUNNEL ROUNDS
SPRINGLINE
6 6 77
11
1720' 8"
10' 4"
SmoothwallHoles
Buffer Holes
Buffer Holes
z
z112 2
3
4
4
3
5
5
5
5
6 6
7
7
7
7
88
8
9
99
9
9
1010
1010
1111 11
11
11
11
10
10
10
12
1212
1212
13
13
13
13
13
13
13
13
13
1313
1314
1414141414
1414
14
8810 1011
15 15 1515 15 16 1717 16
68
7
SmoothwallHoles
2.5'
2.5'
2.5'
2.5'2.5'
CONTROLLING OVERBREAK
0.50
0.50
0.50
0.50
00.25
0.751.0
00.25
0.75
00.25
0.7500.25
0.75STRESSLEVEL
Effect of hole size and decoupling on rock stress -- after Hunter
6"
Fully Coupled
Distance to observation point
36"
Fully Coupled2"
Deoupled in air
Deoupled in water
BoreholeWall
SMOOTHWALL BLASTING
Desired Perimeter of Excavation
SMOOTHWALL MECHANICS
Detonating light charges along the perimeter of an excavation with minimum time separation creates tensile stress that cleaves rock at the desired limits of the excavation.
Some overbreak caused by joints and other structure in rock may occur
Minor radiial cracks
CompressionalStress
TensileStress
TYPICAL CHARGES
Buffer Load
Blasthole Load
Smoothwall Load
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DRILL LOOKOUT LIFTER CHARGES HEAVE ROCK
Lifter CollarPipe
L if te r H o leL if te r H o le
LiftersKnee Holes
OVERBREAK CAUSES CHARGE SEPARATION
Ground Shift Cut-off and Charge Separation in Jointed Rock MassCaused by:
OverloadingPoor Tamping or Plugging
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HIGH SHOCK EFFECTS
Shock Wave
Rock is DisplacedInto HoleHigh Pressure
Gas PenetratesInto Hole
PRE-COMPRESSION CAUSESIN DELAYED HOLES
COMPRESSIVE SHOCK WAVEHOLE TO HOLE
UndetonatedCharge
DetonatingCharge
Detonation Front
Plasma FrontOutruns Detonation
Plasma FrontCauses LateralPre-compression
Cross Section
Channel Effect
CONVENTIONAL VERSUS ELECTRONIC DETONATORS
SHIELDED BURN CUTS POWDER FACTOR Face area Powder Factor Range
Displacement and corresponding strain causedby Earthquake is 416 Times greater than that ofHigh-frequency Blast-Induced Motion
PPV(in/s)
PPV(in/s)
BLAST VIBRATION CRITERIA
1
FREQUENCY, Hz
PAR
TIC
LE V
ELO
CIT
Y, in
/s
0.1
0 .2
0.4
0.6
0.8
1
2
4
6
8
10
0.75 in/s
2.0 in/s
0.50 in/s
2 4 6 8 10 20 40 60 80 10030
40
10
USBM RI 8507 Safe PPV Curves - Dashed Lines
Plaster & LathDrywall
Constan
t 0.008 in
Displac
ement
Constan
t 0.03 in
Displac
ement
1) Intended for prevention of cosmetic damage in plaster-lath and gypsum drywall.
2) Too often misapplied to protect new or cured concrete structures.
3) These limits can make some work impossible or needlessly increase cost.
VIBRATION IMPACT TO ROCK
Reduction in Quality (%)
0
20
40
60
80
100
Peak Particle Velocity (mm/sec x 1000)
Peak Particle Velocity (in/sec)
0 1 2 3 4
Approximate adjustment of rock mass quality after vibration. After Page 1987
0 40 79 118 157
"weak" rockQ<4
MRMR<20
"fair" rockQ-4
MRMR - 56
"good" rockQ>50
MRMR > 80
Effect(in/s) (mm/s)
10 254 No fracturing of intact rock10 to 25 254 to 635 Minor tensile slabbing will occur25 to 100 635 to 2540 Strong tensile and some radial cracking
> 100 >2540 Complete breakup of the rock massAfter Bauer and Calder (1971)
Peak Particle Velocity
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19
ORIARD Mass Concrete PPV LimitsConcrete Age Allowable
From Batching PPV - mm/s (in/s)
0 to 4 hours 102 (4) x DF4 hours to 1 day 152 (6) x DF1 to 3 days 229 (9) x DF3 to 7 days 305 (12) x DF7 to 10 days 375 (15) x DF10 days or more 508 (20) x DF
RISK INCREASES WHEN ANY OF THESE SUPPORTING MEASURES AND CONTINUITY
OF PURPOSE ARE WEAK
3
4
2
Preq
ualificatio
n
De
sig
n
Sp
ec
ifica
tion
s
BEST MANAGEMENT PRACTICES
• Evaluate Area Property- Pre-construction Inspections
• Apply Blasting Controls- Charge Weight Limits- Noise Control Measures
• Public Communication- Project Hotline- Open Meetings
• Government Approvals• Perform Work Safely• Continuous Blast Effects Monitoring
11/16/2013
26
SUCCESSFULLY MANAGING HIGH-RISK BLASTING WORK
There are four layers of expertise:
The first layer starts with designers who develop specifications, geotechnical reports, and other documents that:
1) define challenges of the work; 2) limit allowable methods; 3) specify performance requirements and;4) establish experience requirements for key
participants
SUCCESSFULLY MANAGING HIGH-RISK BLASTING WORK
The third layer of risk management is expected from third-party blasting / vibration consultants representing the contractor.
SUCCESSFULLY MANAGING HIGH-RISK BLASTING WORK
The last layer of risk management is delivered by a third-party construction manager, supported by inspectors, project designers, and additional specialists as needed.